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trevort
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Stereo ears

Posted here for the "acoustic" component of the content.

I really enjoyed reading the vintage article recently posted on the site:

http://www.stereophile.com/asweseeit/1286awsi/

It put me in mind of a chapter in the book I recently read:

http://www.oliversacks.com/musicophilia.htm

Here is another opportunity for addressing the "final frontier" in audiophile experience, the step between the listener's ears and their understanding of the sound.

One point of convergence between these two is the inquiry into how we hear stereo. In Musicophilia, Sacks mentions a study of concert-goers. They are observed often making minute head adjustments while listening.

I have observed my own cat when she is listening -- she dramatically swivel her ears.

The point is that the ears themselves have complex acoustic properties. Apparently that's why they have such a funny shape (on the inside, I mean, no comment on how they look on a guy's head). My cat's ear is even weirder on the inside.

This complex shape will receive sound from a source differently at different head angles, and our brain can use the changing sound with respect to position to pinpoint the source of a sound.

Sachs goes further in his book to study folks who have lost hearing in one ear, and are able to get some sense of sound positioning (quasi-stereo) with one the one ear.

The practical result of such an arcane theory? Listening to the new radiohead album the other night (holding out for the higher quality cd release), I exercised some minute head movements and lo and behold, I got a much clearer sense of positioning of the instruments this way. In fact I drawn to employ this technique because I couldn't believe the overpower sense of the guitar at the beginning, hard into the left channel.

So, I encourage you guys to give a try to subtle head movements when checking out your soundstage.

Elk
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Paging Ethan!!!!!!! Comb Filtering Alert!

ethanwiner
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Re: Stereo ears


Quote:
I encourage you guys to give a try to subtle head movements when checking out your soundstage.


This is correct, and reported in detail HERE in an entirely different context.

Note that in a domestic size listening room, the changes from small changes in head position are reduced dramatically when the room is treated properly with absorption at the first reflection points.

--Ethan

syntheticwave
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Re: Stereo ears

...i think itwould be interesting in that connection, to include the rendition room properties into a sound field synthesis.
The procedure is described by http://www.syntheticwave.de

H.

trevort
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Re: Stereo ears

Ethan:

I don't think your comb filtering effect is what is responsible for improving the brains ability to locate the source of a sound. I did read up on your references to this effect last time you mentioned it.

Rather, the ear can
a) process the minute differences in phase between the various reflections, which results in a sort of triangulation

b) differentiate between sounds coming from different angles relative to the ear, due to the shape of the ear

The first is discussed in both articles, the second is perhaps my own speculation, though the principle might have been mentioned in the Sacks book.

... and incidentally, I have been thinking about this when listening, and even just keeping an awareness that your neck is "active and engaged" is enough to enhance the sense of positioning. You don't actually need to do dramatic gyrations to sharpen your perspective.

ethanwiner
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Re: Stereo ears


Quote:
Rather, the ear can
a) process the minute differences in phase between the various reflections, which results in a sort of triangulation


I agree in principle, but the triangulation probably uses comb filtering more than phase shift. Phase shift is mostly inaudible, but comb filtering is very audible. So it makes more sense to me that the wildly different response at each ear has more effect than small changes in phase. But I've never tested this so I'm just going by common sense.

--Ethan

trevort
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Re: Stereo ears

... here comes Idle Speculation, the enemy of reason.

My take on comb filtering as you've presented, is that it is a sort of jumble of sound from reflections on reflections, etc. Like the confused sea when multiple wave sources combine.

Hard to see how that would contribute to locating sound sources, despite being audible.

According to the sources cited, just as we can pick up relatively faint sounds out of a confused mix -- distant voice in an airport -- so can we use micro details to pinpoint location.

Besides, your manifesto claims that comb filtering is the root of all evil, while I testify that freeing up your head on your neck (no hair band head banging required) to make tiny adjustments while listening attentively is a good thing.

ethanwiner
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Re: Stereo ears


Quote:
My take on comb filtering as you've presented, is that it is a sort of jumble of sound from reflections on reflections, etc ... Hard to see how that would contribute to locating sound sources, despite being audible.


I think you miss my point. In a typical rectangle room the most damaging reflections are the "first" reflections from the side walls, ceiling, and floor if no carpet. Yes, other reflections combine with those, but they're much softer. That said, comb filtering is the enemy of localization. That is, it doesn't help localization, it harms it.


Quote:
your manifesto claims that comb filtering is the root of all evil


Well, the root of many acoustic problems anyway.

--Ethan

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