Glossary
- Sound: A form of energy that produces a sensation of hearing when it reaches the ear. It is caused by vibrations of objects in a medium (solid, liquid, or gas).
- Vibration: A rapid back-and-forth movement of an object. Vibrations are the cause of sound production.
- Amplitude: The maximum displacement of a vibrating body from its central position. It determines the loudness of the sound.
- Time Period: The time taken to complete one cycle of vibration. It is the time it takes for a vibrating body to return to its starting position.
- Frequency: The number of vibrations or cycles completed by a vibrating body per second. It determines the pitch of the sound.
- Pitch: The perception of how high or low a sound is, depending on the frequency of vibrations. A higher frequency results in a higher pitch.
- Loudness: The perception of the intensity of sound, which depends on the amplitude of the vibrations. Larger amplitude results in louder sound.
- Tuning Fork: A metal instrument that, when struck, vibrates at a particular frequency to produce a clear pitch sound.
- Vocal Chords: The pair of elastic bands in the larynx (voice box) of humans and animals that vibrate to produce sound when air passes through them.
- Syrinx: The vocal apparatus of birds, located where the trachea splits into the bronchi, used for producing sound.
- Infrasound: Sound waves with frequencies below the human hearing range (less than 20 Hz). These sounds are inaudible to humans but can be heard by some animals.
- Ultrasound: Sound waves with frequencies above the human hearing range (greater than 20,000 Hz). Used in medical imaging and animal communication.
- Noise: Unwanted, unpleasant, or disturbing sound that may cause irritation or harm to health. It is often produced by irregular vibrations.
- Music: A form of sound produced by regular, periodic vibrations, generally pleasing to the ear.
- Noise Pollution: The presence of harmful or disturbing noise in the environment, caused by industrialization, transportation, and urbanization.
- Hertz (Hz): The SI unit of frequency, equal to one cycle per second.
- Decibel (dB): A unit used to measure the intensity of sound. It is a logarithmic unit based on the ratio of a particular sound’s pressure relative to a reference level.
- Threshold of Hearing: The faintest sound level that can be detected by the human ear, assigned a value of 0 dB.
- Persistence of Hearing: A characteristic of the human ear that allows the perception of continuity in sounds, even when the sound has stopped, due to the effect remaining on the eardrum for about 0.1 seconds.
- Resonance: The reinforcement or amplification of a sound by the sympathetic vibration of an object. It occurs when the frequency of the external force matches the natural frequency of the object.
- Sound Propagation: The transmission of sound waves through a medium (solid, liquid, or gas) from one location to another.
- Eardrum: A thin membrane in the human ear that vibrates when sound waves hit it, allowing us to hear.
- Sound Wave: A longitudinal wave consisting of compressions and rarefactions, which travels through a medium carrying sound energy.
- Pitch Range: The range of frequencies that an individual can produce or hear. For humans, it generally spans from 20 Hz to 20,000 Hz.
- Threshold of Pain: The sound level at which sound becomes physically painful, typically around 120-130 dB.
- Conduction: The process of sound propagation through a medium by the vibration of particles in the medium. It occurs more effectively in solids than in gases.
- Resonating Body: An object that vibrates in response to a sound wave of matching frequency, amplifying the sound.
- Doppler Effect: The change in frequency or wavelength of a sound wave as the source of the sound moves relative to the observer.
- Echo: A reflection of sound that arrives at the listener after a delay, caused by the sound waves bouncing off a surface.
- Sonar: A system for detecting objects underwater by emitting sound waves and analyzing the echoes that return from the objects.
- Binaural Hearing: The ability to perceive sound from two ears, which helps in locating the direction from which a sound originates.
- Frequencies of Sound: The range of vibrations that produce different sounds. Low frequencies produce deep sounds, and high frequencies produce sharp sounds.
- Sound Intensity: The energy carried by sound waves per unit of area, usually expressed in watts per square meter (W/m²).
- Acoustic Impedance: The resistance of a medium to the propagation of sound waves. It depends on the density and elasticity of the medium.
- Sound Absorption: The process by which a material absorbs sound energy, reducing the intensity of the sound. This is often used in soundproofing.
