Sound Waves Questions and Answers

Review Q The original frequency of the note produced by a sonometer is n The sonometer wire is reduced in length to half of its original value and its tension increases four times The frequency becomes Question Type Single Correct Type 4 1 1 2n 2 4n 3 3n 4 English n

Acoustic Power through a Window A window whose area is 2 m opens on a street where the street noise result in a sound level of 60 dB at window If an acoustic absorber is fitted at the window which absorbs all the acoustic power entering in window find the total energy collected by this absorber in five hours

Sound Velocity in an Artificial Medium In a region air pressure and volume are related as P a v where a is constant Consider air as an ideal gas of density p find sound velocity in the air

6 A rope of length L is clamped at both ends The standing wave is having three antinodes and four nodes Which one of the following is a possible wavelength for standing waves on this rope a L 2 b 2L 3 c 2L d 4L

i A person hums in a wall and finds strong resonance at frequencies 60Hz 100Hz and 140Hz What is the fundamental frequency of the well Explain How deep is the wall veloci of sound 344m ii A violin string 33cm long vibrates at a fundamental frequency of 440Hz Where shold a finger be pressed on the string board so that its decreased length causes it to vibrate in its fundamental mode at five fourth of its original frequency

Create a formula for the velocity of a car that is found by radar gun in other words a formula that is solved for car Operate under the assumption that the car is moving towards the radar gun being held by a non moving police officer The radar gun measures the beat frequency f f of the wave reflected off the car and back to the radar gun The officer isn t moving the wave bounces off the moving car and then back to the gun Assume the speed of the radar wave is equal to the speed of light light Don t use numbers just values to create the formula Your equation should be in terms of f f light

When the same note is played on a sitar and a flute the sound produced can be distinguished from each other because of the difference in A pitch loudness and quality B pitch and loudness C quality only D loudness only

1 The second harmonic of an open organ pipe o length lo cm and of radius of cross section 0 5 cm is equal to first overtone of a closed organ pipe a length le cm and of same radius of cross section i e 0 5 cm Then which of the following is true 1 4 l 0 2 2 4 3 0 6 A 31 AL

Take a long thread Place your hands over y our ears and get someone to place this thre ad round your head and hands Ask her to m ake the thread taut and hold its ends in one hand Now ask her to draw her finger and th umb tightly along the thread Can you hear a rolling sound like that of a thunder Now rep eat the activity while another man stands ne ar both of you Can he hear any sound

B is a source of sound of frequency 650 Hz Coefficient of restitution is 1 2 and velocity of sound in air 330 ms the frequency appearing to A after collision is A m A 10ms 620 Hz 20ms 2m B

LLEN The velocity of sound is V in air If the density 43 of air is increased to 4 times than the new velocity of sound will be Pressure unchanged N 3 12V 2 V raft an m V i afe ang an vara u 4 sukafda 1 Y 3 12V 4

Two sitar strings A and B playing the note Dha are slightly out of tune and produce beats frequency 6 Hz The tension of string B is slightly decreased and the beat frequency is found to be 7 Hz If frequency of A is 440 Hz then frequency of B will be 440 Hz 446 Hz 434 Hz 452 Hz

A cylindrical tube open at both ends has fundamental frequency f in air The tube is dipped vertically in water so that half of it is in water The fundamental frequency of the air column is now 1 1 2 3 f 3f 4 4 2f 2 11

An observer sitting in line of two s cience watches the flashes of two tanks firing at each other at the sa me time but he hear the sound of t he two shots 2 seconds and 3 5 se conds after seeing the flashes If t he distance between the two than ks is 510 m find the speed of the s ound

The threshold of human hearing is 1 10 W m What is the sound intensity of a jet flying over at distance of 300 m with a sound intensity of 1 x10 W m 1 Point 10 000 000 000 dB 100 dB 0 dB 10 dB

Foley sound is recorded after the film is shot O True False

Two small speakers 0 600 m apart are facing in the same direction They are driven by one 657 Hz oscillator and therefore emit identical sound waves in phase with one another at the respective points of origin The speed of sound waves in air is 343 m s a An observer wishes to stand in front of one of the speakers at the closest point i e smallest x value where intensity is at a relative maximum At what distance x from the nearest speaker should she position herself Enter your answer in m m b The observer now wishes to stand at the closest point along that line where intensity is at a relative minimum At what distance x should she position herself now Enter your answer in m

A train is moving past a crossing where cars are waiting for it to pass While waiting the driver of the lead car becomes sleepy and res his head on the steering wheel unintentionally activating the car s horn A passenger in the back of the train hears the horn s sound at frequency of 432 Hz and a passenger in the front hears it at 408 Hz Find the train s speed and the horn s frequency assuming the sound travels along the tracks Take the speed of sound to be 343 m s HINT a the train s speed in m s m s b the horn s frequency in Hz Hz

