1. Put in ascending order of speed of sound in the mediums-
I . Water, II. Steel, III. Nitrogen :
(a) III, II, I
(b) III, I, II
(c) I, III, II
(d) II, I, III
[U.P.P.C.S. (Spl) (Mains) 2008]
Ans. (b) III, I, II
- The speed of sound varies depending on the type of material it is travelling through.
- It is fastest in solids and slowest in gases.
- The density of the material affects the speed of sound, with higher density materials allowing the sound to travel faster.
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2. The sound will have the highest velocity in-
(a) Vacuum
(b) Air
(c) Water
(d) Steel
[U.P. P.C.S. (Pre) 2018]
Ans. (d) Steel
- The speed of sound changes depending on the material it is travelling through.
- For example, sound moves slowest in gas, faster in liquids, and fastest in solids.
- Air is the slowest at 331 m/s, seawater is faster at 1531 m/s, and iron is the fastest at 5950 m/s.
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3. The velocity of sound in air is approximately-
(a) 10 km./sec.
(b) 10 mile/min.
(c) 343 m/sec.
(d) 3 × 1010/sec.
[42nd B.P.S.C. (Pre) 1997]
Ans. (c) 343 m/sec.
- Sound travels at a rate of 343 meters every second when the temperature is 20 degrees Celsius.
- This means that it takes almost 3 seconds for sound to travel one kilometer and almost 5 seconds to travel one mile.
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4. The velocity of sound is maximum in –
(a) Air
(b) Liquid
(c) Metal
(d) Vacuum
[U.P. Lower (Spl) (Pre) 2008, Uttarakhand P.C.S. (Pre) 2010]
Ans. (c) Metal
- Sound moves the fastest through solids. It travels by making particles in the medium vibrate.
- The speed of sound depends on how elastic and dense the material is that it is going through.
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5. If Va, Vw, and Vs respectively are the speed of sound in air, water, and steel, then-
(a) Va < Vw < Vs
(b) Vs < Vw < Va
(c) Vw < Vs < Va
(d) Vs < Va < Vw
[U.P. U.D.A./L.D.A. (Spl) (Mains) 2010]
Ans. (a) Va < Vw < Vs
- We know that sound travels through different materials at different speeds.
- Generally, it moves faster through liquids than gases and faster through solids than liquids.
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6. In which medium the speed of sound is maximum at a temperature of around 20°C?
(a) Air
(b) Granite
(c) Water
(d) Iron
[Chhattisgarh P.C.S. (Pre) 2004]
Ans. (d) Iron
- Sound travels faster depending on how elastic and dense the material it is travelling through is.
- For example, sound travels the fastest through iron at a temperature of 20° C.
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7. Sound waves –
(a) Can travel in vacuum.
(b) Can travel only in solid.
(c) Can travel only in gases.
(d) Can travel both in solid and gaseous medium.
[U.P.P.C.S. (Pre) 2002]
Ans. (d) Can travel both in solid and gaseous medium.
- Sound travels by vibrating the molecules in a material, such as a solid, liquid, or gas.
- The molecules in solids are very close together, not as close in liquids, and very spread out in gases.
- Because of this, sound travels faster through solids than gases.
- Therefore, sound can be transmitted through solids, liquids, and gases.
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8. Sound waves travel fastest in
(a) solids
(b) liquids
(c) gases
(d) vacuum
[M.P.P.C.S. (Pre) 2017]
Ans. (a) solids
- Sound is a kind of wave that requires a material, such as air, water, or steel, to travel through.
- It cannot move through a vacuum.
- Additionally, the speed of sound varies in different materials; it is fastest when traveling through solid matter, and slowest through gas.
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9. In which of the following options sound may not be across/travel?
(a) Water
(b) vacuum
(c) Iron
(d) Air
[U.P.P.C.S. (Pre) 1990]
Ans. (b) vacuum
- Sound cannot go through a vacuum because there is no material for the sound to travel through.
- No sound can be heard in a vacuum.
