Why do we hear different sounds?

Question

Sound is a mental image created by the brain in response to vibrating air molecules (sound waves). Then why is it that we hear such various "sounds" coming out of any number of things?

Essentially, it's these same air molecules that are being vibrated, which in turn are causing the same hair cells in our basilar membrane, time and time again, to fire away messages to our brain.

I realize that there could be differences in pitch and loudness, but a trombone sure does sound very different from a horse! Do you know what I'm saying? I sure hope so... cause I kind of lost my self.

Answer 1

You're describing "timbre" (pronounced as "tamber").

Two sounds that seem to be the same pitch can be very different.  For example, it's easy to tell a guitar from a saxophone, even if they're both playing the same note.  That's because the overtone content of the sound is different.

When you hear a note being sung or played, it has a base frequency, but also many other higher frequencies, each an integer multiple of the first.  The relative strength of these overtones determines the timbre of the sound.

For example, if an instrument played a 100 Hz note, there would also be energy at 200 Hz, 300 Hz, 400 Hz, 500 Hz, etc.  These are the overtones.  One instrument might have more energy at the third overtone, while another might have more at the second and fourth overtones.

An algorithm exists to extract the frequency content from a recorded sound.  This is the "Fourier transform".  You can read about it here:

http://en.wikipedia.org/wiki/Fourier_tra...

Answer 2

because we have different ear drums.

Answer 3

The sound which you hear depends on frequency of the sound which has been generated by the source.It also depends on the

phase difference between the two generated waves which causes us to hear different sounds