Solution of Chapter 13. Sound (Lakhmir Singh & Manjit Kaur - Science Book)

How is sound produced?

What should an object do to produce sound?

How does a sound making object differ from one that is silent?

Name the part which vibrates to produce sound in the following:

(a) Drums

(b) Sitar

(c) Flute

What brings the sound of a ringing telephone bell to our ears?

What is the length of vocal cords in a man?

Out of a man and a woman:

(a) who has shorter vocal cords?

(b) who produces sound of higher pitch?

Give any four sources of sound in a market place.

Name the sound producing organ in humans.

Which part of our body vibrates when we speak?

What does the working of a toy telephone tell us about sound?

Name one solid, one liquid and one gas through which sound can travel.

Which of the following cannot transmit sound?

Water, Vacuum, Aluminium, Oxygen gas

Is the speed of sound more in water or in steel?

Where would sound travel faster-in wood or in water?

In which medium sound travels faster : air or iron?

In which medium sound travels fastest : air, water or steel?

Out of solids, liquids and gases :

(a) in which medium sound travels slowest?

(b) in which medium sound travels fastest?

What is the speed of sound in air?

Which of the following is the speed of sound in water and which in steel?

(a) 5000 m/s

(b) 1500 m/s

(c) 340 m/s

Name the organs of hearing in our body.

Name that part of ear which vibrates when outside sound falls on it.

Name the three tiny bones present in the middle part of ear.

What is the function of three tiny bones in the ear?

Name the nerve which carries electrical impulses from the cochlea of ear to the brain.

What is the name of passage in outer ear which carries sound waves to the eardrum?

Name the quantity whose unit is 'hertz'.

What is the relation between 'time-period' and 'frequency' of an oscillating body?

Name three characteristics which are used to describe oscillations (or vibrations).

What is the scientific name for the following?

What name is given to the maximum displacement of a vibrating body from its central position?

If 125 oscillations are produced in 5 seconds, what is the frequency in hertz?

How does loudness depend on the amplitude of vibrations?

By how much will the loudness of a sound change when the amplitude of vibrations is:

(a) doubled?

(b) halved?

Name the unit used to measure the loudness of sound. Also write its symbol.

What is the loudness of a normal conversation in decibels ?

On what factor does the pitch of a sound depend?

How is pitch related to frequency?

Name the characteristic of sound which enables us to distinguish between a man's voice and a woman's voice even without seeing them.

Arrange the following sounds in the order of increasing frequencies (keeping the sound of lowest frequency first) :

(i) Baby's voice

(ii) Man's voice

(iii) Woman's voice

Which produces sound of a higher pitch : a drum or a whistle?

Name the characteristic of sound which depends on:

(a) amplitude

(b) frequency.

Name the characteristic of sound which can distinguish between the 'notes' (musical sounds) played on a flute and a sitar (both the notes having the same pitch and loudness).

Write the full form of dB.

What is the name of very high frequency sounds which cannot be heard by the human ear?

Why do we not hear the screams of a bat ?

Which of the following frequency of sound can be heard by a dog but not by a man?

(a) 50,000 hertz

(b) 15,000 hertz.

Name the substance which vibrates in a flute to produce sound.

State whether the following statements are true or false:

(a) Sound cannot travel in vacuum.

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

(c) If the amplitude of vibrations is large, sound is feeble.

(d) The lower the frequency of vibration, the higher is the pitch.

(e) If the amplitude of vibrations is doubled, the loudness of sound also gets doubled.

(f) When the amplitude of vibrations is halved, the loudness of sound becomes one-fourth.

(g) Unwanted or unpleasant sound is termed as music.

(h) Noise pollution may cause partial hearing impairment.

Fill in the following blanks with suitable words :

(a) Sounds are produced by .............. objects.

(b) The human voice box is called ..............

(c) Sound cannot travel in ....................

(d) A set of three tiny............in the middle part of ear passes on sound vibrations from the eardrum to the liquid in cochlea.

(e) The unit of frequency is ..............

(f) The time taken by an object to complete one oscillation is called............

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

(h) Unpleasant sound is called...................

(i) Sound which is pleasing to the ear is called................sound.

(j) A person having partial hearing loss can hear properly by wearing a device called hearing ...............on the ear.

What is the name of the strings in the human voice box which vibrate to produce sound?

What makes these strings vibrate?

Describe how sound is produced by the human voice box (or larynx).

What is the frequency of the sound produced when the vocal cords are:

(a) tight and thin ? (b) loose and thick?

Why are the voices of men, women and children different ?

If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?

State one observation from everyday life which shows that sound travels much more slower than light.

Explain why, the flash of lightning is seen first but the sound of thunder is heard a little later (though lightning and thunder take place in the sky at the same time and same distance from us).

Name the object (or part) which vibrates to produce sound in the following musical instruments :

(a) Sitar

(b) Dholak

(c) Flute

(d)Cymbals

(e) Veena

(f) Tabla

Name one musical instrument each in which the sound is produced:

(a) by vibrating a stretched string.

(b) by vibrating air enclosed in a tube.

(c) by vibrating a stretched membrane

(d) by vibrating metal plates.

Give two examples of each of the following :

(a) stringed musical instruments.

(b) wind musical instruments.

