Sound

Yes, sound can travel through both (a) iron, and (b) water.

No, sound cannot travel through vacuum.

The type of waves which are used by astronauts to communicate with one another on moon (or in outer spece) are radio waves.

Iron, water, and air are one solid, one liquid and one gas through which sound can travel.

Vacuum cannot transmit sound.

The physical quantity whose SI unit is ‘hertz’ is frequency.

The SI unit of frequency is hertz.

(a) Longitudinal wave is represented by density-distance graph.

(b) Transverse wave is represented by displacement-distance graph.

The speed of sound is more in steel.

Sound travel faster in iron.

Among the given three sound travels faster in steel.

(a) In gas sound travels slowest.

(b) In solids sound travels fastest.

The speed of sound in copper is 3750 m/s where as the speed of sound in aluminium is 5100 m/s.

If you want to hear a train approaching from far away, it is more convenient to put the ear to the track because sound travels faster in solids.

(a) The speed of sound in air 343 m/s.

(b) The speed of sound in water is 1,484 m/s.

(c) The speed of sound in iron is 5,130 m/s.

Supersonic aircrafts is the name given to those aircraft which fly at speed greater then the speed of sound.

A jet aircraft flies at a speed of 410 m/s. Its speed is known as supersonic.

When any object have move more speed then sound then it is kown as supersonic speed.

During rain we see the lightning first and then we hear the sound followed by it, is a live everyday example which shows that light travels faster then sound.

Transverse waves and Longitudinal waves are the two types of waves which can be generated in a long flexible spring (or slinky).

Transverse (water) wave is prodced when a stone is droped on the surface of water in pond.

Longitudinal wave is produced when a tuning fork is struck in air.

(a) The general name of the waves consisting of compressions and rarefactions is Longitudinal wave.

(b) The general name of the waves consisting of crests and troughs is Trnsverse wave.

(i) The general name of the waves on which the particles of the medium vibrate in the same direction as wave is longitudinal wave.

(ii) The general name of the waves on which the particles of the medium vibrate at right angles to the direction of wave is transverse wave.

Transverse waves are illustrated by the movement of a rope whose one end is fixed to a pole and the other end is moved up and down.

An object should viberate to produce sound.

the name of the strings which vibrate in our voice box when we talk is vocal cords.

The device which is used to produce sound in laboratory experiments tuning fork.

The nature of sound waves in air is to propogate.

The conclusion which can be obtained from the observation that when the prongs of a sound making tuning fork touch the surface of water in a beaker, the water gets splashed is that the prongs of tuning fork vibrates.

False, Sound produced by a vibrating body travels to our ears by the actual movement of particles propogetion.

Sound travels slowest in the air but on the other hand light travels faster in the air.

Supersonic term is used to denote a speed greater than the speed of sound.

Sound travels faster in air.

A tuning fork has a number 256 marked on it. This number signify the frequency of the tunning fork.

The time-period of a tuninh fork whose frequency is 200 Hz is 5 × 10^-3 s.

The frequency of a wave whose time-period is 0.02 s is 50 Hz.

Wavelength is halved when ther is change in the wavelength of a sound wave in air if its frequency is doubled.

If 20 waves are produced per second then the frequency is 20 Hz.

(a) Sound is caused by vibrations.

(b) A sound wave consists of places of higher pressure called compression and places of lower pressure called rarefraction

(c) Wave speed in metres per second equals frequency in hertz Multiplied by wavelength in meters.

(d) Sound cannot travel through vacuum.

(e) The speed of sound in a solid is greater than the speed of sound in air.

(f) When the frequency of the sound is increased, the wavelength decreases.

(a) The name of this effect is echo.

(b) Sound get reflected at the clif.

(c) In 5 seconds sound goes upto 1600 m.

(d) The speed of sound is 320 m/s.

(a) A and D are two sund waves which represent sounds of the same loudness but different pitch.

(b) B and D are two waves which represent sounds of the same frequency but different loudness.

(c) All these sound waves have been produced by the same vibrating body.

(d) Tuning forks could have generated the sound wave shown here.

