5 ms·

I really enjoyed this article. I do take issue with a couple of sentences: "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one d

I really enjoyed this article. I do take issue with a couple of sentences: "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. "We hear better than we see." This is an apples-to-monkeys comparison.

Florin_Andrei 16y ago
Yes and no. There's something funny going on with front-back perception. Normally it shouldn't be doable, but the external part of the ear is like a direction-dependent frequency filter. When the brain hears a familiar sound, but the spectrum is skewed just like this, it goes "aha, this comes from the front side". If the spectrum is skewed the other way, it goes "this comes from behind". It's not 100% reliable, but it works some times.
- sethg 16y ago
  Also: people who depend on behind-the-ear hearing aids do not get the benefit of these echoes, which means that, for example, it’s harder for them to distinguish the voice of someone talking to them from background noise or from echoes off the walls.
- nevinera 16y ago
  http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization There's a lot more to it than that, and it's not just something that occasionally works. The outer-ear notch filtering is also used in vertical localization.
deleted 16y ago
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vaporstun 16y ago
> "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. Put on some headphones and listen to this and tell me you cannot visualize it in 3-D: http://www.youtube.com/watch?v=YuxaOO6PsAw http://www.youtube.com/watch?v=YuxaOO6PsAw This is a binaural recording. More info on these here: http://en.wikipedia.org/wiki/Binaural_recording http://en.wikipedia.org/wiki/Binaural_recording You can hear in multiple dimensions because, as the original article mentions, there is some post-processing in your mind due to the time delay between sounds entering your left ear and sounds entering your right. Just because your ears are aligned on a single axis does not mean that you cannot perceive in multiple axes. No moving of your head is necessary to perceive in more than one dimension.
- hypersoar 16y ago
  I listened to these so much several years ago (in particular one with somebody shaking a matchbox) that my brain apparently realized, to some extent, that it was being tricked. Ever since then, recordings like this don't work properly. Anything that's supposed to sound like it's coming from in front of me gets flipped around so that it's behind me. It's very strange.
- xpaulbettsx 16y ago
  It actually also works because a sound registers differently based on the direction it travels through your own head (i.e. your skull itself is an occlusion source) - your brain recognizes front vs. back based on how your own head dulls the sound
  - 6ren 16y ago
    I assume the shape of our ears also affects the sounds, depending on the location of the sound. This converts vertical location into frequency shaping. And I wonder, why else would we have such oddly shaped ears?
    - squasher 16y ago
      You would be correct. The shaping of the pinna (and resulting sound reflections) help us determine the height of sound sources, even if they're right on our midline.
nevinera 16y ago
>We hear in one dimension, left-to-right. While our localization abilities vary by axis, we do have them in all three directions due to the combination of several mechanisms, none of which are actually 'left-to-right'. http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization
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Derbasti 16y ago
We can hear true 3D. There are actually a couple of ways in which we can sense the direction of sound. One is loudness, which obviously only works for left-right. This is loudness only in the sense of sound-gets-more-silent-farther-from-the-source. Another is the phase difference of the sounds in both ears. Phase difference comes from the fact that sound arriving at one ear had a longer way to travel than sound arriving at the other ear. tells a more complete story of direction than loudness and is very precise. Thirdly, there is frequency response. Both our head and our ears absorb different frequencies at different angles. Also, there are some reflections from our shoulders and chest. Taken all that together, normal people can detect the origin of sound sources to about one degree of precision. But, there is more. Close your eyes and have another person talk while turning his head in different directions. You can clearly detect the direction he is talking to. At the same time, you can roughly sense the size and type of the room you are in. Also, you can do this while being in really noisy environments (say, a car in traffic with the radio playing and the kids in the back). Talking about seeing vs. hearing: The response time of the ear is about 10-50 ms. It usually takes 200-500 ms to make sense of something you see. The human ear has a frequency resolution of about one Hz (at <500 Hz), a dynamic range of about 120 dB and a frequency range of about 10 octaves. The eye can only detect a very small dynamic range in comparison, and about one octave of wavelengths. But most importantly, the eye can only detect averages of three distinct, fixed frequency ranges (red, green, blue; red and green overlap 90%). The ear has floating detection windows and uses an arbitrary amount of different windows at any one time. That is, the ear can detect any spectral distribution with great precision, while the eye only detects three distinct spectral windows. So in a lot of ways, the ear is physically way more precise than the eye. Of course, signal processing makes all the difference and the amount of signal processing going on in our acoustical and visual brain centers is just staggering. There is nothing in the technological world that even comes close to that.
- elptacek 16y ago
  http://en.wikipedia.org/wiki/Impulse_response#Acoustic_and_audio_applications http://en.wikipedia.org/wiki/Impulse_response#Acoustic_and_a... (eta: just posting the link seems kinda snarky -- this ties into your post, but i don't have anything else to add)
- 16y ago

