Extended Range Adiometrics

Mike Alf gmalf19 at mail.nwlink.com
Tue Aug 5 03:24:51 EST 1997


On 9 Aug 97 01:07:47 GMT, "------ Dennis"
<energizer-bunny at bigfoot.com> wrote:

>I need to do some reasearch on if there is
>a portion of the human population. i.e.
>.002 percent which can hear frequencies
>above and below normal hearing.
>
>Unfortunately I have no suitable equipment
>to use.  Any suggestions?
>
>w6089 at cloudnet.com

An audio signal generator connected directly to any of the piezo
tweeters (Motorola) will get you well past 20 kHz.  Calibration will
be somewhat of a problem.

It's a bit more difficult to get a true pure tone below 30 Hz.  Most
of the time the person will be hearing harmonics.  You might look into
a subwoofer that uses an acoustical lowpass filter.  I don't recall
seeing any of them that go below 20 Hz.

There are headphones that claim to go down to 20 Hz and up to at least
25 kHz but that would be difficult to verify.  Distortion would be an
important element also.

Most audio signal generators have no problem producing clean sine
waves above 20 kHz and below 20 Hz but the problem comes with the
transducers.

Mike




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