16 Oct
2003
16 Oct
'03
5:50 p.m.
This is a little off-topic, but I hope you don't mind. I get quite a
lot of noise from my soundcard. There is a pulsing that sounds
something like a very fast morse code at a consistent pitch, and it's
unacceptably loud. I notice variations in this noise based on how I
move my mouse.
At first I thought this was just because of my shoddy 5-year-old
Soundblaster Live, but I have a new Audiophile 2496 and it does the same
thing.
Today I tried removing the stereo mini plug from my soundcard and
touching it to the metal on my case. The sound was nearly identical.
From the little that I know about electronics, I
conclude that the
problem is voltage fluctuations in the metal of the case. Does
this
mean my case needs to be grounded somehow?
What can I do to fix this problem?
Josh
16 Oct
16 Oct
6:06 p.m.
Today I tried removing the stereo mini plug from my
soundcard and
touching it to the metal on my case. The sound was nearly identical.
Do you hear the same noise with headphones in the Sound Blaster card and
all other outputs/inputs disconnected from all cards?
I suggest that you take your electricity for the computer and amplifier
and all that get's physically connected to them from one grounded outlet.
And beware if you have antennas connected to the system, they give ground
loop humming also.
I have all my vcr, amplifier, cd-player, computer, monitor, etc. taken
from one grounded outlet. So they all should share same ground. Also easy
to plug just one socket out in case of thunder.
Tommi
From the little that I know about electronics, I
conclude that the
problem is voltage fluctuations in the metal of the case. Does
this
mean my case needs to be grounded somehow?
What can I do to fix this problem? 
6:07 p.m.
This is a little off-topic, but I hope you don't
mind. I get quite a
lot of noise from my soundcard. There is a pulsing that sounds
something like a very fast morse code at a consistent pitch, and it's
unacceptably loud. I notice variations in this noise based on how I
move my mouse.
At first I thought this was just because of my shoddy 5-year-old
Soundblaster Live, but I have a new Audiophile 2496 and it does the same
thing.
Today I tried removing the stereo mini plug from my soundcard and
touching it to the metal on my case. The sound was nearly identical.
Josh,
Not at all sure about the case grounding part. That's pretty strange.
Maybe your external speakers and your PC are on different power grounds?
Watch out if either is 2-prong. People get killed in the US every year due
to our unsafe power system.
The mouse part of this is a great example of what happens in some systems
when the sound card IRQ is 'behind' the mouse IRQ, or possibly shared with
the mouse IRQ. The 'IRQ ordering' in a standard PCI (non-SMP, non-IOAPIC)
is:
0,1,8,9,10,11,12,13,14,15,3,4,5,6,7
(sometimes the #8 is replace by the #2 - don't worry about that.)
Do an lspci to see what IRQ's you mouse and sound card have.
The reason you'd get a noise when you move you mouse is that the mouse
interrupt handler is called, it takes time, and that delays the sound card
doing it's work. This delay empties a buffer or something and that causes a
problem.
A consistent sound could be some other device, like a disk drive, creating
interrupts and your sound card being on a bad IRQ.
If you put a sound blaster on IRQ 5, 6 or, then in my experience I have had
a lot of problems.
This could all be correct and solve your problems, or it could have nothing
to do with your system. ;-)
Hope this helps,
Mark
From the little that I know about electronics, I
conclude that the
problem is voltage fluctuations in the metal of the case. Does
this
mean my case needs to be grounded somehow?
What can I do to fix this problem?
Josh 
6:39 p.m.
Joshua Haberman wrote on Thu, 16-Oct-2003:
This is a little off-topic, but I hope you don't
mind. I get quite a
lot of noise from my soundcard. There is a pulsing that sounds
something like a very fast morse code at a consistent pitch, and it's
unacceptably loud. I notice variations in this noise based on how I
move my mouse.
It appears to be system load based, it might be an internal voltage
interaction when your CPU goes from idle to active. I've seen
this before..... try to run this at a bash prompt:
while true; do yes > /dev/null ; done
Then try your audio, and see how it changes. The noise might
go away entirely with a non-idle processor. Try different buffer sizes and see
if the pitch changes.
jlc
6:57 p.m.
Thanks for the responses everyone!