(a) When Anhad adjusts the signal to the loudspeaker to give a sound of frequency 200 Hz then the air between Anhad and the loudspeaker vibrates with the frequency of 200 Hz.

(b) Both the ear of Anhad recives the sound. His right ear recives the sound by the sound waves coming directly from the loudspeaker (through air)where as his left ear recives the sound from sound waves reflected from the wall of classroom.

(a)

(b)

(a) X is ultrasonic sound, Y is infrasonic sound, and Z is audiable sound.

(b) Ultrasound machine can produce sound like X.

(c) A device in a science laboratory which can produce sound like Y is simple pendulum.

(d) The frequency range of sounds like Z is 20 Hz to 20000 Hz.

(a) if the man hears lot of noise of heavy traffic then he is in a city.

(b) if the man hears very little noise of traffic then he is in a village.

(c) if he hears echoes of person talking he is in a bare room.

(d) if he hears less echoes then he is in a furnished room.

Vacuum is a space of matter which is empety of matter.

Sound is a mechanical energy, and this requires a material medium for the transfer of its energy. Since there is no material (matter) in a vacuum, sound energy cannot travel through it.

Amplitude is the vertical distance between a peak or a valley and the equilibrium point of a wave.

Longitudinal waves :- The general name of the waves on which the particles of the medium vibrate in the same direction as wave is longitudinal wave. Where as

Transverse waves:- The general name of the waves on which the particles of the medium vibrate at the right angle is known as transverse wave.

Sound waves are longitudinal in nature.

This happens because the speed of light is faster in air then that of the speed of sound.

The flash of lightning reaches us first and the sound of thunder is heard a little later, this happens because the speed of light is faster in air then that of the speed of sound.

The flash of a gun shot reaches us before the sound of the gun shot because the speed of light is faster in air then that of the speed of sound.

The term apply to sound waves in air are; Longitudinal, Compression, Rarefaction.

The term apply to water waves are; Transverse, Crest, Trough.

The four ways are tapping, clapping, throwing, and beating.

the speed of a sound wave whose frequency is 2 kHz and wavelength 65 cm is 1300 m/s.

Because the vibrations it produced is absorbed by our hand and not allowed to propagate in the air.

(i) Strings of sitar or veena vibrate to produce sound.

(ii) The skin of the tabla vibrate to produce sound.

(iii) Prongs of the turning fork vibrate to produce sound.

(iv) Wings of the mosquito or a bee vibrate to produce sound.

(v) Air column inside the flute vibrates to produce sound.

The lowest frequency that anyone can hear is 20 Hz. Hence time period is = 1/20 = 0.05 Sec. Due to Persistence of vision in our eyes we can not see the vibration of less than 0.1 sec. Therefore we are not able to see the vibrations of any sound producing objects.

Suspend a tennis ball on a rigid support by means of a string. Touch the Vibrating turning fork. You will be able to see that the tennis ball is set into motion by the vibrations.

The speed of Sound is much higher than the speed of gas. So we can hear the sound of escaping gas much before we smell it.

A sound signal of 128 vibrations per second has a wavelength of 2.7 m. The speed with which the wave travels is 345.6 m/s.

A wave is moving in air with a velocity of 340 m/s. 0.66 m is the wavelength if its frequency is 512 vibrations/sec.

Frequency (f) = Number of Vibrations produced in one second.

Time Period (T) = Time of one variation.

Relation between Time Period and Frequency ⇒ T = 1/f

As sound is a mechanical wave it cannot travel in vacuum. So, the bell ringing inside a vacuum chamber can not be heard.

Compression : Particles of the medium are pushed close to each other. It is a region of high density and pressure.

Rarefaction : Particles of the medium move away It is a region of low density and pressure.

Sound is a form of energy which gives the sensation of hearing waves. Sound waves are longitudinal waves.

