Hello developers,
some cards (most notably, Intel HD audio) have the PCM control as softvol, and default to S16_LE as a format for dmix. Since softvol is configured to attenuate signal, and not many people set this control to 100% (especially those who have no other volume controls), this effectively leaves less than 16 bits per sample.
The card can surely produce sound of better quality in most cases, if one changes defaults.pcm.dmix.format in ~/.asoundrc. However, one should now search a lot of forums in order to know about this setting. Not everyone does this, and not everyone is even able to diagnose the "noisy sound in Linux" problem properly as "too few bits per sample in the default configuration". A much better situation would be if ALSA defaulted to good quality (i.e.: S24_LE or S32_LE on all cards that require softvol and support this sample format). Could you please change the files in /usr/share/alsa/cards accordingly?