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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child. |
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Answer» Velocity of sound in air= 346 m/s Velocity of sound wwave in aluminium= 6420 m/s Let length of rode be 1 Time taken for sound wave in air, `t_(1)`= 1 / Velocity in air Time taken for sound wave in Aluminium, `t_(2)`= 1 / Velocity in aluminium Therefore, `t_(1)// t_(2)` = Velocity in aluminium / Velocity in air = 6420 / 346 = `18.55: 1` |
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| 2. |
To detect the obstacles in their path, bats produce:(a) infrasonic waves (b) ultrasonic waves(c) electromagnetic waves (d) radio waves |
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Answer» Ultrasonic waves |
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| 3. |
How do bats avoid obstacles in their way, when in flight? |
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Answer» Bats can produce and detect the sound of very high frequency up to about 1000kHz. The sounds produced by flying bats get reflected back from any obstacle in front of it. By hearing the echoes, bats come to know even in the dark where the obstacles are. So they can fly safely without colliding with the obstacles. |
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| 4. |
Fill in the blanks:i. Bats detect the obstacles in their path by receiving the reflected ………….. .ii. An object that moves back and forth is called ……………. .iii. If the length of a pendulum is increased the time period of oscillation ………………. .iv. The …………… of a wave is the maximum distance moved by the object on either side of the mean position.v. Sound waves do not travel through ……………… . |
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Answer» i. ultrasonic waves ii. an oscillator iii. increases iv. amplitude v. vaccum |
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| 5. |
A student is given an iron cube of side 1cm, a measuring cylinder of range 100 mL and least count 1 mL, and a spring balance of range 100g wt and least count 1g wt. He can use these to measure:A. both the mass and the volume of the given iron cubeB. neither the mass nor the volume of the given iron cubeC. only the mass of the given iron cube but not its volumeD. only the volume of the given iron cube but not its mass |
| Answer» Correct Answer - A | |
| 6. |
Explain how does a sound making object differ from one that is silent. |
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Answer» A sound making object is a vibrating object for which it can produce sound while a silent body is a non-vibrating object. |
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| 7. |
A wire stretched between two fixed supports, is plucked exactly in the middle and then released. It executes (neglect the resistance of the medium):(a) resonant vibrations (b) free vibrations(c) damped vibrations (d) forced vibrations |
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Answer» It executes free vibrations. Hint: The periodic vibrations of a body of constant amplitude in the absence of any external force on it are called free vibrations. |
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| 8. |
A stringed musical instrument, such as the Sitar, is provided with a number of wires of different thicknesses. Explain the reason for this. |
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Answer» In stringed instruments, frequency depends on thickness or radius of string. So to produce different frequencies different strings of different thicknesses are provided. |
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| 9. |
Why is a loud sound heard at resonance? |
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Answer» At resonance, the body vibrates with large amplitude thus conveying more energy to the ears so a loud sound is heard. |
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| 10. |
If an observer places his ear at the end of a long pipe, he can hear two distinct echoes when the pipe is hammered at the other end. Explain. |
| Answer» When the metallic pipe is hammered, the sound so produced travels through (i) the solid layer of the pipe and (ii) at the same time through the air within the pipe. Since sound travels much faster through solids (16 times) faster in air than in case of steel), the sound through the solid reaches much earlier than the sound through air. | |
| 11. |
A person places his ear at the end of a long steel pipe. He hears two distinct sounds at an interval of `0.5 s` when another person hammers at the other end of the pipe. If the speeds of sounds in metal and air are `3630 m//s and 330 m//s` respectively, find the distance between the two persons. |
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Answer» If `d` is the distance between the two persons, `(d)/(330) - (d)/(3630) = 0.5 s` or `(d)/(330) [1 - (1)/(11)] = (1)/(2)` or `(d)/(330) xx (10)/(11) = (1)/(2)` or `d = ((1)/(2) xx 330 xx (11)/(10)) m = 181.5 m`. |
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| 12. |
Drapery and furniture often improve the acoustics of a room. Explain. |
| Answer» This is due to the reason that drapery and furniture absorb sound and reduce reverberation time. | |
| 13. |
Why do auditoriums have curved roofs, curtains, carpets and false ceiling? |
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Answer» The roofs of auditoriums are curved, so that sound after reflection reaches all corners of the auditorium. In auditorium excessive reverberation is highly undesirable. So, sound absorbent material like curtains, carpets and false ceiling are used to reduce reverberation. |
