Chapter-13 Sound

1. Choose the right response.

Noise can pass through

(a) Gases exclusively.

(b) Only solids

(c) Only liquids

(d) Gases, liquids, and solids

Explanation:

(d) Solids, liquids, and gases is the correct response .

The sound needs a medium to pass through. A medium through which sound can travel is made up of solids, liquids, and gases.


2.Which of the following voice types is most likely to have a minimum frequency?

(a) A young girl

(b) Boy infant

(c) A man

(d) A lady

Explanation:

The appropriate response is (c) a man.

The voice of a man has a lower pitch when compared to the sounds of a baby boy, baby girl, and lady. A man's voice has the lowest frequency of all sounds due to his low pitch, which is inversely related to frequency of a sound.


3.  In the following statements, tick ‘T’ against those which are true and ‘F’ against those which are false.

(a) Sound cannot travel in a vacuum. (T/F)

(b) The number of oscillations per second of a vibrating object is called its time period. (T/F)

(c) If the amplitude of the vibration is large, the sound is feeble. (T/F)

(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F)

(e) The lower the frequency of vibration, the higher the pitch. (T/F)

(f) Unwanted or unpleasant sound is termed as music. (T/F)

(g) Noise pollution may cause partial hearing impairment. (T/F)

Explanation:

a)True or False: For sound to move, a medium is necessary.

b) False - The frequency of an oscillating object is measured by the number of oscillations per second. A time period is the duration required to complete one oscillation.

c) FALSE: Loudness of sound is related to the square of the vibration's amplitude. The vibration's amplitude is high when there is loud sound. Small amplitudes are typical of weak sounds.

d) Accurate - Human ears are not capable of hearing sounds at all frequencies. Human ears can hear frequencies in the range of 20 Hz to 20,000 Hz. Human ears cannot perceive sounds outside of these frequencies.

e) False - As the pitch of a sound is proportional to its frequency, the greater the frequency, the higher the pitch of the sound. It vibrates at a high frequency for high-pitched sounds and a low frequency for low-pitched ones.

f)False : It's enjoyable to hear music because it has a melodic, attractive tone. Unpleasantsounds are noises.

g) True - Noises are unwanted, unpleasant sounds that, when heard repeatedly over an extended length of time, temporarily impair hearing.


4.  Fill in the blanks with suitable words.

(a) Time taken by an object to complete one oscillation is called __________.

(b) Loudness is determined by the __________ of vibration.

(c) The unit of frequency is __________

(d) Unwanted sound is called __________.

(e) The shrillness of a sound is determined by the __________ of vibration.

Explanation:

(A) The time period refers to the length of time it takes an object to complete one oscillation.

(b) The vibration's amplitude determines how loud something is.

(c) The hertz unit of frequency.

(d) Noise is defined as unwanted sound.

(e) The frequency of vibration affects how shrill a sound is.


5.A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.

Explanation:

The frequency of oscillation is defined as the number of oscillations the vibrating body makes each second.

Total number of oscillations equals frequency.

Total duration

= 50/5

= 10 Hz

The oscillation's duration is measured in time units. Moreover, it is opposite of frequency.

= 1/10

= 0.1 s

frequency equals 10 Hz

Time = 0.1 seconds.


6. A mosquito makes sound by vibrating its wings, which do so 500 times every second on average. What is the vibration's time period?

Explanation:

The length of time is determined by how long it takes to complete one oscillation. Moreover, it is opposite of frequency.

Period Equals 1 in time

Oscillation rate

500 Hz is the oscillation frequency.

The vibration's time period is 1/500, or 0.002 seconds.


7. For each of the following instruments, identify the component that vibrates to create sound.

A ) Dholak

b) Sitar 

c) The flute

Explanation:

a) The dholak, which has a head made of a stretched membrane. These stretched strings have vibrations built into them. These vibrations result in sound when the head is lightly pounded, which is how the dholak creates sound.

b) Sitar: This instrument is used for music. It includes stretched-out strings. When the string is played, vibrations are produced. Sitar makes sound as a result of these vibrations.

c) Flute - A flute is a musical instrument with holes in it. The pipe is hollow. When air is blown across the pipe's mouth, the air inside the pipe is sent into vibration, creating a pleasing sound.


8. How do noise and music differ from one another? Can music occasionally just become noise?

Explanation:

The sound of music is one that is enjoyable to hear. Flute, piano, and violin sounds are soothing to hear.

Noises are unpleasant sounds that can be heard.

The following sounds are unpleasant to hear:

(a) Horn blasts from trucks and buses.

(B)Electrical generator noises .

(c) Shots being fired.

(d) Sounds of a jackhammer

Yes, occasionally, when music is played loudly, it also turns into noise.


9. Make a list of the noise pollution sources in your area.

Explanation:

The following is a list of sources of noise pollution in our area:

Bus and automobile horns

(a) Loudspeakers and fireworks

(b) Loud audio in transistors and televisions

(c) Home mixers

(d) Industrial sirens


10.Describe the harm that noise pollution causes to people.

Explanation:

There are several health problems connected to noise pollution. These are what they are:

(a) Anxiety

(b) Migraine

(c)Hearing loss 

(d) Nightmares

(e)Hypertension 


11. Your parents will purchase a home. One is available at the side of the road, and the other is three lanes distant. Which residence would you advise your parents to purchase? Describe your response.

Explanation:

The property three lanes away from the roadside is preferable than the one on the main road since it will be quieter. Vehicles may be the source of the noises; when distance grows between the source and the listener, the noise level diminishes. So, it is preferable to purchase a home that is three lanes away from the highway.


12.  Sketch the larynx and explain its function in your own words.

Explanation:

vocal cords Larynx

The larynx moves during the swallowing process. The larynx has two vocal cords. Between them, there is a tiny gap through which air can pass. When we talk, the lungs push air into the gap, which causes the vocal cord to vibrate and produce sound.