Glossary of Terms
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dBm
- Short for “decibels as referenced to milliwatt,” dissipated in a standard load of 600 ohms.
1 dBm into 600 ohms results in 0.775 volts RMS.
dBV
- Short for “decibels as referenced to voltage,” without regard for impedance; thus, one volt
equals one dBV.
Dynamic range -
The difference between the loudest sections of a piece of music and the softest
ones. The dynamic range of human hearing (that is, the difference between the very softest passages
we can discern and the very loudest ones we can tolerate) is considered to be approximately 120 dB.
Modern digital recording devices are able to match (or even exceed) that range.
FET –
An acronym for “Field Effect Transistor,” a type of solid-state semiconductor.
Flat frequency response
-
No boost or attenuation in any frequency range.
Gain reduction -
A synonym for compression or limiting.
Insert
-
A place where a signal path can be broken so that a processing device can be placed in line
with the signal at unity gain (no cut or boost). An insert is most commonly a TRS jack with one
conductor being an output (send) and the other being an input (return). The jack is wired with a
normalled
connection
so that with nothing plugged in, the send and return are connected together.
Knee
-
A compressor's
knee
determines whether the device will reach maximum gain reduction
quickly or slowly. A gradual transition is called "soft knee,” while a more rapid transition is called
“hard knee.” Soft knee compression and limiting is generally more desirable for musical
applications.
Limiter -
A compressor that operates at high compression ratios of 10:1 or higher.
Limiting -
A more severe form of compression, where a high compression ratio (of 10:1 or higher) is
being used.
Limiting Amplifier -
A synonym for “limiter.”
Line level
- Refers to the voltages used by audio devices such as mixers, signal processors, tape
recorders, and DAWs. Professional audio systems typically utilize line level signals of +4 dBM (which
translates to 1.23 volts), while consumer and semiprofessional audio equipment typically utilize line
level signals of –10 dBV (which translates to 0.316 volts).
Low shelving filter
- An equalizer circuit that cuts or boosts signal below a specified frequency, as
opposed to boosting or cutting on both sides of the frequency.
Makeup gain -
A control that allows the overall output signal to be increased in order to compensate
(“make up”) for the gain reduction applied by the compressor.
Microsecond (
μ
s)
- A millionth of a second.
Millisecond (ms)
- A thousandth of a second.
Noise floor
- Unwanted random sound (noise) added by an electronic device.
Patch bay
- A passive, central routing station for audio signals. In most recording studios, the
line-level inputs and outputs of all devices are connected to a patch bay, making it an easy matter
to re-route signal with the use of patch cords.
Patch cord
- A short audio cable with connectors on each end, typically used to interconnect
components wired to a patch bay.