Take an electric bell and an airtight glass bell jar. The electric bell is suspended inside the airtight bell jar. The bell jar is connected to a vacuum pump. If you press the switch, you will be able to hear the bell. Now start the vacuum pump. Then the air in the jar is pumped out gradually, the sound becomes fainter, although the same current is passing through the bell. After some time when less air is left inside the bell jar you will hear a very- feeble sound. When all air is removed no sound is heard. This shows that sound can not pass through vacuum.

Sound is produced by the vibrations of any object These vibrations are transferred to air particles and reach to us. For example - In school bell, when the gong strikes the bell, vibrations are produced in the bell which are transmitted through the air to our ears. These vibration produce sensation of sound in our ears.

When a body vibrates the air in its neighbourhood is alternately compressed and rarefied. The compressed air has higher pressure than surrounding air. It therefore pushes the air particles near it causing compression to move forward. A rarefaction or low pressure is created at the original place. These compressions and rarefaction cause particles m the air to vibrate about their mean position. The energy is carried forward in these vibration. This is how sound travels.

As the air inside the vacuum tube is pumped out, it becomes fainter. Then all air is pumped out, no sound is heard. This is because air requires a material medium to travel.

There is no atmosphere in the moon, so sound cannot propagate. Astronauts talk through radio wave.

Since sound travels faster m solids, we can hear the sound of train by putting our ear on the solid and only later we can hear though air.

Take a slinky end tie one end to the wall and give the other end a push or pull alternately Compressions and rarefactions move towards the wall i.e. wave moves but the parts of the slinky just vibrates about Its mean position.

In the same way compressions and rarefactions are produced in air and no net movement of air particles is required for sound to travel.

The distance over which the wave's shape repeats is known as wavelength. The freaquency is defined as the rate of viberation of sound traveling through air , on the other hand the term velocity shows the speed in a given direction and its magnitude.

A single frequency traveling wave will take the form of a sine wave. A snapshot of the wave in space at an instant of time can be used to show the relationship of the wave properties frequency, wavelength and propagation velocity.

The motion relationship "distance = velocity x time" is the key to the basic wave relationship. With the wavelength as distance, this relationship becomes λ = vT. Then using f=1/T gives the standard wave relationship

V= fλ Calculation

This is a general wave relationship which applies to sound and light waves, other electromagnetic waves, and waves in mechanical media.

A body vibrating with a time-period of s produces a sound wave which travels in air with a velocity of 350 m/s will have the wave length of 1.36 m.

Those waves which moves in parallel direction with the direction of waves are known as Longitudinal waves. Where as when the motion of the wave is perpendicular to the direction of waves is called Transverse wave.

The examples of transverse waves are:- viberation in string and ripples in water. Where as the examples of longitudinal wave are:- tsunami waves and sound waves.

A compression is a part of longitudinal wave where the particles are closest together. Where as the rarefraction is that part of the longitudinal wave where the particals are furthest apart. Longitudinal waves consists of compression and rarefraction.

The time taken by the sound of factory siren take 4s to reach the worker when a worker lives at a distance of 1.32 km from the factory. If the speed of sound in air be 330 m/s.

The crest appears as the highest point, while the trough is the lowest, forming a dip or valley in the wave's motion. The crest, also called the peak, forms the maximum height of every wave, including water waves, radio waves and electrical waves. The distance and height between the trough and crest varies depending on the type of wave and local conditions, such as wind speed and direction. Transverse waves consists of creast and thoughs.

Since the speed of lght is 3*10⁸, for all the purpose, the flash is seen at the same time that the gun is fired.

So we know that formula of speed= distance/time;

So, distance= speed*time (i)

Sped of sound in air is 332 m/s (given) and time= 3s.

Subustituing the value in equation (i) we get

(D)= 332 m/s*3s

We get D= 996 m.

The number of comlete vibrations per second.

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

If the speed of a wave is 340 m/s and its frequency is 1700 Hz, then l for this wave in cm will be 20.

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 vacuum.

Musical notes of an orchestra does not consist of transverse waves.

Sound travels in air if disturbance moves.

half the wavelength is represented by BD.

The maximum speed of vibrations which produce audible sound will be in ground glass.

The sound waves travel fastest in solids.

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 speeds of sound is 1530.

