Questions & Answers
CBSE - Grade - 8
Subject: Science
Chapter - 10 - Sound
Types of Questions
MCQ
- Sound is always produced by:
(a) Still objects
(b) Vibrating objects
(c) Moving vehicles
(d) Heat energy
Answer: (b) Vibrating objects - The to and fro motion of an object is called:
(a) Rotation
(b) Vibration
(c) Revolution
(d) Translation
Answer: (b) Vibration - Which part of the school bell vibrates to produce sound?
(a) Hammer
(b) Clapper
(c) Metal body
(d) Chain
Answer: (c) Metal body - In humans, sound is produced by:
(a) Nose
(b) Larynx
(c) Ears
(d) Tongue
Answer: (b) Larynx - Another name for larynx is:
(a) Ear drum
(b) Voice box
(c) Windpipe
(d) Resonator
Answer: (b) Voice box - Vocal cords in men are about:
(a) 15 mm
(b) 20 mm
(c) 10 mm
(d) 25 mm
Answer: (b) 20 mm - The vocal cords in women are about:
(a) 20 mm
(b) 15 mm
(c) 25 mm
(d) 30 mm
Answer: (b) 15 mm - Children’s voices are shrill because:
(a) Their vocal cords are shorter
(b) Their vocal cords are longer
(c) They sing loudly
(d) They talk faster
Answer: (a) Their vocal cords are shorter - Sound cannot travel through:
(a) Solids
(b) Liquids
(c) Gases
(d) Vacuum
Answer: (d) Vacuum - In which medium does sound travel the fastest?
(a) Air
(b) Water
(c) Steel
(d) Vacuum
Answer: (c) Steel - The funnel-shaped part of the ear is called:
(a) Ear canal
(b) Eardrum
(c) Outer ear
(d) Inner ear
Answer: (c) Outer ear - The thin stretched membrane in the ear is called:
(a) Cochlea
(b) Vocal cord
(c) Ear canal
(d) Eardrum
Answer: (d) Eardrum - The eardrum sends vibrations to the:
(a) Nose
(b) Inner ear
(c) Vocal cords
(d) Larynx
Answer: (b) Inner ear - Vibrations received by the inner ear are sent to the:
(a) Heart
(b) Brain
(c) Vocal cords
(d) Windpipe
Answer: (b) Brain - Unit of frequency is:
(a) Decibel
(b) Newton
(c) Hertz
(d) Metre
Answer: (c) Hertz - Symbol for hertz is:
(a) Hz
(b) H
(c) ht
(d) hr
Answer: (a) Hz - If a body makes 20 vibrations in one second, its frequency is:
(a) 10 Hz
(b) 20 Hz
(c) 30 Hz
(d) 40 Hz
Answer: (b) 20 Hz - Loudness of sound depends on:
(a) Frequency
(b) Amplitude
(c) Pitch
(d) Medium
Answer: (b) Amplitude - Loudness is measured in:
(a) Hertz
(b) Decibels
(c) Newtons
(d) Joules
Answer: (b) Decibels - The shrillness of sound is determined by:
(a) Amplitude
(b) Frequency
(c) Medium
(d) Ear canal
Answer: (b) Frequency - Human audible range is:
(a) 10 Hz – 100 Hz
(b) 20 Hz – 20,000 Hz
(c) 50 Hz – 10,000 Hz
(d) 200 Hz – 20,000 Hz
Answer: (b) 20 Hz – 20,000 Hz - Sounds below 20 Hz are called:
(a) Ultrasound
(b) Infrasound
(c) Audible sound
(d) Music
Answer: (b) Infrasound - Sounds above 20,000 Hz are called:
(a) Ultrasound
(b) Infrasound
(c) Noise
(d) Audible sound
Answer: (a) Ultrasound - Which animal can hear ultrasound?
(a) Cat
(b) Dog
(c) Horse
(d) Cow
Answer: (b) Dog - Ultrasound is used in:
(a) Cooking
(b) Medical equipment
(c) Fuel combustion
(d) Photosynthesis
Answer: (b) Medical equipment - Sound that is pleasant to hear is called:
(a) Noise
(b) Music
(c) Pitch
(d) Frequency
Answer: (b) Music - Sound that is unpleasant is called:
(a) Music
(b) Noise
(c) Frequency
(d) Amplitude
Answer: (b) Noise - Example of a musical instrument with vibrating strings:
(a) Tabla
(b) Veena
(c) Manjira
(d) Ghatam
Answer: (b) Veena - Vibrating part of tabla is:
(a) String
(b) Membrane
(c) Air column
(d) Wooden frame
Answer: (b) Membrane - Vibrating part of flute is:
(a) Membrane
(b) String
(c) Air column
(d) Wooden body
Answer: (c) Air column - Too much noise causes:
(a) Sleep
(b) Relaxation
(c) Health problems
(d) None
Answer: (c) Health problems - Noise pollution means:
(a) Excess oxygen in air
(b) Excessive unwanted sound
(c) Lack of sound
(d) Pleasant music
Answer: (b) Excessive unwanted sound - A harmful effect of noise pollution is:
(a) Increased appetite
(b) Hypertension
(c) Clearer hearing
(d) Lower stress
Answer: (b) Hypertension - Sound level of normal breathing is about:
(a) 60 dB
(b) 10 dB
(c) 30 dB
(d) 80 dB
Answer: (b) 10 dB - Busy traffic produces about:
(a) 20 dB
(b) 30 dB
(c) 70 dB
(d) 90 dB
Answer: (c) 70 dB - Factory sounds produce around:
(a) 60 dB
(b) 80 dB
(c) 20 dB
(d) 40 dB
Answer: (b) 80 dB - Above what sound level does noise become painful?
(a) 40 dB
(b) 60 dB
(c) 80 dB
(d) 100 dB
Answer: (c) 80 dB - Excessive exposure to loud sound may cause:
(a) Temporary or permanent hearing loss
(b) Better sleep
(c) Improved hearing
(d) None
Answer: (a) Temporary or permanent hearing loss - Which of these is a measure to reduce noise pollution?
(a) Using more horns
(b) Planting trees
(c) Playing loud music
(d) Bursting crackers
Answer: (b) Planting trees - Which household item contributes to noise pollution?
(a) Books
(b) Desert cooler
(c) Table lamp
(d) Carpet
Answer: (b) Desert cooler - What part of the ear vibrates when sound enters?
(a) Cochlea
(b) Eardrum
(c) Nose
(d) Vocal cords
Answer: (b) Eardrum - Which sound has higher pitch?
(a) Drum
(b) Whistle
(c) Lion roar
(d) Thunder
Answer: (b) Whistle - Which sound is low-pitched but loud?
(a) Bird chirping
(b) Lion roar
(c) Whistle
(d) Flute
Answer: (b) Lion roar - Whose voice generally has the highest frequency?
(a) Men
(b) Women
(c) Children
(d) Old people
Answer: (c) Children - Which of the following produces sound by vibrating air column?
(a) Tabla
(b) Flute
(c) Veena
(d) Manjira
Answer: (b) Flute - Which of the following is NOT a source of noise pollution?
(a) Loudspeakers
(b) Television at high volume
(c) Bursting crackers
(d) Books in library
Answer: (d) Books in library - The sound heard by dolphins under water proves that sound can travel through:
(a) Vacuum
(b) Solids
(c) Liquids
(d) Gases only
Answer: (c) Liquids - The “Did you know?” example in the chapter refers to:
(a) Taj Mahal
(b) Qutub Minar
(c) Golconda Fort
(d) Red Fort
Answer: (c) Golconda Fort - Golconda Fort’s dome was designed to:
(a) Store water
(b) Reflect sunlight
(c) Carry sound over long distance
(d) Block sound
Answer: (c) Carry sound over long distance - Which of the following correctly matches?
(a) Loudness → Frequency
(b) Pitch → Amplitude
(c) Loudness → Amplitude
(d) Pitch → Loudness
Answer: (c) Loudness → Amplitude
Fill in the Blanks
- Sound is produced by __________ objects.
Answer: vibrating - The back-and-forth motion of an object is called __________.
Answer: vibration - In humans, sound is produced by the __________.
Answer: voice box (larynx) - The voice box is located at the upper end of the __________.
Answer: windpipe - Sound cannot travel through __________.
Answer: vacuum - Sound travels fastest in __________.
Answer: solids - The outer part of the ear is shaped like a __________.
Answer: funnel - The thin stretched membrane in the ear is called __________.
Answer: eardrum - Vibrations from the eardrum are sent to the __________.
Answer: inner ear - From the inner ear, sound signals are carried to the __________.
Answer: brain - The number of oscillations per second is called __________.
Answer: frequency - Frequency is measured in __________.
Answer: hertz (Hz) - One hertz means __________ oscillation per second.
Answer: one - The time taken by one oscillation is called __________.
Answer: time period - Loudness of sound depends on __________ of vibration.
Answer: amplitude - Loudness is measured in __________.
Answer: decibels (dB) - The shrillness or pitch of a sound depends on its __________.
Answer: frequency - Human audible range is __________ to __________ Hz.
Answer: 20 to 20,000 - Sounds below 20 Hz are called __________.
Answer: infrasound - Sounds above 20,000 Hz are called __________.
Answer: ultrasound - Dogs can hear sounds of __________ frequency beyond human range.
Answer: high - Ultrasound is used in __________ equipment.
Answer: medical - Pleasant sound is called __________.
Answer: music - Unpleasant sound is called __________.
Answer: noise - Excessive unwanted sound in the environment is called __________.
Answer: noise pollution - Sound of normal breathing is about __________ dB.
Answer: 10 - Sound of normal conversation is about __________ dB.
Answer: 60 - Busy traffic produces about __________ dB sound.
Answer: 70 - Average factory sound is around __________ dB.
Answer: 80 - Above __________ dB, sound becomes physically painful.
Answer: 80 - Noise pollution may cause lack of sleep, __________ and anxiety.
Answer: hypertension - Continuous exposure to loud sound may cause __________ impairment.
Answer: hearing - A stretched string instrument example is __________.
Answer: Veena - A stretched membrane instrument example is __________.
Answer: Tabla - A vibrating air column instrument example is __________.
Answer: Flute - The vocal cords in men are about __________ mm long.
Answer: 20 - The vocal cords in women are about __________ mm long.
Answer: 15 - Children have very __________ vocal cords.
Answer: short - Larger the amplitude, __________ the sound.
Answer: louder - Higher the frequency, __________ is the pitch.
