On Mon, 20 May 2002, T.C. Phelps wrote:

>> Sets of to work early in the morning leaving the
>> speaker driven with considerable number of watts at
>> about 10Hz. Arrives home in the evening to find the
>> neighbours just about climbing the walls with
>> madness at the continuous sub-sonic high power
>> levels.
>
>Ha! That's hilarious. Not too surprising though, and
>still preferable to putting Yoko Ono or Sid Vicious'
>solo album on. :)
>
>Got another subsonics story for you. I have an old
>copy of Borland Turbo C++ 3, and if you look for
>sound() in the help file it provides this little tale:
>
>
>   True story: 7 Hz is the resonant
>   frequency of a chicken's skull cavity.
>   This was determined empirically in
>   Australia, where a new factory
>   generating 7-Hz tones was located too
>   close to a chicken ranch: When the
>   factory started up, all the chickens
>   died.
>
>Some Internet sources attribute it as an urban legend,
>but it's amusing nonetheless. At any rate I suppose
>listening to a subwoofer put out 10 Hz all day is like
>living next to a factory!

There are places in shopping malls and factories and such where dodgy
acoustics cause the infrasound from the A/C ducts to sum. Standing there
is a very unnerving experience, especially for people who don't know what
is up. You get a free diaphragm massage (it is said that too much of this
will have people running for the loo). The pressure level on one I know is
high enough that it makes a sheet of paper held loosely between two hands
flap with several mm of amplitude. Normal hearing is affected (normal
sounds sound strangely modulated - probably infrasound overloading the
cochlea). No ducts are obvious anywhere near it.  It's just the focus of a
natural lens in the building.

Peter

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