ACOUSTICS

1. An instrument for recording waveforms of audio

frequency

PHONOSCOPE

2. Designates the sensation of low or high in the sense of

the base and treble.

PITCH

7.The sound energy per unit area at right angles to the

propagation direction per unit time.

Sound intensity

8.Speaker is a device that ___________

converts current variations into sound waves

9.One-hundred twenty µbars of pressure variation is equal

to

10.The term that describes the highness or lowness of a

sound in the study of acoustics is called a

Pitch

11.The method of measuring absorption coefficient of

sound which considers all angles of incidence is called

reverberation chamber method

12.The midrange frequency range of sound is from

256 to 2048 Hz

12.A large speaker having a large diameter (15 cm and

above).

Woofer

ECE Board Exam April 1997

_______ is the transmission of sound from one to an adjacent

room thru common walls, floors or ceilings.

Flanking transmission

___________ is the advantage rate of transmission of sound

energy in a given direction through a cross sectional area of

1 sq. m. at right angle to the direction.

Sound intensity

A method of expressing the amplitude of a complex non-

periodic signals such as speech.

Volume

The sound power level of a jet plane flying at a height of 1

km is 160 dB (re 10^-12). What is the maximum sound

pressure level on the ground directly below the plane

assuming that the aircraft radiates sound equally in all

directions?

The unit of pitch.

Mel

The tendency of the sound energy to spread.

Diffraction

Which of the following is considered the most commonly

used measurable components of sound?

Particle displacement

Lowest frequency produced by a musical instrument.

Fundamental

Sound intensity is given as

dP/dA

Tendency of sound energy to spread

Diffraction

The lowest frequency produced by an instrument.

Fundamental

A car horn outdoors produces a sound intensity level of 90

dB at 10 ft away. At distance, what is the sound power in

watt?

1. 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

2. Which of the following can not travel through a

vacuum?

a. Electromagnetic wave

b. Radio wave

c. Soundwave

d. Light wave

3. Through which medium does sound travel fastest?

a. Air

b. Water

c. Steel

d. Mercury

4. Speed that is faster than that of sound.

a. Ultrasonic

b. Supersonic

c. Subsonic

d. Transonic

5. 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

6. Calculate a half wavelength sound for sound of

16000 Hz

a. 35 ft

b. 10 ft

c. 0.035 ft

d. 100 ft

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

a. 5 Hz

b. 20 Hz

c. 30 Hz

d. 20 Hz

8. Sound that vibrates at frequency too high for the

human ear to hear (over 20 kHz)

a. Subsonic

b. Ultrasonic

c. Transonic

d. Stereo

9. The frequency interval between two sounds whose

frequency ratio is 10

a. Octave

b. Half octave

c. Third-octave

d. Decade

10. A 16 KHz sound is how many octaves higher than a

500 Hz sound

a. 2

b. 5

c. 4

d. 8

11. Sound waves composed of but one frequency is

a/an

a. Infra sound

b. Pure tone

c. Structure borne

d. Residual sound

12. Sound wave has two main characteristics which are

a. Highness and loudness

b. Tone and loudness

c. Pitch and loudness

d. Rarefactions and compressions

13. When waves bend away from straight lines of travel,

it is called

a. Reflection

b. Diffraction

c. Rarefaction

d. Refraction

14. 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

15. It is the weakest sound that average human hearing

can detect.

a. SPL = 0 dB

b. Threshold of hearing

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

d. A, b, c

16. What is a device that is used to measure the

hearing sensitivity of a person?

a. Audiometer

b. OTDR

c. SLM

d. Spectrum analyzer

17. 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

18. 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

19. 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

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

a. Microphone

b. Pistonphone

c. Telephone

d. Filter

21. _____ is the sound power measured over the area

upon which is received.

a. Sound pressure

b. Sound energy

c. Sound intensity

d. Sound pressure level

22. A measure of the intensity of sound in comparison

to another sound intensity

a. Phon

b. Decibel

c. Pascal

d. Watts

23. Calculate the sound intensity level in dB of a sound

whose intensity is 0.007 W/m2.

a. 95 dB

b. 91 dB

c. 98 dB

d. 101 dB

24. What is the sound pressure level for a given sound

whose RMS pressure is 200/m2?

a. 200 dB

b. 20 dB

c. 140 dB

d. 14 dB

25. What is the sound intensity for an RMS pressure of

200 Pascal?

a. 90 W/m2

b. 98 W/m2

c. 108 W/m2

d. 88 W/m2

26. The sound pressure level is increased by _____ dB if

the pressure is doubled.