Answer: higher - The roar of a lion is low pitched but very __________.
Answer: loud - A bird makes a high pitched but __________ sound.
Answer: feeble - The vibrating part of the tabla is its __________.
Answer: stretched membrane - The vibrating part of the sitar is its __________.
Answer: stretched string - The vibrating part of the flute is the __________.
Answer: air column - Excessive use of automobile __________ adds to noise pollution.
Answer: horns - Plantation of __________ along roads helps reduce noise.
Answer: trees - __________ language helps children with hearing impairment to communicate.
Answer: Sign - Golconda Fort in Hyderabad has a dome where a __________ could be heard 1 km away.
Answer: clap - Larger the amplitude of vibration, __________ is the loudness of sound.
Answer: greater
Name the Following
- The motion that produces sound.
Answer: Vibration - The organ in humans that produces sound.
Answer: Larynx (voice box) - The organ where vocal cords are located.
Answer: Voice box (larynx) - The passage connected to the larynx.
Answer: Windpipe - The thin stretched membrane in the ear.
Answer: Eardrum - The outer funnel-shaped part of the ear.
Answer: Outer ear - The unit of frequency.
Answer: Hertz (Hz) - The unit of loudness.
Answer: Decibel (dB) - The time taken for one complete oscillation.
Answer: Time period - The number of oscillations per second.
Answer: Frequency - The property of sound that depends on amplitude.
Answer: Loudness - The property of sound that depends on frequency.
Answer: Pitch (shrillness) - The range of frequencies audible to humans.
Answer: 20 Hz – 20,000 Hz - Sounds with frequency below 20 Hz.
Answer: Infrasound - Sounds with frequency above 20,000 Hz.
Answer: Ultrasound - Animals that can hear ultrasound.
Answer: Dogs - Equipment that uses ultrasound.
Answer: Medical scanning equipment - Sound that is pleasant to hear.
Answer: Music - Sound that is unpleasant to hear.
Answer: Noise - The presence of excessive or unwanted sounds in the environment.
Answer: Noise pollution - One example of string instrument.
Answer: Veena / Sitar - One example of membrane instrument.
Answer: Tabla / Dholak - One example of an air column instrument.
Answer: Flute - One percussion instrument struck to produce sound.
Answer: Manjira / Ghatam - The vibrating part of the sitar.
Answer: Stretched string - The vibrating part of the tabla.
Answer: Stretched membrane - The vibrating part of the flute.
Answer: Air column - The vibrating part of the veena.
Answer: String - The vibrating part of the dholak.
Answer: Membrane - The vibrating part of the ghatam.
Answer: Whole body of the pot - A sound source that can cause noise pollution in homes.
Answer: Television / Desert cooler / Radio at high volume - The level of sound from normal breathing.
Answer: 10 dB - The level of sound from normal conversation.
Answer: 60 dB - The level of sound from busy traffic.
Answer: 70 dB - The level of sound from an average factory.
Answer: 80 dB - The sound level beyond which noise becomes painful.
Answer: Above 80 dB - One harmful effect of noise pollution on health.
Answer: Hypertension / Anxiety / Hearing impairment - A simple device used to show sound travels through strings.
Answer: Toy telephone - The body part that sends sound signals to the brain.
Answer: Inner ear - The organ where signals are processed into hearing.
Answer: Brain - The voice box length in men.
Answer: About 20 mm - The voice box length in women.
Answer: About 15 mm - The type of voice children have due to shorter vocal cords.
Answer: Shrill voice - The type of sound a lion’s roar represents.
Answer: Low pitched but loud sound - The type of sound a bird’s chirping represents.
Answer: High pitched but feeble sound - A method to reduce noise pollution in residential areas.
Answer: Planting trees - A communication method for children with hearing loss.
Answer: Sign language - A technological aid for hearing-impaired persons.
Answer: Hearing aid - A historical fort in Hyderabad famous for sound reflection.
Answer: Golconda Fort - The sound demonstration in Golconda Fort involved a __________.
Answer: Clap
Answer in One Word
- What type of motion produces sound?
Answer: Vibration - Which organ in humans produces sound?
Answer: Larynx - What is the other name of the larynx?
Answer: Voice box - Which body part vibrates to let us hear sound?
Answer: Eardrum - Through which organ do sound signals reach the brain?
Answer: Inner ear - In which medium does sound travel the fastest?
Answer: Solid - In which medium does sound travel the slowest?
Answer: Gas - Which unit is used to measure frequency?
Answer: Hertz (Hz) - Which unit is used to measure loudness?
Answer: Decibel (dB) - What is the time taken for one oscillation called?
Answer: Time period - Which property of sound depends on amplitude?
Answer: Loudness - Which property of sound depends on frequency?
Answer: Pitch - What is the human audible range’s lower limit?
Answer: 20 Hz - What is the human audible range’s upper limit?
Answer: 20,000 Hz - What are sounds below 20 Hz called?
Answer: Infrasound - What are sounds above 20,000 Hz called?
Answer: Ultrasound - Which animal can hear ultrasound?
Answer: Dog - Which medical field commonly uses ultrasound?
Answer: Diagnosis - What do we call pleasant sounds?
Answer: Music - What do we call unpleasant sounds?
Answer: Noise - What is unwanted sound in the environment called?
Answer: Noise pollution - Which instrument has vibrating strings?
Answer: Veena - Which instrument has vibrating membrane?
Answer: Tabla - Which instrument has vibrating air column?
Answer: Flute - Which percussion instrument is struck to produce sound?
Answer: Manjira - What is the vibrating part of a sitar?
Answer: String - What is the vibrating part of a dholak?
Answer: Membrane - What is the vibrating part of a flute?
Answer: Air column - What is the vibrating part of a ghatam?
Answer: Body of the pot - What is the approximate sound level of normal breathing?
Answer: 10 dB - What is the approximate sound level of normal conversation?
Answer: 60 dB - What is the approximate sound level of busy traffic?
Answer: 70 dB - What is the approximate sound level of a factory?
Answer: 80 dB - Above which level does sound become painful?
Answer: 80 dB - What health issue can noise pollution cause?
Answer: Hypertension - What impairment can loud noise cause?
Answer: Hearing - What type of voice do children have?
Answer: Shrill - What type of voice do men generally have?
Answer: Deep - What type of voice do women generally have?
Answer: High-pitched - Whose roar is low-pitched but loud?
Answer: Lion - Whose chirping is high-pitched but feeble?
Answer: Bird - Which toy proves sound can travel through strings?
Answer: Toy telephone - Which body organ processes sound signals into hearing?
Answer: Brain - What is the length of vocal cords in men?
Answer: 20 mm - What is the length of vocal cords in women?
Answer: 15 mm - Which communication method helps hearing-impaired children?
Answer: Sign language - What device helps hearing-impaired persons?
Answer: Hearing aid - Which fort in Hyderabad is famous for sound reflection?
Answer: Golconda Fort - What action in Golconda Fort’s dome could be heard far away?
Answer: Clap - Planting of what reduces noise pollution?
Answer: Trees
ICSE - Grade 9 - Physics
All Chapters
- Chapter 1 Measurement and Experimentation
- Chapter 2 Motion in one dimension
- Chapter 3 Laws of Motion
- Chapter 4 Pressure in fluids and Atmospheric pressure
- Chapter 5 Upthrust in Fluids, Archimedes’ Principle and Floatation
- Chapter 6 Heat and energy
- Chapter 7 Reflection of light
- Chapter 8 Propagation of Sound waves
- Chapter 9 Current Electricity
- Chapter 10 Magnetism
ICSE - Grade 9 - Chemistry
All Chapters
- Chapter 1 The Language of Chemistry
- Chapter 2 Chemical Changes and Reactions
- Chapter 3 Water
- Chapter 4 Atomic Structure and Chemical Bonding
- Chapter 5 The periodic table
- Chapter 6 Study of the first Element Hydrogen
- Chapter 7 Study of Gas laws
- Chapter 8 Atmospheric Pollution
ICSE - Grade 9 - Mathematics
All Chapters
- Chapter 1 Rational and Irrational Numbers
- Chapter 2 Compound Interest [Without Using Formula]
- Chapter 3 Compound Interest [Using Formula]
- Chapter 4 Expansions
- Chapter 5 Factorisation
- Chapter 6 Simultaneous Equations
- Chapter 7 Indices
- Chapter 8 Logarithms
- Chapter 9 Triangles
- Chapter 10 Isosceles Triangles
- Chapter 11 Inequalities
- Chapter 12 Midpoint and Its Converse
- Chapter 13 Pythagoras Theorem
- Chapter 14 Rectilinear Figures
- Chapter 15 Construction of Polygons
- Chapter 16 Area Theorems
- Chapter 17 Circle
- Chapter 18 Statistics
- Chapter 19 Mean and Median
- Chapter 20 Area and Perimeter of Plane Figures
- Chapter 21 Solids
- Chapter 22 Trigonometrical Ratios
- Chapter 23 Trigonometrical Ratios of Standard Angles
- Chapter 24 Solutions of Right Triangles
- Chapter 25 Complementary Angles
- Chapter 26 Coordinate Geometry
- Chapter 27 Graphical Solution
- Chapter 28 Distance Formula
ICSE - Grade 9 - Biology
All Chapters
- Chapter 1 Introducing Biology
- Chapter 2 Cell: The Unit Of Life
- Chapter 3 Tissues: Plant And Animal Tissue
- Chapter 4 The Flower
- Chapter 5 Pollination and Fertilization
- Chapter 6 Seeds: Structure and Germination
- Chapter 7 Respiration in Plants
- Chapter 8 Five Kingdom Classification
- Chapter 9 Economic Importance of Bacteria and Fungi
- Chapter 10 Nutrition
- Chapter 11 Digestive system
- Chapter 12 Skeleton: Movement and Locomotion
- Chapter 13 Skin: The Jack of all trades
- Chapter 14 The Respiratory System
- Chapter 15 Hygiene: [A key to Healthy Life]
- Chapter 16 Diseases: Cause and Control
- Chapter 17 Aids to Health
- Chapter 18 Health Organizations
- Chapter 19 Waste Generation and Management
ICSE - Grade 9 - History
All Chapters
- Chapter 1 – The Harappan Civilisation
- Chapter 2 – The Vedic Period
- Chapter 3 – Jainism and Buddhism
- Chapter 4 – The Mauryan Empire
- History — Chapter 5