The pitch of note produced by a harmonium is lowered, then the wavelength of the note increases.

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. S medium could be a liquid substance.

Slinky can produce longitudinal waves as well as transverse waves under different conditions.

(a) 5cm would be their wavelength.

(b) Their frequence should be 120 Hz.

(c) Their speed should be 6m/s.

Through all the materials sound can travel.

(a) Medium Z could be the one having no fixed shape and no fixed volume.

(b) Medium W could be the one having a fixed volume but no fixed shape.

(c) Medium Y could be the one having the same composition as that on the moon.

(d) Medium X could be the one having a fixed shape and a fixed volume.

(i) The longitudinal waves travel in a coiled spring at a rate of 4 m/s. The distance between two consecutive compressions is 20 cm then its wavelength is 20 cm.

(ii) The longitudinal waves travel in a coiled spring at a rate of 4 m/s. The distance between two consecutive compressions is 20 cm then its frequency of the wave is 20 Hz.

The property of sound which leads to an echo is reflection of sound.

The name given to the repetition of sound caused by the reflection of sound waves is echo.

Reverberation is the name given to the persistence of sound in a big hall or auditorium.

megaphone, soundboard and stethoscope are devices which work on the reflection of sound.

The other name of a loud-hailer is megaphone.

The three characteristic of sound are:- loudness, pitch and timber.

The loudness of sound is measured in decibel. Its symbol is dB.

The characteristic which helps us distinguish between a man’s voice and woman’s voice, even without seeing them is pitch.

Pitch of a sound is directly proportional to frequency. Higher the frequency, higher is the pitch of sound.

(a) The characteristic of sound which depends on amplitude is loudness.

(b) The characteristic of sound which depends on frequency is pitch.

(c) The characteristic of sound which depends on waveform is timber.

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) is quality or timber.

The organs of hearing in our body are ears.

Ear drums of ear viberates when outside sound falls on it.

The three tiny bones present in the middle part of ear are:- anvil, hammer and stirrup.

(a) Hammer is in touch with ear-drum.

(b) The bones which is in touch with oval window is stirrup.

To increase the strength of vibration coming from ear drum is the main fuction of the three tiny bones in the ear.

The tube which connects the middle ear to throat is eustachain tube.

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

The name of passage in outer ear which carries sound waves to the ear-drum is ear canal.

To monitor the growth of developing baby in the uterus of the mother we use ultrasound scans.

X-ray can damage the delicate body cell of the unborn baby, so ultrasound scan for fetus (unborn baby) better than X-ray.

To find the depth of sea (or ocean) by using ultrasonic sound waves we use a device, named SONAR

The full name of ‘SONAR’ is Sound Navigation And Ranging.

The principle on which a soundboard works is reflection of sound.

The device which is used to address a small gathering of people megaphone.

The device used by doctors to listen to our heartbeats is stethoscope.

a soundboard kept behind the speaker on the stage of a big hall is concave in shape.

The two sound absorbing materials are :- Mass- loaded vinyl and sound courtains.

(a) NO, we cannot hear infrasonic sound.

(b) NO, we cannot here ultrasound.

The name given to the sound waves of frequency too low for humans to hear is infrasound.

Ultrasound name is given to the sound waves of frequency too high for humans to hear.

Infrasound waves are produced by a vibrating simple pendulum.

We hear less loud sound as amplitude affects volume.

We hear less loud sound as amplitude affects volume.

Ultrasonic sound wave is the name given to sound waves of frequencies higher than 20 kHz.

(a) An echo is simply a reflected Sound.

(b) Pitch od sound depends on frequency.

(c) Loudness of sound depends on amplitude.

(d) Quality of sound depends on waveform.

(e) Echoes are caused by the reflection of sound.

During a hot day an echo is heard sooner. The speed of sound is high when the temperature is high, so on a hot day an echo is heard sooner.

In water an echo is heard sooner. Because in water the speed of sound is more then that of the air.

Due to the repeted reflection from the walls, and celing a presistance sound is produced which is known as reverberation. When the reverberation time is too long in a big hall, the sound becomes confusing due to overlapping of sounds.

