 # MCQ in Acoustics Part 4 | ECE Board Exam

(Last Updated On: October 12, 2018) This is the Multiples Choice Questions Part 4 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.

### MCQ Topic Outline included in ECE Board Exam Syllabi

• 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

### Continue Practice Exam Test Questions Part 4 of the Series

Choose the letter of the best answer in each questions.

151. Which best describe the sound wave?

A. It may be longitudinal

B. It is always transverse

C. It is always longitudinal

D. All of the above

View Answer:

Answer: Option C

Solution:

152. Which of the following can not travel through a vacuum?

A. Electromagnetic wave

B. Radio wave

C. Sound wave

D. Light wave

View Answer:

Answer: Option C

Solution:

153. Through which medium does sound travel fastest?

a. Air

b. Water

c. Steel

d. Mercury

View Answer:

Answer: Option C

Solution:

154. Speed that is faster than that of sound.

A. Ultrasonic

B. Supersonic

C. Subsonic

D. Transonic

View Answer:

Answer: Option B

Solution:

155. What is the speed of sound in air at 20°C?

A. 1087 ft/s

B. 1100 ft/s

C. 1126 ft/s

D. 200 ft/s

View Answer:

Answer: Option A

Solution:

156. Calculate a half wavelength sound for sound of 16000 Hz

A. 35 ft

B 10 ft

C. 0.035 ft

D. 100 ft

View Answer:

Answer: Option C

Solution:

157. The lowest frequency that a human ear can hear is

A. 5 Hz

B. 20 Hz

C. 30 Hz

D. 20 Hz

View Answer:

Answer: Option B

Solution:

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

A. Subsonic

B. Ultrasonic

C. Transonic

D. Stereo

View Answer:

Answer: Option B

Solution:

159. The frequency interval between two sounds whose frequency ratio is 10.

A. Octave

B. Half octave

C. Third-octave

D. Decade

View Answer:

Answer: Option A

Solution:

160. A 16 KHz sound is how many octaves higher than a 500 Hz sound

A. 2

B. 5

C. 4

D. 8

View Answer:

Answer: Option B

Solution:

161. Sound waves composed of but one frequency is a/an

A. Infra sound

B. Pure tone

C. Structure borne

D. Residual sound

View Answer:

Answer: Option B

Solution:

162. Sound wave has two main characteristics which are

A. Highness and loudness

B. Tone and loudness

C. Pitch and loudness

D. Rarefaction and compression

View Answer:

Answer: Option C

Solution:

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

A. Reflection

B. Diffraction

C. Rarefaction

D. Refraction

View Answer:

Answer: Option D

Solution:

164. The amplitude of sound waves, the maximum displacement of each air particle, is the property which perceive as _______ of a sound

A. Pitch

B. Intensity

C. Loudness

D. Harmonics

View Answer:

Answer: Option C

Solution:

165. It is the weakest sound that average human hearing can detect.

A. SPL = 0 dB

B. Threshold of hearing

C. Reference pressure = 2 x 10^-5 N/m2

D. All of these

View Answer:

Answer: Option D

Solution:

166. What is a device that is used to measure the hearing sensitivity of a person?

A. Audiometer

B. OTDR

C. SLM

D. Spectrum analyzer

View Answer:

Answer: Option A

Solution:

167. What is the device used in measuring sound pressure levels incorporating a microphone, amplification, filtering and a display.

A. Audiometer

B. OTDR

C. SLM

D. Spectrum analyzer

View Answer:

Answer: Option C

Solution:

168. What weighted scale in a sound level meter gives a reading that is most closely to the response of the human ear?

A. Weighted scale A

B. Weighted scale B

C. Weighted scale C

D. Weighted scale D

View Answer:

Answer: Option A

Solution:

169. For aircraft noise measurements, the weighting scale that is used is ________.

A. Weighted scale A

B. Weighted scale B

C. Weighted scale C

D. Weighted scale D

View Answer:

Answer: Option D

Solution:

170. It is the device used to calibrate an SLM?

A. Microphone

B. Pistonphone

C. Telephone

D. Filter

View Answer:

Answer: Option B

Solution:

171. _________ is the sound power measured over the area upon which is received.

A. Sound pressure

B. Sound energy

D. Sound intensity

D. Sound pressure level

View Answer:

Answer: Option C

Solution:

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

A. Phon

B. Decibel

C. Pascal

D. Watts

View Answer:

Answer: Option B

Solution:

173. Calculate the sound intensity level in dB of a sound whose intensity is 0.007 W/m^2.

A. 95 dB

B. 91 dB

C. 98 dB

D. 101 dB

View Answer:

Answer: Option C

Solution:

174. What is the sound pressure level for a given sound whose RMS pressure is 200/m^2?

A. 200 dB

B. 20 dB

C. 140 dB

D. 14 dB

View Answer:

Answer: Option C

Solution:

175. What is the sound intensity for an RMS pressure of 200 Pascal?

A. 90 W/m^2

B. 98 W/m^2

C. 108 W/m^2

D. 88 W/m^2

View Answer:

Answer: Option B

Solution:

176. The sound pressure level is increased by _________ dB if the pressure is doubled.

A. 3

B. 4

C. 5

D. 6

View Answer:

Answer: Option D

Solution:

177. The sound pressure level is increased by _________ dB if the intensity is doubled.

A. 3

B. 4

C. 5

D. 6

View Answer:

Answer: Option A

Solution:

178. If four identical sounds are added what is the increase in level in dB?

A. 3

B. 4

C. 5

D. 6

View Answer:

Answer: Option D

Solution:

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

A. Flanking transmission

B. Reflection

C. Refraction

D. Reverberation

View Answer:

Answer: Option A

Solution:

180. __________ is the continuing presence of an audible sound after the sound source has stop.