The Sangam Age - Chapter 6 – The Age of the Guptas
- Chapter 7 – Medieval India — (A) The Cholas
- Chapter 8 – Medieval India — (B) The Delhi Sultanate
- Chapter 9 – Medieval India — (C) The Mughal Empire
- Chapter 10 – Medieval India — (D) Composite Culture
- Chapter 11 – The Modern Age in Europe — (A) Renaissance
- Chapter 12 – The Modern Age in Europe — (B) Reformation
- Chapter 13 – The Modern Age in Europe — (C) Industrial Revolution
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All Chapters
- Chapter 1: Our Constitution
- Chapter 2: Salient Features of the Constitution — I
- Chapter 3: Salient Features of the
- Constitution — II
- Chapter 4: Elections
- Chapter 5: Local Self-Government — Rural
- Chapter 6: Local Self-Government — Urban
ICSE - Grade 9 - Geography
All Chapters
- Ch 1 – Earth as a Planet
Ch 2 – Geographic Grid: Latitudes and Longitudes
Ch 3 – Rotation and Revolution
Ch 4 – Earth’s Structure
Ch 5 – Landforms of the Earth
Ch 6 – Rocks
Ch 7 – Volcanoes
Ch 8 – Earthquakes
Ch 9 – Weathering
Ch 10 – Denudation
Ch 11 – Hydrosphere
Ch 12 – Composition and Structure of the Atmosphere
Ch 13 – Insolation
Ch 14 – Atmospheric Pressure and Winds
Ch 15 – Humidity
Ch 16 – Pollution
Ch 17 – Sources of Pollution
Ch 18 – Effects of Pollution
Ch 19 – Preventive Measures
Ch 20 – Natural Regions of the World
Find the Odd Man Out
- Veena, Sitar, Flute, Guitar
Answer: Flute
Explanation: Flute produces sound by vibrating air column, others use strings. - Tabla, Dholak, Mridangam, Flute
Answer: Flute
Explanation: Flute is a wind instrument, others are membrane instruments. - Manjira, Ghatam, Kartal, Veena
Answer: Veena
Explanation: Veena is a string instrument, others are percussion instruments. - Air, Water, Steel, Vacuum
Answer: Vacuum
Explanation: Sound cannot travel in vacuum but can travel in air, water, and solids. - Amplitude, Frequency, Time Period, Colour
Answer: Colour
Explanation: Colour is not a property of sound, others are properties of vibration. - Loudness, Pitch, Amplitude, Density
Answer: Density
Explanation: Density is a property of matter, not of sound. - Noise, Music, Ultrasound, Infrasound
Answer: Music
Explanation: Music is pleasant sound, others refer to sound ranges/types. - Dog, Cat, Human, Lion
Answer: Dog
Explanation: Dogs can hear ultrasound, the others cannot. - 10 Hz, 20 Hz, 15 Hz, 18 Hz
Answer: 10 Hz
Explanation: 10 Hz is infrasound, others are within human audible range. - 20 Hz, 200 Hz, 2000 Hz, 25,000 Hz
Answer: 25,000 Hz
Explanation: 25,000 Hz is ultrasound, beyond human audible range. - 20 Hz, 2,000 Hz, 20,000 Hz, 200,000 Hz
Answer: 200,000 Hz
Explanation: 200,000 Hz is ultrasound, inaudible to humans. - Eardrum, Larynx, Vocal cords, Veena string
Answer: Veena string
Explanation: Veena string is not part of the human body; others are related to sound in humans. - Brain, Inner ear, Cochlea, Tabla
Answer: Tabla
Explanation: Tabla is a musical instrument, others are parts of the hearing system. - Hertz, Decibel, Newton, Time period
Answer: Newton
Explanation: Newton is a unit of force, not related to sound. - Amplitude, Frequency, Loudness, Temperature
Answer: Temperature
Explanation: Temperature is not a sound property, others are. - Whisper, Conversation, Breathing, Vacuum
Answer: Vacuum
Explanation: Vacuum does not produce or carry sound, others are sound levels. - 10 dB, 30 dB, 60 dB, 600 dB
Answer: 600 dB
Explanation: 600 dB is unrealistic, human hearing limit is much below this. - Hypertension, Hearing loss, Anxiety, Photosynthesis
Answer: Photosynthesis
Explanation: Photosynthesis is a plant process, not caused by noise pollution. - Lion roar, Bird chirp, Drum beat, Whistle
Answer: Lion roar
Explanation: Lion’s roar is low-pitched, others are high-pitched sounds. - Bird song, Veena, Harmonium, Factory noise
Answer: Factory noise
Explanation: Factory noise is unpleasant (noise), others produce music. - Windpipe, Voice box, Vocal cords, Eardrum
Answer: Eardrum
Explanation: Eardrum helps in hearing, others help in producing sound. - Sound, Light, Noise, Music
Answer: Light
Explanation: Light is not related to sound, others are types of sound. - Veena, Tabla, Manjira, Tree
Answer: Tree
Explanation: Tree is not a musical instrument. - Television, Mixer, Refrigerator, Book
Answer: Book
Explanation: Book does not produce noise pollution, others do. - Flute, Clarinet, Trumpet, Tabla
Answer: Tabla
Explanation: Tabla is a percussion instrument, others are wind instruments. - Brain, Ear canal, Eardrum, Nose
Answer: Nose
Explanation: Nose is not part of the hearing system, others are. - Shrill, Pitch, Frequency, Temperature
Answer: Temperature
Explanation: Temperature is not related to sound properties. - Decibel, Hertz, Metre, Amplitude
Answer: Metre
Explanation: Metre is a unit of length, not for sound. - Sign language, Hearing aid, Cochlear implant, Guitar
Answer: Guitar
Explanation: Guitar is a musical instrument, others are aids for hearing-impaired. - Human ear, Dog, Dolphin, Vacuum
Answer: Vacuum
Explanation: Vacuum cannot detect or carry sound. - Thunder, Lightning, Whistle, Roar
Answer: Lightning
Explanation: Lightning is seen, not heard, others are sounds. - Normal breathing, Whisper, Conversation, Silence
Answer: Silence
Explanation: Silence does not produce sound, others do. - Windpipe, Nose, Mouth, Ear canal
Answer: Ear canal
Explanation: Ear canal is for hearing, others help in producing sound. - Sitar, Guitar, Veena, Tabla
Answer: Tabla
Explanation: Tabla is a membrane instrument, others are string instruments. - Loudspeaker, Cracker, Drum, Tree
Answer: Tree
Explanation: Tree does not cause noise, others can produce noise. - Hearing loss, Hypertension, Anxiety, Digestion
Answer: Digestion
Explanation: Digestion is not affected by noise pollution. - Hertz, Frequency, Time period, Colour
Answer: Colour
Explanation: Colour is not a sound property. - Man, Woman, Child, Dog
Answer: Dog
Explanation: Dog has a different hearing range from humans. - Golconda Fort, Red Fort, Qutub Minar, Taj Mahal
Answer: Golconda Fort
Explanation: Golconda Fort is famous for sound reflection, others are not. - Whisper, Breathing, Conversation, Explosion
Answer: Explosion
Explanation: Explosion is extremely loud, others are soft sounds. - Amplitude, Frequency, Loudness, Oxygen
Answer: Oxygen
Explanation: Oxygen is not a sound property. - Veena, Tabla, Flute, Pen
Answer: Pen
Explanation: Pen is not a musical instrument. - Trees, Silencers, Horns, Plantation
Answer: Horns
Explanation: Horns increase noise, others reduce noise. - Inner ear, Brain, Eardrum, Hand
Answer: Hand
Explanation: Hand is not part of the hearing system. - Whisper, Breathing, Shouting, Sleeping
Answer: Sleeping
Explanation: Sleeping does not produce sound, others do. - Normal conversation, Busy traffic, Factory, Silence
Answer: Silence
Explanation: Silence is absence of sound. - Toy telephone, String, Metal rod, Glass
Answer: Toy telephone
Explanation: Toy telephone is a device, others are mediums of sound travel. - Child’s voice, Woman’s voice, Man’s voice, Stone
Answer: Stone
Explanation: Stone does not produce voice, others do. - Golconda Fort, Clap dome, Sound reflection, Photosynthesis
Answer: Photosynthesis
Explanation: Photosynthesis is unrelated to sound, others are. - Amplitude, Loudness, Pitch, Photosynthesis
Answer: Photosynthesis
Explanation: Photosynthesis is a plant process, others are sound terms.
Match the Pair
Set 1
Column A
- Larynx
- Eardrum
- Frequency
- Amplitude
- Decibel
Column B
a. Unit of loudness
b. Determines pitch
c. Produces sound in humans
d. Thin stretched membrane in ear
e. Determines loudness
Correct Answers:
1 – c
2 – d
3 – b
4 – e
5 – a
Set 2
Column A
- Infrasound
- Ultrasound
- Audible range
- Dog
- Humans
Column B
a. 20 Hz – 20,000 Hz
b. Can hear above 20,000 Hz
c. Below 20 Hz
d. Above 20,000 Hz
e. Cannot hear infrasound
Correct Answers:
1 – c
2 – d
3 – a
4 – b
5 – e
Set 3
Column A
- Veena
- Tabla
- Flute
- Ghatam
- Manjira
Column B
a. Stretched string
b. Air column
c. Beaten pot
d. Struck cymbals
e. Stretched membrane
Correct Answers:
1 – a
2 – e
3 – b
4 – c
5 – d
Set 4
Column A
- Loudness
- Pitch
- Whisper
- Conversation
- Factory noise
Column B
a. 80 dB
b. Depends on amplitude
c. 60 dB
d. 30 dB
e. Depends on frequency
Correct Answers:
1 – b
2 – e
3 – d
4 – c
5 – a
Set 5
Column A
- Windpipe
- Vocal cords
- Outer ear
- Inner ear
- Brain
Column B
a. Collects sound like a funnel
b. Processes sound into hearing
c. Produces vibration in larynx
d. Carries air from lungs
e. Sends signals to brain
Correct Answers:
1 – d
2 – c
3 – a
4 – e
5 – b
Set 6
Column A
- Noise
- Music
- Bird chirp
- Lion roar
- Whistle
Column B
a. High-pitched sound
b. Low-pitched but loud
c. Shrill sound
d. Pleasant sound
e. Unpleasant sound
Correct Answers:
1 – e
2 – d
3 – a
4 – b
5 – c
Set 7
Column A
- Hearing aid
- Sign language
- Cochlear implant
- Speech problem in children
- Partial hearing loss
Column B
a. Helps hearing-impaired communicate
b. Occurs due to disease, injury or age
c. Improves quality of life technologically
d. Caused due to hearing loss
e. Device to amplify sound
Correct Answers:
1 – e
2 – a
3 – c
4 – d
5 – b
Set 8
Column A
- Normal breathing
- Busy traffic
- Explosion of crackers
- Soft whisper
- Average factory
Column B
a. 10 dB
b. Above 80 dB
c. 80 dB
d. 30 dB
e. 70 dB
Correct Answers:
1 – a
2 – e
3 – b
4 – d
5 – c
Set 9
Column A
- Golconda Fort
- Clap dome
- Sound cannot travel
- Medium of sound
- Toy telephone
Column B
a. Demonstrates sound travels through string
b. Architectural marvel in Hyderabad
c. Without medium
d. Reverberates clap over long distance
e. Gas, liquid or solid
Correct Answers:
1 – b
2 – d
3 – c
4 – e
5 – a
Set 10
Column A
- Amplitude
- Frequency
- Time period
- Oscillation
- Pitch
Column B
a. To and fro motion
b. Determines shrillness
c. Number of vibrations per second
d. Time for one vibration
e. Determines loudness
Correct Answers:
1 – e
2 – c
3 – d
4 – a
5 – b
Short Answer Questions
- What produces sound?