- Harmonics: Overtones or additional frequencies that are integer multiples of the fundamental frequency, contributing to the timbre or quality of a sound.
- Vocalization: The production of sound by the vocal cords, used by humans and animals for communication.
- Hearing Impairment: A condition in which a person has partial or total loss of hearing ability. It can be congenital or acquired.
- Sound Reflection: When sound waves encounter a surface and bounce back, often resulting in an echo or reverberation.
- Psychoacoustics: The study of the psychological and physiological effects of sound, including perception, hearing, and interpretation of sound.
Something To Know
A. Fill in the blanks.
- Birds have a ring of cartilage, called ____________ in their wind pipes.
Answer – syrinx
- The SI unit of ‘loudness’ of sound, is____________.
Answer – decibel (dB)
- The pitch of a sound is determined by its____________ .
Answer – frequency
- Sounds, of frequency more than 20 kHz, are known as____________ .
Answer – ultrasonic
- An irregular, irritating sound is referred to as a____________ .
Answer – noise
B. State True or False for the following statements.
- Human beings, as well as all animals, have a voice box for producing their characteristic sounds.
Answer – False
(Not all animals have a voice box; for example, birds have a syrinx instead of a voice box.)
- Of the three mediums, solids, liquids and gases, sound propagates fastest in liquids.
Answer – False
(Sound propagates fastest in solids, followed by liquids, and slowest in gases.)
- Sound cannot propagate through vacuum.
Answer – True
(Sound requires a medium to propagate, and there is no medium in a vacuum.)
- Light propagates, through vacuum, with a speed that is nearly a million times more than the speed of sound in air.
Answer – True
(The speed of light in vacuum is approximately 3 × 10^8 m/s, while the speed of sound in air is around 343 m/s.)
- The frequency of a given sound determines its ‘shrillness’ or ‘flatness’.
Answer – True
(The frequency of sound determines its pitch; higher frequencies are perceived as shrill and lower frequencies as flat.)
- Irregular non-periodic vibrations generally produce musical sounds.
Answer – False (Musical sounds are produced by regular, periodic vibrations; irregular vibrations produce noise.)
C. Tick (✓) the correct option.
- The maximum displacement of a vibrating body, on either side of its mean position, is known as its—
frequency
amplitude
loudness
pitch
Answer – amplitude
- The frequency of a given sound is 1.5 kHz. The vibrating body is then—
completing 1,500 vibrations in one second.
taking 1,500 seconds to complete one vibration.
taking 1.5 seconds to complete one vibration.
completing 1.5 vibrations in one second.
Answer – completing 1,500 vibrations in one second.
- Sound can propagate through—
vacuum as well as gases.
only through gases and liquids.
only through gases and solids,
all the three states of matter.
Answer – all the three states of matter.
- When lightning and thunder take place, they occur—
together and are also observed together.
one after the other but are observed together.
together but the thunder is observed a little after the lighting.
together but the thunder is observed a little before the lightning.
Answer – together but the thunder is observed a little after the lighting.
- A given sound is inaudible to the human ear. We can then say that this is so—
only because its amplitude is too small.
only because its frequency is below 20 Hz.
only because its frequency is above 20 kHz.
because it has any one, or more, of the three characteristics listed above.
Answer – because it has any one, or more, of the three characteristics listed above.
- The following are some statements about sound:
(i) Sound propagates faster in steel than in air.
(ii) Sounds are produced through vibrations.
(iii) Sound propagates faster than light.
(iv) Sound does not require a medium for its propagation.
Out of these, the correct statements are—
(iii) & (iv) only
(i) and (iii) only
(i) and (ii) only
(ii) and (iv) only
Answer – (i) and (ii) only
D. Answer the following questions in brief:
- Name the cause that is regarded as the basic cause of all sounds?
Answer – Vibration is the basic cause of all sounds.
- Name two musical instruments which produce sound through vibrating strings.
Answer – Guitar and Violin.
- Through which state of matter does sound propagate with the—
(a) slowest speed?
Answer – Sound propagates slowest in gases.
(b) fastest speed?
Answer – Sound propagates fastest in solids.
- Define the following terms. Also, write their SI units.