a. 3

b. 4

c. 5

d. 6

27. The sound pressure level is increased by _____ dB if

the intensity is doubled.

a. 3

b. 4

c. 5

d. 6

28. If four identical sounds are added what is the

increase in level in dB?

a. 3

b. 4

c. 5

d. 6

29. 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

30. _____ 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

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

a. Echo time

b. Reverberation time

c. Delay time

d. Transient time

32. A room containing relatively little sound absorption

a. Dead room

b. Anechoic room

c. Live room

d. Free-field

33. 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

34. Calculate the reverberation time of the room, which

has a volume of 8700 ft3 and total sound absorption 140

sabins.

a. 0.3 sec

b. 3.5 sec

c. 3 sec

d. 0.53 sec

35. It is an audio transducer that converts acoustic

pressure in air into its equivalent electrical impulses

a. Loudspeaker

b. Amplifier

c. Baffle

d. Microphone

36. _____ is a pressure type microphone with permanent

coil as a transducing element.

a. Dynamic

b. Condenser

c. Magnetic

d. Carbon

37. A microphone which has an internal impedance of

25 kΩ is _____ type.

a. High impedance

b. Low impedance

c. Dynamic

d. Magnetic

38. A microphone that uses the piezoelectric effect

a. Dynamic

b. Condenser

c. Crystal

d. Carbon

39. _____ is a type of loudspeaker driver with an

effective diameter of 5 inches used at midrange audio

frequency.

a. Tweeter

b. Woofer

c. Mid-range

d. A or C

40. _____ is measure of how much sound is produced

from the electrical signal.

a. Sensitivity

b. Distortion

c. Efficiency

d. Frequency response

41. It describes the output of a microphone over a

range of frequencies.

a. Directivity

b. Sensitivity

c. Frequency response

d. All of the above

42. 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

43. 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

44. 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

45. The impedance of most drivers is about _____ ohms

at their resonant frequency.

a. 4

b. 6

c. 8

d. 10

46. It is a transducer used to convert electrical energy

to mechanical energy.

a. Microphone

b. Baffle

c. Magnetic assemble

d. Driver

47. It is an enclosure used to prevent front and back

wave cancellation.

a. Loudspeaker

b. Driver

c. Baffle

d. Frame

48. 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

49. _____ is early reflection of sound.

a. Echo

b. Pure sound

c. Reverberation

d. Intelligible sound

50. Noise reduction system used for film sound in

movie.

a. Dolby

b. DBx

c. dBa

d. dBk

51. 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

52. What is the unit of loudness?

a. Sone

b. Phon

c. Decibel

d. Mel

53. A unit of noisiness related to the perceived noise

level

a. Noy

b. dB

c. Sone

d. Phon

54. 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

55. What is the process of sending voice, speech, music

or image intended for reception by the general public?

a. Navigation

b. Telephony

c. Broadcasting

d. Mixing

56. What is the frequency tolerance for the RF carrier in

the standard AM radio broadcast band?

a. Zero

b. 20 Hz

c. 10 Hz

d. 20 KHz

57. The transmitting antenna for an AM broadcast

station should have a _____ polarization.

a. Vertical

b. Horizontal

c. Circular

d. Elliptical

58. The part of a broadcast day from 6 PM to 6 AM local

time

a. Daytime

b. Nighttime

c. Bed time

d. Experimental period

59. The service area where the signal is not subject to

fading and co-channel interference.

a. Primary Service Area

b. Secondary Service Area

c. Intermittent Service Area

d. Quarternary Service Area

60. It is a resistive load used in place of an antenna to

test a transmitter under normal loaded condition without

actually radiating the transmitter’s output signal.

a. Auxiliary Tx

b. Main Tx

c. Secondary Tx

d. Artificial Antenna

61. The operating power of the auxiliary transmitter

shall not be less than _____% or never greater than the

authorized operating power of the main transmitter.

a. 5

b. 10

c. 15

d. 20

62. What are the frequency limits of the MF BC band?

a. 300-3000 kHz

b. 3-30 MHz

c. 535-1605 kHz

d. 88-108 MHz

63. The center to center spacing between two adjacent

stations in the Phil. AM BC band is ____.

a. 9 kHz

b. 200 kHz

c. 36 kHz

d. 800 kHz

64. How many AM stations can be accommodated in a

150-kHz bandwidth if the highest modulating frequency is

10 kHz?

