Sound

Sound is produced by vibrating objects.

An object should vibrate in order to be table to produce sound.

A sound making object vibrates while a silent does not. You can feel the vibrations by touching them.

(a) Its stretched membrane

(b) Its strings.

(c) Its long hollow pipe.

The vibration of our eardrums brings us the sound of a ringing telephone bell.

The male vocal chords are between 17 mm and 25 mm in length.

(a) Woman has short vocal chords. The male vocal chords are between 17 mm and 25 mm in length whereas of a woman are between 12.5 mm and 17.5 mm long.

(b) Woman produces sound of higher pitch.

The four sources of sound in a market place are:

1. Vendors selling eatables or other things.

2. Shopkeepers selling their things.

3. Vehicles in the market area, example, autorickshaw, car, etc.

4. Machines or generators noise.

Vocal chords are the sound producing organ in humans.

Vocal chords vibrates when we speak.

The working of a toy telephone tells us that vibrating objects produce sound and it is carried in all directions in a medium.

Solid: Metal- Iron, Aluminium etc.

Liquid: Water

Gas: Air

Vacuum cannot transmit sound because sound needs a material medium to travel.

The speed of sound is faster in solid as compared to liquid. Thus, the speed of sound is more in steel.

The speed of sound is faster in solid as compared to liquid. Thus, the speed of sound is more in wood.

The speed of sound is faster in solid as compared to gas. Thus, the speed of sound is more in iron.

The speed of sound is faster in solid as compared to liquid, and then slowest in gases. Thus, the speed of sound is more in steel, then water and then air.

(a) Sound travels slowest in gas medium

(b) Sound travels fastest in solid medium.

The speed of sound in air is 343m/s.

The speed of sound is faster in solid as compared to liquid, and then slowest in gases. Thus, the speed of sound is more in steel, then water and then air.

(a) 5000 m/s - Speed of sound in steel.

(b) 1500 m/s - Speed of sound in water.

(c) 340 m/s - Speed of sound in air.

Our ears are the organs of hearing in our body.

Eardrum vibrates when outside sound falls on it.

The three tiny bones – the malleus, incus, and stapes – are found in the middle ear. Each bone is named in Latin for its shape.

The three bones help in transmitting the sound into the middle ear.

The auditory nerve carries electrical impulses from the cochlea of ear to the brain

As seen from the figure given below, the sound is carried through the Ear canal.

The unit of frequency is called “hertz”.

Time Period given by the inverse of the frequency.

Frequency, amplitude and Phase are the three characteristics which are used to describe oscillations (or vibrations).

Frequency is the term used for number of vibrations made per second.

Amplitude is called as the maximum displacement of a vibrating body from its central position.

Frequency is

Loudness is directly related to amplitude. If amplitude is high, then loudness is high. But if amplitude is low, then the loudness is low.

(a) Loudness is also doubled.

(b) Loudness is halved.

Decibel is the unit used to measure the loudness of sound. Its symbol is dB

The Normal conversation is at 60 dB

The pitch of a sound depends on the frequency of the sound.

The pitch of a sound you hear depends on the frequency of the sound wave. A high frequency sound wave has a high pitch, and a low frequency sound wave has a low pitch.

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

The following sounds in the order of increasing frequencies :

Man's voice

Woman's voice

Baby's voice

Drum produces higher pitch.

(a) Loudness of the sound depends on amplitude.

(b) Pitch of the sound depends on frequency.

The tone of the sound will distinguish between the 'notes' (musical sounds) played on a flute and a sitar (both the notes having the same pitch and loudness).

Decibels is the full form of dB.

Ultrasonic waves is the name of very high frequency sounds which cannot be heard by the human ear.

We cannot hear the screams of a bat because its frequency is higher than 20,000Hz.

Option (a) is correct. 50,000Hz can be heard by dog but not human being.

The air particles vibrate in the air column in the flute, which produces sound.

(a) True

(b) False

(c) False

(d) False

(e) True

(f) False

(g) False

(h) True

(a) Sounds are produced by vibrating objects.

(b) The human voice box is called larynx

(c) Sound cannot travel in vacuum

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

(e) The unit of frequency is Hertz (Hz)

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

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

(h) Unpleasant sound is called noise.

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

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

The vocal chords of the human voice box vibrate to produce sound.

The vocal chords are stretched across the larynx and they vibrate to produce sound.