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| 14. |
Shirin went to an opera house. She appreciated its architecture and furnishing. The curved ceiling draperies, cushions and curtains were perfectly placed. She also saw sound board behind the stage. She now wondered if each of these accessories were placed for the sake aesthetics of the hall or had a scientific reason too. (a) What is the purpose of curtains, cushions and draperies in an opera house? (b) How does curved ceiling and sound board help? (c) List some characteristic qualities of Shirin. |
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Answer» (a) Curtains, draperies and cushions are sound absorbent materials, they reduce reverberation. (b) Sound boards and curved cutting focuses the sound such that sound after reflection reaches all corners of the hall and spreads evenly across the width of the hall. Also to avoid the reverberation the walls and roof of the hall are made curved so that sound waves don’t suffer multiple reflections and quality of sound improves. (c) Shirin is curious, scientific and intelligent. |
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| 15. |
A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air = 335 m/s, the number of beats heard per second by a passenger on the bus will be (a) 3 (b) 4 (c) 5 (d) 6 |
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Answer» Correct Answer is: (c) 5 |
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| 16. |
Abhishek lives in society flats alongwith his parents. He is studying in class IX. For the last few days, his mother has been complaning that the milk being supplied by the milkman is not pure. When she talked to other neighbours, they told her that they are also facing the same problem. Abhishek through over this problem for a while. He then went to the market and purchased a glass instrument to check the purity of milk being supplied by the milkman. when milkman brought milk the next day, Abhishek took this milk in a tall vessel and placed the instrument in it vertically. He explained to the milkman how this instrument indicated that the milk was not pure, it was adulterated. The milkman admitted his fault and promised to supply pure milk in future. Abhishek told about this incident to all his neighbours. Ultimately all the households in the society flats purchased the instrument to test the purity of milk. (a) Name the instrument which was purchased by Abhishek to check the purity of milk. (b) Name the principle on which the above instrument works. (c) What substance is usually mixed with pure milk by the dishonest milkmen to adulterate it and increase their profit? (d) Which physical quantity of pure milk is used to detect the presence of the substance mixed in it (which is measured by the above instrument)? (e) How does the instrument purchased by Abhishek show the presence of the substance mixed in pure milk by the milkman? (f) Which position of the instrument placed in two containers of milk A and B (one by one) shows (i) pure milk, and (ii) adulterated milk? (g) What values are displayed by Abhishek in this episode? |
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Answer» (a) Lactometer (It is used to find out the amount of water mixed in pure milk). (b)Lactometer works on the principle of flotation. (c) Water is mixed with pure milk to adulterate it. (d) Relative density (Relative density of pure milk is higher than that of impure milk containing water). (e) (i) Since the relative density of pure milk is higher, therefore, pure milk will exert more upward (buoyant) force on the lactometer bulb due to which lactometer will float higher (with more of its calibrated tube above the milk level) when placed in a container of pure milk. (ii) The relative density of water is lower than that of pure milk. So, when water is mixed with pure milk, then the relative density of adulterated milk becomes less than that of pure milk. Due to lower relative density, adulterated milk exerts less upward (buoyant) force on lactometer bulb due to which lactometer will sink more and float at lower level when placed in a container of adulterarted milk. (f) (i) Container B contains pure milk (ii) Container A contains adulterated milk (containing water mixed in it). (g) The values displayed by Abhishek in this episode are (i) Awareness of the availability of lactometer to check the purity of milk (ii) Knowledge of principle of flotation and working of lactometer (iii) Idea of relative density of pure milk and water, and (iv) Desire to protect his family and neighbours from being cheated by dishonest milkma. |
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| 17. |
The distance from crest to crest of any wave is :A. frequencyB. wavelengthC. speedD. amplitude. |
| Answer» Correct Answer - B | |
| 18. |
A series of ocean waves, each 5.0 m from crest to crest, moving past the observer at a rate of 2 waves per second have wave velocity(A) 2.5 m/s (B) 5.0 m/s (C) 8.0 m/s (D) 10.0 m/s |
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Answer» Correct option is: (D) 10.0 m/s |
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| 19. |
The wavelength of an ultrasonic wave is :A. the same as that of the audible soundB. very lowC. more than that of audible soundD. very high. |
| Answer» Correct Answer - B | |
| 20. |
Which of the following frequencies is audible to human beings ?A. 5 HzB. 27 HzC. 5 kHzD. 50 kHz |
| Answer» Correct Answer - C | |
| 21. |
Part ’a’ is A) Larynx B) Vocal cord C) Trachea D) Tongue |
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Answer» Correct option is B) Vocal cord |
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| 22. |