A particular person s eardrum is circular with a diameter of 7 00 mm a How much sound energy in J is delivered to an eardrum in one second at the threshold of human hearing The threshold of human hearing is taken to be 1 00 x 10 12 W m b How much sound energy in J is delivered to an eardrum in one second at the pain threshold for human hearing The pain threshold occurs at 1 00 W m one trillion times as intense as the lowest audible level c Assume that musicians onstage are exposed to sound that is 10 decibels below the human pain threshold Over the course of a two hour concert how much sound energy in J does each ear absorb onstage d Assume that the amplifiers on the stage operate at a combined power of 5 000 Watts and that 80 of this is converted to sound Which of the following best approximates the fraction of this power incident upon each eardrum onstage As in the previous part assume that the musicians are exposed to sound that is 10 dB below the human pain threshold O one thousandth 10 3 O one millionth 10 6 O one billionth 10 O one trillionth 10 12

On a bright winter s day a student notices an echo as he walks between a high school s playing field and the rear wall of its auditorium He decides to estimate how far he stands from the reflective wall He abruptly claps and determines that the sound pulse returns to his as an echo 0 492 seconds later averaging several trials for enhanced reliability The air is a frigid 10 C Six months later the student decides to repeat his experiment on a hot summer day standing at the same exact spot This time the echo takes a slightly shorter 0 454 seconds to return to the student a What is the temperature in C of the air on the summer day C b How far in m does the student stand from the reflective wall m

Two nearby trumpets are sounded together and a beat frequency of 4 Hz is heard If one of the trumpets sounds at a frequency of 506 Hz what are the two possible frequencies of the other trumpet Enter your answers from smallest to largest in Hz to at least three significant figures HINT Hz Hz

If we study the vibration of a pipe open at both ends which of the following statements is not true 1 Open end will be an antinode 2 Odd harmonics of the fundamental frequency will be generated 3 All harmonics of the fundamental frequency will be generated 4 Pressure change will be maximum at both ends

A sound wave travels with a velocity of 300 m s through a gas 9 beats are produced in 3 s when two waves pass through it simultaneously If one of the wave has 2 m wavelength the wavelength of the other wave is 1 98 m 2 04 m 2 06 m 1 99 m

the average power transmitted across a given point in the string 22 A musical note of frequency 256 Hz produces plane waves in air and its amplitude is 1 0 105 m Find the energy of radiation per m CL

When both source and listener approach each other with a velocity equal to half the velocity c sound the frequency of the sound as detected b the listener is frequency of sound n 1 n 2 2n 4 3n 3 n

A vibrating tuning fork of frequency 1000 Hz is placed near the open end of a long cylindrical tube The tube has a side opening and is also fitted with a movable reflecting piston As the piston is moved through x distance the intensity of sound changes from a maximum to a minimum for an observer at the side opening If the speed of sound is 350 meters per second then x is E 1 35 cm 2 17 5 cm 3 8 75 cm 4 10 cm 7

A source S emitting sound of frequency f moves uniformly along a straight line wit a velocity u as shown The velocity of sound in the medium is v u Two detectors D and D are placed on the line perpendicular to line of motion of S Point P one represents the point of closest approach of S to the detectors The frequency detected f by D and D versus time t graph is shown on the same graph paper fp NARA S u P D D Choose the incorrect option s A Graph 1 belongs to detector D fo Graph 2 Graph 1 B t to is the instant when source S is at P C The value of f is f D The value of f is Graph 1 Graph 2

A The decibel level of sound in a quiet office is 100watts m a What is the corresponding sound intensity in decibels b How much more intense is this sound than the least audible sound a human can hear

49 An organ pipe open from both end produces 5 beats per second when vibrated with a source of frequency 200 Hz The second harmonic of the same pipes produces 10 beats per second with a source of frequency 420 Hz The frequency of source is 1 195 Hz 2 205 Hz 3 190 Hz 4 210 Hz

A source of unknown frequency gives 4 beats s when sounded with a source of known frequency 250 Hz The second harmonic of the source of unknown frequency gives five beats per second when sounded with a source of frequency 513 Hz The unknown frequency is NEET 2013 1 246 Hz 3 260 Hz 2 240 Hz 4 254 Hz

2 2 04 m 4 1 99 m 3 VS s 2 61 Sound wave travels with a velocity of 300 ms Q 61 af 300 ms through a gas 9 beats are produced in 3 s when two waves pass through it simultaneously If one of the waves has 2 m wavelength the wavelength of the other wave is 1 1 98 m 3 2 06 m nier 139 41 a 1 1 98 m 3 2 06 m S fe 2 m et at a rat anti 2 2 04 m 4 1 99 m

23 A train moving at a speed of 220 ms 1 towards a stationary object emits a sound of frequency 1000 Hz Some of the sound reaching the object gets reflected back to the train as echo The frequency of the echo as detected by the driver of the train is Speed of sound in air is 330 ms AIPMT Mains 2012 1 3500 Hz 3 5000 Hz 2 4000 Hz 4 3000 Hz 3

29 A resonance tube is resonated with a tuning fork of frequency 256 Hz If the length of resonating air column are 32 cm and 100 cm the end correction is 1 20 cm 3 0 2 cm 2 2 cm 4 1 cm 3