In humans, the sound is produced by the box, which is called voice box or the larynx. Larynx is a part of the throat. It is responsible for production of sound. It has two vocal cord which are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the air. When the lungs force the air through the slit, the vocal cords vibrate, producing sound.

(a) The frequency produced by tight and thin vocal chords is quite high. i.e. its high pitch sound.

(b) The frequency produced by loose and thick vocal chords is quite low i.e. its low pitch sound.

The length of vocal chords varies in all these three, which is the main reason for different voices. Men have the longest vocal chords, while female have little shorter vocal chords than men and children have the smallest vocal chords.

It is more convenient to put the ear to the track, If you want to hear a train approaching from far away because we can hear the vibrations from the ground when we put our ear at the track.

In case of thunder, we see the lightening first and then the sound of thunder. This is because, the velocity of light in air is while the velocity of sound in air is 343 m/s.

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, because, the velocity of light in air is while the velocity of sound in air is 343 m/s. Thus, we can see light first and thunder sound later.

(a) Strings

(b) Diaphragm – Membrane

(c) Air column

(d) The metal plates

(e) Strings

(f) Diaphragm – Membrane

(a) Veena

(b) Flute

(c) Table

(d) Cymbals

(a) Guitar, Veena

(b) Flute, Trumpet

(c) Tabla, Dholak

(d) Cymbals, Matka

(a) Cannot be heard because human being can hear within the range 20Hz to 20,000Hz

(b) Can be heard because human being can hear within the range 20Hz to 20,000Hz

(c) Can be heard because human being can hear within the range 20Hz to 20,000Hz

(d) Cannot be heard because human being can hear within the range 20Hz to 20,000Hz

(e) Can be heard because human being can hear within the range 20Hz to 20,000Hz

20,000Hz is the upper limit of frequency of human hearing.

20Hz is the lower limit of frequency of human hearing.

Bats can produce ultrasonic sounds.

Dogs and cats.

The to- and – fro motion of an object in a medium is called vibration.

Amplitude is the largest distance from the mean position of the object.

Time Period given by the inverse of the frequency.

Two methods of producing sound are:

1. Beating the plate and spoon against each other.

2. Playing guitar.

The air particles near the sound producing body vibrate and exchange energy, which is received by our ears and we are able to hear the sounds.

Because moon does not have any atmosphere and sound its does not have any medium for sound to travel as sound does not travel in vacuum.

The astronauts have sound transmitting devices in the helmets they wear which help them exchange sound waves with one-another. This is because moon does not have any atmosphere and sound its does not have any medium for sound to travel as sound does not travel in vacuum.

The sensation of frequency is called “pitch” The high frequency indicates high pitch and vice-versa.

Ultrasounds mean the sounds having frequency greater than 20,000Hz.

The uses of ultrasound are:

1. They are used in sonography.

2. They used in radars.

(i) The sound will become loud on increasing the amplitude.

(ii) The sound will become shrill on increasing the frequency.

Time Period given by the inverse of the frequency.

We can feel the vibration of table membrane when we hit it to produce sound.

The loudness of a sound depends Amplitude.

Because the track is made of metals and sounds travel faster in solids than air. Thus, 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.

Because sound needs material medium to transfer energy from on particle to another particle. If there is vacuum, then no energy transfer takes place

Noise pollution is caused by the working of mixer and grinder in the kitchen.

No, we must never put a pin or pencil in our ears, because it can tear our ear diaphragm.

The Unwanted sound that is unpleasant to ear is called noise. A pleasant sound is called music.

Music can become noise at many instances. Music is of many types and everybody may not like each type of music. When someone listens very loud music, it can be noise for someone else.

In humans, the sound is produced by the box, which is called voice box or the larynx. Larynx is a part of the throat. It is responsible for production of sound. It has two vocal cord which are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the air. When the lungs force the air through the slit, the vocal cords vibrate, producing sound.

The causes of noise pollution are as follows:

1) Televisions running at high volumes.

2) Use of Loudspeakers in religious or other functions.

3) Use of crackers.

Loud noise and noise pollution are the usual causes of the partial hearing loss suffered by a person.

The bell jar experiment is a common experiment to show that sound cannot travel through a vacuum

A bell jar’s shape is similar to that of a bell. A bell jar is placed on a base and connected to a vacuum pump as shown in the picture below. The air in the jar is varied by pumping the air out of it.

