Gentoo Archives: gentoo-user

From: Michael Mol <mikemol@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Advice Needed: Conexant HD-Audio noisy audio
Date: Tue, 15 May 2012 16:54:27
Message-Id: CA+czFiDsY2wV519gN2gBhKiNsF+Ax0NcWJbU66h3akZc50oBsg@mail.gmail.com
In Reply to: [gentoo-user] Advice Needed: Conexant HD-Audio noisy audio by Ignas Anikevicius
1 On Tue, May 15, 2012 at 12:28 PM, Ignas Anikevicius
2 <anikevicius@×××××.com> wrote:
3 > Dear all,
4 >
5 > It's been quite a while since I noticed this annoying behaviour, but I
6 > could not find any information what might cause this. So the problem is
7 > that at lower volumes my HD-Audio with Conexant becomes very noisy and
8 > this is regardless of the sound system or speakers/headphones I use.
9 >
10 > The noise can be described, as high pitched, sandy texture noise
11 > heard during more expressive parts of the music or speech.
12 >
13 > I experience this on two Thinkpads (x200s and x200) and it very evident
14 > when I connected external speakers, they produced a lot of this noise,
15 > or maybe I just could hear it better, because of the frequency response
16 > of the speakers.
17 >
18 > Does anybody have some similar issues?
19 >
20 > My current audio setup:
21 >
22 >    * PulseAudio (but the problem is experienced with ALSA as well)
23 >    * MPD for music playing
24 >    * Conexant and other related modules compiled in, power-saving
25 >      features enabled.
26 >
27 > What I have tried to eliminate the noise:
28 >
29 >    * Various levels of Master,PCM,Headphone channels via Alsamixer
30 >    * Increase the sample rate in MPD settings.
31 >
32 > The noise can be clearly head when I Have the following setting on my
33 > Alsamixer:
34 >
35 >    * Master ~50
36 >    * PCM 100
37 >    * Headphone 100
38 >
39 > Does anybody has any thoughts on why am I experiencing this?
40
41 I have a strong expectation that part of what you're hearing is system
42 electrical noise.
43
44 What happens when you set:
45
46 * Master -> 100
47 * Headphone -> 100
48 * Everything else -> 0
49
50 ...but you're not playing anything? If you hear anything, then what
51 you're hearing isn't something you can really deal with without using
52 an external sound card. Any USB sound card would do fine. (A pair of
53 'gamer' headphones I bought at Best Buy advertised USB support...and
54 it turns out they were packaged with a tiny USB<->3.5mm sound
55 adapter.)
56
57 If you don't hear the characteristic sound you're describing, then I'd
58 expect you're encountering clipping. That's when the logical amplitude
59 of a signal is greater than the medium holding it, and that happens a
60 *lot* with integer PCM mixing and amplification.
61
62 Unfortunately, there's little to no standardization as to what '0' and
63 '100' mean between audio chipsets, so the best you can really do here
64 is crank all of your sliders to maximum, and decrease some of them
65 until you no longer hear the clipping. (And then remember which
66 positions on the relevant sliders that corresponds to; it usually
67 means you're getting no amplification, but also no attenuation.)
68
69 --
70 :wq

Replies

Subject Author
Re: [gentoo-user] Advice Needed: Conexant HD-Audio noisy audio Ignas Anikevicius <anikevicius@×××××.com>