Following are some of the methods to reduce the reverberation in a big hall or auditorium:-

1) Sound absorbing materials should be used to make panels for the walls of the hall.

2) To absorbe sound and reduce the reverberation carpets are used on the flor.

3) To absorve sound heavy curtains should be used on the doors and windows.

4) Materials with sound absorving properties should be used for making seats.

Curtains are poor reflector of sound and hence they absorve most of the sound falling on them. Due to this it donot let echo to occur. On the other hand echo occurs in the room without curtains. So we hear more clearly in a room with curtains then a room withour curtains.

A large cone shaped device used for amplifying and directing the voice of a person who speaks into it is known as megaphone. Multiple reflection of sound is the prilciple on which it works.

A cone shaped air instrument used for signalling in cars, bicycle, busses etc. is known as bulb horn. A bulb horn works on the principle of multiple reflection of sound.

A medical instrument used by the doctors for listening the sounds inside the human body specialy for the hearts and lungs is known as stethoscope. It works on the principle of multiple reflection of sound.

A concave board is placed behind the speakers of a large hall is known as a sound board. This is used so that voice can be heard to every person sitting in that hall at a considerable distance. The sound board works as follow:- the speakers are mde to stand on the focus of the concave board. The concave sound board reflects the sound back to the audience (meaning it donot allow sound to go in different direction). This helps in uniform distribution of sound in the hall and even the person sitting last in the hall can hear the sound clearly. It can be seen from the diagram

The measure of sound energy reaching per secon the ear is known as loudness of sound. Amplitude of the sound wave is responsible for it.

A characterstic of sound which helps to identify the sound of same loudness is known as pitch. The pitch depends on the amplitude of the sound wave.

A charestristic of sound through which we can distinguish between the sounds having same pitch and loudness produced by different musical instrument is known as quality (or timber). The shape of the sound wave produced decide the quality of the sound produced.

The table top viberates with a less amplitude when we strike it lightly. This lead to produce a soft sound because the energy supplied to the top of the table is low, so the amplitude is low. But on the other hand when we strike the tabe very hard then the energy supplied to the table is very high, this makes the top of the table to viberate rapidely and hence a loud sound is heard.

one use of ultrasound in industry is, for detecting flows in metal block.

One use of ultrasound in hospital is, to investigate the internal organs of the human body.

The bats are able to fly at night without colliding with other objects because they emits a very high frequency ultrasonic soundwaves while flying and listen to the echoes produced by the sound emitted by them from any object or obstacles. From the echo they can determine the distance of the object and hence avoid collision.

The bats emit a very high frequency ultrasonic soundwaves while flying and listen to the echoes produced by the sound emitted by them from any prey. Judging by the time taken by the echo they catches their prey.

The ultrasound waves are prepared to pass through a metal block’s one face and ultrasound detectors are placed on the other face of the block to detect the transmitted wave. When the detector donot detect the transmited wave as desired then in that case the metal block have flaws in it.

TO make the sound audiable to every person sitting in the hall it is nessecary to make the cilings of the hall curved in shape, so that it reflect all the sound waves informaly.

The range of the frequency of infrasound is below 20Hz.

The range of the frequency of audiable sound is form 20Hz to 20000 Hz.

The range of the frequency of the ultrasound is above 20KHz.

The range of the frequency of infrasound is below 20Hz. Where as the range of the frequency of the ultrasound is above 20KHz.

infrasonic sound :- 18Hz, 10Hz., ultrasound :- 30,000 Hz, 50,000 Hz.

The frequency range of hearing in humans is from 20Hz to 20,000 Hz.

sound frequencies cannot be heard by a human ear:- 10 Hz, 15 Hz, and 40,000 Hz.

Speed= distance/time.

So, distance= speed*time.

D= 343 m/s*5

D= 1715 m.

Speed = 1500 m/sec

Distance = 1500 × 0.1 = 150 m

So, Distance between the diver and under sea rock = 150/2 = 75 m

when after heating a hard surface sound bounce back, this is known as reflection of sound. Hard solid surface is best for reflection of sound.

metal sheet and hard wood are good reflector of sound.

