How can multiple frequencies be emitted fr the same speaker?

Question

Please read!!

My book states that music is a conglomeration of frequencies emitted from a loudspeaker. Iv always seen how pressure is manipulated via 1 frequency. But wouldn't the waves interfere, cancelling themselves out?

Maybe I'm just confused.

Answer 1

Audio signals consist of many different frequencies. A good speaker will respond to all of them. It's just physics.

Answer 2

It's an interesting question. A speaker can move in the same fashion as electric signals on a wire or electromagnetic waves in the air. All different frequencies are mixed together onto 1 signal. So you would think that they will interfere but in reality it's all there. If you look at a short plot of the wave, it may seem as some of the signal is getting all messed up by another wave but if you looked at a large picture you would find all the patterns again. A speaker can create many frequencies simultaneously just as a radio antenna can pick up many radio stations at the same time. Let's say you had 20 different frequencies coming in, then you can set up a filter that only let's one frequency through. Even if the other frequencies are stronger and while looking at the wave it seems like the frequency you want is "buried", once it goes through the filter you will again see that frequency, which proofs that it was there all along.

Another experiment to show this. Hold your arm out and wave it slightly up and down by a couple inches and kinda quickly. So there is frequency 1. Now continue this but additionally move your arm slowly up and slowly down by like 2 feet. This is frequency 2. You can see that both frequencies exist on your arm at the same time and that they do not interfere with each other. Again the little motion (frequency 1) may be going downwards at a point in time when your arm is on the rising with frequency 2. So it may seem that going down is canceling out the upwards motion but once you look at a longer time frame you can see both patterns coexist.

Answer 3

If you listen to an orchestra play, all the different frequencies, plus their associated harmonics and sub harmonics, all impinge on your eardrum in a huge mixture. Because the notes played are harmonious, there is no interference. If they play non- harmonious notes, though, you soon notice!

It is up to the tiny bones within your inner ear to transmit these mixtures to the auditory nerve system, and your brain is able to interpret this output as the original music.

Now, all this also happens when music comes from a loudspeaker or loudspeakers, provided they are positioned so the combined sounds are in "normal" relationships.

The speaker cones are rigid, and respond to the electric signals fed them from whatever the source is. In this respect, they are just like those tiny bones in your ear, which are also rigid.

However, like your ear bones, the cones are able to move in a sort of "averaged" manner, producing the SAME mixture of sound wave in the air, as you would have heard directly from the orchestra.

It's hard to explain. But if you listen to a trumpet and a violin, each has a distinctly different sound, even if playing the same note. The difference is that as well as the fundamental sine wave of the musical note, there are harmonics and sub harmonics generated, which mix with the fundamental wave, modifying it to give the unique sound for each. The uniqueness is dependent on the harmonics and sub harmonics present, and the LEVEL of each relative to the fundamental.

You hear the results of the conglomerate of all, as a note from some particular instrument.

So there is NO difference when the sound waves you hear from 2 different instruments mix, as the same sound wave just contains more components!

This conglomerate sound wave is what the loudspeaker cones also generate and impart back into the air, to reach your ears.

Answer 4

Waves can interfere and cancel. If you play a pure tone through stereo speakers, you can find places in the room where the sound cancels and is soft, and other places where it reinforces and is louder.



But as music is all different frequencies, you don't really notice (the magic places are different for each frequency).



Good speakers are linear - they move in proportion to the electrical signal. Given that - a linear system - different frequencies are superimposed in one speaker and can be perceived independently without distortion It's like waves passing through each other at the beach. Nothing to do with sampling theory or persistence of vision - your ear has thousands of receptors that detect each frequency simultaneously and your brain somehow makes sense of it.

Answer 5

A speaker is basically a electromagnetic coil that responds to different amounts of electricity to give different movements of the rod within that coil.



Since ethe coil rod can move back and forth to correlate with the music electrical waves, each one of those changes in to and fro motion, will make a different frequency.



It is true that it only can make one frequency at any instantaneous moment, but since your ears and brain tend to move it all together and smooth it out, it sounds like you are hearing multiple frequencies at once, but you aren't. It is that the spacings between frequency changes are so quick, your ear can't pick up on it that quick.



Kind of like how your eyes can watch a movie which is just a bunch of still frames put together, but when you run them quickly, your brain fuses them together and you think you are watching a real stream of video.



And speaking of interference, waves can overlap with no problem, it is only if the exact same wave is crossed in opposite directions to each other that they cancel out. Think of yourself if you are tapping on the counter with one hand and beating a spoon against a plate with the other at the same time. You definitely can distinguish the sound difference and there is no cancelling