[linux-audio-user] Re: The famous "Jack Hum" (Can't record and desparate)

[Daniel Wagner]

> 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.

daniel