The laws of reflection of sound are:-

(i) The normal, incident wave and the reflected wave all lie on the same plane at the point of incidence.

(ii) the angle of incidence of sound is always equal to the angle of reflaction.

The repetition of sound wave caused by the reflection of sound wave is called echo. For an echo to happen it requires a hard surface like a tall brick wall or clif to bounce the sound back.

The minimum distance in air required from a sound reflecting surface to hear an echo (at 20°C) is 17.2 m.

A man standing 825 metres away from a cliff (steep rock) fires a gun.

Distance=speed*time

Time= distance/speed

Time= 825/330

Time= 2.5 seconds.

The sound wave with the frequency above 20,000 Hz. The ordinary sound wave has the frequency from 20 Hz to 20,000 Hz. Where as the ultrasound wave has the frequency above 20,000 Hz.

The applications of ultrasound are:-

1) in industries to detect the flaws in metal block.

2) in hospitals to see the growth of fetus inside the mother’s uterus.

3) in hospital to detect the problems in liver, kidney.

Infrasonic are vibration of frequency less than 20 Hz. Whales and elephants produced infrasonic.

Sound waves of frequencies greater than 20,000 Hz are called ultrasonic waves. Porpoises and bats produce ultrasonic waves.

λ₁ = v/f = 344/20 = 17.2 m

λ₂ = v/f = 344/20000 = 0.0172 m

(1) Echolocation is the technique by which objects are located by sensing time of echo of the sound emitted

(2) Formation of image of the heart by reflection of ultrasound from heart IS called echocardiography.

(3) Creating images of different parts of the body by means of reflection of ultrasound is called Ultrasonography.

Bats

Whale produces ultrasonic waves

SONAR stand for Sound, Navigation And Ranging. It is a device used to measure distance, direction and speed of underwater objects _ It has a transmitter and detector near its base. The transmitter transmits ultrasonic signals which get reflected by various underwater objects. These are received by the detector which can convert these waves into appropriate electrical signals and give us the required Information.

Time of echo = 3 s

speed of sound = 1440 m/s

Distance = (v × t)/2 = (1440 × 3)/2 = 2160 m

Hearing is possible through auditory organ. But the inner ear also accommodate the sensory orgain for the balance of the sense. Both constitue of one unit. The outer ear, middle ear and cochlea of the inner ear constitute the organ for perceiving sound.

The outer ear includes the auricle (concha auriculae) and the external auditory canal (meatus acusticus externs) together the eardrum (membrana tympani) as boundary between the outer ear and middle ear (cavum tympani).
The middle ear is also called the tympanic cavity (cavum tympani), which is continued in the Eustachian tube (tuba auditiva) as connection to the upper part of the throat.

The inner ear has a highly complex system of passages and cavities called the bony labyrinth. It is filled with a liquid, the perilymph. In this liquid there is a membranous labyrinth similarly filled with liquid (endolymph). This is the organ for auditory sensation but also the organ of balance (vestibular system).
The hearing organ is a particularly important sensory organ since, apart from the ability to hear, it is a prerequisite for developing speech. This is why it is more important than the eye.

In SONAR we use ultrasonic waves.

When we change a feeble sound to a loud sound, we increase its amplitude.

Infrasound is produced in an earthquake before the main shock wave begins.

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 the frequency of the sitar string with the frequency of other musical instruments.

‘Note’ of a sound of a single frequency.

A key of mechanical piano is first struck gently and then struck again but much harder this time. In the second case sound will be louder but pitch will not be different.

Rhinoceros can hear infrasound sound.

An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s after it was sent. If the speed of sound in water is 1500 m/s, the shoal is 300 m deep.

The speed of highly penetrating ultrasonic waves is same as those of audible sound waves.

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

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

Hydrophone, device does not work on the multiple reflections of sound waves.

Sound waves are generated by SONAR device fixed to a fishing ship.

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

At 20°C, the minimum distance of a person from a sound reflecting surface to hear an echo is 17.2 m.