Human Auditory system???

[kramer5150]

I have a niece who's a freshman at Cal, shes in the Bio-engineering department and taking the usual physics and calculus basics. She was asking detailed questions about my MS2 and sound reproduction/perception.

We got into brain waves and were both wondering... What frequency are brain waves?... the elctrical current that goes through the brain? Hearing of course is 20-20kHz. But does the brain alter or amplify that when the sound waves are converted to electrical impulses?

My thinking is Yes... But I'm lacking details... why, and what freq it really is?

my logic to her is that theoretically IF the brain simply translated those 20-20k sounds to electrical impulses of the same freq, there could be some .... UH.... cross-talk.... or noise interference inside the brain.

Im guessing billions of years ago there was a caveman with defective hearing perception... Whos brain didnt interpret electrical signals cleanly. Billions of years of evolution have fine tuned things so that now we hear things the way we do.


thanks,
Garrett

 

[gsferrari]

The answer is not that simple. The tymapnic membrane acts as a transducer...or a reverse trransducer, if you will, that converts the energy of the sound waves into mechanical energy. This mechanical energy is trtansmitted through the three middle ear bones - malleus, Incus and Stapes. Finally the cochlea (inner ear) is stimulated. the cochlea is fluid filled and has several nerve endings that are sensitive to vibrations. Each nerve ending has a neural path from there to the auditory section of the brain.

Therefore transmission from outer ear to inner ear is mechanical. From there it is electrtochemical (google for neurons or nerve cells for information on the chemicals involved in creating the connections).

Fascinating...the final part, of course, is how the brain decodes these signals into something we understand...the sensation of sound...just utterly fascinating...

 

[Ozric]

Brain activity produces waves measurable by EEG at several different frequencies depending on the nature of wakefulness or restfulness of the individual: alpha waves, beta waves, delta waves, theta waves, sawtooth waves etc. It is possible for the different lobes to be producing different waves as they are processing tasks independently and utilizing glucose differently.

Here's a link which explains more. Incidentally, alpha waves increase during relaxed alertness type states which can be voluntarily produced by meditation or biofeedback training.