How do sound waves create different timbres?

[SuperBassSam]

WARNING: The following message contains physics!

Hi all,

So I was wondering, we're doing a bit of the physics of sound for music tech at school, and I can't understand how a sound wave form can produce different timbres. Obviously the louder the sound, the bigger the waves, the higher or lower the pitch the higher or lower the frequency, I understand those, but how does a sound wave carry timbral information? What makes a middle C on a piano sound different from a middle C on a guitar if theyre both played with the same velocity? And also, how would this information be converted by a microphone into an electronic signal which could then be sent down a wire?

Cheers

[tbone409]

n00b here, but i believe it has something to do with harmonics, overtones, and sympathetic vibrations.

[maestrovert]

Originally Posted by tbone409

n00b here, but i believe it has something to do with harmonics, overtones, and sympathetic vibrations.

yes, harmonic overtones. Fundamental tones by themselves are quite dull sounding, overtones convey tone/timbre...

you can think of it kinda like this(and it's a huuuge "kinda sorta" 'k ?):
An AM radio station broadcasts a "carrier wave" at a specific frequency, yet contained therein is all the audio information you hear from your radio...

[MalcolmAmos]

Originally Posted by SuperBassSam

...... And also, how would this information be converted by a microphone into an electronic signal which could then be sent down a wire?

I think you need to look at frequencies. Might have better luck finding things on early telephones - voice instead of music. Same principal. My voice vs your voice, i.e middle C on the guitar and piano - same concept. You and I produce different frequencies, these frequencies are transmitted through a wire - when received they are converted to sound - same sound as transmitted. Question is how do we produce the frequencies and then how do we turn the frequencies into sound that we recognize.

Try here.
http://windworld.com/features/tools-...th-calculator/

http://www.howstuffworks.com/ham-radio.htm

Ask that same question here:
http://www.eham.net/

Have fun.

[WalterBush]

Google, "harmonics." There's a lot more involved in creating a sound than a simple fundamental frequency.

Electronic signals have frequencies and harmonics, as well. A microphone works as an analog of a human tympanic membrane, and uses an electromagnetic device to generate a signal in response to the changing pressure waves that our ears identify as sound. This signal can be interpreted as darn near anything, but we generally take it, amplify it a few times, and reproduce it through a speaker of some kind. Both the microphone and speaker are referred to as transducers because they both change one type of signal (air pressure) into another (electrical signal) or vice-versa.

The human ear and brain both have an effect on what frequencies we hear and how we interpret them, as well. Google, "psychoacoustics." People who designed sounds for synthesizers depended on people hearing what they thought they would hear, sort of "fooling" people into hearing a few wierd waveforms as guitar or sax.

[ggunn]

In a word (well two words, actually) harmonic content. Very few naturally occurring sounds are a pure sine wave. BTW, in addition to the identifying nature of a timbre due to its complex harmonics, it's also what enables you to distinguish different instruments in a mix. The very earliest synthesizers produced very pure tones from simple oscillators and consequently would get buried very quickly.

[TrooperFarva]

Short answer: Timbre is the result of the shape of the wave

A flute has a reasonable approximation of a sinusoidal wave. So does whistling. Most other things, not so much.

My recommendation would be to download Max/MSP (it's freeware) and play around with some signal generators. Keep the frequency and amplitude the same, just change the shape, like sinusoidal, square, sawtooth, etc, and see what the results are.

[m0nst3r]

The plain and simple answer is that it's the harmonics that give an instrument its timbre. For instance, if you sing a note normally, and then sing the same note after inhaling helium, it'll be perceived as higher, even though the pitch didn't change, because the helium makes the higher harmonics in your voice more dominant.

[Sarbecue Boss]

What Trooper said, Sine wave are very simple sound, for exmple, if you break down a voice into sine waves, you get some barely comprehensable whistles. Timbre comes from the complexity of the waves