How is sound waves with timbre, etc. represented electronically?

[The_Lobster]

Sorry if this is a no-brainer, but I just can't seem to find much info about this.. All sources only talk about a single wave, most often a sinusoidal wave, and never mentions how the situation is like when there is a complicated sound signal with lots of stuff going on (different timbres for example.)

Please correct me if I'm wrong, but to my understanding timbre is a product of many sound waves together (if it was an instrument, a fundamental of the instrument and related overtones, etc.). So we have many sound waves at the same time, together creating a sense of timbre. What I don't get is how this is recorded by a microphone with a diaphragm that only senses *one* instantaneous frequency and amplitude, and then transmitted electronically via voltage signals that also only has *one* value for frequency and one for amplitude at a given time, how does this actually carry complicated sound signals with timbre, and not only single sine waves?

This relates to the whole chain I guess, from mic to speaker.. I have a fundamental hole in my understanding of sound waves and I'm having a hard time finding info besides the usual sine wave intro...

Would love some explanation regarding this!:-)

 

[schip666!]

Here's the first link I got googling "sound timbre", which may help:
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/timbre.html

A mic does not sense "frequency" only instantaneous amplitude. Sound pressure waves take many shapes, from pure tone sines to random noise. At any moment in time the electrical signal from a mic is an (almost) exact analog of the air pressure is "hears". That is in fact why it's called an "analog signal".

Was that the question?

 

[sophiecentaur]

I think you could benefit by googling "Fourier analysis" of periodic signals. Mr.F. discovered that you can analyse and build up complex repeated waveforms by considering a whole family of harmonics of the fundamental frequency (note).
The timbre of each instrument depends upon the relative levels of all these harmonic components. The most 'interesting' sounds mostly have the highest levels of harmonics. The recorder has about the purest note and is, consequently, a bit on the boring side (no offense intended - it's very nice in its place but it's not often used as an orchestral instrument!).

 

[arildno]

A linguistic correction for sophiecentaur:

"Monsieur Fourier" should be referred to as M. F...

 

[sophiecentaur]

There's always one, isn't there?

 

[Dr Lots-o'watts]

Here's a nice link where the visual wave is matched with the corresponding sound (including synthesized violin):

http://www.espace-cubase.org/anglais/page.php?page=appaudiobc1

 

[JS85]

The diaphragm of a microphone records a position at any given instant, not a frequency. Therefore, yes, a microphone can record multiple sine waves added together in a complex wave.