Name the part of the body which produces sound (voice). |
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Answer» The part of the body which produces sound is the voice box or larynx. |
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| 23. |
The frequencies of notes given by flute, guitar and 500 Hz. Which one of these has the highest pitch? |
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Answer» Trumpet. Because its frequency is highest. |
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| 24. |
What is the audiable range of frequencies for human beings? Explain. |
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Answer» 1. Sound of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. 2. Such sounds are called inaudible. 3. On the other side, sound of frequencies more than about 20,000 vibrations per second (20,000 Hz) are also not audible to the human ears. 4. Thus for human ears, the range of audible frequencies is roughly between 20 to 20,000 Hz. |
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| 25. |
What is audible sounds? What is audible range? |
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Answer» The sounds that a normal human being can hear is called audible sounds. Frequency of audible sound ranges from 20 cycles / second to 20000 cycles / second. |
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| 26. |
Mention the position of muscles of vocal cord when we are not speaking. |
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Answer» The position of muscles of vocal cord when we are not speaking is loose and relaxed. |
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| 27. |
How does a musician playing on a flute change the pitch of sound produced by it ? |
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Answer» In musical instruments like flute and clarinet, the pitch of sound is changed by changing the length of vibrating air column when different holes in it are closed. |
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| 28. |
Define audible sounds and inaudible sounds. |
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Answer» Audible sounds: The sounds that a normal human being can listen are called audible sounds. Frequency range is 20 cycles/sec – 20000 cycles/sec. Inaudible sounds: The sounds that a normal human being can’t listen are called inaudible sounds. Frequency range is less than 20 cycles/sec. or greater than 20000 cycles/sec. |
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| 29. |
For hearing the loudest ticking sound heard by the ear, find the angle 1x . |
| Answer» For loudest ticking, sound waves must be reflected along the dotted paths so that `/_ i = /_r`. Here, `/_ i = 90^@ - 50^@ = 40^@`. Obviously, `/_ = /_ = 40^@`. | |
| 30. |
Whether sound can travel without medium? |
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Answer» No, sound cannot travel without medium. |
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| 31. |
In toy telephone the sound travels through which medium? |
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Answer» In toy telephone the sound travels through the string i.e. a solid medium. |
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| 32. |
A source of frequency `500 Hz` emits waves of wavelength `0.2 m`. How long does it take to travel `300 m` ?A. 70 sB. 60 sC. 12 sD. 3 s |
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Answer» Correct Answer - D `v = v lamda = (500 Hz)(0.2 m) = 100 m//s` Time taken by the wave to travel `300 m = (300 m)/(100 m//s) = 3 s`. |
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| 33. |
which of the following frequencies is inaudible to a human being ?A. 50 HzB. 1 kHzC. 40 kzD. 15 kHz |
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Answer» Correct Answer - C Audible range : `20 Hz` to `20 kHz`. |
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| 34. |
Name the vibrating part of Veena and flute. |
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Answer» The vibrating parts of Veena and flute are stretched string and air column respectively. |
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| 35. |
Name the part which vibrates to produce sound in the following: (a) Drums (b) Sitar (c) Flute |
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Answer» (a) Its stretched membrane (b) It’s strings. (c) Its long hollow pipe. |
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| 36. |
Explain why you can predict the arrival of a train by placing your ear on the rails without seeing it. |
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Answer» The sound produced by the moving wheels of train travels much faster through the track than through the air. Therefore they hear through the track much before it is heard through the – air. |
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| 37. |
Explain the reason of not putting the sharp or pointed things into the ear. |
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Answer» If sharp or pointed things are put into the ear it can damage the eardrum inside our ear. This can make us deaf. |
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| 38. |
The sound of distant horses can br heard by applying the ear to the ground whereas it is inaudible if the ear is held a little distance above the ground. Explain. |
| Answer» We know that loudness is directly proportional to the density of the medium. The density of ground is much higher than that of air. Thus, the sound of distant horses, when conveyed through ground, is louder than when through air. Therefore, by applying ear to the ground, we can hear this sound. But when the ear is a little distance above the ground, the sound travels through air and is hardly audible. | |
