On Behalf Of cpghost
> On Sun, 8 Jun 2008 21:40:17 -0600
> James <[EMAIL PROTECTED]> wrote:
>> I have a high pitched whine coming from my motherboard when the EHCI
>> USB 2.0 controller is enabled in the BIOS.  The whine only starts
>> FreeBSD 7.0-RELEASE is halfway through booting.
>> The whine also goes away when I plugin a USB drive in with EHCI
>> controller enabled (usb keyboard and mouse being already plugged in).
>> Is this a hardware problem, or could it possibly be software
>> related???
> Hard to tell. I've had whining EPIA-boards when run at 1000 Hz,
> and after switching kern.hz to 100 Hz in /boot/loader.conf, the
> high-pitched whine stopped entirely. It also stopped when I
> slightly deviated from the 1000 Hz (to, say, 900 Hz or 1100 Hz),
> so there was obviously some hardware component on the boards
> oscillating like mad at this very frequency.
> I'm no specialist and it may be an urban legend, but from
> what I gathered, some coils could exhibit the behavior of
> generating those high-pitched whines when exposed to certain
> frequencies.
> -cpghost.

No legends here. The horizontal sweep frequency for televisions in the
US is 17,500 Hz. Many people could hear that whistle from cheap flyback
transformers. Other devices would buzz, hum or rattle when they
resonated with EM fields. Occasionally they can be heard by humans, more
frequently they can be heard by their pets. As I have gotten older, I
don't notice it as much.

Bob McConnell
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