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10. Sound waves do not travel in –
(a) Solids
(b) Liquids
(c) Gases
(d) Vacuum
[U.P.P.C.S. (Pre) 2014]
Ans. (d) Vacuum
- Sound cannot travel through empty space because there is nothing for it to move through (no air or other matter).
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11. The walls of the hall, built for music concerts should –
(a) Amplify sound
(b) Transmit sound
(c) Refect sound
(d) Absorb sound
[U.P.P.C.S. (Mains) 2007]
Ans. (d) Absorb sound
- The walls of a music hall should be able to absorb sound instead of reflecting it.
- If the walls reflect sound, the audience will hear echoes.
- To prevent this, the walls should be made of a material that allows sound to be absorbed.
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12. To hear a clear echo, the minimum distance between the reflecting surface and the observer should be –
(a) 165 feet
(b) 165 metre
(c) 16.5 feet
(d) 16.5 meter
[U.P.P.C.S. (Mains) 2007]
Ans. (d) 16.5 meter
- Echo is when someone makes a sound and it bounces off of an obstacle like a wall, hill or mountain.
- If the distance between the person and the obstacle is ‘d’, the speed of the sound is ‘v’, and the time it takes for the sound to travel is ‘t’, then the speed of the sound is calculated by using the equation: v = 2d/t. For example, if it takes 1/10 of a second for the sound to travel back to the person, then the speed of the sound will be calculated using that time.
- It is the minimum time required to distinguish between two sounds
- v = velocity of sound = 330 m/sec at 20° C
then d = vt/2 = 1/2 ( 330×( 1/10) )
= 16.5 m (about 17m)
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13. How much should the minimum distance be between the source of sound and the reflecting surface, so that an echo can be heard clearly?
(a) 10 metre
(b) 17 metre
(c) 24 metre
(d) 30 metre
[R.A.S./R.T.S.(Pre) 2007]
Ans. (b) 17 metre
- The distance between the sound source and the reflector is twice as much as the distance between the reflecting surface and the observer.
- So, if the obstacle is 17 m away, then after 0.1 seconds, the reflected sound or the echo can be heard clearly.
- Therefore, the minimum distance needed to hear a clear echo is 17 m.
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14. One important characteristic of sound is ‘Pitch’, which depends upon
(a) Intensity
(b) Frequency
(c) Quality
(d) Amplitude
[U.P. P.C.S. (Mains) 2017]
Ans. (b) Frequency
- The sound’s pitch is often called its frequency.
- A sound with a high pitch has a high-frequency wave and a sound with a low pitch has a low-frequency wave.
- High pitch means it’s moving quickly and low pitch means it’s moving more slowly.
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15. Two astronauts cannot hear each other on the moon’s surface, because –
(a) Their ears have stopped working on the moon.
(b) No atmosphere on the moon.
(c) They wear special space suits on the moon.
(d) The sound travels much more slowly on the moon.
[U.P.U.D.A./L.D.A. (Pre) 2002]
Ans. (b) No atmosphere on the moon
- Sound needs an area or something to travel through in order to go from one place to another.
- On Earth, sound travels through the air.
- But because there is no air on the moon, sound cannot move around there, so it is silent.
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16. An astronaut cannot hear his companion at the surface of the moon because –
(a) Produced frequencies are above the audio frequency.
(b) Temperature is too low during night and too high during day.
(c) There is no medium for sound propagation.
(d) There are many craters on the surface of the moon.
[U.P.P.C.S. (Mains) 2013]
Ans. (c) There is no medium for sound propagation
- An astronaut on the moon cannot hear their friend on the ground because there is no air.
- This is because sound is a type of wave that needs something to travel through, like air.
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17. Consider the following statements :
1. A future of a smaller length produces waves of lower frequency.
2. Sound travels in rocks in the form of longitudinal elastic waves only.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
[I.A.S. (Pre) 2007]
Ans. (d) Neither 1 nor 2
- A flute that is long will produce sound waves with a longer wavelength.
- A flute that is shorter will make sound waves with a higher frequency.
- This means statement 1 is incorrect. Sound travels through gases, liquids, and plasma using longitudinal waves.
