Merlin Integrated Signal Processor ISP-100, User Manual

Page: 112 / 146

8-42
10 July 1998
Gate
Figure 8-18 Gate component.
A gate (see Figure 8-18) is used in situations where the input signal is
characterized by long periods of silence and a noticeably high noise
floor, such as a signal taken from magnetic tape or from an open
microphone. Gating is accomplished by attenuating the output signal
during the periods of input silence in order to reduce the audibility of the
noise.
Familiar Controls
Most of the controls in the ISP-100 Gate are common to nearly all
traditional noise gates. These controls should be familiar to anyone
with experience in the operation of any gate.
Threshold
The Threshold control adjusts the input signal level below which
attenuation is applied. When the average input signal level is
above the threshold value, no attenuation is applied and the
level of the output signal exactly matches the level of the input
signal. When the average input signal is below the threshold
value, attenuation is applied and the level of the output signal is
less than the level of the input signal by the amount dictated by
the selected gated attenuation value.
Threshold is adjustable in the range {-60 dBFS to 0 dBFS}.
Opening Time
A gate monitors the level of the input signal and controls the
level of the output signal accordingly. When the average input
signal level increases from below threshold to above, a gate
opens (removes all attenuation) so that the output signal level
matches the input signal level. Desirable sound effects can
sometimes be created if a gate is forced to ramp the output
signal level to its new value gradually rather than
instantaneously. The Opening Time control adjusts the duration
of this ramp.
Opening Time is adjustable in the range 20 µSec (one sample)
to 50 mSec.