Speakers

[Mish]

I remember when this forum used to be called "Science, Creation and Evolution" and I want to post a science question. So to the person who changed the name.

How does a speaker with a single diaphragm make complex sounds with more than one note? In the typical (school) science experiment one would pass an AC across a speaker electromagnet to make squeaky noises and then make a low noise and loud and quiet etc.

What I don't understand is how the speakers can make more than one note at once, and then, how different timbres of sound can be made. How can one replicate a complex wave on a single diaphragm?

Since I own a copy of Windows Media Player, I can watch the waves of sound track osciliscope-wise across the screen, so I can see that the waves of sound produced are not regular sine waves, but I dont see how that could ever produce more than one note. Surely if you add one sound to another you just get a louder sound?

Feel free to respond with long words and blindingly complicated science, I can take it.

 

[Deamiter]

I'm not sure you can trust the output of Windows Media Player to give an oscilliscope's precise output (not that you claimed you could) but you're on the right track looking there. Any time you look at that output, and see a complex and seemingly random wave, what you are actually looking at is the sum of many sine waves with different frequencies and amplitudes.

When you put many sine waves together, they obviously don't have the same wavelength, so they don't stack on top of each other nicely. It gets really messy, and in this field, there's actually a lot of work being done in a very advanced way, usually with some sort of Fourier Transforms in the areas I've looked into. Basically, the tough part isn't putting them together. To do that, you just throw them on top of each other and add or cancel the sine waves together as appropriate. The tough part is taking a complex signal and trying to figure out what its componant parts were.

Anyway, our ears and eyes pick up the whole signal (within biological limits) and our brain processes it out much the same way a Fast Fourier Transform can on a computer and we hear complex sounds or see complex images.

Hope that helps. If you have some background in physics (and it sounds like you do) you might consider looking up FFT or Fast Fourier Transforms on Google. It can get really really complicated, but Google always pulls up some intro level pages for people like me.