(c) membrane musical instruments.

(d) plate type musical instruments.

Which of the sounds having the following frequencies can be heard by the human beings and which cannot?

(a) 6 hertz

(b) 5000 hertz

(c) 10000 hertz

(d) 35000 hertz

(e) 18kHz

What is the upper limit of frequency of human hearing?

What is the lower limit of frequency of human hearing?

Name one animal which can produce ultrasonic sounds.

Name two animals which can hear ultrasonic sounds.

What is a vibration (or an oscillation)? Define 'amplitude' of vibration of an object.

What is the frequency of a vibrating body whose time-period is 0.05 second ?

State two methods of producing sound.

How does sound from a sound producing body travel through air to reach our ears?

Why a sound cannot be heard on the moon?

How do astronauts talk to one another on the surface of moon and why?

What is meant by the (a) 'pitch' of sound, and (b) 'quality' of sound?

What is ultrasound? State two uses of ultrasound.

What differences will you hear in a sound if there is an increase in

(i) amplitude, and (ii) frequency?

Calculate the time period of a pendulum which is vibrating with a frequency of 10 hertz.

How can you show that a sounding tabla is vibrating?

On what factor does the loudness of a sound depend?

When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?

Why sound cannot travel through vacuum (or through outer space)?

What type of pollution is caused by the working of mixer and grinder in the kitchen?

Why should we not put a pin or pencil in our ears?

Name any two common musical instruments and identify their vibrating parts.

What is the difference between noise and music? Can music become noise sometimes?

Draw a labelled diagram of larynx and explain its functions.

Give two causes of noise pollution from the homes.

What are the usual causes of the partial hearing loss suffered by a person?

How can you show that sound cannot travel through a vacuum? Draw a labelled diagram of the apparatus used.

What is meant by the 'time-period' of a vibrating object? State its unit.

Define 'frequency' of a vibrating object. Name the unit in which frequency is measured.

A pendulum oscillates 40 times in 4 seconds. Calculate its

(i) time-period, and

(ii) frequency.

Can we hear the sound produced by the oscillations of this pendulum? Give reason for your answer.

Draw a neat and labelled diagram of the human ear. Explain its working.

What is noise? Give two examples of sounds which are considered noise.

What is a musical sound ? Give two examples of musical sounds.

What is meant by noise pollution? Mention some of the sources of noise pollution in your surroundings.

Explain how, noise pollution (or excessive loud noise) is harmful to human beings.

State the various measures which can be taken to control (or reduce) noise pollution in our surroundings.

What can be done along the roads to reduce noise pollution caused by traffic from reaching the residents of the area?

Voice of which of the following is likely to have the minimum frequency?

Sound can travel through:

Which of the following vibrates when a musical note is produced by the cymbals in an orchestra?

A musical instrument is producing a continuous note. This note cannot be heard by a person having a normal hearing range. This note must then be passing through:

Which of the following sound frequencies can be heard by a woman having a normal hearing range?

A) 25000 Hz

B) 15kHz

C) 40000 Hz

D) 25Hz

When we change a feeble sound to a loud sound, we increase its:

Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the strings suitably. By doing so he is adjusting:

A key of mechanical piano is first struck gently and then struck again but much harder this time. In the second case:

One of the following can hear infrasound. This one is:

The speed of highly penetrating ultrasonic waves is:

The ultrasound waves can penetrate into matter to a large extent because they have:

The frequencies of four sound waves are given below. Which of these sound waves can be used to measure the depth of sea?

Which of the following frequency of sound can be generated by a vibrating simple pendulum as well as by the vibrating vocal cords of a rhinoceros?

Which of the following are used to study the growth of fetus inside the mother's womb?

We can distinguish between the musical sounds produced by different singers on the basis of the characteristic of sound called:

The maximum speed of vibrations which produce audible sound will be in:

The sound waves travel fastest:

The speeds of sound in four different media are given below. Which of the following is the most likely speed in m/s with which the two under water whales in a sea talk to each other when separated by a large distance ?

The velocities of sound waves in four media P, Q, R and S are 18,000 km/h, 900 km/h, 0 km/h, and 1200 km/h respectively. Which medium could be a liquid substance?

Which of the following modes is utilized in the production of sound by humans?

Three different vibrating objects produce three types of sounds X, Y and Z. The sounds X and Y cannot be heard by a man having normal range of hearing but sound Z can be heard easily. The sound X can be heard by a bat whereas the sound Y can be heard by a rhinoceros. What type of sounds are X, Y and Z?

Your parents are going to buy a house. They have been offered one house on the roadside and another house three lanes away from the roadside. Which house would you suggest your parents should buy ? Explain your answer.

The sound from an insect is produced when it vibrates its wings at an average rate of 500 vibrations per second:

(a) What is the time-period of the vibrations ?

(b) What is the frequency of the vibrations in hertz ?

(c) Can we hear this sound? Why or why not?

There are three small bones in the middle ear.

(a) Name the three bones

(b) Which of these bones is in touch with oval window ?

(c) Which of these bones is in touch with the ear drum ?

(d) Which bone is in touch with the other two bones?

Explain why, if we strike a steel tumbler with a metal spoon lightly, we hear a feeble sound but if we hit the tumbler hard, a loud sound is heard.