View Single Post
  #192   Report Post  
Old July 8th 07, 05:15 AM posted to sci.electronics.basics,rec.radio.shortwave,rec.radio.amateur.antenna,alt.cellular.cingular,alt.internet.wireless
Ron Baker, Pluralitas![_2_] Ron Baker,    Pluralitas![_2_] is offline
external usenet poster
 
First recorded activity by RadioBanter: May 2007
Posts: 92
Default AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency


"Bob Myers" wrote in message
...

"Ron Baker, Pluralitas!" wrote in message
...

"Bob Myers" wrote in message
...

"Ron Baker, Pluralitas!" wrote in message
...

First of all, do you think you could possibly learn to trim your posts?


Apparently, no, you can't. Too lazy to take the trouble to
perform this common courtesy, or what?


You could always plonk me.


An audible beat tone is produced by the constructive and destructive
interference between two sound waves in air. Look at a pictorial
representation (in the time domain) of the sum of sine waves,of similar
amplitudes, one at, say, 1000 Hz and the other at 1005, and you'll
see it.

Bob M.


How come you don't hear a 200 Hz beat
with a 1000 Hz tone and a 1200 Hz tone?


For the simple reason that there isn't actually a "tone" involved -
in other words, there is no actual signal at the difference frequency.
There can't be, since there is no "mixing" (multiplication) of the
two original tones.


There is no multiplication of 1000 Hz and 1005 Hz
either, is there? Why don't you hear 1000 Hz and
1005 Hz rather than a single tone varying in amplitude?

The "beat" is really just the perception of
the amplitude variation caused by the interference previously
mentioned. You cannot sense such variations if they occur
rapidly enough, any more than you can detect the flicker of a
light source which is varying rapidly enough.

Bob M.


Could it be that the human auditory system is not
linear?