- When travelling through a solid, like rocks, it can go through as both longitudinal and transverse waves. This means statement 2 is also incorrect.
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18. Consider the following statements about ultrasonic waves :
1. They can destroy insects.
2. They can clean clothes by removing dust.
3. They can be used to treat diseases.
4. They can control automatic doors.
Of the above statements
(a) 1 and 2 are correct
(b) 3 and 4 are correct
(c) 1, 2, and 3 are correct
(d) All are correct
[U.P.P.C.S. (Mains) 2004]
Ans. (d) All are correct
- Sound is divided into three groups based on the frequency range: Audible (able to be heard), Infrasonic (lower than audible range) and Ultrasonic (higher than audible range).
- Ultrasonic waves are used for various purposes such as killing bugs, cleaning clothes of dust, treating illnesses, opening automatic doors, finding aircraft and submarines, and measuring the depth of the sea.
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19. Ultrasonics are sound waves of frequency
(a) Greater than 20,000 Hz
(b) Less than 10,000 Hz
(c) Equal to 1000 Hz
(d) None of these
[U.P.P.C.S.(Pre) 2012]
Ans. (a) Greater than 20,000 Hz
- Ultrasonic waves are sound waves with frequencies higher than what humans can hear (20,000 Hz or more).
- Animals such as whales and bats, however, can detect these higher frequency sounds.
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20. What is the audible range (hearing range) of humans?
(a) 20 Hz – 20000 Hz
(b) 80 Hz – 100 Hz
(c) 2 lac Hz – 4 lac Hz
(d) 0 Hz – 20 Hz
[M.P. P.C.S. (Pre) 2018]
Ans. (a) 20 Hz – 20000 Hz
- Human ears can hear sounds in the range of 20 Hz to 20,000 Hz.
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21. A biotechnique in which ultrasonic sound is used-
(a) Sonography
(b) E. C. G.
(c) E. E. G.
(d) X-ray
[R.A.S./R.T.S.(Pre) 2012]
Ans. (a) Sonography
- Sonography, also known as ultrasonography, is an important tool used by doctors to diagnose illnesses.
- It works by using ultrasound to get an image of what’s going on inside the body.
- It’s very useful in medical science, especially when it comes to monitoring the health of a pregnant woman and her baby.
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22. Bats can fly during dark nights and also prey. This is because –
(a) The pupil of their eyes is large.
(b) Their night vision is very good.
(c) Every bird can do this.
(d) They produce ultrasonic waves and are guided by them.
[U.P.P.C.S. (Mains) 2005]
Ans. (d) They produce ultrasonic waves and are guided by them
- Bats are an amazing group of animals that have the ability to use sound waves to find their way around.
- They make loud high-pitched noises as they fly, and the echoes that come back tell them about what’s ahead, like the speed and size of an insect, and which direction it’s moving.
- This special way of detecting their prey is called echolocation.
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23. Consider the following statements :
1. The heart vibrates at infrasonic.
2. The speed of sound is more in gas than in liquid and solid.
3. Mach number is used to describe the speed of sound.
4. Ultrasonic sound has a frequency of more than 20,000 Hz.
Of these statements –
(a) 1, 2 and 3 are correct
(b) 2, 3 and 4 are correct
(c) 1, 3 and 4 are correct
(d) 1, 2 and 4 are correct
[U.P.P.C.S. (Mains) 2002]
Ans. (c) 1, 3 and 4 are correct
- The heart makes low frequency sound that we can hear with a stethoscope.
- The speed of sound in solid is the fastest.
- The Mach number measures how quickly an object is going compared to the speed of sound.
- Sounds with a frequency higher than 20,000 Hz are called ultrasonic, so statements 1, 3 and 4 are true.
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24. In Stethoscope, the sound of the patient’s heartbeat reaches the doctor’s ears by :
(a) Multiple diffraction of sound
(b) Multiple reflections of sound
(c) Polarisation of sound
(d) Multiple refraction of sound
[R.A.S./ R.T.S. (Pre) 2021]
Ans. (b) Multiple reflections of sound
- A stethoscope works by using sound waves. When a doctor or nurse puts the diaphragm on a patient’s chest, the sound waves travel through the body and cause the diaphragm to vibrate.
