A few years ago I used to work beside someone whose old CRT monitor
had a very noisy flyback transformer. The 15kHz noise drove me
absolutely nuts yet no-one else seemed to be able to hear it. I was
always turning the sqealing thing off when she wasn't around.

I haven't had any problems like this for a couple of years. I'd like
to think it's because most monitors are LCD these days, but more
likely as I've got older my hearing doesn't stretch to 15kHz any more.

Cheers,
Zik

On 9/6/06, Jinx <joecolquitt@clear.net.nz> wrote:
> A friend has been giving me grief for some few weeks about
> noise she says is coming from a microwave tower about 300m
> from her home and keeping her awake in the quiet of the night.
> She describes the sound as a constant high-pitched tone. I have
> every reason to believe she is not crazy, and she assures me she
> has not got tinnitus or any other hearing problems. She may be
> dwelling on the problem (though she says she isn't), which might
> tend to aggravate any auto-suggestion. I'm getting all this from a
> woman who is quite frazzled and cranky after many sleepless night
> but who hasn't lost the plot. She's still quite rational about possible
> causes, but not being technical at all she has a limited number of
> causes to think about. There aren't many houses around where this
> tower was put up so she hasn't neighbours to discuss it with
>
> She reckons she's being fobbed off or stonewalled by the owner
> of the tower (BCL) and the local council and as she doesn't seem
> to be getting anywhere on her own I've offered to try and gather
> evidence. Including, if I have to, trying to record the noise to
> present to someone as hard evidence. What she has so far are
> just opinion and supposition.
>
> I haven't heard the noise myself, she's quite some distance away
> and a visit hasn't been possible yet. She said a tech, ISTR, had
> suggested (I don't know the circumstances or context of the
> conversation) it was 15kHz, which made me think perhaps a
> switch-mode with something loose, but the tone she sung over the
> phone is nowhere near 15kHz. Probably more like 3/4 the way up
> a piano, definitely within almost everyone's hearing range, which
> you'd think would be easily heard by anyone. A late-shift engineer
> came to her home and thought he kind of heard something, but
> seems not in the "my god, how do you sleep with that racket ?"
> league or a problem would have been immediately apparent
>
> If the tower is in fact putting out this mysterious tone, I wonder
> about a couple of things
>
> (1) Apparently the sound is no louder at the tower. I would have
> thought it would be, given the sqrt law unless -
>
> (2) there is some beat frequency being created at her home by
> two or more inaudible frequencies, and she just happens to lucky
> enough to be at a place where a combination of beat frequency
> and distance make a node
>
> Any thoughts ? Any similar experiences ?
>
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