(a) amplitude
Answer – Amplitude is the maximum displacement of a vibrating body from its mean position. The SI unit is meter (m).
(b) time period
Answer – Time period is the time taken to complete one vibration. The SI unit is second (s).
(c) frequency
Answer – Frequency is the number of vibrations per second. The SI unit is hertz (Hz).
- Name the characteristic of a vibrating body which determines the—
(a) loudness
Answer – Amplitude.
(b) pitch of the sound produced by it.
Answer – Frequency
- The frequencies, of the male and female voices in human beings, are nearly 1 kHz and 1.5 kHz. Which of the two voices—
(a) is likely to be flatter?
Answer – The male voice is likely to be flatter.
(b) has a higher pitch?
Answer – The female voice has a higher pitch.
- When is a given sound regarded as a ‘musical sound’ or ‘music’?
Answer – A given sound is regarded as a ‘musical sound’ or ‘music’ when it is produced by regular vibrations (periodic vibrations) and has a definite frequency and pitch.
E. Answer the following questions.
- Explain briefly the mechanism of production of sound in human beings.
Answer – The production of sound in human beings involves the vibration of the vocal cords or voice box (larynx) located in the throat. When air from the lungs passes through the trachea, it causes the vocal cords to vibrate. The sound produced by these vibrations is then modified by the mouth, tongue, lips, and nasal cavity to form different sounds, such as speech. The frequency of vibration of the vocal cords determines the pitch of the sound, and the force of the airflow affects the loudness.
- How does the mechanism of production of sounds in birds differ from that in human beings?
Answer – In birds, the production of sound occurs through a specialized structure called the syrinx, which is located at the base of the trachea, where the trachea splits into the bronchi. The syrinx is a highly flexible organ that can produce a wide range of sounds. Unlike humans, who use the vocal cords, birds control the sound by adjusting the tension and position of the muscles around the syrinx. The syrinx’s structure allows birds to produce complex sounds, including songs, with varying pitches and volumes. This is a significant difference from human beings, who produce sound primarily through the vibration of the vocal cords.
- Describe a simple experiment to show that sound cannot propagate through vacuum.
Answer – To demonstrate that sound cannot propagate through a vacuum, a simple experiment can be performed using a bell and a vacuum pump. Take a bell inside a glass bell jar, place a vacuum pump connected to the jar, and ring the bell. As the air is pumped out of the jar, the sound from the bell becomes gradually quieter. Once the air is removed completely, no sound is heard, even though the bell is still ringing. This happens because sound requires a medium (air, water, or solids) to travel through, and in a vacuum, there are no particles to vibrate and carry the sound.
- On a hot summer day, a little mosquito produces a warning sound near your ear by vibrating its wings at the rate of 3,000 wing beats per five seconds. State the frequency, in hertz, of this sound.
- Answer – The frequency of the sound is calculated by dividing the number of wing beats by the time taken.
Given:
Number of wing beats = 3,000
Time = 5 seconds
The frequency (f) is:
f=3000/5=600 Hz
So, the frequency of the sound produced by the mosquito is 600 Hz.
- Explain why we always hear the thunder a little after we see the flash of lightning.
Answer – The reason we hear the thunder after seeing the flash of lightning is due to the difference in the speed of light and sound. Light travels at a speed of approximately 3 × 10^8 meters per second, which is much faster than sound, which travels at about 343 meters per second in air. This vast difference in speeds causes the light from the lightning to reach us almost instantaneously, while the sound from the thunder takes longer to travel the same distance. Therefore, there is a delay between seeing the lightning and hearing the thunder.
- (a) Define ‘loudness’ and ‘pitch’.
Answer – Loudness is the perception of the intensity or volume of a sound. It depends on the amplitude of the sound waves; the larger the amplitude, the louder the sound. The SI unit of loudness is the decibel (dB).
Pitch is the perception of the frequency of a sound, which determines whether a sound is high or low. Higher frequency sounds have a high pitch, and lower frequency sounds have a low pitch. The unit of pitch is hertz (Hz).
(b) State the effect on the—
(i) loudness of a sound when the amplitude of the vibrating body increases.
Answer – When the amplitude of the vibrating body increases, the loudness of the sound also increases. A larger amplitude results in more energy being transferred to the surrounding medium, producing a louder sound.
