On Tue, May 15, 2012 at 12:28 PM, Ignas Anikevicius <[email protected]> wrote: > Dear all, > > It's been quite a while since I noticed this annoying behaviour, but I > could not find any information what might cause this. So the problem is > that at lower volumes my HD-Audio with Conexant becomes very noisy and > this is regardless of the sound system or speakers/headphones I use. > > The noise can be described, as high pitched, sandy texture noise > heard during more expressive parts of the music or speech. > > I experience this on two Thinkpads (x200s and x200) and it very evident > when I connected external speakers, they produced a lot of this noise, > or maybe I just could hear it better, because of the frequency response > of the speakers. > > Does anybody have some similar issues? > > My current audio setup: > > * PulseAudio (but the problem is experienced with ALSA as well) > * MPD for music playing > * Conexant and other related modules compiled in, power-saving > features enabled. > > What I have tried to eliminate the noise: > > * Various levels of Master,PCM,Headphone channels via Alsamixer > * Increase the sample rate in MPD settings. > > The noise can be clearly head when I Have the following setting on my > Alsamixer: > > * Master ~50 > * PCM 100 > * Headphone 100 > > Does anybody has any thoughts on why am I experiencing this?
I have a strong expectation that part of what you're hearing is system electrical noise. What happens when you set: * Master -> 100 * Headphone -> 100 * Everything else -> 0 ...but you're not playing anything? If you hear anything, then what you're hearing isn't something you can really deal with without using an external sound card. Any USB sound card would do fine. (A pair of 'gamer' headphones I bought at Best Buy advertised USB support...and it turns out they were packaged with a tiny USB<->3.5mm sound adapter.) If you don't hear the characteristic sound you're describing, then I'd expect you're encountering clipping. That's when the logical amplitude of a signal is greater than the medium holding it, and that happens a *lot* with integer PCM mixing and amplification. Unfortunately, there's little to no standardization as to what '0' and '100' mean between audio chipsets, so the best you can really do here is crank all of your sliders to maximum, and decrease some of them until you no longer hear the clipping. (And then remember which positions on the relevant sliders that corresponds to; it usually means you're getting no amplification, but also no attenuation.) -- :wq
