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# MCQ in Acoustics Part 4 | ECE Board Exam

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

• 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

#### 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

Solution:

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

A. Electromagnetic wave

C. Sound wave

D. Light wave

Solution:

153. Through which medium does sound travel fastest?

a. Air

b. Water

c. Steel

d. Mercury

Solution:

154. Speed that is faster than that of sound.

A. Ultrasonic

B. Supersonic

C. Subsonic

D. Transonic

Solution:

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

A. 1087 ft/s

B. 1100 ft/s

C. 1126 ft/s

D. 200 ft/s

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

Solution:

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

A. 5 Hz

B. 20 Hz

C. 30 Hz

D. 20 Hz

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

Solution:

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

A. Octave

B. Half octave

C. Third-octave

Solution:

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

A. 2

B. 5

C. 4

D. 8

Solution:

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

A. Infra sound

B. Pure tone

C. Structure borne

D. Residual sound

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

Solution:

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

A. Reflection

B. Diffraction

C. Rarefaction

D. Refraction

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

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

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

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

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

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

Solution:

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

A. Microphone

B. Pistonphone

C. Telephone

D. Filter

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

Solution:

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

A. Phon

B. Decibel

C. Pascal

D. Watts

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

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

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

Solution:

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

A. 3

B. 4

C. 5

D. 6

Solution:

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

A. 3

B. 4

C. 5

D. 6

Solution:

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

A. 3

B. 4

C. 5

D. 6

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

Solution:

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

A. Flutter echo

B. Sound concentration

D. Reverberation

Solution:

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

A. Echo time

B. Reverberation time

C. Delay time

D. Transient time

Solution:

182. A room containing relatively little sound absorption

B. Anechoic room

C. Live room

D. Free-field

Solution:

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

B. Anechoic room

C. Live room

D. Closed room

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

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

Solution:

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

A. Dynamic

B. Condenser

C. Magnetic

D. Carbon

Solution:

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

A. High impedance

B. Low impedance

C. Dynamic

D. Magnetic

Solution:

188. A microphone that uses the piezoelectric effect

A. Dynamic

B. Condenser

C. Crystal

D. Carbon

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

Solution:

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

A. Sensitivity

B. Distortion

C. Efficiency

D. Frequency response

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

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

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

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

Solution:

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

A. 4

B. 6

C. 8

D. 10

Solution:

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

A. Microphone

B. Baffle

C. Magnetic assemble

D. Driver

Solution:

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

A. Loudspeaker

B. Driver

C. Baffle

D. Frame

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

Solution:

199. _________ is early reflection of sound.

A. Echo

B. Pure sound

C. Reverberation

D. Intelligible sound

Solution:

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

A. Dolby

B. DBx

C. dBa

D. dBk

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

Solution:

202. What is the unit of loudness?

A. Sone

B. Phon

C. Decibel

D. Mel

Solution:

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

A. Noy

B. dB

C. Sone

D. Phon

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

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 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: included

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

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