Computer Speaker Problem

I'm having trouble playing sound on my computer. When the speakers are
turned on, and no sound is playing it's fine, but once I start to play
a sound, a horrible, loud garbled sound comes out. I've noticed that
if I move my mouse, even just scroll the mouse wheel, it clears up the
sound. Once I stop moving the mouse, the garbled sound comes back.

dplatt...

I have seen (well, heard) this sort of problem occur on systems which
implement a power-saving mode.

Specifically: on an Athlon-based system, with an AudioPCI sound card,
the sound would start garbling badly if I turned on the CPU's
"disconnect from the bus during idle" power-saving feature. This
feature causes the Athlon to turn off its memory-cache-snooping
hardware when entering a CPU-idle state, shutting down this part of
the CPU core and saving quite a bit of power (and reducing CPU
temperature by many degrees). However, this forces the CPU to do a
complete cache-flush when it wakes up again, and this apparently adds
a _lot_ of latency to the wakeup process. The latency (or the
conflicts on the memory bus during the cache cleanup) were so great
that the AudioPCI would fail to get valid data from memory, and would
start snarling.

I ended up having to put in a tweak which disabled the heat-reduction
mode whenever the sound drivers were loaded, and reenabled it after
they were unloaded.

Similar things might happen if the sound interface were trying to
share an IRQ with another device. In general ISA devices cannot share
IRQs. PCI devices can, _if_ their drivers are well-behaved.

Also, if I play a cd on my computer, it sounds fine as well. I've also

dplatt...

CD playback is usually performed by having the CD-ROM drive convert
the signal to analog. It's then mixed, in analog form, with the
output of the sound chip's PCM channel. As a result, it'll work fine
even if something is interfering with the PCM.

noticed when I shutdown my computer, that sound is messed up, but the
startup sound is fine. This leads me to believe there's some sort of
excessive current issue. Does anyone have any ideas at all?

dplatt...

I suspect that it's probably not a current issue, but has to do with
something in the system software which is interfering with the sound
card/chip's ability to get the audio data it needs. Conflicts with
powersaving, another device driver (e.g. IRQ conflicts), etc. might be
the problem.

More details about your motherboard, sound card/chip, IRQ and other
hardware assignments, etc. might clarify the situation.