On Sat, 03 Jul 2004 18:41:00 GMT, Richard Clark
wrote:

Let's take that same 92dB @ 1M @ 1 Watt and compare to the several
reports of hi-Z headsets. The first translation is of course against
application. Headphones encompass far less distance than 1M. I will
arbitrarily assign a path link of 1cM for the ear canal and re-specify
my Pioneer speakers to 112dB @ 1W (basically with the ear pressed next
to the speaker cone).

Should be 132dB @ 1W - which, of course, does nothing to the spread of
reported responses. However, even this correction is fraught with
error because it presumes a free field (violated at the ear canal
where it becomes a pressure field) - well, such are the pitfalls of
computing with sound.

For those seriously interested in the Physics of sound, vibration, and
its measurement, the preeminent authority in this field is in Denmark
with Brüel and Kjær:
http://www.bksv.com/pdf/Sound_Intensity.pdf
who offer microphones that can pick up sound 40dB below the threshold
of hearing.

By the way, one of the interesting points about their anechoic
chambers is mention that if you sat in one, you could hear your heart
beating (and this not just simply the blood pumping through veins near
the ears - which are self canceling anyway).

73's
Richard Clark, KB7QHC