Is It Possible to make a noise gate with side chain Sigma Delta DSP

You can implement a noise gate using any of the blocks in the dynamics processing section of the library that use a look-up table. The screen shot below shows an example of a graph set up for noise gating; below a certain input signal level (about -60 dB here), the output will be gated off.

You can also see in this figure that the processing block has a red input pin. This red pin is used to input a signal to the level detector so that a signal other than the one being processed can control the gate. For your application, you could input the microphone signal on the green audio path input pin and the sidechain control on to the red pin.

The input-to-output latency of your signals will typically be dominated by the audio converters. The SigmaDSP core itself will only have a latency of just a few samples as the data is latched in and out of the core.

Hello I looked at data sheet and could not find any latency specs on the audio converters, I am just not seeing it, Thanks. Ted Polito

The group delay of the converters is listed in the Digital Filters spec table (pg 10 of the ADAU1761 datasheet). At fs=48 kHz, the group delay of the ADCs is 479 us and the DACs is 115 us.

The noise gate described in the datasheet is in the analog ALC before the ADCs. The dynamics processor I described above is running in the SigmaDSP core and is flexibly programmed using the SigmaStudio blocks.

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Thank you,
EZ Admin