3 ms·

> It does this because the sounds processed by the ear are often localized in time. What would it mean for a sound to not be localized in time?

by lgas 1y ago

littlestymaar 1y ago
A continuous sinusoidal sound, I guess?
hansvm 1y ago
It would look like a Fourier transform ;) Zooming in to cartoonish levels might drive the point home a bit. Suppose you have sound waves |---------|---------|---------| What is the frequency exactly 1/3 the way between the first two wave peaks? It's a nonsensical question. The frequency relates to the time delta between peaks, and looking locally at a sufficiently small region of time gives no information about that phenomenon. Let's zoom out a bit. What's the frequency over a longer period of time, capturing a few peaks? Well...if you know there is only one frequency then you can do some math to figure it out, but as soon as you might be describing a mix of frequencies you suddenly, again, potentially don't have enough information. That lack of information manifests in a few ways. The exact math (Shannon's theorems?) suggests some things, but the language involved mismatches with human perception sufficiently that people get burned trying to apply it too directly. E.g., a bass beat with a bit of clock skew is very different from a bass beat as far as a careless decomposition is concerned, but it's likely not observable by a human listener. Not being localized in time means* you look at longer horizons, considering more and more of those interactions. Instead of the beat of a 4/4 song meaning that the frequency changes at discrete intervals, it means that there's a larger, over-arching pattern capturing "the frequency distribution" of the entire song. *Truly time-nonlocalized sound is of course impossible, so I'm giving some reasonable interpretation.
- jancsika 1y ago
  > It's a nonsensical question. Are you talking about a discrete signal or a continuous signal?
xeonmc 1y ago
Means that it is a broad spectrum signal. Imagine the dissonant sound of hitting a trashcan. Now imagine the sound of pressing down all 88 keys on a piano simultaneously. Do they sound similar in your head? The localization is located at where the phase of all frequency components are aligned coherently construct into a pulse, while further down in time their phases are misaligned and cancel each other out.
kragen 1y ago
The 50-cycle hum of the transformer outside your house. Tinnitus. The ≈15kHz horizontal scanning frequency whine of a CRT TV you used to be able to hear when you were a kid. Of course, none of these are completely nonlocalized in time. Sooner or later there will be a blackout and the transformer will go silent. But it's a lot less localized than the chirp of a bird.

> It does this because the sounds processed by the ear are often localized in time. What would it mean for a sound to not be localized in time?

by lgas 1y ago

> It does this because the sounds processed by the ear are often localized in time. What would it mean for a sound to not be localized in time?

littlestymaar 1y ago

A continuous sinusoidal sound, I guess?

hansvm 1y ago

It would look like a Fourier transform ;) Zooming in to cartoonish levels might drive the point home a bit. Suppose you have sound waves |---------|---------|---------| What is the frequency exactly 1/3 the way between the first two wave peaks? It's a nonsensical question. The frequency relates to the time delta between peaks, and looking locally at a sufficiently small region of time gives no information about that phenomenon. Let's zoom out a bit. What's the frequency over a longer period of time, capturing a few peaks? Well...if you know there is only one frequency then you can do some math to figure it out, but as soon as you might be describing a mix of frequencies you suddenly, again, potentially don't have enough information. That lack of information manifests in a few ways. The exact math (Shannon's theorems?) suggests some things, but the language involved mismatches with human perception sufficiently that people get burned trying to apply it too directly. E.g., a bass beat with a bit of clock skew is very different from a bass beat as far as a careless decomposition is concerned, but it's likely not observable by a human listener. Not being localized in time means* you look at longer horizons, considering more and more of those interactions. Instead of the beat of a 4/4 song meaning that the frequency changes at discrete intervals, it means that there's a larger, over-arching pattern capturing "the frequency distribution" of the entire song. *Truly time-nonlocalized sound is of course impossible, so I'm giving some reasonable interpretation.

jancsika 1y ago
> It's a nonsensical question. Are you talking about a discrete signal or a continuous signal?

xeonmc 1y ago

Means that it is a broad spectrum signal. Imagine the dissonant sound of hitting a trashcan. Now imagine the sound of pressing down all 88 keys on a piano simultaneously. Do they sound similar in your head? The localization is located at where the phase of all frequency components are aligned coherently construct into a pulse, while further down in time their phases are misaligned and cancel each other out.

kragen 1y ago

The 50-cycle hum of the transformer outside your house. Tinnitus. The ≈15kHz horizontal scanning frequency whine of a CRT TV you used to be able to hear when you were a kid. Of course, none of these are completely nonlocalized in time. Sooner or later there will be a blackout and the transformer will go silent. But it's a lot less localized than the chirp of a bird.