(ii) pitch of a sound when the frequency of the vibrating body increases.
Answer – When the frequency of the vibrating body increases, the pitch of the sound increases as well. Higher frequencies produce higher-pitched sounds, while lower frequencies produce lower-pitched sounds.
- Why is noise pollution regarded as harmful for human beings?
Answer – Noise pollution is harmful for human beings because it can cause various physical and psychological health problems. Prolonged exposure to high levels of noise can lead to hearing loss, stress, sleep disturbances, and increased blood pressure. It can also affect concentration, communication, and lead to mental fatigue. Additionally, continuous noise can cause anxiety and irritability, which can negatively impact overall well-being.
Value Based Questions
It was Shikha’s birthday. Her friends and cousins came to her house to wish her and to celebrate the day. They all wanted to dance and enjoy, with loud music in the background. Shikha, however, kept the music only at a moderate level. She was aware of the harms and dangers of noise pollution. She also did not want to cause any discomfort and irritation to the old lady, in the neighbourhood, who was recovering from her illness. She was of the firm view that our happiness and celebrations should not cause any inconvenience and discomfort to others.
- State the values displayed by Shikha.
Answer – The values displayed by Shikha include:
Consideration for others: Shikha was mindful of the old lady in the neighborhood and did not want to cause her discomfort.
Empathy: She understood that loud music could disturb others, especially those who might be unwell or need peace and quiet.
Responsibility: Shikha took the responsibility of ensuring that her celebration did not disturb the peace of others.
Social awareness: She was aware of the impact of noise pollution on the community and took steps to minimize it.
- Why is ‘noise pollution’ undesirable? Suggest some ways of minimising it.
Answer – Noise pollution is undesirable because it has several harmful effects on both human health and the environment. It can cause:
Health issues: Prolonged exposure to loud noise can lead to hearing impairment, stress, anxiety, and sleep disturbances.
Disruption of peace: It disrupts the calm and peace of residential areas, especially during the night, which can be disturbing for people trying to rest or concentrate.
Environmental impact: Animals may also be disturbed by loud noises, affecting their natural behaviours and habitats.
Increased risk of accidents: High noise levels can impair the ability to concentrate, leading to accidents.
Ways to minimize noise pollution:
Keep music and sound systems at a moderate volume, especially in residential areas.
Avoid honking unnecessarily in traffic.
Use soundproof materials in buildings to contain noise.
Promote awareness about the harmful effects of noise pollution.
Encourage silent hours during night-time, especially in residential and hospital areas.
Adopt quieter machines and vehicles that cause less noise.
- Have a ‘group discussion’ in which different students think of situations in which they can have their ‘happiness calibrations’ without causing discomfort, or inconvenience, to others.
Answer – In a group discussion, students can brainstorm various situations and solutions to ensure their celebrations do not cause discomfort to others. Some points that could be raised:
Celebrations at home: Students can suggest having parties in large spaces like halls or open areas instead of small apartments, ensuring the noise doesn’t disturb neighbors.
Music control: Playing music at a reasonable volume or using headphones for private listening during celebrations.
Outdoor activities: Instead of loud indoor parties, outdoor activities such as picnics, sports, or nature walks can be considered to avoid noise pollution.
Silent celebrations: In some situations, students could consider holding silent parties where people communicate through gestures, or with low-volume background music.
Time management: Keeping celebrations during the day, and not at night, so that people can rest during quiet hours.
Respecting the environment: Ensuring that decorations, food, and waste are disposed of responsibly, and avoiding any actions that might disrupt the peace of the neighborhood.
Virtual celebrations: In some cases, students can host virtual parties to avoid physical noise pollution and ensure everyone can participate from the comfort of their own space.
Something To Do
- Take some steel or porcelain bowls of the same size. Put different amounts of water in all the bowls. Beat them slowly with a spoon one by one. You will hear different types of sound from different bowls. This is your Jaltrang.
Answer – By varying the amount of water in each bowl, you change the pitch of the sound produced when the bowls are struck. The bowls with less water will produce a higher-pitched sound, while those with more water will produce a lower-pitched sound. This setup mimics the Jaltrang, a traditional Indian musical instrument where water-filled vessels are used to produce different notes.