Florin_Andrei 16y ago

Yes and no. There's something funny going on with front-back perception. Normally it shouldn't be doable, but the external part of the ear is like a direction-dependent frequency filter. When the brain hears a familiar sound, but the spectrum is skewed just like this, it goes "aha, this comes from the front side". If the spectrum is skewed the other way, it goes "this comes from behind". It's not 100% reliable, but it works some times.

sethg 16y ago
Also: people who depend on behind-the-ear hearing aids do not get the benefit of these echoes, which means that, for example, it’s harder for them to distinguish the voice of someone talking to them from background noise or from echoes off the walls.
nevinera 16y ago
http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization There's a lot more to it than that, and it's not just something that occasionally works. The outer-ear notch filtering is also used in vertical localization.

deleted 16y ago

[deleted]

vaporstun 16y ago

> "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. Put on some headphones and listen to this and tell me you cannot visualize it in 3-D: http://www.youtube.com/watch?v=YuxaOO6PsAw http://www.youtube.com/watch?v=YuxaOO6PsAw This is a binaural recording. More info on these here: http://en.wikipedia.org/wiki/Binaural_recording http://en.wikipedia.org/wiki/Binaural_recording You can hear in multiple dimensions because, as the original article mentions, there is some post-processing in your mind due to the time delay between sounds entering your left ear and sounds entering your right. Just because your ears are aligned on a single axis does not mean that you cannot perceive in multiple axes. No moving of your head is necessary to perceive in more than one dimension.

hypersoar 16y ago
I listened to these so much several years ago (in particular one with somebody shaking a matchbox) that my brain apparently realized, to some extent, that it was being tricked. Ever since then, recordings like this don't work properly. Anything that's supposed to sound like it's coming from in front of me gets flipped around so that it's behind me. It's very strange.
xpaulbettsx 16y ago
It actually also works because a sound registers differently based on the direction it travels through your own head (i.e. your skull itself is an occlusion source) - your brain recognizes front vs. back based on how your own head dulls the sound
- 6ren 16y ago
  I assume the shape of our ears also affects the sounds, depending on the location of the sound. This converts vertical location into frequency shaping. And I wonder, why else would we have such oddly shaped ears?
  - squasher 16y ago
    You would be correct. The shaping of the pinna (and resulting sound reflections) help us determine the height of sound sources, even if they're right on our midline.

nevinera 16y ago

>We hear in one dimension, left-to-right. While our localization abilities vary by axis, we do have them in all three directions due to the combination of several mechanisms, none of which are actually 'left-to-right'. http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization

deleted 16y ago

[deleted]

Derbasti 16y ago

We can hear true 3D. There are actually a couple of ways in which we can sense the direction of sound. One is loudness, which obviously only works for left-right. This is loudness only in the sense of sound-gets-more-silent-farther-from-the-source. Another is the phase difference of the sounds in both ears. Phase difference comes from the fact that sound arriving at one ear had a longer way to travel than sound arriving at the other ear. tells a more complete story of direction than loudness and is very precise. Thirdly, there is frequency response. Both our head and our ears absorb different frequencies at different angles. Also, there are some reflections from our shoulders and chest. Taken all that together, normal people can detect the origin of sound sources to about one degree of precision. But, there is more. Close your eyes and have another person talk while turning his head in different directions. You can clearly detect the direction he is talking to. At the same time, you can roughly sense the size and type of the room you are in. Also, you can do this while being in really noisy environments (say, a car in traffic with the radio playing and the kids in the back). Talking about seeing vs. hearing: The response time of the ear is about 10-50 ms. It usually takes 200-500 ms to make sense of something you see. The human ear has a frequency resolution of about one Hz (at <500 Hz), a dynamic range of about 120 dB and a frequency range of about 10 octaves. The eye can only detect a very small dynamic range in comparison, and about one octave of wavelengths. But most importantly, the eye can only detect averages of three distinct, fixed frequency ranges (red, green, blue; red and green overlap 90%). The ear has floating detection windows and uses an arbitrary amount of different windows at any one time. That is, the ear can detect any spectral distribution with great precision, while the eye only detects three distinct spectral windows. So in a lot of ways, the ear is physically way more precise than the eye. Of course, signal processing makes all the difference and the amount of signal processing going on in our acoustical and visual brain centers is just staggering. There is nothing in the technological world that even comes close to that.

elptacek 16y ago
http://en.wikipedia.org/wiki/Impulse_response#Acoustic_and_audio_applications http://en.wikipedia.org/wiki/Impulse_response#Acoustic_and_a... (eta: just posting the link seems kinda snarky -- this ties into your post, but i don't have anything else to add)
16y ago