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Audio and sound reinforcement > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

What is dynamic range ?

A

The difference, in decibels, between the loudest and the quietest portion of a program.

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2
Q

True or False

Every sound system has an inherent noise floor

A

True

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3
Q

What is the dynamic range formula?

A

= (Peak Level) - (Noise Floor)

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4
Q

What is the unit of measurement for Dynamic range?

A

dB

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5
Q

What is nominal program level?

A

The average electronic line level corresponding to an average sound level at the microphone

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6
Q

What is the unit of measurement of headroom?

A

dB

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7
Q

What is the dynamic range of a sound system

is equal to?

A

the difference between the peak output level of the system and the electro-acoustic noise floor

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8
Q

True or False

dynamic range can be expressed in dB SPL, dBm, dBu or any other specifically referenced dB value

A

dynamic range is nearly always specified in dB, and should never be expressed in dB SPL, dBm, dBu or any other specifically referenced dB value

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9
Q

What is headroom?

A

The difference between the nominal and the highest (peak) levels in a program

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10
Q

What is Signal-To-Noise Ratio?

A

represents the difference between the nominal level and the noise floor

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11
Q

True or False

you can always add the S/N ratio to the headroom and come up with the dynamic range.

A

False

You can’t

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12
Q

Headroom requirements change with ____________________________ and ________________________________

A

the nature of the program material and the purpose for which the sound system is operated

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13
Q

What is the result when the dynamic range of the

program material exceeds the dynamic range capability of the sound system?

A

a) Program peaks will be distorted due to clipping and/or loudspeaker break-up, and/or
b) Quiet passages will not be heard because they will be below the electrical and/or acoustic noise floor

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14
Q

Why is headroom important?

A

tells us something about the ability of the

sound system to handle loud program peaks

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15
Q

Give the formula for headroom

A

= (Peak Level) - (Nominal Level)

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16
Q

Measure the some new electronics and found that they have an electronic noise floor of -56 dBu (1.23 millivolts), and a peak output level of +18 dBu (6.16 volts). What is the dynamic range of this newly assembled system?

A

dynamic range…
=(Peak Level) - (Noise Floor)
= +18 dBu - (-56 dBu)
=74dB

17
Q

A sound system’s dynamic range can

be increased by ________________, or _____________________

A

increasing the maximum sound level capability or by making the environment quieter.

18
Q

What is the importance of the Signal-To-Noise Ratio?

A

It is shown so you can see how this specification is related to dynamic range and headroom.

19
Q

What are the side effects of compression?

A

such as making quiet breath sounds louder, creating a

pumping effect in some cases, and increasing the distortion of low frequency signals

20
Q

Describe limiters

A

Some devices permit compression to be applied above a set threshold, and the compression ratio to be very high

21
Q

What would occur if the threshold were set lower,

or the compression ratio to a higher value?

A

then more dynamic range would be conserved, and the overall signal level at the compressor output could be increased to stay above the console’s noise floor.

22
Q

Describe the purpose of a compander noise reduction system

A

allows the original program dynamics to be maintained throughout the recording and playback process by
compressing the program dynamic range before it goes onto the tape

23
Q

What is the purpose of a compressor?

A

By setting the compressor for a relatively gentle compression ratio of 2:1, every dB of input level change will result in half a dB of output level change

24
Q

What determines the choice of headroom figure?

A

depends on the type of program material, the application, and the available budget for amplifiers

25
Q

Why is limiting a suitable name for the process?

A

The term is appropriate, since such a device limits the
output level from rising any higher, with infinite compression, or very much higher, with 10:1 compression, regardless of further increases in input signal.

26
Q

What is the process of permitting compression to

be applied above a set threshold, and the compression ratio to be very high?

A

limiting

27
Q

What is a compander?

A

a noise reduction system

28
Q

There is a special case where compression and its opposite, expansion, are used to overcome limited dynamic range in one portion of a sound system. That case occurs with

A

an analog audio tape recorder

Audio and sound reinforcement (5 decks)

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