Now, we put an electrical bell in the bell jar. As the air is pumped, vacuum is being created inside the jar slowly and steadily and the sound from the bell jar fades. At a point when complete vacuum is maintained, no more sound is heard from the bell. Thus, the sound is not audible to our ears because of the vacuum inside the jar.

Time Period given by the inverse of the frequency.

Its unit is seconds.

The frequency is described as the number of vibrations or oscillations per second. Its unit is Hertz (Hz)

Frequency = 40 vibration/ 4 seconds = 10 Hz

Thus, time period = 1/f = 1/10 = 0.1 seconds.

No, we cannot hear because the audible human range is from 20Hz to 20,000 Hz.

The ear has three main parts:

1) External part – It is called the pinna and is made of ridged cartilage covered by skin.

2) Middle – This is the part through which sound travels inside the ear to the eardrum, through auditory canal. Sound causes the eardrum and its tiny attached bones in the middle portion of the ear to vibrate, and the vibrations are conducted to the nearby cochlea.

3) Inner part – The cochlea is part of the inner ear. Its main function is to transform sound into nerve impulses.

The Unwanted sound that is unpleasant to ear is called noise.

Example- 1) Loud music

2) The noise of machines.

A pleasant sound is called music. Its like a treat to the ears.

Example – 1) Beats

2) Tones

The harmful and annoying noise to the ears is called noise pollution. The sources of noise pollution are as follows:

1) Televisions running at high volumes.

2) Use of Loudspeakers in religious or other functions.

3) Use of crackers.

4) Horns of buses, cars and trucks

Noise pollution has adverse effects physical as well as mental behavior. The constant exposure to noise pollution can create many health related problems like hypertension, insomnia, mental disorder and may even lead to loss of hearing.

The following measures which can be taken to control (or reduce) noise pollution in our surroundings:

1) Ban the use of loudspeakers after 9pm.

2) Ban the use of horns in the areas nearby hospital and school.

The following measures which can be taken to reduce noise pollution caused by traffic from reaching the residents of the area:

1) The residential area must be declared as no use of horns.

2) The colonies must be established at a distance than the roads.

The voice of man has the least frequency.

Sound does not need any material medium to travel.

Metal plates vibrates when a musical note is produced by the cymbals in an orchestra.

This note must then be passing through vacuum.

25Hz because the human audible range is 20Hz to 20,000 Hz.

Amplitude.

He is adjusting the frequency of the sitar string, with the frequency of other musical instruments.

In the second case sound will be louder but pitch will not be different.

dog can hear both the infrasound as well as ultrasound.

The speed of sound waves is same in a particular medium.

The ultrasound waves can penetrate into matter to a large extent because they have very high frequency.

The ultrasound waves can be used to measure the depth of sea.

10Hz can be generated by a vibrating simple pendulum as well as by the vibrating vocal cords of a rhinoceros.

Infra-red Waves are used to study the growth of foetus inside the mother's womb

Timbre can distinguish between the musical sounds produced by different singers on the basis of the characteristic of sound.

The sound travels faster in solids than liquids than gases.

The sound travels faster in solids than liquids than gases.

1530

Because the speed of sound in liquids is more than gas but less than solids.

The vibrating strings modes is utilized in the production of sound by humans.

X : Ultrasonic sound waves (Greater than 20,000Hz)

Y : Infrasonic sound waves (0-20 Hz)

Z : Audible sounds (20Hz-20,000Hz)

There will be more noise in the house which is along the roadside due to noise produced by transportation vehicles. But, the house which is three lanes away from the roadside would have comparatively less noise . Therefore, it is better to take the house that is three lanes away from the roadside.

(a) The time period = 1/f = 1/500 = 0.002 secs.

(b) The frequency of the vibrations in hertz is 500 Hz. Because 1Hz = 1 vibration/second.

(c) We can hear this because it is in the range of 20Hz to 20,000Hz.

(a) Hammer, Anvil, Stirrup are the three ear bones.

(b) Strirrup is in touch with oval window.

(c) Hammer is in touch with the ear drum.

(d) Anvil is in touch with the other two bones.

This is because the amplitude of vibrations is small when we beat the spoon lightly and so feeble sound is produced but when it is beaten with force then, amplitude of vibrations is large, so loud sound is produced.