- Identify the sources of noise pollution in your locality. Suggest ways and means to control the noise pollution caused by them. Discuss your report with your friends, parents and teachers.
Answer – Sources of noise pollution in many localities can include:
Vehicles: Horns, engine noise, and traffic jams.
Construction work: Use of heavy machinery.
Loud music from parties and events: Especially at night or in residential areas.
Factories and industrial areas: Machinery and operations causing constant noise.
Public announcements: Loudspeakers used in public places for announcements.
Ways to control noise pollution:
Encourage the use of quieter machinery in construction and industrial activities.
Implement noise barriers along highways and busy roads.
Promote silent zones, especially near hospitals and residential areas.
Regulate the volume of music during late hours, especially during festivals or celebrations.
Educate people on the harmful effects of noise pollution and encourage responsible behavior, such as reducing honking and unnecessary use of loudspeakers.
Discussing such reports with family, friends, and teachers can help raise awareness and work towards controlling noise pollution.
- Musical instruments are categorised into three main types Stringed (Tantu vadyd) instruments, wind (Sushir vaidya) instruments and membrane (Avnaddhu Vadyd) instruments. Make a list of some well-known musical instruments of each type and try to understand the way they work.
Answer – Stringed Instruments (Tantu Vadya):
Guitar: Produces sound by vibrating strings that are plucked or strummed.
Violin: Sound is produced by bowing the strings, causing them to vibrate.
Sitar: A plucked string instrument used in classical Indian music.
Harp: Sound is created when the strings are plucked or strummed.
Wind Instruments (Sushir Vadya):
Flute: Sound is produced by blowing air through an opening, causing the air inside the flute to vibrate.
Trumpet: Sound is made when air is forced through the instrument, causing vibrations in the brass.
Clarinet: Air is blown through a reed, which vibrates to produce sound.
Harmonica: Sound is produced by blowing air through metal reeds attached to chambers.
Membrane Instruments (Avnaddhu Vadya):
Drums (e.g., Tabla, Dholak): Sound is produced when the membrane (skin) of the drum is struck.
Bongo Drums: Small, hand-played drums that produce sound when their membranes are struck.
Bata (a type of drum): A traditional drum with a membrane that vibrates when struck, creating sound.
Timpani: Large orchestral drums that are tuned by adjusting the tension of the membrane.
Each type of instrument works based on the vibration of strings, air, or membranes to produce musical sounds.
- Solve the crossword puzzle.
Across —»
- sound of frequencies above 20 kHz.
- amplitude of sound.
- ring of cartilage.
- unpleasant sound.
- reciprocal of time period.
Down X
- form of energy produced due to vibrations.
- voice box.
- SI unit of frequency.
- sound of frequencies below 20 Hz.
- shrillness or flatness of sound.
Answer – Across
Ultrasound – Sound of frequencies above 20 kHz.
Amplitude – Amplitude of sound.
Larynx – Ring of cartilage (the voice box).
Noise – Unpleasant sound.
Frequency – Reciprocal of time period.
Down
Sound – Form of energy produced due to vibrations.
Larynx – Voice box.
Hertz – SI unit of frequency.
Infrasound – Sound of frequencies below 20 Hz.
Pitch – Shrillness or flatness of sound.
Additional Questions and Answers -01
Short Questions and Answers
Question. What is sound?
Answer: Sound is a form of energy that is produced by vibrating objects and travels through a medium (solid, liquid, or gas) as waves.
Question. What is the unit of frequency?
Answer: The SI unit of frequency is Hertz (Hz).
Question. How does sound travel?
Answer: Sound travels in the form of longitudinal waves through a medium by the vibration of particles.
Question. What is the effect of temperature on the speed of sound?
Answer: The speed of sound increases with an increase in temperature because molecules move faster at higher temperatures, facilitating quicker transmission of sound.
Question. What do we mean by the ‘pitch’ of a sound?
Answer: The pitch of a sound refers to how high or low a sound seems, and it depends on the frequency of the sound waves.
Long Questions and Answers
Question. Explain how the speed of sound varies in different mediums.