a. 10

b. 15

c. 7

d. 14

65. Short wave broadcasting operates in what band?

a. MF

b. HF

c. VHF

d. VLF

66. What does the acronym STL stand for?

a. Station-to-link

b. Signal-to-loss-ratio

c. Shout-to-live

d. Studio-to-transmitter-link

67. One of the main considerations in the selection of

antenna site is (AM)

a. Conductivity of the soil

b. Height of the terrain

c. Elevation of the site

d. Accessibility

68. One of the broadcast transmission auxiliary services

is:

a. Remote pick-up

b. STL

c. Communication, Coordination and Control

d. All of the above

69. What is the spacing between any two adjacent

channels in the FM broadcast band?

a. 20 KHz

b. 36 KHz

c. 200 KHz

d. 800 KHz

70. The first channel in the FM BC band has a center

frequency of

a. 88 MHz

b. 88.1 MHz

c. 88.3 MHz

d. 108 MHz

71. What is the radio transmission of two separate

signals, left, and right, used to create a multidimensional

effect on the receiver?

a. SCA

b. Stereo system

c. Pilot transmission

d. Monophonic transmission

72. The carrier frequency tolerance for FM broadcasting

is _____.

a. 25 kHz

b. 2 kHz

c. 20 kHz

d. 30 kHz

73. What is the modulation used by the stereophonic

subcarrier?

a. FM

b. PM

c. ISB

d. DSB

74. What is the pilot signal for stereo FM?

a. 4.25 MHz

b. 10 kHz

c. 19 KHz

d. 38 KHz

75. With stereo FM transmission, does a monaural

receiver produce all the sounds that a stereo does?

a. Yes

b. No

c. Either a or b

d. Neither a or b

76. Where is de-emphasis added in a stereo FM system?

a. Before the matrix at the TX

b. Before the matrix at the RX

c. After the matrix at the TX

d. After the matrix at the RX

77. Where is the pre-emphasis added in a stereo FM

system?

a. Before the matrix at the TX

b. Before the matrix at the RX

c. After the matrix at the TX

d. After the matrix at the RX

78. The normal frequency for an SCA subcarrier is _____

KHz.

a. 67

b. 76

c. 38

d. 19

79. A monaural FM receiver receives only the _____

signal of a stereo multiplex transmission.

a. L + R

b. L – R

c. Both a & b

d. 67 KHz

80. When fed to the stereo FM modulator, in what form

are the L – R signals?

a. AF

b. DSBSC

c. 19 kHz

d. 38 kHz

81. An additional channel of multiplex information that

is authorized by the FCC for stereo FM radio stations to feed

services such as commercial-free programming to selected

customers.

a. STL

b. EBS

c. EIA

d. SCA

82. The class of FM station, which has an authorized

radiated power not exceeding 125 KW:

a. Class C

b. Class A

c. Class D

d. Class B

83. An FM broadcast station, which has an authorized

transmitter power not exceeding 10 KW and ERP not

exceeding 30 KW:

a. Class D

b. Class C

c. Class A

d. Class B

84. A class of FM station which is limited in antenna

height of 500 ft. above average terrain

a. Class D

b. Class C

c. Class A

d. Class B

85. What type of broadcast service might have their

antennas on top of hills?

a. FM

b. AM

c. TV

d. A & C

86. How are guardbands allocated in commercial FM

stations?

a. 25 kHz on either sides of the transmitting

signal

b. 50 kHz on each side of the carrier

c. 75 kHz deviation

d. 15 kHz modulation

87. How many commercial FM broadcast channels can

fit into the bandwidth occupied by a commercial TV station?

a. 10

b. 20

c. 30

d. 40

88. How many international commercial AM broadcast

channels can fit into the bandwidth occupied by a

commercial TV station?

a. 100

b. 200

c. 125

d. 600

89. What kind of modulation is used for the sound

portion of a commercial broadcast TV transmission?

a. PM

b. FM

c. C3F

d. AM

90. Estimate the bandwidth occupied by the sound

portion of a TV transmission in US.

a. 25 kHz

b. 800 kHz

c. 80 kHz

d. 200 kHz

91. What is the main reason why television picture

signal uses amplitude modulation, while voice is frequency

modulated?

a. Better efficiency

b. Eliminate attenuation of both video and audio

c. Maintain synchronized scanning between transmit

and received video

d. To minimize interference between signals at

received end

92. The picture and sound carrier frequencies in a TV

receiver are _____ respectively.

