Surround sound with only 1 speaker

[horvendile]

So, anyway, mix a 40000 Hz wave and a 40100 Hz wave and they interfere to a 100 Hz wave. IIRC.

Really?, I have never heard of that before, have you got links explaning how this works.

Not really, since I can't remember the English word (enormously irritating). I can probably find Swedish links, but...

Tell you what, take a look at this. It demonstrates the concept. First two waves of slightly different frequency:
(...)
Aaarrgh, I actually made pictures only to discover that I don't know how to post them! It appears that you must host them yourself. Understandable but unconvenient right now.

I'll see if I can e-mail them to you. They are quite small.

 

[horvendile]

Even so, this does not map to how sound travels, sound is a "longitudinal wave" the most people image a sound wave as a sinusoidal pressure time representation but this is not really how it is.

I'm quite sure sound travels like a slinky spring being compressed horizontally (longitudinal) rather than a slinky wiggeled up and down vertically.

I'm actually not sure whether we disagree or not. Yes, sound is a longitudinal wave. So if a sound wave was to be plotted in an xy-plot it would not be a sinus. But a plot of pressure versus time or propagation direction would be a sinus.

 

[arjan de lumens]

Not really, since I can't remember the English word (enormously irritating). I can probably find Swedish links, but...

I suspect that the word you are looking for is "beating". Does http://hyperphysics.phy-astr.gsu.edu/hbase/sound/beat.html match what you are trying to describe?

 

[horvendile]

I suspect that the word you are looking for is "beating".

Yes, that's it.
Thank you!
And micb: That link does roughly the same jobs as the pictures I never sent you.

 

[GodZero]

So, anyway, mix a 40000 Hz wave and a 40100 Hz wave and they interfere to a 100 Hz wave. IIRC.

Frequency mixing results in 4 fequencys as the output, if you were to call the two input frequency a and b; the output would be: a, b, a-b, and a+b.

You would wind up with an unwanted tone at 80100 hz also, that's why you want the mixer frequencys so high.

Immagine the tone you want is 15000 hz, you would have reference "a" at 40000, "b" at 25000 hz, and the one extra output tone at 55000. This is how radio works. The radio station you tune into (say 100Mhz) is reference "a" (generated by the PLL circuit), the recieved signal is "b", the two are mixed, and you get music. This is of course over simplifed.