shriekingly tinny sound in 10.10 at higher volumes

[Gilles Gravier]

 Hi!

On 10/09/2010 08:02, K V wrote:
> Heyas all,
> Just a quick question.  Running an Asus ATI Mobo with an ATI HD48x0
> sound card (output from lspci) with Ubuntu 10.10 desktop version.
>
> It seems to me that all sound is pretty quiet unless it is cranked way
> up (as compared to my ancient Turtle Beach Santa Cruz, which I hated
> to give up), but any sound level above 'unamplified' in sound
> preferences gains a tinny note at first which grows exponentially to a
> pure shriek, as if a thousand fingernails were being scraped across
> miniature blackboards through a really high pitched feedback loop, or
> a bunch of psychotic bats were calling the days news directly into
> your ear canal.  It's unpleasant, dig?  :-D
> Anyway, any ideas gentles?  This is painful.
> Oh, btw, it is the same from the main output in the back panel or over
> headphones from the front/headphone jack...
>
> Peace,
> V

What you are describing here sounds (pun intended) like a Larsen effect
(or loopback). Probably in your sound mixer you have enabled hearing the
"mic input". Which means that your machine's microphone is picking up
sound... that sound gets amplified, comes out of the speakers, and gets
(again) picked up by the microphone, re-amplified, re-output through the
speakers, and re-picked up... you get the picture.

The higher you set the volume, the more violent the effect.

Open your sound mixer (not just the simple volume applet, but the full
one where you can control individual volumes) and make sure that in the
output section (where you have playback volumes) your microphone is muted.

Gilles