a. 41.25 MHz, 45.75 MHz

b. 45.25 MHz, 41.75 MHz

c. 41.75 MHz, 45.25 MHz

d. 45.75 MHz, 41.25 MHz

93. What is the separation between visual and aural

carrier in TV broadcasting?

a. 1.25 MHz

b. 4.5 MHz

c. 5.75 MHz

d. 0.25 MHz

94. What is the separation between the lower limit of a

channel and the aural carrier?

a. 1.25 MHz

b. 4.5 MHz

c. 5.75 MHz

d. 0.25 MHz

95. What is the visual carrier for channel 12?

a. 205.25 MHz

b. 55.25 MHz

c. 65.75 MHz

d. 59.75 MHz

96. What is the aural carrier for channel 3?

a. 61.25 MHz

b. 55.25 MHz

c. 65.75 MHz

d. 59.75 MHz

97. What is color subcarrier for channel 2?

a. 68.83 MHz

b. 211.25 MHz

c. 58.83 MHz

d. 214.83 MHz

98. If the sound carrier for UHF channel 23 is 529.75

MHz, what is the frequency of the tuner’s local oscillator,

when turned to this channel?

a. 571 MHz

b. 511 MHz

c. 498 MHz

d. 500 MHz

99. What is the frequency tolerance in the color carrier

of TV broadcasting?

a. 2 kHz

b. 20 Hz

c. 10 Hz

d. 1 kHz

100. What is the exact picture carrier frequency for

frequency for channel 7 offset by – 10 KHz?

a 175.25 MHz

b 175.26 MHz

c 174 MHz

d 175.24 MHz

101. TV channels 7, 11 and 13 are known as _____.

a. Mid band UHF

b. Low band UHF

c. High band VHF

d. low band UHF

102. What is eliminated by using interlaced scanning?

a. Noise

b. Excessive BW

c. Frame

d. Flicker

103. What percentage of the primary colors used in color

TV are needed to produce the brightest white?

a. 30% red, 59% green, 11% blue

b. 33% red, 33% green, 33% blue

c. 50% red, 28% green, 22% blue

d. 58% red, 20% green, 22% blue

104. The color with the most luminance is

a. Red

b. Yellow

c. Green

d. Blue

105. Suppose the signal from a color camera has R=0.8,

G=0.4 and B=0.2, where 1 represents the maximum signal

possible. Determine the value at the luminance signal

a. 0.498

b. 0.254

c. 0.1325

d. 1.4

106. In the previous problem, calculate the chrominance

signal

a. 0.305

b. 0.304

c. 0.498

d. 0.022

107. The three complementary colors are:

a. White, yellow, cyan

b. Black, white, gray

c. Yellow, magenta, cyan

d. Violet, indigo, fushcia

108. When the colors Magenta and Yellow are mixed the

resultant color is:

a. Red

b. White

c. Blue

d. Green

109. Which of the following consist of two of the three

primary colors in television signal? a) red, b) violet, c)

yellow, and d) blue

a. A and B

b. B and C

c. C and D

d. A and D

110. The studio camera produces a luminance signal that

contains information about

a. The musical content

b. The speech content

c. The brightness of the scene

d. The color content of the scene

111. Brightness variations of the picture information are

in which signal?

a. I

b. Q

c. Y

d. Z

112. Which of the following is the color video signal

transmitted as amplitude modulation of the 3.58 MHz C

signal with bandwidth of 0 to 1.3 MHz?

a. I signal

b. Q signal

c. Y signal

d. X signal

113. Which of the following is the color video signal

transmitted as amplitude modulation of the 3.58 MHz C

signal in quadrature with bandwidth of 0 to 0.5 MHz?

a. I signal

b. Q signal

c. Y signal

d. Z signal

114. The _____ affects the difference between black and

white on the picture tube and controls the gain of the video

amplifier

a. Brightness control

b. Volume control

c. Power control

d. Contrast control

115. Which of the following is not a requirement for a

color TV signal?

a. compatibility with b lack and white receivers

b. Within 6 MHz bandwidth

c. Simulate a wide variety of colors

d. Functional with baron super antenna

116. How many electron beams actually leave the

electron gun of a single-gun color CRT?

a. 1

b. 2

c. 3

d. 1/3

117. What is the difference between the sound carrier

and color subcarrier frequencies?

