- May 11, 2008
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WG, just a suggestion:
Passive stereo-audio reception might work if you had a way to compare the original sound to an echo and recognise both.
Could you do a wave-mapping of each or would that take too long to compare?
Woulf it be better to transform it into a limited bandwidth frequency domain representation and then compare other noises to it to see what might match, but at a lower amplitude? Kind of like what we do with our minds when walking into a dark room. We hear our own footsteps, or other ambient noises and get a "feel" for the rooms dimensions.
We usually do not get the feel for the coffee table we bang our shins into, but still, you can usually tell the difference between a living room and a warehouse.....
well, i want to use sound recognition for determining the source in the future. But i do not know much about it. I myself have to look into it more then you i think. I do know, that when determining the position of a sound, that sound must have a certain minimal frequency. That is why humans have difficulties determining the location of a low frequency sound source.
For example with humans, the size of the skull, the distance between the ears, the shape of the ears all are important factors to be able to discriminate between phase variance in a sound of a certain minimum frequency that reaches both ears. I do noticed that animals that can move their ears independently from each other as for example cats can move their ears around, following their prey just by pointing their ears into the direction of the sound. I wondered what would happen if i would build an microphone
in an ear that i can rotate with a servo. It would produce a similar effect as a lesley speaker, a doppler effect. But with the rotating microphone you can track because of the doppler effect the sound source. At least , that is what i think. Another example is a bat. Some bat species use frequency sweeps to determine what kind of insect is flying in front of the particular bat.
The reflection is a combination of destructive and constructive interference of the frequency modulated sound. The bat knows from the resulting reflection what kind of shape the insect has, it what speed the insects wings move.
To be honest, i really only have clues at the moment. Maybe some of the matlab specialists can present you with a simplified but functional model.