| 39. |
An approaching train can be felt by applying ears to rails but through air its approach cannot felt easily Discuss. |
| Answer» Intensity of sound is directly proportional to the density of the medium. Thus, sound travelling through rails (of larger density than that of air) is louder than the sound through air. Moreso, sound travels faster through the rails (solid medium) tan through the air (gaseous medium). | |
| 40. |
Give scientific reason:The sounds generated by a tabla and sitar are different. |
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Answer» 1. In tabla where leather is fitted, sound gets generated when the leather surface is thumped by fingers or palm. 2. The waves thus created travel in two dimensions. Sitar is having strings attached to pumkin box called sound box. 3. Sounds generated by tabla and a sitar are different because they have different pitch and frequencies. |
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| 41. |
What should we do:The silencer of a motorcycle is broken. |
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Answer» 1. If the silencer of a motorcycle is broken, vehicle should be immediately taken to the garage for repair. 2. If silencer is not maintained properly, it will continue making loud noise on the road while in motion, resulting in increasing noise pollution. |
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| 42. |
Name the following:i. The sound frequencies above 20,000 Hz.ii. The medium through which sound is most clearly propagated.iii. The range of frequency in which humans can hear sound.iv. The sound level physically painful to humans.v. The technique used by bats to find their way. |
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Answer» i. ultrasonic ii. solids iii. 20 – 20,000 Hz iv. above 100 dB v. echolocation |
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| 43. |
Match the following :List- AList- B1) Tabla a) Stringed instrument2) Flute b) Membrane instrument3) Veenac) Air blowing instrumentA) 1 – c, 2 – b, 3 – a B) 1 – c, 2 – a, 3 – b C) 1 – b, 2 – a, 3 – c D) 1 – b, 2 – c, 3 – a |
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Answer» D) 1 – b, 2 – c, 3 – a |
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| 44. |
Complete the tableSource of soundThe main part which produces sound by vibrationThe part which vibrates with the main partVoicebox….. a ……..Throat, lipsFluteAir column…. b …..ChendaLeather, diaphragm…… c …….Violine……… d ……….Frame, air |
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| 45. |
Flute is an instrument of ……….. type. A) drum instrument B) fringed instrument C) stringed instrument D) none of these |
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Answer» Correct option is B) fringed instrument |
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| 46. |
Table the natural source and manmade source from the following. Lips, chenda, flute, tabla, violin, vocal cord, sound of birds |
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| 47. |
Give scientific reason:In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rails. |
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Answer» 1. It was a technique that worked better in those days when train speed were slower than they are today and when there were more rail joints. 2. When people would put their ear to the rail they could hear vibration caused by the wheels moving over the joints. 3. Metal being a solid is an efficient medium for the sound to travel and so the sound can propagate further in the rail than would in air as speed of sound is faster in solids than in air. |
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| 48. |
Fill in the blanks with the proper words.i. The propagation of sound does not occur through a ………….. .ii. Noise pollution is a …………… issue.iii. The sound which is disagreeable to our ears is called …………… .iv. Noise has adverse effects on our …………….. . |
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Answer» i. vacuum ii. social/serious iii. noise iv. health |
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| 49. |
Fill in the blank with appropriate word:(i) The region in a sound wave, with higher pressure and density is called ………….. and that with low pressure and density is called ……….. .(ii) Medium is …………… for generation of sound.(iii) The total number of compressions and rarefactions produced per second in a sound wave is 1000. The frequency of the sound wave is ………… .(iv) Different sound notes have different ……………….(v) In a loudspeaker, …………… energy is converted into ………….. energy. |
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Answer» (i) The region in a sound wave, with higher pressure and density is called compression and that with low pressure and density is called rarefaction. (ii) Medium is needed (or necessary) for generation of sound. (iii) The total number of compressions and rarefactions produced per second in a sound wave is 1000. The frequency of the sound wave is 500 Hz. [Note: Total number: 100. ∴ 500 compressions and 500 rarefactions are produced per second.] (iv) Different sound notes have different frequencies. (v) In a loudspeaker, mechanical energy is converted into sound energy. |
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| 50. |
Match the pairs.Column ‘A’Column ‘B’1. Flutea. Frequency less than 20 Hz2. Frequencyb. Frequency more than 20,000 Hz3. Sound levelc. Vibrations in the air4. Ultrasonic soundd. Measured in Hz5. Infrasonic sounde. Decibel |
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