a. 1.25 MHz

b. 3.58 MHz

c. 4.5 MHz

d. 0.92 MHz

118. What does aspect ratio mean?

a. Ratio of the screen width to its height

b. Ratio of the screen height to its width

c. Ratio of the screen diagonal to its width

d. Ratio of the screen diagonal to its height

119. What is the aspect ratio for HDTV system?

a. 4/3

b. 9/7

c. 19/6

d. 16/9

120. The signal that will give the exact color wavelength

is _____.

a. Hue

b. Saturation

c. Carrier

d. Monochrome

121. Which of the following represents the intensity of a

given color?

a. Hue

b. Saturation

c. Carrier

d. Monochrome

122. The _____ ensures that the electron beam will strike

the correct phosphor dot on the TV screen.

a. Coating

b. Aperture Mask

c. Diplexer

d. Duplexer

123. In a TV receiver, what is the horizontal signal

frequency?

a. 30 Hz

b. 60 Hz

c. 15750 Hz

d. 157625 Hz

124. In a TV receiver, what is the vertical signal

frequency?

a. 30 Hz

b. 60 Hz

c. 15750 Hz

d. 157625 Hz

125. What scheme is employed to cause the electron

beam in the TV receiver and the electron beam in the

studio camera to track identically?

a. Interlacing

b. NTSC

c. Interleaving

d. Transmission of sync pulses

126. Equalizing pulses in TV are sent during

a. Horizontal blanking

b. Vertical blanking

c. The serrations

d. Equalizing intervals

127. What is the return of the electron beam in a CRT

from right to left or from bottom to top?

a. Relay

b. Flyback

c. Utilization

d. Resolution

128. What is the North American TV standard video?

a. PAL

b. SECAM

c. NTSC

d. FCC

129. What is the maximum allowable frequency deviation

in the audio section of a TV signal for PAL/SECAM?

a. 25 kHz

b. 50 kHz

c. 75 kHz

d. 100 kHz

130. What is the frame frequency in the US TV system?

a. 30 Hz

b. 60 Hz

c. 15750 Hz

d. 157625 Hz

131. What is the highest video frequency set by the FCC

for commercial TV?

a. 4.2 MHz

b. 15 MHz

c. 6 MHz

d. 5.5 MHz

132. What determines the maximum number of vertical

picture elements?

a. Number of frames per second

b. Number of lines on the screen

c. Number of pixels

d. Number of fields per second

133. How many horizontal lines are used to develop a TV

raster?

a. 615

b. 525

c. 750

d. 15750

134. The channel width in the U.S. TV system is :

a. 2 MHz

b. 6 MHz

c. 7 MHz

d. 8 MHz

135. It is the popular TV camera designed with much

smaller package and lower cost than its earlier designs

a. Image orthicon

b. Iconoscope

c. Vidicon

d. Plumbicon

136. In a composite video signal, what is the relationship

between the amplitude of the signal and the intensity of the

electron beam in the receiver picture tube?

a. The greater the amplitude the darker the

picture

b. The lower the amplitude the darker the picture

c. The greater the amplitude the lighter the picture

d. No effect

137. If there are 625 lines per TV picture then the

number of lines per field are:

a. 1250

b. 312.5

c. 625

d. 2500

138. What is the process of placing the chrominance

signal in the band space between portions of the luminance

signal?

a. Interlacing

b. Fitting

c. Sneaking

d. Interleaving

139. How much time elapses between the start of one

horizontal sync pulse and the next?

a. 10.2 μs

b. 63.5 μs

c. 16.67 μs

d. 100 μs

140. Which of the following frequencies is wrong?

a. 15,750 Hz for horizontal sync and scanning

b. 60 Hz for vertical sync and scanning

c. 31,500 Hz for the equalizing pulses and serrations

in the vertical sync pulse

d. 31,500 Hz for the vertical scanning frequency

141. The camera tube that uses selenium, arsenic and

tellurium

a. Plumbicon

b. Vidicon

c. Saticon

d. Silicon Vidicon

142. The components of composite video signal are:

a. Chroma signal

b. Blanking pulse

c. Synchronizing pulse

d. All of these

143. What is the smallest amount of information that can

be displayed on a television screen?

a. Blip

b. Burst

c. Pixel

d. Bits

144. It is the quality of the TV picture after imperfections

a. Aspect ratio

b. Utilization ratio

c. A1

d. Monochrome

145. What section of a TV receiver determines the

bandwidth and produces the most signal gain?

a. RF amplifier

b. Audio amplifier

c. IF amplifier

d. Tuned circuit