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CTS-D > Audio Principles of Design > Flashcards

Audio Principles of Design Flashcards

1
Q

The most common unit of measurement for sound is the ____.

A

decibel

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2
Q

A __ decibel (dB) change is the smallest perceptible change noticeable.

A

1

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3
Q

A “just noticeable” change—either louder or softer—requires a __ dB change

A

3

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4
Q

A __ dB change is required for listeners to perceive subjectively a sound that is twice or one-half as loud as it was before.

A

10

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5
Q

A decibel measures ____.

A

perceived change

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6
Q

____ refers to the electronic amplification of a signal.

A

Gain

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7
Q

The formula for calculating a decibel change for power is as follows:

A

10-log equation.

dB = 10 * log (P1 /Pr )

where:
• dB = The change in decibels
• P1 = The new or measured power measurement
• Pr = The original or reference power measurement

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8
Q

The formula for calculating decibel changes in sound pressure level over distance is as follows:

A

20-log equation

dB = 20 * log (D1 /D2 )

where:
• dB = The change in decibels
• D1 = The original or reference distance
• D2 = The new or measured distance

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9
Q

The formula for calculating decibel changes in voltage is as follows:

A

20-log equation

dB = 20 * log (V1 /Vr )

where:
• dB = The change in decibels
• V1 = The new or measured voltage
• Vr = The original or reference voltage

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10
Q

In AV, the ____ formula is for power calculations only.

A. 10-log
B. 20-log

A

A. 10-log

Just remember: 10 for power, 20 for everything else.

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11
Q

In AV, the ___ formula is for voltage, pressure, and distance calculations.

A. 10-log
B. 20-log

A

B. 20-log

Just remember: 10 for power, 20 for everything else.

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12
Q

A decibel can be a comparison of two values, or it can be a comparison of a value to a predetermined starting point, known as a ____.

A

reference level (also: zero reference)

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13
Q

0 __ is equivalent to 0.775 volts.

A. DBu
B. DBV

A

A. DBu

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14
Q

0 __ is equivalent to 1 volt.

A. DBu
B. DBV

A

B. DBV

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15
Q

0 dBu is equivalent to ____ volt(s).

A

0.775

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16
Q

0 dBV is equivalent to ____ volt(s).

A

1

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17
Q

Sound pressure level should always fall between __ and __ dB SPL.

A

0 and 140

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18
Q

Microphone level, which is typically measured in dBu, should be ___ to ___ dBu, well below the zero reference of 0.775 volts for the dBu.

A

−60 to −50

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19
Q

Line level should be between __ and __ dBu for pro audio.

A

0 and +4

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20
Q

The consumer audio level is ____.

A

−10 dBV (0.316 V).

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21
Q

The threshold of human hearing is __ dB SPL at __ kHz

A

0 / 1

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22
Q

____ is a measurement of all the acoustic energy in an environment

A

Sound pressure level

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23
Q

SPL Meter Settings

A setting commonly used for environmental, hearing conservation, and noise ordinance enforcement. It closely reflects the response of the human ear to noise and its insensitivity to lower frequencies at lower listening levels.

A. A-weighting
B. B-weighting
C. C-weighting
D. Z-weighting

A

A. A-weighting

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24
Q

SPL Meter Settings

More uniform response over the entire frequency range.

A. A-weighting
B. B-weighting
C. C-weighting
D. Z-weighting

A

C. C-weighting

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25
Q

SPL Meter Settings

A flat frequency response, with no filtering.

A. A-weighting
B. B-weighting
C. C-weighting
D. Z-weighting

A

D. Z-weighting

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26
Q

A space should acoustically have a minimum __ dB acoustic signal-to-noise ratio (the level of a desired signal compared to the level of background noise).

A

25

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27
Q

SPL Meter Classes

A lab-reference standard. It supports the strictest tolerances and should be used when extreme precision is needed.

A. Class 0
B. Class 1
C. Class 2
D. Class 3

A

A. Class 0

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28
Q

SPL Meter Classes

Precision measurement. It is useful for taking flat, engineering-grade measurements, rather than wide-range or field measurements.

A. Class 0
B. Class 1
C. Class 2
D. Class 3

A

B. Class 1

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29
Q

SPL Meter Classes

For general purpose. It has the widest tolerances with respect to level linearity and frequency response.

A. Class 0
B. Class 1
C. Class 2
D. Class 3

A

C. Class 2

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30
Q

SPL Meter Classes

Intended for noise surveys

A. Class 0
B. Class 1
C. Class 2
D. Class 3

A

D. Class 3

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31
Q

For many audio purposes, a Class __ meter is acceptable.

A

2

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32
Q

The A-weighting is useful in low-listening-level situations, roughly __ to __ dB SPL.

A

20 to 55

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33
Q

The C-weighting is useful in higher-listening-level situations, roughly __ to __ dB SPL.

