[pulseaudio-discuss] acceptable noise level for mic boost

Oleksij Rempel linux at rempel-privat.de
Fri Nov 29 12:56:46 PST 2013

Am 29.11.2013 17:22, schrieb Tanu Kaskinen:
> On Fri, 2013-11-22 at 18:34 +0100, Oleksij Rempel wrote:
>> Am 22.11.2013 17:48, schrieb Tanu Kaskinen:
>>> On Thu, 2013-11-21 at 16:42 +0100, Oleksij Rempel wrote:
>>>> Hello all,
>>>> i posted this email to ALSA, but probably PA devs have some ideas too.
>>>> ======================================================================
>>>> Hello Takashi,
>>>> what is acceptable noise level for mic boost?
>>>> My laptop has three levels of mic boost (+36dB). Level 3 is useless
>>>> since noise level will be about 0db. With level 1 i get -12dB noise, so
>>>> there is almost 12dB room for data... but it is not enough for normal
>>>> speech, which is about 20dB.
>>>> Are there any ALSA guide for HW designers, which will say some thing
>>>> like acceptable levels are 90-20dB?
>>>> There are some Skype and Microsoft prescriptions for certification.
>>>> For example M$ prescribe 18dB or more for speech to noise ration for
>>>> build in mics. It sound like good number to start.
>>>> In my case, i need to remove mic boost completely to guarantee minimum
>>>> 18dB SpNR. Suddenly i didn't found correct way to do it.
>>>> I will be thankful for some tip.
>>>> =====================================================================
>>>> So my question to PA devs. Do pulse audio need to know about noise level
>>>> of microphone? Will it help to make correct decisions? Especial for VoIP
>>>> and automatic gain control.
>>> We don't currently have any idea of the noise level, so we don't have
>>> code for adjusting our decisions based on that information either. So,
>>> I'd say that pulseaudio doesn't *need* to know about the noise level. Of
>>> course, if someone someday complains that pulseaudio does bad decisions
>>> because it doesn't take the noise level into account, then we would need
>>> that information.
>> Thank you for your response.
>> I have more questions:
>> Skype continuously trying to adjust record level.
> I've never used Skype, but I think I've heard that it allows you to
> disable the automatic gain control. I'd expect that to help with your
> problem.

Well, it is workaround but not fix. To make conference call we need
automatic gain control. Disabling it will work only for single person
call. The question is how to fix it?
I tested 7 different notebooks, and 4 of them had this issue. It is
nearly impossible for alsa to know about all of them.

I'll snip other part of discussion. Right now it is less important.

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