David, Rodel c. - Broadcasting Hw

Name: David, Rodel C. Topic: Acoustics

Question: What is the sound pressure level (SPL) of a sound having an RMS pressure of 200 N/m2 ?

Choices: A. 150 dB C. 170 dB

B. 140 dB D. 160 dB

Solution:

SPL=20 logPPo

=20 log200 N /m2

2x 10−5 N /m2

SPL=140dB

Reference: 3001 Questions in Communications Engineer; Cuervo, S., Tan, S., p.35

Answer. B

Name: David, Rodel C. Topic: Broadcasting

Question A measure of how well the receiver can respond to every weak signals.

Choices: A. Selectivity C. Fidelity

B. Sensitivity D. Quality factor

Background:

Selectivity is the ability to separate the wanted signal from nearby unwanted signals (other stations). Sensitivity defines the limit of detection of weak signals. Fidelity is the ability of the receiver to reproduce the original signal. Quality factor is the ratio of the resonant frequency/center frequency to the bandwidth of a certain frequency response of a filter.

Reference: http://www.pinoybix.com/2014/10/mcqs-in-broadcasting-and-cable-tv-systempart2.html

Answer. B

http://www.pinoybix.com/2014/10/mcqs-in-broadcasting-and-cable-tv-systempart2.html



Question: A church has an internal volume of 90050 ft3 (2550 m3). When it contains 2,000 customary sabines of absorption (186 metric sabines), what will be its reverberation time ine seconds?

Choices: A. 2.0 C. 2.5

B. 2.2 D. 3.0

Solution:

RT60=0.161V

∑ Sa

RT60=0.161(2550)

186=2.21


Answer. B

Name: David, Rodel C. Topic: Television

Question: Calculate the equivalent IRE unit of a video signal with a luminance of 72%.

Choices: A. 4.1 IRE units C. 74.1 IRE units

B. 53.8 IRE units D. 66.4 IRE units

Solution:

Luminance Level to IRE Unit Conversion:

𝑙𝑚𝑎𝑥 = 100 𝑙𝑚𝑖𝑛 = 7.5 𝐼𝑅𝐸 = 7.5 + 𝑙 × (𝑙𝑚𝑎𝑥 − 𝑙𝑚𝑖𝑛)

= 7.5 + 72%(100 − 7.5) = 74.1 𝐼𝑅𝐸 𝑢𝑛𝑖𝑡𝑠

Reference: Self-Sufficient Guide to Electronics Communications Engineering; Ampoloquio, J.M., p.2-55

Answer. C


Question: What is the channel number of an FM station with 88.1 Mhz carrier?

Choices:

A. 201 C. 203

B. 202 D. 204

Solution:

N=5 (f c−47.9)

N=5 (88.1−47.9 )

N=201


Answer. A


Question: 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.

Choices: A. 10 Hz C. 30 Hz

B. 20 Hz D. 40 Hz

Solution:

f=√ 250h

h=static of deflection ,mm

f=√ 2502.5

f=10 Hz


Answer. A


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

Choices: A. 0.15 W C. 0.24 W

B. 0.21 W D. 0.18 W

Solutions:

SPL=PWL−20 log r−8

PWL=SPL+20 log r+8

PWL=87+20 log 7.5+8=112.5dB

PWL=10 logWW o

;W o=10−12W

W=10−12 log−1 112.510

=0.18W


Answer. D


Question: From the low-frequency end of a channel, what is the visual carrier frequency?

Choices: A. 3.58 MHz C. 1.25 MHz

B. 0.25 MHz D. 4.5 MHz

Background:

The visual carrier frequency of a TV channel is usually 1.25 MHz above the low-frequency end of it. The sound carrier is 4.5 MHz above the visual carrier. The Chrominance carrier frequency is 3.58 MHz above the visual carrier. The 0.25 MHz is the location of the sound carrier below the high-frequency end of a channel.


Answer. C


Question: The maximum power suggested by KBP (Kapisanan ng mga Brodkaster ng Pilipinas) on 919-1312 AM broadcast station in Metro Manila is

Choices: A. 5 kW C. 15 kW

B. 10 kW D. 20 kW

Background:

AREA LOW BAND

(525-918 kHz)

MIDBAND

(919-1312 kHz)

HIGH BAND

(1313-1705kHz)

Metro Manila 10 kW 20 kW 30 kW

Metro Cebu 10 kW 20 kW 30 kW

Other areas 5 kW 10 kW 15 kW




Answer. D


Question: What class of TV camera lens used to cover long distances?

Choices: A. Normal C. Telephoto

B. Wide Angle D. Zoom

Background:

Normal Lens: is one that sees in a similar proportion to the human eye.

Wide Angle Lens: A regular wide-angle lens is defined as anything shorter than 20-35mm.

Telephoto Lens: are technically defined as anything exceeding 50-100mm.

Zoom Lens: Basically Lenses with the ability to zoom in and zoom out focus.


Answer. C


Question: What class of TV camera lens used to cover short distances?