Answer: Vibrations of objects produce sound. - Which organ in humans produces sound?
Answer: The larynx or voice box produces sound. - What part of the body vibrates to create human voice?
Answer: Vocal cords vibrate to create human voice. - What is the function of the eardrum?
Answer: The eardrum vibrates when sound waves fall on it. - What is the unit of frequency?
Answer: Frequency is measured in Hertz (Hz). - What is the unit of loudness?
Answer: Loudness is measured in Decibels (dB). - Define time period in sound.
Answer: Time period is the time taken for one oscillation. - Define frequency.
Answer: Frequency is the number of oscillations per second. - On what factor does loudness depend?
Answer: Loudness depends on amplitude of vibration. - On what factor does pitch depend?
Answer: Pitch depends on frequency of vibration. - What is the audible range of humans?
Answer: Humans can hear between 20 Hz and 20,000 Hz. - What is infrasound?
Answer: Sound with frequency below 20 Hz is called infrasound. - What is ultrasound?
Answer: Sound with frequency above 20,000 Hz is called ultrasound. - Name one animal that can hear ultrasound.
Answer: Dogs can hear ultrasound. - Give one use of ultrasound in medicine.
Answer: Ultrasound is used for scanning internal organs. - What type of sound is pleasant to hear?
Answer: Music is pleasant to hear. - What type of sound is unpleasant to hear?
Answer: Noise is unpleasant to hear. - What is noise pollution?
Answer: Noise pollution is the presence of excessive or unwanted sound in the environment. - Name one household source of noise pollution.
Answer: Loud television is a household source of noise pollution. - Name one health effect of noise pollution.
Answer: Noise pollution can cause hypertension. - What is the sound level of normal breathing?
Answer: Normal breathing is about 10 dB. - What is the sound level of a whisper?
Answer: A whisper is about 30 dB. - What is the sound level of conversation?
Answer: Conversation is about 60 dB. - What is the sound level of busy traffic?
Answer: Busy traffic is about 70 dB. - What is the sound level of a factory?
Answer: A factory produces about 80 dB. - Above what level does sound become harmful?
Answer: Sound above 80 dB becomes harmful. - Name one way to reduce noise pollution.
Answer: Planting trees reduces noise pollution. - What is the vibrating part of a sitar?
Answer: The string is the vibrating part of a sitar. - What is the vibrating part of a tabla?
Answer: The stretched membrane is the vibrating part of a tabla. - What is the vibrating part of a flute?
Answer: The vibrating part of a flute is the air column. - What is the vibrating part of a ghatam?
Answer: The whole pot vibrates to produce sound in a ghatam. - Which part of the ear collects sound?
Answer: The outer ear collects sound. - Which part of the ear sends signals to the brain?
Answer: The inner ear sends signals to the brain. - Which organ processes sound into hearing?
Answer: The brain processes sound into hearing. - What is the length of vocal cords in men?
Answer: In men, vocal cords are about 20 mm long. - What is the length of vocal cords in women?
Answer: In women, vocal cords are about 15 mm long. - Whose voice is shrill due to short vocal cords?
Answer: Children’s voices are shrill due to short vocal cords. - Give one example of a string instrument.
Answer: Veena is a string instrument. - Give one example of a membrane instrument.
Answer: Tabla is a membrane instrument. - Give one example of an air column instrument.
Answer: Flute is an air column instrument. - Give one example of a percussion instrument.
Answer: Manjira is a percussion instrument. - Which toy shows that sound travels through strings?
Answer: A toy telephone shows that sound travels through strings. - Which animal makes a loud but low-pitched sound?
Answer: A lion makes a loud but low-pitched sound. - Which animal produces a high-pitched sound?
Answer: A bird produces a high-pitched sound. - Name one appliance that causes noise pollution.
Answer: A mixer grinder causes noise pollution. - Which historical fort in Hyderabad is famous for sound reflection?
Answer: Golconda Fort is famous for sound reflection. - What demonstration was done in Golconda Fort?
Answer: A clap at one dome was heard far away in the fort. - What device helps hearing-impaired people hear better?
Answer: A hearing aid helps hearing-impaired people. - What language is used by hearing-impaired people for communication?
Answer: Hearing-impaired people use sign language. - What impairment may continuous loud noise cause?
Answer: Continuous loud noise may cause hearing impairment.
Puzzles
- I am produced when objects vibrate, but I vanish in vacuum. What am I?
Answer: Sound - I am a thin membrane in your ear that vibrates when sound reaches me. Who am I?
Answer: Eardrum - I decide whether your voice is shrill or deep. What am I?
Answer: Frequency - I decide whether your voice is loud or soft. What am I?
Answer: Amplitude - I roar loud but in low pitch. Who am I?
Answer: Lion - I chirp soft but in high pitch. Who am I?
Answer: Bird - You see me before you hear me in a thunderstorm. Who am I?
Answer: Lightning - I cannot travel without a medium. Who am I?
Answer: Sound - My length is about 20 mm in men and 15 mm in women. Who am I?
Answer: Vocal cords - I am measured in Hertz. What am I?
Answer: Frequency - I am measured in Decibels. What am I?
Answer: Loudness - I am below 20 Hz and you cannot hear me. Who am I?
Answer: Infrasound - I am above 20,000 Hz and you cannot hear me. Who am I?
Answer: Ultrasound - Dogs can hear me but you cannot. Who am I?
Answer: Ultrasound - I carry sound faster than air or water. Who am I?
Answer: Solid - I am the part of the ear that collects sound like a funnel. Who am I?
Answer: Outer ear - I convert vibrations into signals for the brain. Who am I?
Answer: Inner ear - I am the final organ that processes sound. Who am I?
Answer: Brain - I am a string instrument often paired with sitar. Who am I?
Answer: Veena - I am a membrane instrument played with hands. Who am I?
Answer: Tabla - I am an air column instrument. Who am I?
Answer: Flute - I am a percussion instrument shaped like a pot. Who am I?
Answer: Ghatam - I am a percussion instrument struck with cymbals. Who am I?
Answer: Manjira - I am pleasant sound. Who am I?
Answer: Music - I am unpleasant sound. Who am I?
Answer: Noise - I am sound pollution caused by vehicles and factories. Who am I?
Answer: Noise pollution - I cause hearing impairment and anxiety if too loud. Who am I?
Answer: Noise - I am the decibel level of breathing. Who am I?
Answer: 10 dB - I am the decibel level of whisper. Who am I?
Answer: 30 dB - I am the decibel level of conversation. Who am I?
Answer: 60 dB - I am the decibel level of busy traffic. Who am I?
Answer: 70 dB - I am the decibel level of a factory. Who am I?
Answer: 80 dB - I am the level beyond which sound becomes harmful. Who am I?
Answer: Above 80 dB - I am a small device used by hearing-impaired people. Who am I?
Answer: Hearing aid - I am a language of gestures for the hearing-impaired. Who am I?
Answer: Sign language - I am a Hyderabad fort famous for sound reflection. Who am I?
Answer: Golconda Fort - I am the action done at Golconda Fort to demonstrate sound reflection. Who am I?
Answer: Clap - I am a toy that proves sound travels through string. Who am I?
Answer: Toy telephone - I am the softest sound activity listed in your textbook. Who am I?
Answer: Breathing (10 dB) - I am the loudest sound activity mentioned in your textbook. Who am I?
Answer: Factory noise (80 dB) - I am the part of the larynx that vibrates to produce voice. Who am I?
Answer: Vocal cords - I am the scientific reason children’s voices are shrill. Who am I?
Answer: Short vocal cords - I am the unit that measures time for one oscillation. Who am I?
Answer: Time period - I am the number of oscillations per second. Who am I?
Answer: Frequency - I am the to-and-fro motion that produces sound. Who am I?
Answer: Vibration - I am the sound of shrillness. Who am I?
Answer: Pitch - I am the sound property that depends on amplitude. Who am I?
Answer: Loudness - I am the organ that carries air to vocal cords. Who am I?
Answer: Windpipe - I am one of the health problems caused by loud noise. Who am I?
Answer: Hypertension - I am a simple act that reduces noise pollution in cities. Who am I?
