- #1
NatanijelVasic
- 19
- 5
Hello everyone,
I have been thinking about binaural beats, and after learning about the inner workings of the ear, there is something that I cannot explain. A binaural beat is the pulsating effect perceived by the brain when slightly offset frequencies are played in each ear.
In my example, the left ear receives a sine wave of 100 Hz, and the right ear receives a sine of 106 Hz. The person is wearing headphones, so the audio waves do not mix in the air, and therefore there is no interference in the air.
( ) ,
Inside each ear, the mechanical vibrations cause a certain region of hair cells to vibrate and each region corresponds to a certain resonant frequency. This means that the information sent by neurones from the ear to the brain is a Fourier representation of the original sound (neurones cannot handle fast switching, which is why audio frequencies cannot be transported in the original form through the nerve).
From the example above, this means that the brain is receiving a CONSTANT signal input from the left ear, and a constant signal input from the right - the only difference being that the left and right neurones correspond to different frequency ranges.
The mystery is this: where does the signal interference occur in order to cause the beating effect? An inverse Fourier cannot occur in the brain as the neurones "don't support" frequencies as high as audio. The brain might well add the Fourier representation of the signals from each ear, but that won't explain where the interference comes from. What is even more interesting, is that the beating effect from the interference is exactly the correct frequency i.e. the same frequency as would occur in the medium of sound. This suggests that the perceived interference is not than just an illusion, but "mathematical" signal progressing within the brain.
I would be extremely grateful for any responses :)
Nat
An example of binaural beats:
(try taking out the Left earbud only, then the right only, then listen to both at the same time)
I have been thinking about binaural beats, and after learning about the inner workings of the ear, there is something that I cannot explain. A binaural beat is the pulsating effect perceived by the brain when slightly offset frequencies are played in each ear.
In my example, the left ear receives a sine wave of 100 Hz, and the right ear receives a sine of 106 Hz. The person is wearing headphones, so the audio waves do not mix in the air, and therefore there is no interference in the air.
( ) ,
Inside each ear, the mechanical vibrations cause a certain region of hair cells to vibrate and each region corresponds to a certain resonant frequency. This means that the information sent by neurones from the ear to the brain is a Fourier representation of the original sound (neurones cannot handle fast switching, which is why audio frequencies cannot be transported in the original form through the nerve).
From the example above, this means that the brain is receiving a CONSTANT signal input from the left ear, and a constant signal input from the right - the only difference being that the left and right neurones correspond to different frequency ranges.
The mystery is this: where does the signal interference occur in order to cause the beating effect? An inverse Fourier cannot occur in the brain as the neurones "don't support" frequencies as high as audio. The brain might well add the Fourier representation of the signals from each ear, but that won't explain where the interference comes from. What is even more interesting, is that the beating effect from the interference is exactly the correct frequency i.e. the same frequency as would occur in the medium of sound. This suggests that the perceived interference is not than just an illusion, but "mathematical" signal progressing within the brain.
I would be extremely grateful for any responses :)
Nat
An example of binaural beats:
(try taking out the Left earbud only, then the right only, then listen to both at the same time)
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