Answer: The speed of sound depends on the medium through which it travels. It is fastest in solids, slower in liquids, and slowest in gases. This is because particles in solids are more tightly packed, allowing sound waves to travel faster compared to the less dense arrangement of molecules in liquids and gases. In air, the speed of sound is approximately 343 meters per second at 20°C. In water, it is about 1,480 m/s, and in steel, it is about 5,100 m/s.
Question. What are the different characteristics of sound? Explain each briefly.
Answer: The main characteristics of sound are:
Pitch: It determines the shrillness or flatness of the sound, influenced by frequency. High-frequency sounds have a high pitch, and low-frequency sounds have a low pitch.
Loudness: It refers to the intensity of sound and depends on the amplitude of the sound waves. Larger amplitudes produce louder sounds.
Quality (Timbre): It is the characteristic that differentiates two sounds of the same pitch and loudness, such as the difference between a piano and a violin playing the same note.
Duration: The length of time the sound lasts.
Question. Describe the mechanism of sound production in the human voice.
Answer: The human voice produces sound using the vocal cords located in the larynx (voice box). When air from the lungs is forced through the trachea, it passes through the larynx, causing the vocal cords to vibrate. The pitch of the sound is controlled by the tension of the vocal cords, while the loudness is determined by the force of the air. The sound produced is then modified by the mouth, tongue, and lips to form speech.
MCQs (Multiple Choice Questions)
Question. Which of the following determines the pitch of a sound?
- a) Frequency
- b) Amplitude
- c) Speed of sound
- d) Medium
Answer: a) Frequency
Question. What happens to the loudness of a sound if the amplitude of the vibrations increases?
- a) It decreases
- b) It increases
- c) It remains the same
- d) It becomes inaudible
Answer: b) It increases
Question. Which of the following is NOT a source of sound?
- a) Vibrating strings of a guitar
- b) The movement of light waves
- c) The vibration of vocal cords
- d) A ringing telephone
Answer: b) The movement of light waves
Question. Which of the following materials is the best conductor of sound?
- a) Air
- b) Wood
- c) Steel
- d) Water
Answer: c) Steel
Question. The frequency range of human hearing is approximately:
- a) 10 Hz to 10 kHz
- b) 20 Hz to 20 kHz
- c) 100 Hz to 100 kHz
- d) 1 Hz to 100 kHz
Answer: b) 20 Hz to 20 kHz
Question. What is the speed of sound in air at 20°C?
- a) 343 m/s
- b) 500 m/s
- c) 3430 m/s
- d) 1100 m/s
Answer: a) 343 m/s
True or False Questions
Question. The pitch of a sound is determined by the amplitude of the sound wave.
Answer: False (Pitch is determined by the frequency, not amplitude.)
Question. Infrasonic sounds have frequencies below 20 Hz.
Answer: True
Question. The loudness of sound depends on the speed of the vibrating object.
Answer: False (Loudness depends on the amplitude of the sound wave, not the speed of vibration.)
Question. The human ear can detect sounds with frequencies between 10 Hz and 20 kHz.
Answer: False (The range is approximately 20 Hz to 20 kHz.)
Question. Sound waves are transverse waves.
Answer: False (Sound waves are longitudinal waves.)
Question. Noise pollution can affect mental health and lead to hearing loss.
Answer: True
Additional Questions
Question. What is meant by ‘ultrasound’? How is it used in medical science?
Answer: Ultrasound refers to sound waves with frequencies above 20 kHz, which are beyond the range of human hearing. In medical science, ultrasound is used for imaging purposes, such as in obstetric ultrasound to observe the developing fetus, as well as in physiotherapy for muscle and tissue healing.
Question. Explain the difference between musical sounds and noise.
Answer: Musical sounds are periodic, regular vibrations that are harmonious and pleasant to the ear. Noise, on the other hand, consists of irregular, non-periodic vibrations that are often unpleasant and disruptive.
Question. What is resonance? Give an example.
Answer: Resonance is the phenomenon that occurs when an object vibrates at its natural frequency due to an external force. For example, when a singer hits a note that matches the natural frequency of a glass, the glass can resonate and break.
