# MCQ in Acoustics Part 1 | ECE Board Exam

(Last Updated On: June 20, 2020) This is the Multiples Choice Questions Part 1 of the Series in Acoustics as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

#### Online Questions and Answers Topic Outline

• MCQ in Acoustics Terms and Definition
• MCQ in Frequency Range
• MCQ in Sound Pressure Level
• MCQ in Sound Intensity
• MCQ in Loudness Level
• MCQ in Pitch and Frequency
• MCQ in Internal and Octave
• MCQ in Sound Distortion
• MCQ in Room Acoustics
• MCQ in Electro-Acoustics Transducers
Watch Audio MCQ in Acoustics

#### Start Practice Exam Test Questions Part 1 of the Series

1. An instrument designed to measure a frequency-weighted value of the sound pressure level.

a. Sound-level meter

b. Transducer

c. Sound pressure meter

d. Sound analyzer

Solution:

2. A unit of noisiness related to the perceived noise level

a. Noy

b. Sone

c. dB

d. phone

Solution:

3. An agreed set of empirical curves relating octave-band sound pressure level to the center frequency of the octave bands

a. C-message weighting curves

b. Psophometric weighting curves

c. Noise rating curves

d. F1A weighting curves

Solution:

4. The frequency of free vibration

a. Resonant frequency

b. Natural frequency

c. Center frequency

d. Normal frequency

Solution:

5. The transmission of sound from one room to an adjacent room, via common walls, floors or ceilings.

a. Flanking transmission

b. Refraction

c. Reflection

d. Reverberation

Solution:

6. A measure of threshold hearing, expressed in decibels relative to a specified standard of normal hearing.

a. Hearing loss

b. Sensation level

c. Hearing level

d. Sound pressure level

Solution:

7. A certain machine with a slightly out-of-balance motor rotating at 1800/min is fixed on a perfectly elastic mount with a static compression of 2.50 mm. Calculate the resonant frequency of mount.

a. 10 Hz

b. 20 Hz

c. 30 Hz

d. 40 Hz

Solution:

8. Calculate the lowest resonant frequency for a brick partition 120 mm thick, 4 m by 2 m in area with longitudinal wave velocity of 2350 m/s. (Assume that it is supported at its edges.)

a. 10 Hz

b. 20 Hz

c. 30 Hz

d. 40 Hz

Solution:

9. Velocity of sound in air.

a. 300 m/s

b. 330 m/s

c. 1130 m/s

d. 344 m/s

Solution:

10. What is the expected critical frequency for a 120 mm thick brick wall? Assume a longitudinal wave velocity in brick of 2350 m/s and that the velocity of sound in air is 330 m/s.

a. 114.5 Hz

b. 214.5 Hz

c. 314.5 Hz

d. 414.5 Hz

Solution:

11. The sound power level of a certain jet plane flying at a height of 1km is 160 dB (re10^-12 W). Find the maximum sound pressure level on the ground directly below the flight path assuming that the aircraft radiates sound equally in all directions.

a. 59.1 dB

b. 69.1 dB

c. 79.1 dB

d. 89.1 dB

Solution:

12. Speaker is a device that

a. Converts sound waves into current and voltage

b. Converts current variations into sound waves

c. Converts electrical energy to mechanical energy

d. Converts electrical energy to electromagnetic energy

Solution:

13. Which type of microphone operates on the principle that the electrical resistance of carbon granules varies as the pressure on the granules vary?

a. Dynamic

b. Crystal

c. Carbon

d. Ribbon-type

Solution:

14. Bass response is

a. Maximum high frequency response

b. Emphasizing the high audio frequency

c. Bypassing high audio frequencies

d. Bypassing low audio frequencies

Solution:

15. Pure tone of sound used as standard on testing

a. 1 Hz

b. 10 Hz

c. 100 Hz

d. 1000 Hz

Solution:

16. ___________ is early reflection of sound.

a. Echo

b. Reverberation

c. Pure sound

d. Intelligible sound

Solution:

17. Noise reduction system used for film sound in movie.

a. Dolby

b. dBa

c. dBx

d. dBk

Solution:

18. What is the sound energy per unit area at right angles to the propagation direction per unit time?

a. Loudness

b. Coherence

c. Sound pressure

d. Sound intensity

Solution:

19. ________ is the unit of loudness level of a sound.

a. Sone

b. Decibel

c. Mel

d. Phon

Solution:

20. ____________ is the average rate of transmission of sound energy in a given direction through a cross-section area of 1 sqm at right angles to the direction.

a. Sound pressure

b. Loudness

c. Sound intensity

d. Pressure variation

Solution:

21. What is the unit of pitch?

a. Sone

b. Phon

c. Decibel

d. Mel

Solution:

22. A measure of the intensity of sound in comparison to another sound intensity.

a. Phon

b. Decibel

c. Pascal

d. Watts

Solution:

23. Sound wave has two main characteristics which are

a. Highness and loudness

b. Tone and loudness

c. Pitch and loudness

d. Rarefraction and compression

Solution:

24. Which type of microphone operated by electromagnetic induction that generates an output signal voltage?

a. Carbon

b. Dynamic

c. Crystal

d. Condenser

Solution:

