In message
<calvemi_04vk4qkvyehcfqdwhkbvepr1no7-dfgolazu5em2...@mail.gmail.com>,
dated Thu, 27 Mar 2014, S Drysdale <sdd...@gmail.com> writes:
I am pulling up an old thread here, because it may relate to my
question. Is there any requirement or guidance for sound pressure
level limits from ultrasonic equipment operating 40-50 kHz and used in
a residential environment?
It's usually held that 'if you can't hear it, the pressure level doesn't
matter' (within reason, not 240 dB!). But a few people CAN hear 40kHz to
50 kHz, mostly children, and since they don't know that others can't,
they may be at a loss to explain why they are distressed.
In addition, some ultrasonic equipment produces subharmonics; the
half-frequency is still above most people's range, and the one-third
frequency is above that of many, so they don't understand when someone
says, 'What's that awful screaming noise?'
So for a quiet life (!), make the emissions as weak as is practicable.
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
Nondum ex silvis sumus
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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