Additional Questions and Answers -02
Short Answer Questions (1-2 marks each)
- Basics of Sound
Question. What is sound?
Answer – Sound is a form of energy produced by vibrations that create the sensation of hearing.
Question. How is sound produced?
Answer -Sound is produced when an object vibrates, creating pressure waves in a medium (air, water, solids).
Question. Why can’t sound travel in a vacuum?
Answer -Sound requires a medium (solid, liquid, or gas) to propagate. In a vacuum, there are no particles to transmit vibrations.
Question. What is the speed of sound in air?
Answer -~330 m/s (varies with temperature and pressure).
Question. Why does lightning appear before thunder?
Answer -Light travels faster (~3×10⁸ m/s) than sound (~330 m/s), so we see lightning first.
- Human Sound Production & Hearing
Question. How do humans produce sound?
Answer -Air from lungs passes through the vocal cords in the larynx, making them vibrate.
Question. Why do men and women have different voice pitches?
Answer -Men have thicker, longer vocal cords, producing lower-frequency (deeper) sounds.
Question. What is the audible range for humans?
Answer -20 Hz to 20,000 Hz (20 kHz).
Question. Define infrasound and ultrasound.
Answer -Infrasound: Below 20 Hz (e.g., earthquakes).
Ultrasound: Above 20 kHz (e.g., bats, medical imaging).
Question. What is the function of the eardrum?
Answer -It vibrates when sound waves hit it, transmitting signals to the inner ear.
- Properties of Sound
Question. What determines loudness?
Answer -Amplitude of vibrations (higher amplitude = louder sound).
Question. What determines pitch?
Answer -Frequency of vibrations (higher frequency = higher pitch).
Question. What is the unit of frequency?
Answer -Hertz (Hz).
Question. Why do dogs hear sounds humans can’t?
Answer -Dogs detect ultrasonic sounds (above 20 kHz).
Question. What is noise pollution?
Answer -Harmful or irritating sounds from traffic, machines, etc., causing health issues.
Long Answer Questions (3-5 marks each)
- Sound Production & Propagation
Question. Explain how sound is produced and propagates.
Answer -Production: Vibrations (e.g., vocal cords, guitar strings) create sound waves.
Propagation: Waves travel via particle collisions in solids > liquids > gases (fastest in solids).
Vacuum: No medium = no sound propagation.
Question. Compare the speed of sound in solids, liquids, and gases.
Answer -Solids (e.g., steel): ~5000 m/s (fastest, tightly packed particles).
Liquids (e.g., water): ~1500 m/s.
Gases (e.g., air): ~330 m/s (slowest, particles far apart).
- Human Ear & Hearing
Question. Describe how the human ear processes sound.
Answer -Outer Ear: Collects sound waves.
Eardrum: Vibrates and transmits to ossicles.
Cochlea: Converts vibrations to electrical signals.
Auditory Nerve: Sends signals to the brain.
Question. What is noise pollution? List its effects and solutions.
Answer -Effects: Hearing loss, stress, sleep disturbance.
Solutions: Silencers, tree plantations, noise regulations.
MCQs (1 mark each)
Question. Sound travels fastest in:
- a) Air
- b) Steel (Correct)
- c) Water
Question. The pitch of sound depends on:
- a) Amplitude
- b) Frequency (Correct)
Question. Ultrasound has a frequency above:
- a) 20 Hz
- b) 20 kHz (Correct)
Question. Which part vibrates in the human ear first?
- a) Cochlea
- b) Eardrum (Correct)
Question. Noise pollution can cause:
- a) Hearing loss (Correct)
- b) Improved vision
True/False (1 mark each)
Question. Sound can travel in a vacuum.
False (Requires a medium).
Question. Women’s voices typically have a higher pitch than men’s.
True (Shorter vocal cords).
Question. Infrasound is audible to humans.
False (Below 20 Hz).
Question. Planting trees reduces noise pollution.
True (Absorbs sound).
Question. Loudness is measured in hertz (Hz).
False (Decibels (dB)).
Bonus: Activity-Based Question
Question. How can you demonstrate that sound needs a medium?
Experiment: Place a ringing phone in a sealed jar and pump out air. The sound fades as vacuum forms.