Dynamic Processors

Question 1

What are 3 technical reasons to control dynamic range?

Answer 1

• meeting the technical limitations of recording/broadcast media
• safety compression
• noise reduction

Question 2

What are 6 sonic reasons to control dynamic range?

Answer 2

• increased perceived loudness
• greater detail of low level signals
• increased sustain/length in string instruments and drums
• shaping/reshaping amplitude envelope
• increased intelligibility
• performance smoothing

Question 3

What are 3 macro ways dynamic range is controlled over time?

Answer 3

musical phrases and mixes

• gain riding
• console/DAW automation
• program bus and stem compression

Question 4

What are some ways the amplitude envelope is controlled over time?

Answer 4

individual notes

• gain riding
• console/DAW automation
• compressor/limiter
• gate/expander

Question 5

What are some micro ways dynamic range is controlled over time?

Answer 5

individual waveform

• compressor/limiter
• gate/expander

Question 6

What are seven types of dynamic processors?

Answer 6

• compressor
• limiter
• expander
• gate
• de-esser
• stressor
• ducker

Question 7

What does a compressor do?

Answer 7

reduces dynamic range

Question 8

What does a limiter do?

Answer 8

prevents dynamic range from going beyond a certain amplitude

Question 9

What does an expander do?

Answer 9

increases dynamic range

Question 10

What does a gate do?

Answer 10

allows signals of only a sufficient gain to pass

Question 11

What does a de-esser do?

Answer 11

reduces dynamic range of a particular range of frequencies (sibilants)

Question 12

What does a stressor do?

Answer 12

expands the dynamic range of a particular range of frequencies

Question 13

What does a ducker do?

Answer 13

reduces dynamic range when another event (another track) occurs

Question 14

What is crest factor, and what is the equation for it?

Answer 14

relationship between peak and rms levels crest factor=peak/rms

Question 15

What are peaks and what are their time scales?

Answer 15

transients/attacks

-very short time scale (micro to milliseconds)

Question 16

What is RMS and what is its time scale?

Answer 16

root mean squared

• average level, more or less
• longer time scales (milliseconds to seconds)
• perceived as loudness

Question 17

What is transfer function?

Answer 17

input:output ratio

Question 18

What is a true compressor (3 parts)?

Answer 18

• linear gain device with variety of ratios
• gain before threshold is applied to all input levels below 0dB
• attenuation applied to all input levels above 0dB

Question 19

What is a downward compressor?

Answer 19

signals below threshold pass at unity gain (1:1 ratio)

Question 20

What is threshold?

Answer 20

the point at which a dynamic processor begins to act

• in downward compressor/limiter, gain reduction is applied to signals that rise above threshold
• in downward expander, gain reduction is applied to signals that fall below threshold

Question 21

What is knee?

Answer 21

transition into gain reduction

• soft knee is smooth transition
• hard knee is sudden transition

Question 22

What is the difference between fixed and variable threshold?

Answer 22

• fixed threshold: adjust gain before threshold
• variable threshold: adjust gain after threshold

Question 23

What is ratio?

Answer 23

amount of gain reduction in compressor/limiter or expander/gate; expressed as input:output ratio

-ratio of 2:1 will yield an output of 1dB for every 2dB of input

Question 24

What is gain range?

Answer 24

sets amount of gain reduction when the gate is closed

Question 25

What is attack?

Answer 25

time it takes for compression to take effect (63% of intended gain reduction)

Question 26

What is release?

Answer 26

time it takes for compression to end once signal falls below threshold (90% of gain recovery)

Question 27

What is slope?

Answer 27

dB/millisecond

Question 28

What is time hysteresis?

Answer 28

offset between attack and release

Question 29

What type of attack and release times are determined by the crest factor of an input signal?

Answer 29

program dependent/automatic

Question 30

What are the 7 possible parameters for a compressor?

Answer 30

- input - ratio - threshold - attack - release - output/makeup gain - meter display (input, output, gain reduction)

Question 31

What is a limiter?

Answer 31

compressor with ratio of 10:1 or higher

Question 32

What makes gain reduction increase perceived loudness?

Answer 32

- gain reduction increases headroom - increased headroom allows makeup gain to be used to raise overall level - increase in overall gain (RMS) increases perceived loudness of signal

Question 33

What are the two types of expanders, and which one is more common?

Answer 33

- upward - downward - most common is downward

Question 34

What is range in expanders?

Answer 34

maximum amount of attenuation

Question 35

What is a gate?

Answer 35

expander with infinite range (full attenuation) - signals below threshold are eliminated by full attenuation - many equipped with key input and filter set in sidechain

Question 36

In a gate, what is threshold hysteresis?

Answer 36

lower mute threshold than unmute threshold

Question 37

How does a feed-forward dynamic processor work?

Answer 37

- audio is split after input and sent to gain reduction device and detector circuit - detector circuit reacts to input signal and applies gain reduction as signal rises above threshold

Question 38

How does a feed-back dynamic processor work?

Answer 38

- audio split after gain reduction device and to detector circuit - detector reacts to output signal and applies gain reduction as signal rises above threshold

Question 39

What is a detection circuit and what are the two types?

Answer 39

device that determines when and how much gain reduction will take place - RMS: average (compressors) - peak: responds to peak amplitude (limiters, gates)

Question 40

What is the sidechain/detection path?

Answer 40

signal path that feeds detection circuitry

Question 41

What are 4 examples of frequency dependent sidechain processing?

Answer 41

- de-essing - stressing - gating - sidechain high-pass filter

Question 42

What are 3 characteristics of a multiband compressor?

Answer 42

- crossover is used to divide audio input into two or more bands - each band is compressed separately - compressed signal is recombined before output

Question 43

Where are 4 places that multiband compressors usually used?

Answer 43

- broadcasting - mastering - program bus compression - parallel compression

Question 44

What is important to remember in stereo compression?

Answer 44

identical parameters must be set to avoid moving stereo image

Question 45

What is parallel processing?

Answer 45

-adding a compressed signal to an uncompressed signal in a mix

Question 46

What does an upward expander do?

Answer 46

increase gain of signals above threshold

Question 47

What does a downward expander do?

Answer 47

compress signals below threshold