- This vibration is sent through a tube and is reflected off the walls of the tube multiple times.
- The waves then travel to the ear pieces and finally reach the listener’s eardrums.
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25. Which one of the following is the effect of the fight of a supersonic jet?
(a) Air pollution
(b) Eye disease
(c) Depletion in the ozone layer
(d) None of these
[M.P. P.C.S. (Pre) 1993]
Ans. (c) Depletion in the ozone layer
- A jet engine is a device used to turn fuel into thrust.
- This thrust is created when the exhaust gases push backward, causing an equal and opposite force called thrust which moves the vehicle.
- Jet planes that can fly faster than the speed of sound are called supersonic jet planes.
- Unfortunately, jet engines are harmful to the environment, as they release nitrogen oxide at stratosphere heights, which can damage the ozone layer.
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26. Assertion (A): A jet aircraft moving at Mach number equal to 1 travels faster at an altitude of 15 km than while moving at Mach number equal to 1 near the sea level.
Reason (R): The velocity of sound depends on the temperature of the surrounding medium.
Codes :
(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
[I.A.S. (Pre) 2007]
Ans. (d) (A) is false, but (R) is true
- The speed of an airplane is measured by its Mach number.
- This is the ratio of the airplane’s speed compared to the speed of sound in the atmosphere.
- The speed of sound increases as the temperature increases.
- At higher altitudes (15 km above sea level), the temperature is lower, so the speed of sound decreases.
- Statement (1) is not true. The speed of a sound wave through air does not depend on air pressure but is determined by the temperature of the air. Therefore, reason (R) is correct.
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27. Decibel is used to measure –
(a) Hemoglobin in blood
(b) Sugar in urine
(c) Sound in the atmosphere
(d) Particles in the air
[M.P.P.C.S. (Pre) 2005]
Ans. (c) Sound in the atmosphere
- The decibel (dB) is used to measure how loud sound is in an environment.
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28. Consider the following statements:
1. A widely used musical scale called the diatonic scale has seven frequencies.
2. The frequency of the tone Sa is 256 Hz and that of Ni is 512 Hz.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
[I.A.S. (Pre) 2008]
Ans. (d) Neither 1 nor 2
- The diatonic scale is the most commonly used musical scale.
- It is made up of 8 notes, which have a 2:1 frequency ratio.
- This is why it is called an octave.
- The major diatonic scale is made up of notes with frequencies that have a ratio of 1, 9/8, 5/4, 4/3, 3/2, 5/3, 15/8 and 2, relative to a keynote.
- The notes are C, D, E, F, G, A, B and C1.
- The higher frequency C1 is known as the octave of the lower C.
- If the frequency of the first note (C) is set as 256 Hz, then the frequency of the note Ni is 480 Hz, and the octave C1 is 512 Hz. This disproves both of the given statements.
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29. A decibel unit is used to measure the –
(a) Speed of light
(b) Intensity of heat
(c) Intensity of sound
(d) Radioactive frequency
[Uttarakhand Lower Sub. (Pre) 2010]
Ans. (c) Intensity of sound
- In other words, decibel is what is used to figure out how loud a sound is.
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30. What is the decibel level of sound produced by two persons in conversation?
(a) About 5 Decibel
(b) About 10 Decibel
(c) About 30 Decibel
(d) About 100 Decibel
[R.A.S./R.T.S.(Pre) 2003]
Ans. (c) About 30 Decibel
- The intensity of sound is measured in decibels.
| Source of sound |
Intensity (In decibels) |
| Whisper |
15-20 |
| Normal Conversation |
30-60 |
| Anger Conversation |
70-80 |
| Truck Motorcycle |
90-95 |
| Instrument factory |
100-110 |
| Jet Plane |
140-150 |
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31. A noise level of 100 decibels would correspond to :
(a) Just audible sound
(b) Ordinary conversation
(c) Sound from a noisy street
(d) Noise from a machine shop
[I.A.S. (Pre) 2000]
Ans. (d) Noise from a machine shop
- The sound of a machine shop is equal to 100 decibels (dB).
