Week 28 Chapter 13 Part 2 - Pages 13-38 to 13-69 Flashcards
In an audio conferencing environment, the microphones are placed at the periphery of the loudspeaker coverage pattern in order to _____ the echo return loss (ERL) of the room.
a. Balance
b. Minimize
c. Maximize
d. Cancel
c. Maximize
p 13-68
The microphones are at the periphery of the loudspeaker coverage pattern to maximize the ERL of the room.
For program audio, adequate electrical SNR greater than ___ dB should be acquired.
a. 20
b. 30
c. 40
d. 50
e. 60
e. 60
p 13-45
Adequate electrical SNR (greater than 60 dB). Factors that contribute to intelligibility are:
–Achieving at least 25 dB SNR (room noise).
–Meeting the required frequency response.
–No perceived distortion (less than 1 percent total harmonic distortion).
–Good direct-to-reverberant sound ratios.’
Key word “Jazz”
Which one of the following is not a requirement for speech reinforcement
a. Loud enough
b. Intelligible
c. Clear
d. Stable
c. Clear
p 13-46
The main requirements for a speech reinforcement system are similar to those for program audio, with one addition. A speech reinforcement system must be:
• Loud enough.
• Intelligible.
• Stable.
For point source loudspeaker placement, when considering a central cluster system for an environment, a general rule is that D2 should not exceed ___ times D1
a. 2
b. 4
c. 6
d. 8
b. 4
p 13-48
When considering a central cluster system for an environment, a general rule is that D2 should not exceed four times D1.
Within a speech reinforcement distributed loudspeakers system, the optimal distribution of the full range of important frequencies, overlap of as much as ___ percent in adjacent loudspeaker distribution patterns is recommended.
a. 20
b. 30
c. 40
d. 50
e. 60
d. 50
p 13-51
For optimal distribution of the full range of important frequencies, overlap of as much as 50 percent in adjacent loudspeaker distribution patterns is recommended. The lower the ceiling, the more loudspeakers are required, and vice versa.
Conference rooms should be designed to an NC ___ standard.
a. 20
b. 30
c. 40
d. 50
b. 30
p 13-56
Conference rooms should be designed to an NC 30 standard. An NC 30 rating corresponds to approximately 40 dBA SPL of background noise, leaving about 30 dB of SNR for normal talkers (70 to 77 dB SPL at ≈1 m [3.3 ft]).
The ICT distribution designer should keep in mind transformer losses of approximately 1 dB for each loudspeaker and choose an amplifier at ___ to ___ percent larger than the sum of the required loudspeaker power.
a. 20, 50
b. 30, 40
c. 25, 50
d. 20, 55
c. 25, 50
p 13-69
This will allow some headroom for additional loudspeakers or louder transient signals.
In audio conferencing environments, if the period between the time a word is spoken and the time its echo is heard exceeds _____ milliseconds (ms), the echo will cause most talkers to stutter.
a. 400
b. 300
c. 200
d. 100
b. 300
p 13-61
In fact, if the period between the time a word is spoken and the time its echo is heard is more than 300 ms, the echo will actually cause most talkers to stutter.
In order for an audio conference system to have good intelligibility, the signals heard by the local talker should be at least _____ dB above the background noise level.
a. 25
b. 20
c. 15
d. 10
a. 25
p 13-56
For an audio system to have good intelligibility, the signals heard by the local talker should be at least 25 dB above the background noise level.
In audio conferencing systems, the absence of a(n) _____ echo canceller will allow loudspeaker audio to be captured by microphones and sent back to the remote participants as an echo of their voices.
a. Line
b. Noise
c. Audio
d. Acoustic
d. Acoustic
p 13-55
In the absence of an AEC, the loudspeaker audio is sent back to the remote participants, who, as a result, hear a delayed echo of their voices.
In audioconferencing environments, echoes can overload communication circuits, resulting in a feedback condition called:
a. Gain
b. Squelch
c. Reverb
d. Howling
d. Howling
p 13-61
Echoes can overload communication circuits, resulting in a feedback condition called howling.
In order for an audio conference system to have good intelligibility, the signals heard by the local talker should be at least ___ dB above the background noise level.
a. 25
b. 20
c. 15
d. 10
a. 25
p 13-56
For an audio system to have good intelligibility, the signals heard by the local talker should be at least 25 dB above the background noise level.
Using the sound pressure level (SPL) method of approximating distance and power, calculate the power required to produce 89 dB at 4 m (13.1ft) with a loud speaker that is rated at a SPL of 95 dB. What input power level (in watts) is required to appropriately power the speaker?
a. 1 watt
b. 2 watts
c. 4 watts
d. 8 watts
c. 4 watts
p 13-69 inverse log equation
- Calculate 89 dB @ 4 m to 1 m = 89 + 12 (doubling distance 2x or 6 dB + 6 dB) = 101 dB @ 1 m
- 101 - 95 = 6 dB
- 6 dBW = 10 log (needed watts/1 W)
- 0.6 = log (needed W/1 W)
- 0.6 = log needed W
- Inverse log ~ 3.98 needed W
You are designing a four story retail mall and multiple sound systems within it. Which system should you design to support general music programming within common retail areas?
a. Distributed paging
b. Life safety
c. Sound masking
d. Sound reinforcement and playback
d. Sound reinforcement and playback
A space has all hard surfaces including architecture and furnishings. The audio programming produced from the distributed sound system has become unintelligible. Which of the following will NOT mitigate the problem?
a. Add tapestries to the walls.
b. Provide additional speakers at lower output.
c. Increase the volume to the existing speakers.
d. Reduce the distance of the existing speakers to the listener.
c. Increase the volume to the existing speakers.