A

85 to 140

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34
Q

Loudspeaker coverage is typically stated at the __ dB down points. This means the level at the edge of the stated coverage pattern would be found to be __ dB less than the energy measured on-axis.

A

6

35
Q

To create a loudspeaker layout, you must first determine two things: ____ and ____.

A

loudspeaker coverage angle and listener ear level.

36
Q

The formula for calculating the diameter (twice the radius) of the circle that represents the coverage area of a loudspeaker is as follows:

A

D = 2 * (H - h) * tan (C∠ / 2)

where:
• D is the diameter of the coverage area.
• H is the ceiling height.
• h is the height of the listeners’ ears.
• C∠ is the loudspeaker’s angle of coverage in degrees.

37
Q

____ coverage places the loudspeakers in such a way that the furthest extent of their acoustic energy comes together at listeners’ ear level. There is no overlap with this pattern.

A. Edge-to-edge
B. Partial overlap
C. Edge to center

A

A. Edge-to-edge

38
Q

In ____, each loudspeaker’s cov- erage pattern overlaps about 20 percent of the adjoining speaker’s coverage pattern.

A. Edge-to-edge
B. Partial overlap
C. Edge to center

A

B. Partial overlap

39
Q

A(n) _____ layout, or 50 percent overlap, will provide excellent coverage at most frequencies (with 1.4 dB variation).

A. Edge-to-edge
B. Partial overlap
C. Edge to center

A

C. Edge to center

40
Q

The term ____ is used when you are working with DC circuits, such as those that are powered by a battery.

A

resistance

41
Q

The term ____ is used when working with AC circuits, such as loudspeaker circuits.

A

impedance

42
Q

The formula for calculating the total impedance of a series loudspeaker circuit is as follows:

A

ZT = Z1 + Z2 + Z3+ …Zn

where:
• ZT is the total impedance of the loudspeaker circuit.
• ZN is the impedance of each loudspeaker.

43
Q

The formula for finding the circuit impedance for loudspeakers wired in parallel with the same impedance is as follows:

A

ZT = Z1 / N

where:
• ZT is the total impedance of the loudspeaker system. • Z1 is the impedance of one loudspeaker.
• N is the quantity of loudspeakers in the circuit.

44
Q

The formula for finding the circuit impedance for loudspeakers wired in parallel with differing impedance is as follows:

A

ZT = 1 / ( 1 / Z1 + 1 / Z2 + 1 / Z3 …. 1 / Zn )

where:
• ZT is the total impedance of the loudspeaker circuit.
• Z1-N is the impedance of each individual loudspeaker.

If you have three loudspeakers wired in parallel, with the first rated at 4 ohms, the second rated at 8 ohms, and the third rated at 16 ohms, the circuit’s impedance is 2.29 ohms, or ZT = 1/((1/4 ohms)+(1/8 ohms)+(1/16 ohms)).

45
Q

For a speech application, the recommended headroom is __ dB SPL.

A

10

46
Q

For program audio, or music, the recommended headroom is __ dB SPL.

A

20

47
Q

____ is the difference in dB SPL between the peak and average-level performance of an audio system.

A

Headroom

48
Q

For speech application, the sound pressure level required from the sound system at the listener position is typically __ dB SPL.

A

70

49
Q

To determine the power required at the loudspeaker, you need to know the following:

A
  • The sound pressure level required from the sound system at the listener position. For speech applications, this is typically 70 dB SPL.
  • The headroom required. For speech applications, 10 dB is considered adequate. For music applications, as much as 20 dB or more may be required.
  • Loudspeaker sensitivity. Typically this will be stated as SPL in decibels expected at a distance of 1 meter away from the loudspeaker with 1 watt applied.
  • Distance to the farthest listener from the loudspeaker.
50
Q

The EPR formula is as follows:

A

EPR = 10^ ( [Lp+H-Ls ( 20 log(D2 / Dr))] / 10 ) * Wref

where:

  • EPR is the amount of electrical power required at the loudspeaker.
  • LP is the SPL required at distance D2.
  • H is the headroom required.
  • LS is the loudspeaker sensitivity reference, usually 3.28 feet (1 m).
  • D2 is the distance from the loudspeaker to the farthest listener.
  • Dr is the distance reference value.
  • Wref is the wattage reference value; assume a Wref of 1, unless otherwise noted.
51
Q

EPR stands for ____.

A

Electrical Power Required

52
Q

EPR is defined as ____.

A

The amount of power needed at the loudspeaker

53
Q

A loudspeakers ____ defines the loudspeakers acoustic output signal level, given a reference input level.

A

sensitivity specification

54
Q

____ is the remote power required to power a microphone.

A

Phantom power

55
Q

Phantom power typically ranges from __ to __ volts DC

A

12 to 48

56
Q

A microphones pickup pattern is also known as the _____, or the microphone’s directionality.

A

polar pattern

57
Q

Microphone pickup patterns:

Sound pickup is uniform in all directions.

