Fernando Lopez-Lezcano wrote:
>On Sat, 2006-11-11 at 13:51 +0100, Daniel Wagner wrote:
>
>
>>>But the most intriguing part of the whole story: Not only did the noise
>>>get louder at a lower latency, it also seemed to precisely double its
>>>frequency when running at halve the number of frames. I even tried to
>>>measure the frequency of the noise. As far as I remember, when running
>>>jack for instance at 44100Hz, periodsize 32, the noise was at exactly
>>>44100/32 = 1378Hz!
>>>
>>>
>>Is an interrupt fired at each period? If so the cpu will use more power
>>(or woken if it was asleep); a small power 'surge' which can of course
>>have an influence on any analog hardware near by.
>>
>>
>
>Really sounds like the power supply, the high frequency transformers can
>"sing" with changes in load if the windings are a bit loose. I think
>capacitors can also do that.
>
>Somebody I know had a fanless computer in his room (a very old machine
>that really did not need fans if the case was left wide open) and the
>only remaining sound was some component singing with the network
>traffic...
>
>
A simple test to see if the load is causing the hum:
Open a PDF in acroread (if you have it installed). I noticed that I can
make some computer sing by dragging the view (hand tool) in acrobat
reader. acroread seems to contignously redraw when you use the hand tool.
The solution: get a high quality power supply & possibly a high quality
mainboard too. But as you are experiencing this with a laptop there's
not much you can do.
Pieter
PS: Maybe this is the one good reason to choose Apple over Dell... ?
Received on Mon Nov 13 04:15:21 2006
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