Answer: Planting trees
Difference Between:
- Difference between Music and Noise
Music:
- Pleasant and harmonious sound
- Has regular vibrations
- Soothing to the ear
- Example: Sound of a flute or sitar
Noise:
- Unpleasant and jarring sound
- Has irregular vibrations
- Disturbing and harmful to the ear
- Example: Sound of traffic or machines
- Difference between Loudness and Pitch
Loudness:
- Depends on the amplitude of vibration
- Indicates how soft or loud a sound is
- Measured in decibels (dB)
- Example: Whisper (30 dB), Conversation (60 dB)
Pitch:
- Depends on the frequency of vibration
- Indicates how shrill or deep a sound is
- Measured in Hertz (Hz) indirectly
- Example: Bird’s chirp (high pitch), Lion’s roar (low pitch)
- Difference between Amplitude and Frequency
Amplitude:
- Maximum displacement of vibration from its mean position
- Determines loudness of sound
- Larger amplitude → louder sound
Frequency:
- Number of vibrations per second
- Determines pitch of sound
- Higher frequency → shriller sound
- Difference between Infrasound and Ultrasound
Infrasound:
- Frequency less than 20 Hz
- Cannot be heard by humans
- Example: Some animals like elephants use it
Ultrasound:
- Frequency more than 20,000 Hz
- Cannot be heard by humans
- Example: Dogs, bats can hear it
- Difference between Sound and Light
Sound:
- Mechanical wave
- Needs a medium (air, water, solid)
- Travels at about 343 m/s in air
Light:
- Electromagnetic wave
- Does not need a medium
- Travels at about 3 × 10⁸ m/s
- Difference between Men’s voice and Women’s voice
Men’s Voice:
- Vocal cords about 20 mm long
- Vibrate slowly
- Produces deep and low-pitched voice
Women’s Voice:
- Vocal cords about 15 mm long
- Vibrate faster
- Produces sharper and higher-pitched voice
- Difference between Children’s voice and Adults’ voice
Children’s Voice:
- Shorter vocal cords
- Vibrate very quickly
- Produces shrill and sharp voice
Adults’ Voice:
- Longer vocal cords
- Vibrate more slowly
- Produces deeper voice
- Difference between Mechanical Waves and Electromagnetic Waves
Mechanical Waves:
- Require a medium to travel
- Example: Sound waves, water waves
- Cannot travel in vacuum
Electromagnetic Waves:
- Do not need a medium
- Example: Light waves, radio waves
- Can travel in vacuum
- Difference between Loud Sound and Soft Sound
Loud Sound:
- Produced by large amplitude vibrations
- More energy is carried
- Example: Shouting
Soft Sound:
- Produced by small amplitude vibrations
- Less energy is carried
- Example: Whispering
- Difference between Shrill Sound and Deep Sound
Shrill Sound:
- High frequency vibrations
- High pitch
- Example: Chirping of a bird
Deep Sound:
- Low frequency vibrations
- Low pitch
- Example: Roaring of a lion
- Difference between Outer Ear and Inner Ear
Outer Ear:
- Collects sound like a funnel
- Directs sound waves to eardrum
Inner Ear:
- Converts vibrations into electrical signals
- Sends them to the brain for interpretation
- Difference between Human Audible Range and Dog’s Audible Range
Human Audible Range:
- 20 Hz to 20,000 Hz
- Cannot hear sounds below or above this range
Dog’s Audible Range:
- Wider than humans
- Can hear ultrasonic sounds (>20,000 Hz)
- Difference between String Instruments and Wind Instruments
String Instruments:
- Produce sound by vibrating strings
- Examples: Veena, Sitar, Guitar
Wind Instruments:
- Produce sound by vibrating air columns
- Examples: Flute, Clarinet, Trumpet
- Difference between Membrane Instruments and Percussion Instruments like Ghatam
Membrane Instruments:
- Sound produced by vibrating stretched membranes
- Example: Tabla, Dholak
Percussion Instruments (like Ghatam):
- Sound produced by vibrating whole body of the instrument
- Example: Ghatam, Cymbals (Manjira)
- Difference between Noise Pollution and Air Pollution
Noise Pollution:
- Unwanted and loud sound disturbing environment
- Causes hearing loss, hypertension, lack of sleep
Air Pollution:
- Presence of harmful gases and dust in air
- Causes respiratory diseases and climate problems
- Difference between Whisper and Conversation
Whisper:
- Around 30 dB
- Soft and low amplitude sound
Conversation:
- Around 60 dB
- Louder with larger amplitude
- Difference between Breathing Sound and Factory Noise
Breathing Sound:
- Around 10 dB
- Very soft and harmless
Factory Noise:
- Around 80 dB
- Loud, disturbing, and harmful to health
- Difference between Hearing Aid and Sign Language
Hearing Aid:
- Device used to amplify sound
- Helps partially hearing-impaired people
Sign Language:
- Visual communication using hand gestures
- Used by people with complete hearing loss
- Difference between Golconda Fort and Toy Telephone
Golconda Fort:
- Demonstrates reflection of sound
- Clap can be heard far inside the fort
Toy Telephone:
- Demonstrates that sound travels in solids
- Vibrations pass through the string
- Difference between Pleasant Loud Sound and Unpleasant Loud Sound
Pleasant Loud Sound:
- Harmonious and musical
- Example: Loud music from a concert (if enjoyed)
Unpleasant Loud Sound:
- Disturbing and noisy
- Example: Loud honking of vehicles
Assertion and Reason
- (A) Both Assertion and Reason are true, and Reason is the correct explanation.
- (B) Both Assertion and Reason are true, but Reason is NOT the correct explanation.
- (C) Assertion is true, Reason is false.
- (D) Assertion is false, Reason is true.
- Assertion: Sound is produced by vibrating objects.
Reason: Vibrations create disturbances in a medium which our ears detect.
Answer: (A) - Assertion: Sound can travel in air, water, and solids.
Reason: Sound needs a medium to propagate.
Answer: (A) - Assertion: Sound can travel through vacuum.
Reason: Sound is a form of energy.
Answer: (C) - Assertion: In humans, sound is produced by the larynx.
Reason: Larynx contains the vocal cords.
Answer: (A) - Assertion: Vocal cords in children are very short.
Reason: That is why their voices are shrill.
Answer: (A) - Assertion: Loudness depends on frequency of vibration.
Reason: Higher frequency produces higher loudness.
Answer: (C) - Assertion: Loudness depends on amplitude of vibration.
Reason: Larger amplitude produces louder sound.
Answer: (A) - Assertion: Pitch of sound depends on frequency.
Reason: Higher frequency means higher pitch.
Answer: (A) - Assertion: Amplitude of vibration determines the pitch of sound.
Reason: More amplitude → higher pitch.
Answer: (C) - Assertion: Sound cannot be heard in outer space.
Reason: Outer space is a vacuum.
Answer: (A) - Assertion: The eardrum vibrates when sound waves fall on it.
Reason: It is a thin stretched membrane sensitive to vibrations.
Answer: (A) - Assertion: The inner ear sends vibrations directly to the windpipe.
Reason: The windpipe carries air from lungs.
Answer: (D) - Assertion: Frequency is measured in Hertz.
Reason: One hertz means one vibration per second.
Answer: (A) - Assertion: Time period is the time taken for one oscillation.
Reason: Frequency is the number of oscillations per second.
Answer: (A) - Assertion: Loudness is measured in decibels.
Reason: Decibel is a special unit used for sound levels.
Answer: (A) - Assertion: Noise and music are both types of sound.
Reason: Noise is pleasant, while music is unpleasant.
Answer: (C) - Assertion: Ultrasound is sound of frequency above 20,000 Hz.
Reason: Humans can hear ultrasound easily.
Answer: (C) - Assertion: Infrasound has frequency below 20 Hz.
Reason: Humans cannot hear infrasound.
Answer: (A) - Assertion: Sound in water travels faster than in air.
Reason: Density of water is greater than that of air.
Answer: (A) - Assertion: A lion’s roar is loud but low-pitched.
Reason: Its frequency is low but amplitude is high.
Answer: (A) - Assertion: Bird chirping is shrill and high-pitched.
Reason: Birds produce sound of high frequency.
Answer: (A) - Assertion: Factory noise is an example of music.
Reason: Music is always pleasant to hear.
Answer: (C) - Assertion: Sound travels faster in steel than in air.
Reason: Steel particles are more closely packed.
Answer: (A) - Assertion: Normal breathing produces about 10 dB of sound.
Reason: Low amplitude vibrations create feeble sound.
Answer: (A) - Assertion: Conversation produces about 60 dB.
Reason: It is louder than whisper but softer than traffic.
Answer: (A) - Assertion: Busy traffic produces 70 dB of sound.
Reason: Traffic noise is one of the main sources of noise pollution.
Answer: (A) - Assertion: Sound above 80 dB may be harmful.
Reason: Prolonged exposure damages hearing ability.
Answer: (A) - Assertion: Noise pollution may cause hypertension.
Reason: Continuous loud noise affects the nervous system.
Answer: (A) - Assertion: Planting trees helps reduce noise pollution.
Reason: Trees absorb and block sound waves.
Answer: (A) - Assertion: Use of silencers in vehicles reduces noise.
Reason: Silencers decrease the amplitude of vibrations.
Answer: (A) - Assertion: Golconda Fort in Hyderabad is famous for sound effects.
Reason: A clap at a dome could be heard 1 km away.
Answer: (A) - Assertion: Lightning is heard before thunder.
Reason: Light travels faster than sound.
Answer: (D) - Assertion: Noise is always useful for humans.
Reason: It helps us to relax and study better.
Answer: (D) - Assertion: Music can become noise if too loud.
Reason: Excessive loudness makes sound unpleasant.
Answer: (A) - Assertion: Children with hearing loss may also have speech problems.
Reason: Speech develops as a direct result of hearing.
Answer: (A) - Assertion: Sign language is used by hearing-impaired persons.
Reason: It allows them to communicate effectively.
Answer: (A) - Assertion: Hearing aids help amplify sound for hearing-impaired persons.
Reason: They make weak vibrations stronger.
Answer: (A) - Assertion: Sound travels equally well in all media.
Reason: The speed of sound depends on density of medium.
Answer: (C) - Assertion: Frequency determines loudness.
Reason: Loudness depends on amplitude, not frequency.
Answer: (C) - Assertion: Whisper produces around 30 dB.
Reason: It is a soft sound of low amplitude.
Answer: (A) - Assertion: Noise pollution can cause anxiety.
Reason: Continuous loud sound disturbs the nervous system.
Answer: (A) - Assertion: Desert coolers and mixers contribute to noise pollution.
Reason: They produce unwanted sound at high volume.
Answer: (A) - Assertion: The unit of loudness is hertz.
Reason: Hertz measures frequency.
Answer: (C) - Assertion: The frequency of a child’s voice is higher than that of an adult.
Reason: Children have shorter vocal cords.
Answer: (A) - Assertion: Human ears can hear up to 50,000 Hz.
Reason: Human audible range ends at 20,000 Hz.
Answer: (C) - Assertion: Sound cannot travel in vacuum.
Reason: There are no particles in vacuum to carry vibrations.
Answer: (A) - Assertion: Amplitude determines the pitch of sound.
Reason: Pitch depends on frequency.
Answer: (C) - Assertion: Larger amplitude means louder sound.
Reason: Loudness ∝ square of amplitude.
Answer: (A) - Assertion: The lion’s roar is high-pitched but feeble.
Reason: Lion produces sound of high frequency.
Answer: (C) - Assertion: Ultrasound is used in medical diagnosis.