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32. Which of the following represents the decibel level of rustling of tree leaves in normal circumstances?
(a) 10 db
(b) 20 db
(c) 60 db
(d) 100 db
[U.P. P.C.S. (Pre) 2018]
Ans. (b) 20 db
- Under regular conditions, the sound of rustling tree leaves is usually around 20 decibels.
- A decibel is one tenth of a bel which is a unit of sound intensity that is named after Alexander Graham Bell.
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33. As per the WHO, the safe noise level for a city is –
(a) 45 db
(b) 50 db
(c) 55 db
(d) 60 db
[U.P.P.C.S. (Mains) 2010]
Ans. (a) 45 db
- The World Health Organization (WHO) states that the maximum sound level for cities should be 45 decibels (db).
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34. The tolerable limit of noise for human being is around-
(a) 45 decibel
(b) 85 decibel
(c) 125 decibel
(d) 155 decibel
[R.A.S./R.T.S. (Pre) 1993]
Ans. (b) 85 decibel
- Normal conversation is usually between 30-60 decibels, which is enough to wake someone up from sleep.
- It is not safe to be in a place where the sound is constantly at 80 decibels, and 90 decibels is the highest sound level humans can tolerate.
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35. Sound above what level (in decibels) is considered hazardous noise pollution?
(a) 30 db
(b) 100 db
(c) 80 db
(d) 120 db
[U.P.P.C.S.(Pre) 2013, U.P.P.C.S. (Mains) 2008]
Ans. (c) 80 db
- Noise that is louder than 80 decibels is dangerous.
- If someone is exposed to this kind of loud noise over a long period of time, it can lead to tiredness, hearing problems, or even complete hearing loss, as well as changes in blood flow and breathing.
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36. Which one of the following units is used for the measurement of noise pollution?
(a) Nanometer
(b) Decibel
(c) Hertz
(d) None of the above
[U.P. P.C.S. (Mains) 2017]
Ans. (b) Decibel
- Noise pollution is measured in decibels (dB). Decibels are a logarithmic unit that measure sound level.
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37. The optimum sound level for human beings is-
(a) 90 db
(b) 60 db
(c) 120 db
(d) 100db
[R.A.S./R.T.S.(Pre) 2012]
Ans. (b) 60 db
- In a normal conversation, the sound level is usually around 60 decibels, which is safe for our ears.
- But if the sound is louder than 80 decibels, it can damage our ear cells.
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38. Loudness of sound is measured in terms of the following :
(a) Frequency
(b) Amplitude
(c) Velocity
(d) Wavelength
[U.P. R.O./A.R.O. (Mains) 2017]
Ans. (b) Amplitude
- When a sound wave passes by, it causes a change in pressure which is the amplitude.
- If the amplitude is decreased, the sound becomes softer.
- The amount of energy a sound wave carries is related to its amplitude; a sound wave with a high amplitude carries a lot of energy while a low amplitude wave carries very little.
- The amount of energy that passes through a unit area in a certain amount of time is called the intensity, and when the amplitude of the sound wave increases, so does the intensity.
- Sounds with higher intensity are perceived to be louder, and the intensity of sound is often measured in decibels (dB).
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39. A worker was working on the rail track. A boy at a distance holds his ear near the rail track. This boy was able to hear the sound of the blow of a workman twice. It is because of :
(a) The speed of sound is greater in steel than in air.
(b) The speed of sound is greater in air than in steel.
(c) Part of the sound wave is reflected between the rail tracks.
(d) His ears are at different distance from the source.
[R.A.S./R.T.S. (Pre) 1994-95]
Ans. (a) The speed of sound is greater in steel than in air
- Sound travels faster through steel than it does through air, so the boy hears the sound twice – first through the rail track and then through the air.
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40. Which of the following statements is/are true in relation to sound waves?