A. Flutter echo

B. Sound concentration

C. Sound shadow

D. Reverberation

View Answer:

Answer: Option D

Solution:

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

A. Echo time

B. Reverberation time

C. Delay time

D. Transient time

View Answer:

Answer: Option B

Solution:

182. A room containing relatively little sound absorption

A. Dead room

B. Anechoic room

C. Live room

D. Free-field

View Answer:

Answer: Option C

Solution:

183. A room in which the walls offer essentially 100% absorption, therefore simulating free field conditions.

A. Dead room

B. Anechoic room

C. Live room

D. Closed room

View Answer:

Answer: Option B

Solution:

184. Calculate the reverberation time of the room, which has a volume of 8700 ft^3 and total sound absorption 140 sabins.

A. 0.3 sec

B. 3.5 sec

C. 3 sec

D. 0.53 sec

View Answer:

Answer: Option C

Solution:

185. It is an audio transducer that converts acoustic pressure in air into its equivalent electrical impulses

A. Loudspeaker

B. Amplifier

C. Baffle

D. Microphone

View Answer:

Answer: Option D

Solution:

186. _________ is a pressure type microphone with permanent coil as a transducing element.

A. Dynamic

B. Condenser

C. Magnetic

D. Carbon

View Answer:

Answer: Option A

Solution:

187. A microphone which has an internal impedance of 25 kΩ is _________ type.

A. High impedance

B. Low impedance

C. Dynamic

D. Magnetic

View Answer:

Answer: Option A

Solution:

188. A microphone that uses the piezoelectric effect

A. Dynamic

B. Condenser

C. Crystal

D. Carbon

View Answer:

Answer: Option C

Solution:

189. _________ is a type of loudspeaker driver with an effective diameter of 5 inches used at mid-range audio frequency.

A. Tweeter

B. Woofer

C. Mid-range

D. A or C

View Answer:

Answer: Option C

Solution:

190. _____ is measure of how much sound is produced from the electrical signal.

A. Sensitivity

B. Distortion

C. Efficiency

D. Frequency response

View Answer:

Answer: Option C

Solution:

191. It describes the output of a microphone over a range of frequencies.

A. Directivity

B. Sensitivity

C. Frequency response

D. All of the above

View Answer:

Answer: Option C

Solution:

192. A loudspeaker radiates an acoustic power of 1 mW if the electrical input is 10 W. What is its rated efficiency?

A. -10 dB

B. -20 dB

C. -30 dB

D. -40 dB

View Answer:

Answer: Option D

Solution:

193. An amplifier can deliver 100 W to a loudspeaker. If the rated efficiency of the loudspeaker is -60 dB. What is the maximum intensity 300 ft from it?

A. 10 dB

B. 20 dB

C. 30 dB

D. 40 dB

View Answer:

Answer: Option C

Solution:

194. 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

View Answer:

Answer: Option B

Solution:

195. The impedance of most drivers is about __________ ohms at their resonant frequency.

A. 4

B. 6

C. 8

D. 10

View Answer:

Answer: Option C

Solution:

196. It is a transducer used to convert electrical energy to mechanical energy.

A. Microphone

B. Baffle

C. Magnetic assemble

D. Driver

View Answer:

Answer: Option D

Solution:

197. It is an enclosure used to prevent front and back wave cancellation.

A. Loudspeaker

B. Driver

C. Baffle

D. Frame

View Answer:

Answer: Option C

Solution:

198. A circuit that divides the frequency components into separate bands in order to have individual feeds to the different drivers.

A. Suspension system

B. Dividing network

C. Magnet assembly

D. Panel board

View Answer:

Answer: Option B

Solution:

199. _________ is early reflection of sound.

A. Echo

B. Pure sound

C. Reverberation

D. Intelligible sound

View Answer:

Answer: Option A

Solution:

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

A. Dolby

B. DBx

C. dBa

D. dBk

View Answer:

Answer: Option A

Solution:

201. Using a microphone at less than the recommended working distance will create a __________ which greatly increases the low frequency signals.

A. Roll-off

B. Proximity effect

C. Drop out

D. None of the choices

View Answer:

Answer: Option B

Solution:

202. What is the unit of loudness?

A. Sone

B. Phon

C. Decibel

D. Mel

View Answer:

Answer: Option A

Solution:

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

A. Noy

B. dB

C. Sone

D. Phon

View Answer:

Answer: Option A

Solution:

204. What is the loudness level of a 1KHz tone if its intensity is 1 x 10-5W/cm2?

A. 100 phons

B. 105 phons

C. 110 phons

D. 100 phons

View Answer:

Answer: Option C

Solution:

### Questions and Answers 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

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

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