How is audio processed in the brain when receiving sounds with different lengths? I.e. car horn vs bird chirp? How does the brain separate each other when they are intertwined?
In: Biology
Different wavelengths can be separated in your ear.
Your cochlea is a long, thin strip that sits coiled up in your ear. It’s not the same throughout its length: the base is really good at picking up high-frequency (i.e. low wavelength) vibrations and the tip is really good at picking up low-frequency (i.e. large wavelength) vibrations. Between the base and the tip there is a whole spectrum where each frequency gets picked up at a different place along your cochlea.
You then have nerves coming out of each place along your cochlea. If you hear a high-frequency sound, there will be a nerve somewhere near the base that gets triggered and delivers that message to the brain. If you hear a mid-frequency sound, there will be a nerve somewhere near the middle of your cochlea that gets triggered and delivers that message to the brain.
In the case of “mixing,” you still hear two different sounds. The bird sound will trigger a different neuron than a car horn, so two different signals get sent to the brain and the brain takes it from there.
So in response to your question, separation actually occurs *before* the signals ever make it into your brain.
Sound is vibrations in the air.
The pitch is determined by frequency.
Multiple frequencies of waves can coexist, so your brain can pickup the frequency of the car horn and the bird chirp and compare them to the memory of the things you’ve heard in the past to seperate them.
Sensory processing is complicated, but a relatively simple artificial version of it is something called the Fourier transform. Fourier transforms basically take the added-up combinations of a bunch of frequencies of sound and break them up into the component frequencies – which for two different sounds are typically pretty different in a way that isn’t very hard to identify.
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