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Author Topic: Binaural Click Test and Dummy Head Build Progress  (Read 4271 times)

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ihasmario

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Binaural Click Test and Dummy Head Build Progress
« on: October 12, 2013, 02:44:51 PM »

Hi Gang,

I've been working on building a binaural dummy head for recording purposes, figured it'd be a fun thing to post here. At the end of this post, you'll find an mp3 recorded showing the progress of the project and how pronounced the effect is so far. I'll also detail the costings for those who are interested in this kind of thing.

Prior to this I had a Schneider disc, which I will post a similar test of later when I am happy with the head.

At the moment the head is bare bones - literally a hollow dummy head with small electret capsules in the ears. Here are some pictures.


 

Here's an mp3 - it includes a click test, guitar recorded several ways (badly - bad playing and one recording session I was too close. Three recordings at the sound hole, one at about fret 12), and then a song recorded to demonstrate the hollow echo a bit more closely, which is currently the major flaw. The song is aiming to be a perfect reproduction of the original, not a binaural version. I'll do some more sophisticated tests later.

Here's the mp3
https://app.box.com/s/qm0finguto7lpwr2ewq2
If you are interested in comparing the song to the original, it's available for free from the record companies site
http://www.higherlivingrecords.com/index.php/releases?id=75:elin

What I'd like some people to do if they have time, is to try and identify what motion the clicks are doing in the first section. I will be posting the answers in about a week if enough people reply. The aim is to determine without bias, how well the head is producing an image at this stage.

- The first set of clicks begins at 0:00
- The second set begins at 0:11
- The third set begins at 0:20
- The fourth set begins at 0:26.5
- The fifth set begins at 0:32

Thanks everyone


Parts list
Dummy Head - dis-m121 - Bought for $20
Microphones - Naiant U-M 8mm omnidirectional capsules - Cost $15 each
Preamp - LineAudio MP8
Interface - Audiofire 12

Total head cost so far: $50

PS I started to teach myself guitar very recently so the playing is very sloppy.

 :)
« Last Edit: October 12, 2013, 02:53:22 PM by ihasmario »
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Audiofire 12 -> Stax T1 -> Stax Lambda Signature

Interested in recording and making music

ihasmario

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #1 on: October 12, 2013, 02:46:07 PM »

Space reserved for the following head moficiations:
- Filling in the head to remove hollowness
- Implementing proper ear canals
- Sculpting better ears (more pronounced): Possibly removal of the ears to include silicone ears
- Sculpting of the face to accentuate front image.
- Adding hair or windshields to the ears for pops that occur close to the ear.
- Attaching to stand, a better set of recordings at a greater distance.

 :spank:
« Last Edit: October 12, 2013, 02:51:26 PM by ihasmario »
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ihasmario

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #2 on: October 12, 2013, 03:08:41 PM »

Space reserved for new recordings and comparisons to schneider disc setup.

In the meantime, he's a sample recording of the same capsules applied with a Schneider disc. Most of this isn't head on though. Obviously the guitar had better strings for strumming on back then (Elixir PBs).Featured in this recording is; Guitar (strum), Guitar (hybrid), Guitar (Finger pick), Tenor Saxophone, Cornet. Mostly recorded front-on and one shout so excuse sloppiness been a bit busy to maintain/develop them all.

Here's the temp mp3
https://app.box.com/s/gz8u1cb6rx8s7f98et6u
Bonus points if anyone can guess the group whose songs feature heavily :)

You can tell there is an absence of a hollow echo that the head current has.

Thanks
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shipsupt

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #3 on: October 12, 2013, 03:28:25 PM »

Interesting project!  The head is a bit androgynous... :-Z Not that it matters.

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ultrabike

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #4 on: October 12, 2013, 04:33:36 PM »

Thanks! I'll check the tunes tonite! Keep up the great work!
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MuppetFace

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #5 on: October 12, 2013, 05:20:23 PM »

Awesome project! Keep us posted!

Oh, and sorry 'bout the new avatar... I couldn't resist.
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ihasmario

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #6 on: October 12, 2013, 05:40:05 PM »

Oh, and sorry 'bout the new avatar... I couldn't resist.