25. The exciter lamp in the optical sound part of a film projector draws 5 A at 10 V. How much power in watts is this light consuming?

a. 10 watts

b. 20 watts

c. 40 watts

d. 50 watts

Solution:

26. Assume the speed of sound is 1,130 ft/s. What frequency has a wavelength of 1 foot, 1.5 inches?

a. 500 Hz

b. 1000 Hz

c. 1500 Hz

d. 2000 Hz

Solution:

27. The wire must bring 100 average watts to a 4 ohms loudspeaker must safely carry what rms current?

a. 2 A

b. 4 A

c. 5 A

d. 6 A

Solution:

28. A church has an internal volume of 90.05 ft^3 (2550 m^3). When it contains customary sabine sof absorption (186 metric sabines), what will be its reverberation time in seconds.

a. 2.0

b. 2.2

c. 2.5

d. 3.0

Solution:

29. If the RMs sound pressure is 5 lb/ft^2, what is the sound pressure level?

a. 7.6 dB

b. 108 dB

c. 88 dB

d. 10 dB

Solution:

30. Speed that is faster than speed of sound.

a. Ultrasonic

b. Supersonic

c. Subsonic

d. Transonic

Solution:

31. Sound waves travel faster in water at a ______ speed.

a. 12.4 miles/sec

b. 5000 ft/sec

c. 186,000 ft/sec

d. 3141 ft/sec

Solution:

32. What is the sound power from a motor car whose SPL at a distance of 7.5 m is 87 dB assuming that it radiates sound uniformly?

a. 0.15 W

b. 0.21 W

c. 0.24 W

d. 0.18 W

Solution:

33. Crest-to-crest distance along the direction to wave travel.

a. Compression

b. Wavelength

c. Period

d. Sound wave

Solution:

34. Sound intensity level is _________.

a. 10 log I/Iref

b. 10 log P/Pref

c. 20 log I/Iref

d. 30 log P/Pref

Solution:

35. Sound pressure level is _________.

a. 20 log P/Pref

b. 30 log P/Pref

c. 10 log P/Pref

d. 20 log I/Iref

Solution:

36. The most important specification of loudspeakers and microphones.

a. Frequency response

b. Field strength

c. Power density

d. Gain

Solution:

37. Lowest fequency produced by a musical instrument.

a. Midrange

b. Harmonic

c. Reflection

d. Refraction

Solution:

38. Tendency of a sound energy to spread.

a. Diffraction

b. Rarefraction

c. Reflection

d. Refraction

Solution:

39. When waves bend away from straight lines of travel, it is called _________.

a. Reflection

b. Diffraction

c. Rarefraction

d. Refraction

Solution:

40. Required time for any sound to decay to 60 dB.

a. Echo time

b. Delay time

c. Reverberation time

d. Transient time

Solution:

41. The intensity needed to produce an audible sound varies with __________.

a. Frequency

b. Noise

c. Amplitude

d. Tone

Solution:

42. Sound that vibrates too high for the human ear to hear (over 20 kHz).

a. Subsonic

b. Transonic

c. Ultrasonic

d. Stereo

Solution:

43. Which microphone will be damaged if exposed to high temperature above 52°C?

a. Dynamic

b. Crystal

c. Ribbon

d. Capacitor

Solution:

44. A thin springy sheet of bakelite or metal that permits the voice coil in a dynamic loudspeaker to move back and forth along the core of its magnet.

a. Vibrator

b. Diaphragm

c. Hypex

d. Spider

Solution:

45. One hundred twenty µbars of pressure variation is equal to

a. 120 dB SPL

b. 57.78 dB SPL

c. 115.56 dB SPL

d. 41.58 dB SPL

Solution:

46. The reverberation time of a 184.2 cubic meters broadcast studio is 0.84 sec. Find the absorption effect of the materials used in metric sabines.

a. 35.3

b. 10.96

c. 379.8

d. 109.6

Solution:

47. What is the microphone characteristic that results in a boost in bass frequencies for close microphone spacing?

a. Field effect

b. P.A. effect

c. Proximity effect

d. Reverberation

Solution:

48. What is the audio frequency range?

a. 20 kHz to 20 MHz

b. 0 Hz to 20 kHz

c. 300 Hz to 400 Hz

d. 20 Hz to 20 kHz

Solution:

49. What is the bass frequency range?

a. 2500 Hz to 5000 Hz

b. 5000 Hz to 10 kHz

c. 40 kHz to 160 kHz

d. 10 Hz to 20 kHz

Solution:

50. High frequency range of audio signals.

a. 2500 Hz to 5000 Hz

b. 5000 Hz to 10 kHz

c. 10 kHz to 20 kHz

d. 20000 Hz to 30 kHz

Solution:

#### Questions and Answers in Acoustics Series

Following is the list of multiple choice questions in this brand new series:

MCQ in Acoustics
PART 1: MCQ from Number 1 – 50                        Answer key: PART 1
PART 2: MCQ from Number 51 – 100                   Answer key: PART 2
PART 3: MCQ from Number 101 – 150                 Answer key: PART 3
PART 4: MCQ from Number 151 – 200                 Answer key: included

### Complete List of MCQ in Communications Engineering per topic

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