HOW to increase DMIC sensitivity


#1

Hi support team,

i am successfully enable DMIC and it record sound clearly but when we record audio with 2 to 3 feet distance it record with very low volume.

is there any amixer command or any software changes to increase sensitivity of dmic. i refer below link to enable DMIC.

https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/enable-dmic.md.html

Thanks,
Arjun


#2

Well of course you can apply a gain to the signal.
There are a number of ways to do this.

The simplest way would be to use an alsa mixer control, IF there is one available for the dmic, which I don’t know. Look for things labeled volume or gain that seem to be tied to capture and/or dmic. Note that digital microphones don’t technically have a volume control on them, which means that if this mixer is implemented, then what it is doing is applying a digital gain to the signal.

The next option would be to use an alsa filter. First of all, I notice from the instructions you linked to that you are running debian, which means that you will have access to a full blown alsa rather than the tinyalsa in Android. That means that you can add filters. Near the bottom of this link they talk about adding a volume control for a digital microphone, obviously you would have to adjust for the differences between rpi and db410c, but the same approach is applicable; https://learn.adafruit.com/adafruit-i2s-mems-microphone-breakout/raspberry-pi-wiring-and-test

And the third option will be to manually apply a digital gain to a captured audio stream. There are a million tools you can use to do this, like ffmpeg, or audacity.