 # MCQs in Acoustics Part I

(Last Updated On: December 8, 2017) 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

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

### MCQs in Acoustics Series

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

Acoustics MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III

### Start Practice Exam Test Questions Part I 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

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

• a. Noy
• b. Sone
• c. dB
• d. phone

3. An agreed set of empirical curves relating octave-band osund 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

4. The frequency of free vibration

• a. Resonant frequency
• b. Natural frequency
• c. Center frequency
• d. Normal frequency

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

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

• a. Hearing loss
• b. Sensation level
• c. Hearing level
• d. Sound pressure level

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

8. Calculate the lowest resonant frequency for a brick partition 120 mm thick, 4m by 2min 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

9. Velocity of sound in air.

• a. 300 m/s
• b. 330 m/s
• c. 1130 m/s
• d. 344 m/s

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

11. The sound power level of a certain jet plane flying at a height of 1km is 160 dB (re10-12W). 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

12. Speaker is a device that

• a. Converts sound waves into current and voltage
• b. Converts current variations into sound waves
• c. Converts elctrical energy to mechanical energy
• d. Converts elctrical energy to electromagnetic energy

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

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

15. Pure tone of sound used as standard on testing

• a. 1 Hz
• b. 10 Hz
• c. 100 Hz
• d. 1000 Hz

16. ___________ is early reflection of sound.

• a. Echo
• b. Reverberation
• c. Pure sound
• d. Intelligible sound

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

• a. Dolby
• b. dBa
• c. dBx
• d. dBk

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

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

• a. Sone
• b. Decibel
• c. Mel
• d. Phon

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

21. What is the unit of pitch?

• a. Sone
• b. Phon
• c. Decibel
• d. Mel

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

• a. Phon
• b. Decibel
• c. Pascal
• d. Watts

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

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

• a. Carbon
• b. Dynamic
• c. Crystal
• d. Condenser

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

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

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

28. A church has an internal volume of 90.05 ft3 (2550 m3). 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

29. If the RMs sound pressure is 5lb/ft2, what is the sound presure level?

• a. 7.6 dB
• b. 108 dB
• c. 88 dB
• d. 10 dB

30. Speed that is faster than speed of sound.

• a. Ultrasonic
• b. Supersonic
• c. Subsonic
• d. Transonic

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

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 unifomly?

• a. 0.15 W
• b. 0.21 W
• c. 0.24 W
• d. 0.18 W

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

• a. Compression
• b. Wavelength
• c. Period
• d. Sound wave

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

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

36. The most important specification of loudspeakers and microphones.

• a. Frequency response
• b. Field strength
• c. Power density
• d. Gain

37. Lowest fequency produced by a musical instrument.

• a. Midrange
• b. Harmonic
• c. Reflection
• d. Refraction

38. Tendency of a sound energy to spread.

• a. Diffraction
• b. Rarefraction
• c. Reflection
• d. Refraction

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

• a. Reflection
• b. Diffraction
• c. Rarefraction
• d. Refraction

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

• a. Echo time
• b. Delay time
• c. Reverberation time
• d. Transient time

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

• a. Frequency
• b. Noise
• c. Amplitude
• d. Tone

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

• a. Subsonic
• b. Transonic
• c. Ultrasonic
• d. Stereo

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

• a. Dynamic
• b. Crystal
• c. Ribbon
• d. Capacitor

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

• a. Vibrator
• b. Diaphragm
• c. Hypex
• d. Spider

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

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

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

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

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

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

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

MCQs in Acoustics Part I
5 (100%) 1 vote

#### One Response

1. John Arman Arcaya