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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