Dynamic Processing Terminology

Question

This question has led me to request clarification on the names (and uses) regarding dynamic processing more widely.
The table below shows my understanding of the names of the processes when a signal goes above or below a defined threshold, and the action (block, cut, raise) that is then applied to the signal.

            ┌ Threshold ───┬────────────────┐
            │ Below        │ Above          │
  ┌ Action ─┼──────────────┼────────────────┤
  │ Block   │ GATING       │ ?1             │
  │ Cut     │ EXPANSION ?4 │ COMPRESSION ?5 │
  │ Raise   │ ?2           │ ?3             │
  └─────────┴──────────────┴────────────────┘

So, is there a naming convention (and a practical or creative use) for
1. blocking a signal completely when it goes above a threshold?
2. raising the signal when it falls below a threshold?
3. raising the signal when it goes above a certain threshold? 8|
and
4. why is attenuating a signal that falls below a threshold called "expansion"?
finally
5. COMPRESSION would include LIMITING ... so is there a better way of drawing the table?

tia

score 4 · Accepted Answer · answered Jun 03 '11 at 13:40

A few quick answers:

Q1. Probably not useful very often, since it would mean that the loud things you recorded you wanted completely removed. Might be useful perhaps if an otherwise good recording had been spoiled by occasional loud thuds or pops, but you would need a fast attack/lookahead for this to work well.

Q2 & 3. These are kind of the inverse of expansion and compression. For example, after compressing, you usually apply a gain boost ("make-up gain"), so the end result is similar to leaving the loud bits alone and boosting the quiet bits.

Q4. A compressor "compresses" the dynamic range of your music (the loud bits are not so loud compared to the quiet bits any more). An expander "expands" the dynamic range of your music (the loud bits are louder compared to the quiet bits)

Dynamic Processing Terminology

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