User Manual

ALF-DSP 88-U
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Minimum gain: Sets the minimum amount to which the signal level can be adjusted.
Gain sensing ratio: Sets the ratio by which signal level is attenuated or gained.
Speed: The speed at which the signal level is attenuated or gained.
Trim: The amount of gain or attenuation the output signal is adjusted by.
Noise threshold: The threshold / mean dB at which the ANC will activate and adjust signal. Signals greater than
the threshold will be increased, while signals less than the threshold will be reduced.
Distance: The physical distance between reference signal and local signals.
3.4.11 Auto Mixer
In a conference room, if several microphones are opened to the same gain level and there is only one person
speaking, the audio pickup of the microphone may be not clear. Other microphones will pick up noise and
reverberation in the room. When these signals are mixed with the desired ‘speech’ signals, audio output quality
may be greatly reduced and become un-intelligible. In addition, the whole audio signal chain may be over energized
by excessive gain and could start feeding back, result in a feedback loop, or ‘ringing’ sound. To solve the issue, other
unused microphones should be closed or ‘muted” when not in use. The auto mixer is used to automatically open
and close microphones based on signal input level.
There is a built-in gain share auto mixer inside the processor. It supports up to 8-channels. There is also a direct
output at each channel of the auto mixing matrix, which is only influenced by channel mute and bypasses the auto
mixer functions like auto gain and channel fader. Channels suitable for fixed volume like background music need to
be kept at a fixed level without being controlled by the auto mixer. For example, it will keep a microphone normally
open. Its gain will then not be influenced by the auto mixer. At this point, users may directly adjust the output of
the channel in the matrix router as well as turn off the auto mixer button of the channel. Its gain will not be
adjusted and gains at other channels will not be influenced by the signal level at the channel.
There are two groups of control parameters in the auto mixer module: main control parameters and channel
control parameters.