User Manual

ALF-DSP 88-U
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3.4.13 Noise Suppression
The Noise suppression module is used to remove non-human voice interference noise. It may distinguish human
voice from non-human voice and treat the latter as noise. After processing, only human voice audio signal is passed
to the output routing.
There is only one Noise Suppression module in the DSP Controller. Multichannel mixers are preset to realize
multiple channels to participate in the noise cancellation processor as shown in the below figure.
Suppression level: There are three levels of
noise suppression including: Mild (-6dB),
Medium (-10dB) and Aggressive (-15dB). dB here
refers to the re duction in decibel level of the
suppressed
noise. The bigger the value, the
more degradation of v oice signal is cause d,
therefore use noise suppression very cautiously.
3.4.14 Matrix
The audio Matrix has dual functions including routing and mixing. As shown in the figure below, the horizontal ax is
indicates the input channels, and the vertical axis indicates output channels. One-to-one routing of input to output
is set as the default settings. As an example, to mix and route audio signals of channel 1 and channel 2 and then
output both select OUT1 on both IN1 and IN2. If input 1 and 2 participate in auto mixing, then output 1 will not be
influenced by the auto mixe r. In other words, after setting auto mixing, echo cancellation and noise suppression
modules, routing needs to be set in the matrix from the correct input sources, like auto m ix e r, AEC, or ANS to ge t
the correct signal routing.
3.4.15 High and Low Pass Filter
Each output channel provides a pass-through filter module which consists of high-pass and low-pass filters. Each
filter has four parameters to adjust as follows:
Frequency: This sets the cutoff frequency of each filter. The cutoff frequency of Bessel and Butterworth are
selectable in -3 dB steps, and the cutoff frequency of Linkwitz-Riley are selectable in -6dB steps.
Gain: The Gain setting influences the incre ase and attenuation of each filter band.
Type: There are three types of filters to choose from; Bessel, Butterworth, and Linkwitz-Riley. Butterworth has the
flattest knee on the passband.