Re: gentle noise (was: (Offtopic) Humming on ibook2 audio port?)
On Thu, 10 Jan 2002, Siggi Langauf wrote:
> After a night of sleep and some more listening, I found out that these
> sonds occur when there is acces to the hard disk drive.
> I'm using ext3, therefore the regular peaks.
> When I do something like "find / -type f|xargs cat >/dev/null", I get a
> constantly chirping sound (still very high pitch and very low volume...)
>
> I guess it's a hardware issue, but haven't tried with MacOS yet.
I don't boot over to OS-X or MacOS 9 very often, so if you get a chance to
test it before I do, let me know the results.
> Maybe one could filter that out...
I'm hoping so :-)
> It's not that bad; I guess you only hear the sound on earphones because
> the hard disk would be louder if you tried to listen to the speakers...
In all fairness, headphone speakers seem to be matched with their usage
better than the internal speakers on my TiBook (which suck, IMHO, but
they're not THAT bad all things considered)...dunno about the iBook, but I
would expect roughly the same.
> Btw: thanks for your tumbler work! It was really nice to watch more and
> more of the sound features appear ;-)
No prob :-) I have A TON of more work to do, including a possible
rewrite, in the future. My to-do list includes setting up the filtering,
dynamic range compression (which may be the trigger for the rewrite),
enabling stereo controls better (for things like balance and unganged
left and right channel volume control), and I hope to improve on some of
the bits of the code that I'm still not thrilled with how I implemented
them.
> Maybe you want to have a look at the suspend mode: When pmud puts the
> machine to sleep while playing mp3s, I sometimes get strange noises when
> it wakes up again. The only way to fix this is to unload/reload the sound
> modules...
Well, the tumbler is an odd device and probably unlike most sound cards
that people have experienced. Most likely, it's not really the suspend
bits in the sound driver (which there aren't any, really), but rather the
suspend bits in the I2C drivers (since tumbler is an I2C device rather
than a PCI bus device like most sound chips/cards). I am pretty familiar
with the I2C code, so maybe I'll look at that as well. I probably should
be sending the chip a reset on wakeup, but I haven't implemented any real
reset code yet.
C
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