Choices: A. Normal C. Telephoto

B. Wide Angle D. Zoom

Background:

Normal Lens: is one that sees in a similar proportion to the human eye.

Wide Angle Lens: A regular wide-angle lens is defined as anything shorter than 20-35mm.

Telephoto Lens: are technically defined as anything exceeding 50-100mm.

Zoom Lens: Basically Lenses with the ability to zoom in and zoom out focus.


Answer. B


Question: All airtime classifications shall be submitted to and subject for approval by the

Choices: A. NTC C. DOTC

B. KBP – SA D. CCITT

Background:

NTC – responsible for the supervision, adjudication and control over all telecommunications services throughout the country.

DOTC – responsible for the maintenance and expansion of viable, efficient, and dependable transportation and communications systems as effective instruments for national recovery and economic progress.

CCITT – is the primary international body for fostering cooperative standards for telecommunications equipment and systems

KBP-SA – provides broadcast media regulations and guidelines for news, public affairs and commentaries, political broadcasts, children’s shows, religious programming, and including advertising to its members.


Answer. B


Question: The allowable deviation ratio of commercial FM broadcast.

Choices: A. 15 C. 25

B. 5 D. 75

Solution:

Deviation Ratio is defined as:

𝐷𝑅 = 𝛿𝑚𝑎𝑥 (max) For commercial FM broadcast (FCC Standards),

𝛿𝑚𝑎𝑥 = 75 𝑘𝐻𝑧 (Maximum Frequency Deviation)

(max) = 15 𝑘𝐻𝑧 (Maximum Audio Frequency Bandwidth)

Such that,

DR= δmaxf m(max )

=75kHz15kHz

=5


Answer. B


Question: Numerical frequency band designation of Channel 9.

Choices: A. 488 – 494 MHz C. 632 – 638 MHz

B. 530 – 536 MHz D. 186 – 192 MHz

Background:

488 – 494 MHz is for channel 17





Answer. D


Question: Part of broadcast day from midnight to local sunrise.

Choices: A. Daytime C. Nighttime

B. Experimental D. Dawntime

Background:

Based on the broadcasting standards, experimental spans from midnight to local sunrise. For the daytime, itspansfrom 5 AM to 6 PM of local time. For the nighttime, itspansfrom 6 PM to 5 AM of local time. The term downtime cannot be found in broadcasting standards hence, it is not an answer.


Answer. B


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

Choices: A. 10 Hz C. 30 Hz

B. 20 Hz D. 40 Hz

Solution:

f=0.45V Lh[( N x

I x)

2

+( N y

I y)

2] , Hz

V L=longitudinal velocity=2350m / s



h=t h ickness∈m=120 x 10−3 m

I x=lengt h∈m=4m , I y=heigh t∈m=2m

N x , N y=integers 1 ,2 ,3 , etc . ,t h e lowest is1 giving t he lowest f

f=0.45 (2350 ) (120 x10−3 )[( 14 )

2

+( 12 )

2]=39.66 Hz≈40 Hz


Answer. D


Question: What is the reverberation time of a room whose surface area is 75 m 2, whose volume is 42 m3, and whose average absorption coefficient is 0.9, 0.2?

Solution:

for α=0.9

RT60=0.07V

−S log(1−α)=

0.07 (42)−(75) log (1−0.9)

=0 .0392 s

39.2ms is very small value of reverberation time for a typical room.

for a=0.2

RT60=0.07V

−S log(1−α)=

0.07(42)−(75) log (1−0.2)

=0 .4045 s

404.5ms is in the range of typical reverberation time for typical room.

Reference:

http://www.feilding.net/sfuad/musi3012-01/html/lectures/021_environment_II.htm


Question: A unit of noisiness related to the perceived noise level.

Choices: A. Noy C. dB

B. Sone D. Phone

Background:

Noy – a linear unit of noisiness or annoyance. 1 Noy is defined as the noisness of a 1000 Hz tone at a SPL of 40 dB.

Sone – a unit of perceive loudness equal to the loudness of 1000 Hz tone at 40 dB above threshold.

http://www.feilding.net/sfuad/musi3012-01/html/lectures/021_environment_II.htm

dB, decibel – ratio of the sound pressure to the reference sound pressure to something

Phone – a unit of subjective loudness.


Answer. A


Question: Brightness of an image is known as

Choices: A. Radiance C. Reflectance

B. Chrominance D. Luminance

Background:

Radiance – is the radiant flux emitted, reflected, transmitter or received by a surface per unit solid angle per unit projected

Chrominance – is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal (or Y for short).

Reflectance – the measure of the proportion of light or other radiation striking a surface that is reflected off it.

Luminance – is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describe the amount of light that passes through, is emitted or reflected from a particular area, and falls within a given solid.


Answer. D


Question: A third symbol radio emission represents telephone transmission including sound broadcasting.

Choices: A. W C. C

B. F D. E

Background:

For the third symbol for radio emission, we have F is for television (video), C for facsimile, E for telephony (including sound broadcasting), and W for combinations of signals.


Answer. D



David, Rodel c. - Broadcasting Hw

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