Reason: It has frequency above 20,000 Hz and can penetrate tissues.
Answer: (A)
True or False
- Sound is produced by vibrations.
Answer: True - Sound can travel in a vacuum.
Answer: False - Human sound is produced by the larynx.
Answer: True - The eardrum is located in the inner ear.
Answer: False - Vocal cords vibrate when air passes through them.
Answer: True - Pitch of sound depends on amplitude.
Answer: False - Loudness of sound depends on amplitude.
Answer: True - Frequency is measured in Hertz (Hz).
Answer: True - Time period is the number of oscillations per second.
Answer: False - Decibel (dB) is the unit of loudness.
Answer: True - Human audible range is 20 Hz to 20,000 Hz.
Answer: True - Infrasound has frequency above 20,000 Hz.
Answer: False - Ultrasound has frequency above 20,000 Hz.
Answer: True - Dogs can hear sounds beyond human audible range.
Answer: True - Sound travels faster in steel than in air.
Answer: True - Sound travels faster in air than in water.
Answer: False - Music is always unpleasant.
Answer: False - Noise is an unpleasant sound.
Answer: True - Noise pollution can cause hypertension.
Answer: True - Normal breathing produces about 10 dB of sound.
Answer: True - Whisper produces about 60 dB of sound.
Answer: False - Conversation produces about 60 dB of sound.
Answer: True - Busy traffic produces about 70 dB of sound.
Answer: True - Factory noise is around 80 dB.
Answer: True - Sound above 80 dB can be harmful to hearing.
Answer: True - Trees increase noise pollution.
Answer: False - Silencers in vehicles help reduce noise.
Answer: True - A lion’s roar is high-pitched but feeble.
Answer: False - A bird’s chirping is high-pitched.
Answer: True - The length of vocal cords in men is about 20 mm.
Answer: True - The length of vocal cords in women is about 25 mm.
Answer: False - Children’s voices are shriller than adults’.
Answer: True - Larger amplitude vibrations produce louder sound.
Answer: True - Frequency determines loudness of sound.
Answer: False - Pitch depends on frequency of vibration.
Answer: True - Amplitude determines pitch.
Answer: False - The inner ear sends signals to the brain.
Answer: True - The outer ear collects sound waves.
Answer: True - Noise can cause hearing impairment.
Answer: True - Sound can travel through solids, liquids, and gases.
Answer: True - The toy telephone demonstrates that sound travels through vacuum.
Answer: False - The vibrating part of a tabla is its membrane.
Answer: True - The vibrating part of a flute is its string.
Answer: False - The vibrating part of a veena is its string.
Answer: True - The vibrating part of a ghatam is the body of the pot.
Answer: True - Conversation is louder than whisper but softer than traffic noise.
Answer: True - Golconda Fort is famous for its sound reflection system.
Answer: True - A clap under Golconda dome could be heard kilometers away.
Answer: True - Sign language is used to communicate with hearing-impaired persons.
Answer: True - Hearing aids reduce the loudness of sound.
Answer: False
Long Answer Questions
- Explain how sound is produced in humans.
Answer: In humans, sound is produced by the voice box or larynx. Inside the larynx, there are two stretched vocal cords with a narrow slit between them. When air from the lungs is forced through this slit, the vocal cords vibrate. These vibrations produce sound, and the tension and length of the cords determine the pitch of the voice.
- Describe the role of the eardrum in hearing.
Answer: The eardrum is a thin, tightly stretched membrane in the ear. When sound waves strike the eardrum, it vibrates back and forth. These vibrations are transmitted to the inner ear, where they are converted into electrical signals. The signals are then sent to the brain, which interprets them as sound.
- Explain the relation between amplitude and loudness.
Answer: Loudness of sound depends directly on the amplitude of vibration. Larger amplitude means stronger vibrations, which produce louder sounds. Conversely, smaller amplitude produces feeble sounds. Loudness is measured in decibels (dB), and it is proportional to the square of amplitude.
- Explain the relation between frequency and pitch.
Answer: Pitch refers to how shrill or deep a sound is. It depends on the frequency of vibration. A sound with a higher frequency has a higher pitch and is shrill (e.g., bird chirping), while a sound with lower frequency has a lower pitch and is deep (e.g., lion’s roar).
- What is the audible range of humans? Distinguish between infrasound and ultrasound.
Answer: Humans can hear sounds between 20 Hz and 20,000 Hz, called the audible range. Sounds below 20 Hz are called infrasound, while those above 20,000 Hz are called ultrasound. Humans cannot hear either infrasound or ultrasound, though some animals like dogs can hear ultrasound.
- Explain with examples the different types of musical instruments based on vibrating parts.
Answer: Musical instruments are classified based on the vibrating parts that produce sound:
- String instruments: Vibrating strings produce sound (e.g., Veena, Guitar).
- Membrane instruments: Vibrating membranes produce sound (e.g., Tabla, Dholak).
- Wind instruments: Vibrating air columns produce sound (e.g., Flute, Trumpet).
- Percussion instruments: The whole body vibrates (e.g., Manjira, Ghatam).
- Explain the working of the human ear in hearing sound.
Answer: The human ear has three main parts:
- Outer ear: Collects sound and directs it to the eardrum.
- Middle ear: Eardrum vibrates and passes vibrations to three small bones.
- Inner ear: Vibrations are converted into electrical signals, which travel through the auditory nerve to the brain. The brain processes these signals, and we hear sound.
- Explain the difference between music and noise with examples.
Answer: Music is a sound that is pleasant to hear, regular, and harmonious, like that of a flute or sitar. Noise is an unpleasant, irregular, and jarring sound, such as that from traffic or loudspeakers. For example, a melodious song is music, but if played at very high volume, it becomes noise.
- Define noise pollution. Mention its major sources.
Answer: Noise pollution refers to the presence of excessive, unpleasant, or harmful sounds in the environment. Major sources include:
- Vehicles honking and traffic.
- Loudspeakers, music systems, and televisions.
- Industrial machines and factories.
- Household appliances like mixers, coolers, and radios at high volume.
- What are the harmful effects of noise pollution?
Answer: Noise pollution can cause serious health problems:
- Hearing impairment: Continuous loud noise damages the eardrum.
- Hypertension and anxiety: Persistent noise affects the nervous system.
- Lack of sleep: Disturbs rest and reduces concentration.
- Irritation and stress: Leads to inefficiency and frustration in daily life.
- Suggest methods to control noise pollution.
Answer: Methods to control noise pollution include:
- Using silencers in vehicles and machinery.
- Reducing use of loud horns and loudspeakers.
- Keeping household appliances at low volume.
- Planting trees along roads to absorb sound.
- Establishing “no horn zones” near schools and hospitals.
- Explain why sound cannot travel in vacuum.
Answer: Sound is a mechanical wave that requires a medium like air, water, or solids to travel. In vacuum, there are no particles to vibrate and carry the sound waves. Hence, sound cannot travel in vacuum.
- Describe the sound produced by a lion and a bird.
Answer: A lion’s roar is loud but low-pitched because it has high amplitude but low frequency. In contrast, a bird’s chirping is soft and high-pitched because it has low amplitude but high frequency.
- Explain the use of a toy telephone to demonstrate sound transmission.
Answer: A toy telephone consists of two cups connected by a string. When one person speaks into a cup, the vibrations travel along the stretched string to the other cup, where the sound is heard. This demonstrates that sound can travel through solids.
- What is the difference between amplitude and frequency?
Answer: Amplitude is the maximum displacement of particles from their mean position and determines loudness. Frequency is the number of oscillations per second and determines pitch. For example, increasing amplitude makes a sound louder, while increasing frequency makes it shriller.
- Explain how loudness is measured and give examples of different sound levels.
Answer: Loudness is measured in decibels (dB). Some examples are:
- Normal breathing – 10 dB.
- Whisper – 30 dB.
- Conversation – 60 dB.
- Busy traffic – 70 dB.
- Factory noise – 80 dB.
Sounds above 80 dB are harmful to health.
- Explain the effects of amplitude and frequency on sound with examples.
Answer: Amplitude affects loudness: larger amplitude produces louder sounds, like drum beats. Frequency affects pitch: higher frequency produces shrill sounds, like bird chirping, while lower frequency produces deep sounds, like a lion’s roar.
- Describe the structure and function of vocal cords.
Answer: Vocal cords are two stretched tissues inside the larynx. They vibrate when air from the lungs passes through them. The length and tension of the cords determine the pitch of the sound produced. Men’s cords are longer (20 mm), giving deeper voices, while women’s cords are shorter (15 mm), producing higher-pitched voices.
- Why do children’s voices sound shriller than adults’?
Answer: Children have shorter and thinner vocal cords compared to adults. Shorter cords vibrate faster, producing higher frequency sounds, which are shrill. Hence, children’s voices are sharper and higher-pitched than those of adults.
- How is sound harmful to human health?
Answer: Sound becomes harmful when it is too loud or prolonged. It causes hearing impairment, anxiety, hypertension, loss of concentration, disturbed sleep, and long-term damage to the nervous system. Prolonged exposure to noise above 80 dB is especially harmful.
- Differentiate between noise and music. Give examples.
Answer:
- Noise: Unpleasant, irregular, and jarring sounds are called noise. Example – traffic sounds, factory machines, loudspeakers.
- Music: Pleasant, regular, and harmonious sounds are called music. Example – flute, sitar, piano.
Thus, the same sound may be music when soft but noise when played too loud.
- Explain how humans hear sound through the ear.
Answer:
- The outer ear collects sound waves and directs them to the ear canal.
- The eardrum vibrates when struck by sound waves.
- The middle ear bones amplify these vibrations.
- The inner ear (cochlea) converts them into electrical signals.
- These signals are sent to the brain through the auditory nerve, where they are interpreted as sound.
- Describe the harmful effects of noise pollution on human beings.
Answer: Noise pollution affects humans in many ways:
- Causes hearing loss due to continuous loud sounds.
- Leads to hypertension, anxiety, and stress.
- Causes disturbed sleep and loss of concentration.
- May also cause irritability and fatigue.
Thus, controlling noise pollution is essential for healthy living.
- Explain methods to reduce noise pollution at the community level.
Answer:
- Use of silencers in vehicles and industries.
- Ban on loud horns near schools, hospitals, and residential areas.
- Limiting the use of loudspeakers.
- Soundproofing industries and factories.
- Planting trees along roads and colonies.
These measures can significantly reduce noise pollution.
- What is the significance of planting trees in reducing noise pollution?