A suspension bridge is to be built across valley where it is known that the wind can gust at 5 s intervals is estimated that the speed of transverse waves along the span of the bridge would be 400 m s The dange of resonant motions in the bridge at its fundamental frequency would be greater if the span had a length of 1 2000 m 2 1000 m 2 3 400 m 4 80 m

52 A whistle revolves in a circle with angular speed 20 rad s using a string of length 50 cm If the frequency of sound from the whistle is 385 Hz then what is the minimum frequency heard by an observer who is far away from the centre Vsound 340 m s 1 385 Hz 3 394 Hz 2 374 Hz 4 333 Hz

A whistle of frequency 500 Hz tied to the end of string of length 1 2 m revolves at 40 m s A listener standing large distance away in the plane of rotation of whistle hears frequencies of what range velocity of sound 340 m s 1 447 to 567 Hz 3 568 to 880 Hz J 0 2 180 to 380 Hz 4 220 to 384 Hz 2 F

7 An observer is moving with speed v towards a stationary source emitting a sound wave of wavelength The change in wavelength detected by the observer is v speed of sound v 1 Vo vo 2 V

The minimum intensity of audibility of sound is 10 12W m s and density of air 1 293kg m If the frequency of sound in 1000Hz then the corresponding amplitude the vibration of the air particles is Take velocity of sound 332m s

A train is moving with a constant speed 15 m s along a circular track The length of the train mak an angle 90 at the centre A siren in its engine is emitting a sound of frequency 1 5kHz T apparent frequency of sound as heard by a passenger at the rear end of the train is 100x Hz th find x In Hz

In a single slit diffraction of light of wavelength A by a slit of width e the size of the central maximum on a screen at a distance bis 1 2b e 2 26X e 26 3 2b e C 26A e 2 3 4

On an electric guitar a pickup under each string transforms the string s vibrations directly into an electrical signal Part A If a pickup is placed 16 25 cm from one of the fixed ends of a 65 00 cm long string which of harmonics from n 1 to n 12 will not be picked up by this pickup Express your answers as an integers separated by commas VAZO SE

In the figure below P and Q are two equally intense coherent sources emitting radiation of wavelength 20 m The separation between P and Q is 5 m and the phase of P is ahead of that of Q by 90 A B and C are three distinct points of observation each equidistant from the midpoint of PQ The intensities of radiation at A B C will be in the ratio B mathonga mathon mothongs P mathongo mathonde athongo C A 1 0 1 4 2 2 1 0 3 0 1 2nath 4 4 1 02 mathongo

Determine the ratio of the number of nodes in the 13 th harmonic of an open ended pipe of length 6 24 to the number of antinodes in the 2 m 1 th harmonic for m 16 of a closed ended pipe of length 9 29 You may assume that both pipes are full of air

45 by an observer is 10 more than the act frequency If the velocity of sound in air 330 m sec then i The source may be moving towards observer with a velocity of 30 ms ii The source may be moving towards observer with a velocity of 33 ms iii The observer may be moving toward source with a velocity of 30 ms iv The observer may be moving toward source with a velocity of 33 ms 1 ii iv 2 ii iii 3 i iv 4 The following configuration of gate is equi

Tuning fork A of frequency 258 Hz gives beats with a tuning fork B When the tuning fork A is filed and again A and B are sounde the number of beats heard increases The frequency of B is 1 250 Hz 2 264 Hz 3 258 Hz 4 242 Hz

9 A train moves towards a stationary observer with a speed 34 m s The train sounds a whistle and its frequency registered by the observer is f If the speed of the train is reduced to 17 m s the frequency registered is If the speed of sound is 1 340 m s then the ratio is 1 18 19 3 2 19 18

3 44 and 22 4 72 and 36 4 The displacement at a point due to two waves are y 4sin 500xt and y 2sin 506 The result due to their superposition will be 1 3 beats per second with intensity relation between maxima and minima equal to 2 2 3 beats per second with intensity relation between maxima and minima equal to 9 3 6 beats per second with intensity relation between maxima and minima equal to 2 4 6 beats per second with intensity relation between maxima and minima equal to 9

A bat emits ultrasonic sound of frequency 1000 kHz in air If the sound meets a water surface the wavelength of the reflected and transmitted sound are speed of sound in air 340 m s and in water 1500 m s 1 3 4 mm 30 mm 3 0 34 mm 1 5 mm NCERT XI Pg 3911 2 6 8 mm 15 mm 4 6 8 mm 30 mm

3 2 The frequency changes by 10 as a sound source approaches a stationary observer with constant speed V What would be percentage change in the frequency as the source recedes the observer with same speed V V 1 10 5 2 8 5 3 4 5 4 1 5

4 Can t be determined 3 Ten tuning forks are arranged in increasing order of frequency in such a way that any two consecutive tuning forks produce 4 beats per second The highest frequency is twice that of the lowest Possible highest and lowest frequencies in Hz are 1 80 and 40 2 100 and 50 3 44 and 22 4 72 and 36