Fred Bartoli wrote:

"Ian White, G3SEK" a écrit dans le message news:
...
Roy Lewallen wrote:
Multiplying the two original signals of 1500 and 1955 generates the two
new frequencies of 455 and 3455, for a total of four frequencies after
multiplication. Adding them wouldn't do it.

Part of the confusion is that audio engineers talk about "mixing" where
they actually mean adding. Mixing - as RF engineers use the term - is
precisely what they don't want!



Well, ear is also somewhat non linear. So they are also doing mixing.

What the audio engineers do at the "mixing desk" involves only adding.
What our ears do, is something else.

But in fact, our ears are very close to linear. There is a belief that
because we can hear "beat" frequencies, there must be some non-linear
mixing in our ears... but that is actually a fallacy. The way we hear
beat frequencies - the difference frequency between two separate audio
tones - is due to simple linear addition and subtraction of two sound
pressure waves. Non-linear mixing is not required.

(If non-linear mixing were involved, we'd hear the sum frequency as well
as the difference frequency... but in fact we don't, unless there is
some other source of non-linearity outside of our ears.)


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek