![]() ![]() Thankfully these days everything starts out in the digital domain, so you just need a controllable fifo before the DAC. Technically there's a 3rd way: extremely long wires, but that's basically never practical. This is how guitar delay pedals work, but the more delay you have the more distortion you introduce. With active components you can create a feedback loop through an op amp. They also suffer from accumulated imprecision issues. Each "rung" only adds group delay on the scale of a couple usec, so these get very big and expensive fast. With passive components, you build a ladder filter, which is as the name suggests, just a long chain of low pass or all pass filters. There's no simple way to add a delay to some speakers unless you're working in the digital domain. However, the bulk of it was known quite a bit before 1985, and had nothing to do with the "spatialize me" button on a specific car stereo. There's something like 13 different mechanisms that co-operate in sound localization. So, psychoacoustics is incredibly complicated. > I'm pretty sure that lead to a conversation about how we locate sounds. And STILL, the mouse is able to avoid the owl! And the current input is held for processing. This means we perceive a world created by the subconscious's guess of what should be happening now, based on past input. Since this per-force takes time, the subconscious meanwhile sends a "image" to the consciousness with the assumed incoming data based on whatever had happened before, while processing the current data to predict what image will be sent to the consciousness during the next incoming round. Instead the subconscious has to hold each of the incoming sounds for some fractions of a second, and then combine the different sounds (with smell, etc) while matching up the different parts, using the differences to account for direction. Since there are often sounds coming from both directions at once, there is no easy way to match the sounds up. It is not that the brain hears on one side "later", it is that the brain is constantly hearing two different things, what is registered on the right and what is on the left, simultaneously. When the sound is coming from, say, the back left, the difference between the ears is far less than the width of the head.Ģ. It is my understanding that what really happens is far more impressive.ġ. This is crucial for the mouse to quickly avoid the talons of the owl. We must all build and refine our own internal set of pseudo-clocks for sensory and motor systems, in order to define the cumulative temporal context in which we are embedded. This is a computational feat that requires extreme temporal precision in binaural auditory processing across comparatively noisy wetware (transduction noise, phase locking error, synaptic release noise, conduction velocity smear, dendritic integration in MSO).Īnd doubly impressive given that the brain has no “given” time base or oscillator to define a compute cycle. Phase locking and ensemble encoding is used.įor example, adult mice have small heads, and ear separation is merely 5-7 mm yet this is sufficient to locate the position of an ultrasonic squeak generated by a mouse pup at 40 kHz. This is amazing when you realize that neurons cannot fire at a rate above 1 kHz. In some species delays of 10-20 microseconds can be detected and encoded by MSO neurons even tracking up to frequencies well above 40 kHz. This is how the owl catches the mouse at night. Even in humans these MSO neurons are exquisitely sensitive to binaural differences. There are populations of neurons in the auditory system-the medial superior olive-that receive input from both ears. ![]()
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