On Thu, 2003-10-16 at 15:06, Tommi Sakari Uimonen wrote:
Do you hear the same noise with headphones in the
Sound Blaster card and
all other outputs/inputs disconnected from all cards?
No!! The noise goes away completely (and I get good signal levels)! Cool.
I suggest that you take your electricity for the
computer and amplifier
and all that get's physically connected to them from one grounded outlet.
And beware if you have antennas connected to the system, they give ground
loop humming also.
I tried putting everything on the same power strip and I still get the
noise. I have a mixer and an amplifier that the signal is going
through, and I get the same noise going:
computer -> mixer -> headphones
computer -> amp -> speakers
as I get going
computer -> mixer -> amp -> speakers
On Thu, 2003-10-16 at 15:35, Jesse Chappell wrote:
Joshua Haberman wrote on Thu, 16-Oct-2003:
This takes away a large part of the noise. There is still some noise
that sounds different, and I can still hear my mouse move. When I move
my mouse vigorously, it starts sounding closer to what it sounds like
when that shell script is not running.
Josh
This is a little off-topic, but I hope you
don't mind. I get quite a
lot of noise from my soundcard. There is a pulsing that sounds
something like a very fast morse code at a consistent pitch, and it's
unacceptably loud. I notice variations in this noise based on how I
move my mouse.
It appears to be system load based, it might be an internal voltage
interaction when your CPU goes from idle to active. I've seen
this before..... try to run this at a bash prompt:
while true; do yes > /dev/null ; done
17 Oct
17 Oct
4:08 a.m.
Do you hear
the same noise with headphones in the Sound Blaster card and
all other outputs/inputs disconnected from all cards?
No!! The noise goes away completely (and I get good signal levels)! Cool. I suggest that
you take your electricity for the computer and amplifier
and all that get's physically connected to them from one grounded outlet.
And beware if you have antennas connected to the system, they give ground
loop humming also.
I tried putting everything on the same power strip and I still get the
noise. I have a mixer and an amplifier that the signal is going
through, and I get the same noise going: It appears to
be system load based, it might be an internal voltage
interaction when your CPU goes from idle to active. I've seen
this before..... try to run this at a bash prompt:
while true; do yes > /dev/null ; done
This takes away a large part of the noise. There is still some noise
that sounds different, and I can still hear my mouse move. When I move
my mouse vigorously, it starts sounding closer to what it sounds like
when that shell script is not running. 
11:21 a.m.
On Fri, Oct 17, 2003 at 11:08:34AM +0300, Tommi Sakari Uimonen wrote:
There's a lot of info available on proper grounding techniques.
E.g. there's some here:
http://www.cs.uu.nl/wais/html/na-dir/AudioFAQ/pro-audio-faq.html
I tried
putting everything on the same power strip and I still get the
noise. I have a mixer and an amplifier that the signal is going
through, and I get the same noise going:
Then you should have all the equipment physically connected to each other
from their cases, like grounding them together. ** BUT BEWARE, THIS MIGHT
BE DANGEROUS. ** I don't know where you live, but in Finland the
electricity system is pretty darn safe and I wouldn't have any hesitations
to do so. There might be high voltage differences between the cases, so
all equipment should be disconnected from the outlet before grounding them
together. And take life insurance first :) And don't sue me if something
blows :) > > It appears to be system load based, it might
be an internal voltage
> > interaction when your CPU goes from idle to active. I've seen
> > this before..... try to run this at a bash prompt:
> > while true; do yes > /dev/null ; done
>
> This takes away a large part of the noise. There is still some noise
> that sounds different, and I can still hear my mouse move. When I move
> my mouse vigorously, it starts sounding closer to what it sounds like
> when that shell script is not running.
There are various suggestions for this kind of problem in the old
Audio-Quality-HOWTO:
http://www.linuxdj.com/audio/quality
--
Paul Winkler
http://www.slinkp.com
Look! Up in the sky! It's MIGHTY CHAIN WOMAN!
(random hero from isometric.spaceninja.com)
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linux-audio-user@lists.linuxaudio.org
6 comments
5 participants
participants (5)
-
Jesse Chappell -
Joshua Haberman -
Mark Knecht -
Paul Winkler -
Tommi Sakari Uimonen