echo (was: ASU software - pre-pre-release impressions)

Arnout Engelen mokocommunity at
Wed May 21 23:50:09 CEST 2008

On Tue, May 20, 2008 at 07:19:34PM -0700, Mike Montour wrote:
> In my tests the echo went away when I
> muted the Neo's speaker or microphone, so it did not seem to be a
> network issue.
> The audio coupling between the Neo's speaker and microphone can be
> measured independently of the GSM stuff, e.g. with the 'Jaaa' audio
> analyzer from or with 'xoscope'.
> Various ALSA mixer controls will affect the level of the coupled signal,
> but these also affect the intended sound paths (loudness of the speaker
> and sensitivity of the microphone). The mixer settings have to be
> selected to give the best compromise between these factors. 

I once heard an interesting story about the human body: supposedly, the
mouth is so close to the ear that if you'd talk aloud a lot, you'd
damage your own hearing. The body hacks around this by putting some
slight tension on the eardrum while speaking, effectively muting
incoming sound a bit and preventing damage.

I wonder if we could take advantage something like this to reduce echo,
e.g. reducing mic gain when input is high or reducing volume when mic
input is loud.

But, let's not try and fix things before we're sure they're (still) broken :).


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