A. Omnidirectional
B. Cardioid
C. Hypercardioid
D. Supercardioid
E. Bidirectional
A

Omnidirectional

58
Q

Microphone pickup patterns:

Pickup is from the front of the microphone only. It rejects sounds coming from the side but mostly rejects sound from the rear of the microphone.

A. Omnidirectional
B. Cardioid
C. Hypercardioid
D. Supercardioid
E. Bidirectional
A

B. Cardioid

59
Q

Microphone pickup patterns:

A variant of another pickup pattern. It’s more directional because it rejects more sound from the sides.

A. Omnidirectional
B. Cardioid
C. Hypercardioid
D. Supercardioid
E. Bidirectional
A

C. Hypercardioid

60
Q

Microphone pickup patterns:

Provides better directionality with less rear pickup.

A. Omnidirectional
B. Cardioid
C. Hypercardioid
D. Supercardioid
E. Bidirectional
A

D. Supercardioid

61
Q

Microphone pickup patterns:

Pickup is equal in opposite directions with little or no pickup from the sides.

A. Omnidirectional
B. Cardioid
C. Hypercardioid
D. Supercardioid
E. Bidirectional
A

E. Bidirectional

62
Q

The ____ defines the microphone’s electrical output level over the audible frequency spectrum, which in turn helps to determine how a microphone “sounds.”

A

frequency-response

63
Q

The ____ shows the level of decibels by angle, or the pickup pattern of the microphone.

A

polar plot / polar pattern

64
Q

Audio signal levels

Mic Level

A. 0.001 to 0.003 volts (-60 to -50 dBu)
B. 1.23 volts (+4 dBV)
C. 0.316 volts (10 dBV)
D. 4 to

A

A. 0.001 to 0.003 volts (-60 to -50 dBu)

65
Q

Audio signal levels

Line Level (Professional)

A. 0.001 to 0.003 volts (-60 to -50 dBu)
B. 1.23 volts (+4 dBV)
C. 0.316 volts (10 dBV)
D. 4 to

A

B. 1.23 volts (+4 dBV)

66
Q

Audio signal levels

Line Level (Consumer)

A. 0.001 to 0.003 volts (-60 to -50 dBu)
B. 1.23 volts (+4 dBV)
C. 0.316 volts (10 dBV)
D. 4 to

A

C. 0.316 volts (10 dBV)

67
Q

Audio signal levels

Loudspeaker Level

A. 0.001 to 0.003 volts (-60 to -50 dBu)
B. 1.23 volts (+4 dBV)
C. 0.316 volts (10 dBV)
D. 4 to

A

D. 4 to

68
Q

When determining microphone sensitivity, you will need to consider three factors.

A
  • Sound pressure level The acoustic energy is at the microphone.
  • Electrical signal level The goal is to have a line-level signal after the preamplification.
  • Matching levels Can the signal level from the microphone/preamp combination be amplified to the line-level signal that the audio system (mixer) requires?
69
Q

1 Pascal = __ dB SPL

A

94

70
Q

Most microphone preamplifiers will provide around __ dB of amplification.

A

60

71
Q

To work properly, a sound system must accomplish three things.

A
  • It must be loud enough.
  • It must be intelligible.
  • It must remain stable.
72
Q

For a typical speech reinforcement system, the target sound pressure level is around __ to __ dB SPL.

A

60 to 65

73
Q

To determine whether an audio system is stable, a designer calculates _____ —how loud the loudspeakers get before the microphones pick them up.

A

gain before feedback

74
Q

How loud the loudspeakers get before the microphones pick them up is referred to as _____.

A

potential acoustic gain (PAG)

75
Q

How loud the loudspeakers need to be for listeners to hear the intended audio is referred to as _____.

A

needed acoustic gain (NAG)

76
Q

_____ is the farthest distance one can go from the source without needing sound amplification or reinforcement to maintain good speech intelligibility.

A

equivalent acoustic distance (EAD)

77
Q

The formula for PAG is as follows:

A

PAG = 20log[(D0 * D1 ) / (D2 * Ds )]

where
• D0 - The distance between the talker and the farthest listener
• D1 - The distance between the closest loudspeaker to the microphone and the microphone
• D2 - The distance between the loudspeaker closest to the farthest listener and the farthest listener
• Ds - The distance between the sound source (talker) and the microphone

78
Q

NOM stands for ____.

A

number of open microphones

79
Q

FSM stand for ____.

A

feedback stability margin

80
Q

Every time the number of open microphones doubles, acoustic power doubles, so when you double the number of open microphones (one to two, two to four, etc.), you lose __ dB before feedback.

A

3

81
Q

____ refers to how close the system is to actual feedback.

A

FSM (feedback stability margin)

82
Q

The FSM in a carefully equalized system is typically __ dB.

A

6

83
Q

For a sound system to be stable, PAG must be ___ NAG

A

greater than or equal to

CTS-D (17 decks)

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