Answer: Trees act as natural barriers to sound. Their leaves, branches, and trunks absorb and scatter sound waves, reducing noise levels. Planting rows of trees along roadsides, near factories, and in residential colonies is an effective and eco-friendly way of controlling noise pollution.
- Explain the working of a hearing aid.
Answer: A hearing aid is a small electronic device used by people with partial hearing loss. It has a microphone that receives sound, an amplifier that increases the amplitude of the sound, and a speaker that sends the louder sound into the ear. This helps hearing-impaired people detect weak sounds clearly.
- Explain the importance of sign language for the hearing-impaired.
Answer: Sign language is a visual form of communication using hand gestures, body language, and facial expressions. It enables hearing-impaired people to express their thoughts and understand others without spoken words. It plays a vital role in education, social interaction, and daily communication for those with hearing loss.
- Distinguish between amplitude and frequency with suitable examples.
Answer:
- Amplitude: It is the extent of vibration and determines loudness. Example: A drum beat with high amplitude is loud.
- Frequency: It is the number of vibrations per second and determines pitch. Example: A bird’s chirp has high frequency, so it is shrill.
Thus, amplitude affects loudness, while frequency affects pitch.
- Describe the sound levels of different activities.
Answer:
- Normal breathing: 10 dB
- Whisper: 30 dB
- Conversation: 60 dB
- Busy traffic: 70 dB
- Factory noise: 80 dB
Above 80 dB, sound becomes harmful to hearing.
- What is the role of the brain in hearing?
Answer: The brain plays the final role in hearing. Vibrations received by the eardrum are converted into electrical signals in the inner ear. These signals travel through the auditory nerve to the brain. The brain interprets and processes these signals, allowing us to recognize and understand sounds.
- Why does the lion’s roar sound different from a bird’s chirping?
Answer: A lion’s roar is loud but low-pitched because it has a high amplitude and low frequency. In contrast, a bird’s chirping is high-pitched but feeble because it has a low amplitude and high frequency. Thus, the difference lies in amplitude and frequency of vibrations.
- Explain why sound cannot travel in space.
Answer: Space is a vacuum, meaning there are no particles to carry vibrations. Since sound is a mechanical wave that needs a medium like air, water, or solids to propagate, it cannot travel through space. This is why astronauts in space use radios to communicate instead of shouting.
- Explain with examples how the same sound can be music or noise.
Answer: Sound from a musical instrument like a flute is pleasant when played softly, so it is music. However, if the same flute is played very loudly or continuously, it becomes irritating and is considered noise. Thus, whether sound is music or noise depends on intensity and context.
- Describe the functioning of vocal cords in producing sound.
Answer: Vocal cords are two stretched tissues in the larynx. When air from the lungs passes through them, they vibrate and produce sound. The pitch of sound depends on their length and tension: men (20 mm) have deeper voices, women (15 mm) have higher-pitched voices, and children have shrill voices due to shorter cords.
- Explain the differences between infrasound, audible sound, and ultrasound.
Answer:
- Infrasound: Sound with frequency below 20 Hz, inaudible to humans.
- Audible sound: Sound between 20 Hz and 20,000 Hz, heard by humans.
- Ultrasound: Sound with frequency above 20,000 Hz, inaudible to humans but used in medical and industrial applications.
- What is the importance of Golconda Fort in the study of sound?
Answer: Golconda Fort in Hyderabad is famous for its sound reflection properties. A clap made at the entrance dome could be heard a kilometer away inside the fort. This demonstrated the reflection and travel of sound waves in ancient architecture.
- Explain why men’s voices are deeper than women’s voices.
Answer: Men have longer and thicker vocal cords (about 20 mm). These cords vibrate more slowly, producing sounds of lower frequency and deeper pitch. Women have shorter vocal cords (about 15 mm), which vibrate faster and produce higher-pitched sounds.
- Explain the concept of oscillations in sound production.
Answer: Oscillation is the to-and-fro motion of particles. In sound, each vibration consists of one oscillation. Repeated oscillations create compressions and rarefactions in the medium, transmitting sound waves. For example, plucking a guitar string causes oscillations that generate sound.
- How does amplitude affect hearing ability?
Answer: Amplitude determines the loudness of sound. If the amplitude is small, the sound is soft and may not be heard clearly. Large amplitude produces loud sounds that can be heard easily. However, very large amplitudes (above 80 dB) can damage hearing ability.
- Explain why prolonged exposure to loud sound is dangerous.
Answer: Prolonged exposure to loud sound causes permanent damage to the eardrum and inner ear, leading to hearing impairment. It also creates stress, anxiety, hypertension, and sleep disorders. Continuous exposure above 80 dB can cause irreversible health problems.
- Explain the role of amplitude and frequency in everyday sounds.
Answer: In everyday life, amplitude decides how loud a sound is, while frequency decides whether it is shrill or deep. For example, a loud drumbeat has high amplitude, while a baby’s cry has high frequency, making it shrill. Both together determine the nature of the sound.
- Describe how factories contribute to noise pollution.
Answer: Factories use heavy machinery that generates continuous loud sounds, often around 80 dB or more. This adds to environmental noise pollution, affects workers’ hearing, and disturbs nearby residents. Industrial areas are major sources of noise pollution.
- Why is noise pollution more harmful in cities than in villages?
Answer: Cities have dense populations, heavy traffic, factories, loudspeakers, and household appliances, all contributing to noise pollution. In villages, such sources are fewer, so noise levels are lower and less harmful.
- Describe the harmful effects of noise pollution on children.
Answer: Noise pollution affects children severely. It may cause hearing loss, speech and learning problems, lack of concentration, disturbed sleep, and irritability. Prolonged exposure can even hinder mental and emotional development in children.
- Explain the benefits of using silencers in vehicles.
Answer: Silencers reduce the amplitude of sound vibrations produced by engines. They help decrease vehicle noise, thereby reducing overall traffic noise pollution. This creates a healthier environment for people living near roads.
- Why is noise in hospitals especially harmful?
Answer: Patients need rest, concentration, and peaceful surroundings for recovery. Loud noises disturb sleep, increase stress, and slow down healing. Hence, hospitals are declared “no horn” and “silence” zones.
- Explain the difference between shrill and deep sounds with examples.
Answer: Shrill sounds are high-pitched and produced at high frequency, e.g., a whistle or bird chirp. Deep sounds are low-pitched and produced at low frequency, e.g., a lion’s roar or drum beat.
- How does noise pollution affect sleep and concentration?
Answer: Noise pollution disturbs the nervous system, preventing proper sleep and causing fatigue. Lack of rest reduces concentration and efficiency in studies and work. Continuous noise leads to stress and irritability.
- How does a hearing aid amplify sound?
Answer: A hearing aid picks up weak sound waves through a microphone, increases their amplitude using an amplifier, and sends them to the ear through a speaker. This makes the sound loud enough for a hearing-impaired person to hear.
- Explain why sound above 80 dB is considered dangerous.
Answer: Sound above 80 dB creates very strong vibrations that damage the eardrum and inner ear. Prolonged exposure can cause permanent hearing loss, hypertension, lack of sleep, and stress. Hence, it is considered harmful to human health.
Give Reasons
- Give reason: Sound cannot travel in vacuum.
Answer: Sound needs a medium like air, water, or solid to carry vibrations, but vacuum has no particles. - Give reason: A lion’s roar is loud but low-pitched.
Answer: Because it has large amplitude (loudness) but low frequency (deep pitch). - Give reason: A bird’s chirping is shrill.
Answer: Birds produce sound of high frequency, which gives a high pitch. - Give reason: Children’s voices are sharper than adults’.
Answer: Children have shorter vocal cords which vibrate faster, producing higher frequency sounds. - Give reason: Men’s voices are deeper than women’s voices.
Answer: Men’s vocal cords are longer (about 20 mm) and vibrate more slowly, producing low pitch. - Give reason: Sound from a flute is shrill.
Answer: Because the air column inside vibrates with high frequency. - Give reason: Loudness of sound depends on amplitude.
Answer: Larger amplitude vibrations push more air particles, producing louder sound. - Give reason: Pitch of sound depends on frequency.
Answer: Higher frequency vibrations create shriller sounds, while lower frequency produces deeper sounds. - Give reason: Frequency is measured in Hertz.
Answer: Because one Hertz means one vibration per second. - Give reason: Loudness is measured in decibels.
Answer: Decibel is the standard unit that expresses sound intensity relative to hearing threshold. - Give reason: Sound travels faster in solids than in gases.
Answer: Particles in solids are more closely packed, transmitting vibrations faster. - Give reason: Sound cannot be heard in outer space.
Answer: Outer space is vacuum and has no medium to carry sound waves. - Give reason: A whisper is feebler than a shout.
Answer: Whisper has small amplitude vibrations, producing less loudness. - Give reason: Noise is considered unpleasant.
Answer: Because it is irregular, jarring, and disturbs hearing comfort. - Give reason: Music is considered pleasant.
Answer: Because it is regular, harmonious, and soothing to hear. - Give reason: The sound of traffic is considered noise.
Answer: It is irregular, loud, and disturbing to health and concentration. - Give reason: Prolonged exposure to loud sound causes hearing loss.
Answer: Because strong vibrations damage the eardrum and inner ear. - Give reason: Noise pollution can cause hypertension.
Answer: Loud continuous noise disturbs the nervous system, raising blood pressure. - Give reason: Noise pollution reduces sleep quality.
Answer: Because loud sounds disturb the brain and prevent relaxation. - Give reason: Noise pollution affects concentration.
Answer: Continuous noise disturbs the nervous system, making it hard to focus. - Give reason: Trees reduce noise pollution.
Answer: They absorb and scatter sound waves through leaves, branches, and trunks. - Give reason: Silencers are used in vehicles.
Answer: To reduce the amplitude of sound vibrations produced by engines. - Give reason: Loudspeakers near hospitals are banned.
Answer: Because patients need quiet surroundings for rest and recovery. - Give reason: Loud music can become noise.
Answer: Because excessive loudness makes even pleasant music disturbing. - Give reason: Sound above 80 dB is harmful.
Answer: Strong vibrations damage the ear and cause hypertension, anxiety, and hearing loss. - Give reason: People working in factories often use earplugs.
Answer: To protect their ears from loud continuous noise of machines. - Give reason: Golconda Fort is famous for sound reflection.
Answer: A clap at the entrance dome can be heard far inside due to sound reflection. - Give reason: A toy telephone demonstrates that sound travels in solids.
