"Rich Grise" wrote in message
news
On Wed, 11 Jul 2007 22:52:17 -0700, Jeff Liebermann wrote:

"NotMe" hath wroth:

(Please learn to trim quotations)

Actually the human ear can detect a beat note down to a few cycles.

If you are talking about the beat between two close
audio frequencies then one can easily hear a beat way
below 1 Hz.


No, you cannot. Figure on 20Hz to 20KHz for human hearing:
http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml

What happens when you zero beat something is that your brain is filling
in
the missing frequencies. As you tune across the frequency, and the beat
note goes down in frequency, most people overshoot to the other side, and
then compensate by splitting the different.

If you are talking about beat frequency heard when
tuning to a carrier with a radio with a BFO or in SSB mode
then one can't hear any beat below 50 Hz or so.
The audio section of the receiver blocks anything
below about 50 Hz.


No, you've got it all wrong. The beat note happens because, when the
signals are close to 180 degrees out of phase, they cancel out such that
there is, in fact, no sound. This is what your ear detects. Now, if
you're zero-beating, say, 400 Hz against 401 Hz, I don't know if the
801 Hz component is audible or if it's even really there, but
mathematically, it kinda has to, doesn't it?

Are you talking radios or guitars?
With a guitar you might beat 400 Hz against 401 Hz.
With a radio you'd more likely beat 455 kHz against
455.001 kHz.


Thanks,
Rich