This one is better  popcorn

Any ideas on what I should fill the head with? I have a spare sound damping foam that I can feed in there, but I wonder if stryofoam balls might be a cheaper and possibly better option (also easier to remove if I don't like it), as it would add more dead air space than open cell foam.
« Last Edit: October 12, 2013, 05:53:55 PM by ihasmario »
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Marvey

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #7 on: October 12, 2013, 05:54:26 PM »

Very nice and thank you for providing the links for the resources to build this.
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AstralStorm

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #8 on: October 12, 2013, 05:54:37 PM »

Listened using equalized Hifiman RE-400 IEM with custom "tips".

Without crossfeed:
The three left-to-right motions are nearly indistinguishable, there's no depth and almost no height to them. If I were to guess, first was front, second above, third behind the head, but all three sounded wrong, passing through head instead of around.
If I'm right the first two were circle-like outwards from the left/right ear, the depth is hard to describe, but sounds like 10-15 cm at most. Music samples of the first music are (counting from the ear plane) 90 degree - in front, 30 degrees tp the right, 30 degrees to the left, 60 degrees to the left? and again front. Cannot say anything about depth/distance. All samples sound in-head and very flat, much more than the original mix.
Original mix sounds a bit "widened stereo", but not in-head at all.

With crossfeed:
The original music sample sounds properly forward focused and close to the non-crossfed studio version in terms of depth retrieval. Much more centered.
Suprisingly, adding crossfeed to the head samples makes it sound kind of correct, first and second click being moving back and towards the ear about 1.5m (starting from the ear), third being in front close to the head - sounds very discontiguous, with a hole in the middle; fourth being in front further away?, less of a hole in the center; fifth being behind the head, sounds the most correct to me, almost no hole; The guitars are like sitting at a distance of ~1m in front, about 1m to the right; 1m to the left but closer, bassier?; right below the face or at it, in front.
Music also sounds much better, heck, I'd say better in some respects than the original sample via crossfeed - natural room-like reverberation - though it sounded like a bit of a V-shaped bass cut, too nasal with a hole in the middle.

All in all, I think the recordings do sound quite clean, so the capsules and recording environment are reasonably good. It is a very quiet recording though, needs a bunch of dB boost.

This would suggest that the head is highly ineffective in capturing crossfeed - the microphones not being omnidirectional enough, having a half-sphere directionality, not really omni? That or the head is not sonically permeable enough or is internally too reflective.
HRTF must be more or less correct, since with crossfeed front/back is fine I think. Height is uncertain, I'm not sure you've tested it at all.
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ihasmario

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Re: Binaural Click Test and Dummy Head Build Progress
« Reply #9 on: October 12, 2013, 06:02:46 PM »

HRTF must be more or less correct, since with crossfeed front/back is fine I think. Height is uncertain, I'm not sure you've tested it at all.

Thanks for the large and detailed feedback, will PM you the results if you like.

RE: Testing. There hasn't been any testing done so far, there are a few very obvious problems (the head seems to be resonating) that I need to deal with before any of that. The capsules also have a slight upward tilt.

RE: Imaging problems, I expected it wouldn't be as clear as I hear it (since I know which is which...). I think it has to do with the depth of the mics (given that the head has no canals at the moment), which I think would translate to less treble being lost in any direction. Going to the hardware store on Tuesday to buy some rubber tube. Haven't tested the mics atm either, will probably test them later in the week with the Schneider disc, comparing front and back.  :)p4


EDIT:: Just listened to the clicks with my ER4S and found similar problems to you that weren't obvious on headphones. The direction of the clicks also changed compared to what I knew they were, most were projected upward and slightly forward, but like you say mostly through the head rather than slightly around.
EDIT::: A few other things I havent done/request for people listening, try apply a generic diffuse field curve - I haven't taken one of the head yet. I am still learning about binaural recording TBH so it's just dipping my feeti n
« Last Edit: October 12, 2013, 06:44:17 PM by ihasmario »
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