Statement I: The speed of sound decreases when we go from a solid to a gaseous state
Statement II: In any medium as we decrease the temperature, the speed of sound increases
Statement III: The speed of sound is less in the aluminum medium than in glass medium
(a) Statement I, II and III all are true.
(b) Only Statement I and II are true.
(c) Only Statement I is true.
(d) Only Statement II and III are true.
[Chhattisgarh P.C.S. (Pre) 2020]
Ans. (c) Only Statement I is true
- The speed of sound changes depending on the type of material it moves through.
- It goes the fastest through solids and slowest through gases.
- It goes slower through glass than through aluminum.
- The speed of sound increases when the temperature goes up. So, only the first statement is correct.
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41. When a sound wave goes from one medium to another, the quantity that remains unchanged is :
(a) Frequency
(b) Amplitude
(c) Wavelength
(d) Speed
(e) None of the above/More than one of the above
[66th B.P.S.C. (Pre) (Re. Exam) 2020]
Ans. (a) Frequency
- When sound moves from one material to another, its pitch usually stays the same, but its speed and how long it is (wavelength) change.
- The loudness of the sound also gets softer as it gets farther away from where it started.
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42. When the same tone 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
[I.A.S. (Pre) 1995]
Ans. (c) quality only
- Musical sounds can differ from each other with respect to the following three characteristics :
- Loudness (intensity)
- Pitch (shrillness)
- quality (timber)
- Quality of sound is what makes it possible to tell one sound apart from another, even if they have the same pitch and volume.
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43. The basic units of sound are called
(a) Morphemes
(b) Phonemes
(c) Semanteme
(d) Syntax
[U.P. P.C.S. (Mains) 2017]
Ans. (b) Phonemes
- Phonemes are the smallest parts of sound used in language.
- Even though they don’t have any meaning by themselves, they can change the meaning of a word if they are changed.
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44. Assertion (A): Reverberation mainly feels in large churches and in other large buildings.
Reason (R): The walls, roof, and ground may cause multiple sound reflections.
Code :
(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
[U.P. Lower Sub. (Spl) (Pre) 2003, U.P. Lower Sub. (Spl) (Pre) 2002]
Ans. (a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
- Reverberation is caused by multiple sound reflections.
- In large enclosed spaces like churches or big buildings, sound will bounce off of the walls and be broken up.
- Reverberation is the effect of multiple fast echoes being heard as separate sounds.
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45. A Decibel unit is used to measure –
(a) Light intensity
(b) Sound intensity
(c) Magnitude of Earthquake
(d) None of the above
[U.P.P.C.S. (Mains) 2011]
Ans. (b) Sound intensity
- Decibels (dB) are a unit used to measure how loud a sound is.
- They can also be used to measure electronic signals and communication.
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46. When T.V. is switched on :
(a) Audio and video both start simultaneously
(b) Audio is heard immediately but video starts later because video needs some warm up time
(c) Video starts immediately but audio is heard later because sound travels at a lesser speed than light
(d) It depends on the T.V. brand
[U.P.P.C.S. (Pre) 2007]
Ans. (a) Audio and video both start simultaneously
- When you turn on your TV, you can hear sound and see a picture at the same time.
- In older TVs, you would hear the sound right away but there was a delay with the picture as it needed time to warm up.
- Newer TVs have something called an audio synchronizer which fixes this issue.
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47. In television broadcasts, the picture signals are transmitted by –
(a) Amplitude modulation
(b) Frequency modulation
(c) Phase modulation
(d) Angle modulation
[R.A.S./R.T.S.(Pre) 2012]
Ans. (a) Amplitude modulation
- On TV, the visuals are sent using a method called amplitude modulation and the sound is sent using frequency modulation.
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48. The technique used to transmit audio signals in television broadcasts is –
(a) Amplitude modulation
(b) Pulse code modulation
(c) Frequency modulation
(d) Time dimension multiplication.
[U.P. U.D.A./L.D.A. (Spl) (Pre) 2010]
Ans. (c) Frequency modulation
- In Analog TV broadcasts, sound signals are sent out using Frequency Modulation and video signals are sent out using Amplitude Modulation.
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