Answer: Because vibrations pass through the string to the other cup. - Give reason: Vacuum flasks keep liquids warm but do not allow sound inside.
Answer: Because vacuum inside the flask blocks sound vibrations. - Give reason: We hear thunder after seeing lightning.
Answer: Because light travels much faster than sound. - Give reason: Hearing-impaired people face difficulty in speech.
Answer: Because speech develops as a result of hearing ability. - Give reason: Hearing aids are useful for partially deaf people.
Answer: They amplify weak sounds so they can be heard clearly. - Give reason: Sign language is used by hearing-impaired persons.
Answer: Because they cannot hear sound-based communication. - Give reason: Shorter vocal cords produce high-pitched sounds.
Answer: They vibrate faster, producing higher frequency. - Give reason: Longer vocal cords produce deep sounds.
Answer: They vibrate slower, producing lower frequency. - Give reason: Conversation is louder than whisper.
Answer: Conversation has larger amplitude vibrations. - Give reason: Flute, trumpet, and clarinet are grouped together.
Answer: They all produce sound by vibrating air columns. - Give reason: Veena and sitar are grouped together.
Answer: They both produce sound by vibrating strings. - Give reason: Tabla and dholak are grouped together.
Answer: They both produce sound by vibrating membranes. - Give reason: Ghatam produces sound differently.
Answer: Its whole pot body vibrates to produce sound. - Give reason: Too much traffic causes health issues.
Answer: Because continuous honking and engine noise increase stress and hypertension. - Give reason: A baby’s cry sounds shrill.
Answer: Because babies have very short vocal cords that vibrate quickly. - Give reason: Factories are major sources of noise pollution.
Answer: They use heavy machines that produce continuous loud sounds. - Give reason: Loudspeakers used at night disturb people.
Answer: Because they interrupt sleep and rest with unwanted noise. - Give reason: Sound of conversation is about 60 dB.
Answer: Because it is louder than whisper (30 dB) but softer than traffic (70 dB). - Give reason: Desert coolers and mixers add to noise pollution.
Answer: They produce unwanted loud sounds in houses. - Give reason: Patients in hospitals need quiet surroundings.
Answer: Because noise delays recovery by disturbing rest and causing stress. - Give reason: Music teachers advise students to practice softly.
Answer: Because loud continuous sound can strain the ears and voice. - Give reason: Continuous loud noise can cause anxiety.
Answer: Because the nervous system gets disturbed by irregular vibrations. - Give reason: Ear canal is shaped like a funnel.
Answer: To collect and direct sound waves efficiently to the eardrum.
Arrange the Words
Case Studies
Case Study 1 – Human Voice
Rahul noticed that his younger sister’s voice is sharper and shriller than his father’s. He wondered why different people have different voices.
Questions:
- Which organ produces sound in humans?
Answer: Larynx (voice box) - What part inside the larynx vibrates?
Answer: Vocal cords - Why is his sister’s voice shriller than his father’s?
Answer: Children have shorter vocal cords which produce high-frequency sound. - Why is his father’s voice deeper?
Answer: Men have longer vocal cords (about 20 mm) producing low-frequency sound.
Case Study 2 – Sound in Space
Ravi watched a space documentary. He noticed that astronauts communicate with radios, not voices.
Questions:
- Why can’t astronauts talk directly in space?
Answer: Sound cannot travel in vacuum. - What is needed for sound to travel?
Answer: A medium like air, water, or solid. - Which form of wave is sound?
Answer: Mechanical wave. - Why is radio communication possible in space?
Answer: Radio signals are electromagnetic waves that do not need a medium.
Case Study 3 – Noise Pollution in the City
Meera lives near a busy road. She often feels restless and cannot sleep well due to the constant honking of vehicles.
Questions:
- What type of pollution is Meera facing?
Answer: Noise pollution - What is one health effect she may suffer?
Answer: Lack of sleep / Anxiety / Hypertension - Suggest one method to reduce this problem.
Answer: Planting trees near her house or using noise barriers. - How many decibels can busy traffic produce?
Answer: Around 70 dB
Case Study 4 – School Playground
During annual day practice, students noticed that the sound from the loudspeakers was disturbing nearby classrooms.
Questions:
- Which type of sound was created?
Answer: Noise - Why was it considered noise?
Answer: Because it was loud and unpleasant in the situation. - Suggest a method to avoid disturbing others.
Answer: Reduce volume or use soundproof walls. - What happens if students are continuously exposed to such sound?
Answer: It can cause loss of concentration and irritation.
Case Study 5 – Musical Instruments
In a music competition, one student played the tabla, another the veena, and another the flute.
Questions:
- What is the vibrating part of the tabla?
Answer: Membrane - What is the vibrating part of the veena?
Answer: String - What is the vibrating part of the flute?
Answer: Air column - Which one is a string instrument?
Answer: Veena
Case Study 6 – Whisper vs Conversation
Two friends compared a whisper and a conversation using a sound meter. The whisper was about 30 dB while the conversation was about 60 dB.
Questions:
- Which sound is louder?
Answer: Conversation - Why is conversation louder than whisper?
Answer: Because it has greater amplitude. - Which sound is feebler?
Answer: Whisper - What is the unit used for loudness?
Answer: Decibel (dB)
Case Study 7 – Golconda Fort
During a tour to Hyderabad, tourists clapped at the Golconda Fort entrance and heard the sound far inside the fort.
Questions:
- Which scientific principle is demonstrated here?
Answer: Reflection of sound - Which sound activity was used?
Answer: Clap - Why could the clap be heard far away?
Answer: Because the dome reflected and carried the sound waves. - Which fort is famous for this property?
Answer: Golconda Fort
Case Study 8 – Hearing Aid
An old man used a hearing aid to listen to conversations clearly.
Questions:
- What is the purpose of a hearing aid?
Answer: To amplify weak sound vibrations. - Who commonly uses it?
Answer: People with partial hearing loss. - Which part of the ear receives amplified sound?
Answer: Eardrum - Which other communication method helps hearing-impaired people?
Answer: Sign language
Case Study 9 – Bird and Lion
Radha heard a bird chirping and later a lion roaring at the zoo.
Questions:
- Which sound was shrill?
Answer: Bird’s chirp - Why was it shrill?
Answer: Because it had high frequency. - Which sound was deep and loud?
Answer: Lion’s roar - Why was it deep?
Answer: Because it had low frequency but large amplitude.
Case Study 10 – Busy Traffic
Ajay used a sound level meter near a busy traffic signal. It showed about 70 dB.
Questions:
- What does 70 dB indicate?
Answer: Loud traffic noise - Is this level harmful?
Answer: Yes, prolonged exposure can cause health problems. - Name one health problem caused by such noise.
Answer: Hypertension / Anxiety / Hearing loss - Suggest one method to reduce this noise.
Answer: Use of silencers in vehicles
Case Study 11 – Classroom Noise
Students in a class complained about the sound from a nearby construction site disturbing their studies.
Questions:
- Which type of sound was this?
Answer: Noise - Why was it disturbing?
Answer: Because it was loud and irregular. - Which ability does noise pollution reduce?
Answer: Concentration - Suggest one solution for this problem.
Answer: Use soundproof classrooms or restrict construction during study hours.
Case Study 12 – Whispering Child
A child whispered in class and the teacher explained that a whisper is about 30 dB.
Questions:
- Is whisper louder or softer than conversation?
Answer: Softer - Why is whisper soft?
Answer: Because of small amplitude vibrations. - What is the sound level of conversation?
Answer: About 60 dB - What is the unit of sound intensity?
Answer: Decibel (dB)
Case Study 13 – Trees and Noise
A city planted trees along roadsides to reduce noise pollution.
Questions:
- How do trees reduce noise?
Answer: They absorb and scatter sound waves. - Which property of trees makes them natural noise barriers?
Answer: Their leaves, branches, and trunks block vibrations. - Is this method eco-friendly?
Answer: Yes - Name one more method to reduce noise pollution.
Answer: Using silencers in vehicles
Case Study 14 – Mixer Grinder
At home, a mixer grinder made loud noise while running.
Questions:
- Is this sound music or noise?
Answer: Noise - Why is it called noise?
Answer: Because it is unpleasant and loud. - Which type of pollution does it cause?
Answer: Noise pollution - Suggest a precaution to reduce such noise at home.
Answer: Use appliances at low volume and for short durations.
Case Study 15 – Speech Development
A child with hearing loss found it difficult to speak clearly.
Questions:
- Why was speech development affected?
Answer: Because speech develops as a result of hearing ability. - Which device could help this child?
Answer: Hearing aid - Which other method can the child use to communicate?
Answer: Sign language - Which organ converts sound into signals?
Answer: Inner ear
Case Study 16 – Factory Workers
Workers in a factory used earplugs while working on loud machines.
Questions:
- Why did they use earplugs?
Answer: To protect ears from loud continuous noise. - How loud is factory noise generally?
Answer: About 80 dB - What is the harmful effect of long-term exposure?
Answer: Hearing impairment - Suggest one way factory noise can be reduced.
Answer: By installing silencers on machines
Case Study 17 – Thunderstorm
During a thunderstorm, Ramesh saw lightning first and then heard thunder.
Questions:
- Why did he see lightning first?
Answer: Because light travels faster than sound. - What is thunder?
Answer: Sound produced by lightning. - Why did thunder reach later?
Answer: Because sound travels slower than light. - What is the speed of sound in air approximately?
Answer: About 343 m/s
Case Study 18 – Baby’s Cry
A newborn baby’s cry sounded very shrill.
Questions:
- Why was the baby’s cry shrill?
Answer: Because babies have very short vocal cords. - Which sound property is high in the baby’s cry?
Answer: Frequency - Which property does not depend on frequency?
Answer: Loudness - Which unit is used to measure frequency?
Answer: Hertz (Hz)
Case Study 19 – TV Noise
At night, Rohan’s neighbor played the TV at high volume. It disturbed everyone.
Questions:
- Is this sound pleasant or unpleasant?
Answer: Unpleasant - Which type of sound is this?
Answer: Noise - What type of pollution did it cause?
Answer: Noise pollution - Suggest a simple solution.
Answer: Keep TV volume low
Case Study 20 – School Science Fair
In a fair, students demonstrated sound transmission using a toy telephone.
Questions:
- What was the medium of sound in the toy?
Answer: String - Why could sound travel through the string?
Answer: Because sound can travel through solids. - Could sound travel if the string was cut?
Answer: No, because the medium would be broken. - What type of wave is sound?
Answer: Mechanical wave
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