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DIY Binaural Microphone Ears With Anatomically Accurate Ear Canals
DIY Binaural Microphone Ears With Anatomically Accurate Ear Canals
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Old 13th February 2020, 07:38 PM   #31
Baffless is offline Baffless  Europe
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Several years ago i made my binaural head.I thought that ear canal is important, so I have tried it with and without ear canal.My ear canal is kind of straight shape silicone material. That was no way a scientific test, but i recorded noise of plastic bag crushed between hands 0.5meters in front of the head and 0.5meters behind the head. with ear canal and without.
Recorded sounds without ear canal in front and in the back are very similar and impossible to tell with confidence which one is frontal. With ear canal is better, and i could tell where was frontal sound, because of bigger differences in high frequencies. Later i compared this with real world test. Closed my eyes and asked my wife to make that plastic bag sound. And without head movement and visual cues frontal/back sound difference is not so obvious you would imagine. So i was very happy with my binaural head.
Interesting thing that scientific papers says that blocked air canal captures all the directional info. And ear canal just adds its transfer function on top of that. (hence direction independent). Common sense tells that pina+ear canal is one direction dependant system and cannot be analysed independently. But i did't find papers fully supporting this.I am engineer and i am looking for the answers.
You say that
"On the other hand, it is equally wrong to assume that the binaural status quo of the capsule being located at the canalís entrance must not be messed with and regard it as the end all be all of binaural technology. Math disproves this."
Can you point to any paper or some thoughts about that "Math disproves this"?
And the second question is about your silicone ears. How did you managed to do averaged ear canal? How did you get correct measurements of human ear canals??
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Old 13th February 2020, 10:47 PM   #32
sax512 is offline sax512
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Hi Baffless.

Glad to hear you came to similar conclusions by practical trial and error.
Theory is good and all, but there's nothing like making stuff work in practice :-)
As you said, pinna and canal can't be analysed independently, but they work as a pinna+canal whole system. You might look into the work of Angelo Farina too, if you already haven't.

As far as the math goes, it's in the compendium I wrote. Specifically, the part that explains how to make the required EQ independent from the direction of arrival, M needs to be equal to H (Microphone needs to have the same shape of the Head).

Also, physics tells us that by closing the canal at the entrance, one effectively distorts the soundwave in respect of the open ear canal scenario.
So, not only one should't look at the pressure at the ear canal entrance if they want to capture all binaural cues, but capturing the pressure at that point in space would require the use of an infinitesimally small capsule. Anything else and the geometry changes, and the soundwave is distorted as a consequence.

The model for the canal was derived by averaging hundreds of real life casts.
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Old 20th April 2020, 09:21 PM   #33
sax512 is offline sax512
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B&K's new HATS Type 5128 includes anatomically accurate ear canals.
https://www.bksv.com/en/about/waves/...kVmmGRx5R4w5ZM

GRAS KB5000 does the same.
GRAS KB5000 Right Anthropometric Pinna 35 Shore OO
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Old 22nd April 2020, 02:35 PM   #34
Baffless is offline Baffless  Europe
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Very good links, but now i am working on my own design binaural ears and head, with ear canal
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Old 22nd April 2020, 05:35 PM   #35
sax512 is offline sax512
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Very interesting. How are you going to EQ your microphone?
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Old 22nd April 2020, 06:09 PM   #36
Baffless is offline Baffless  Europe
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depends on application. If records will be reproduced over loudspeakers, i will subtract head/ear introduced difference depending on speakers placement angle.
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Old 22nd April 2020, 07:30 PM   #37
sax512 is offline sax512
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What I meant is are you going to use hardware DSP or leave it to the DAW?

I don't think loudspeaker reproduction requires any particularly separate EQ.
The difference between loudspeakers and headphones is accounted for by the headphones own EQ, which is why you can listen to the same song with loudspeakers or headphones without any (major) change in balance.
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Old 22nd April 2020, 08:42 PM   #38
Baffless is offline Baffless  Europe
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i leave it to the DAW, because i need flexibility.And the design would become quite complicated otherwise. Would have to deal with noise,EMI,lots off hardware inside head.Want to keep design simple. Theoretically it will be rain proof will see how it goes..
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Old 22nd April 2020, 10:17 PM   #39
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If you intend to sell it and you have the means I would suggest you also provide some base plug in EQ. So that people can plug and play.
Anything DIY tends to turn the majority of people away.
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Old 26th May 2020, 10:19 PM   #40
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i have found very good paper on ear canal directional dependency.
https://vbn.aau.dk/files/227875888/1..._ller_JASA.pdf
it looks like above 10khz ear canal could start to become direction dependant.
above 10khz variations from person to person are very high, but good thing is that for dummy head microphone this is not o problem, because transfer function of dummy head is well known. So can be compensated, at least for one sound arrival angle.And directional info will still be left. This is kind of analogy where common mode signal is discarded and only the difference signal is taken in balanced circuits.
My dummy head parts arrived, so after assembly i will do some measurements, and share some info.
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