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What do you know about 3D spartial and binaural hearing?

post #1 of 12
Thread Starter 
I highly recommend going to WNYC - Radiolab and listing to their great binaural shows like the second season one about music language while reading this. Yes headphones are required of course

Being an student, as we are thought the river of our life's, I'm studying various part of audiology. Of course being an IT-engineer student and gamer color which areas I like the most to study in details - especially it seems in areas where digital design are now favored over traditional electronic engineering designs. Hence areas where I understand at least all the non-acoustical details due to my engineering studies

In fact what I love about my new favorite area of acoustics is that some parts of it relies heavily on digital processing for any commercial applications where you cannot physically record it as you want your listeners to hear. And even when you can do raw binaural recordings they are never near perfect unless they are recorded with microphones in the listeners own ears. How ever with the right digital HRTF algorithms, DAC, amp and 'phones you might actually come scarily close if they are adjusted to individual listener. At least thats my opinion.

My question or deposit for a debate if you will is what do you know about this subject and what do you like to add for new-commers? How do you feel about the current trends in gaming and cinema playback algorithms like Dolby Headphone? Is this something that you could see replacing your surround sound speaker systems as I have done? What are your experience with binaural recordings?

- As a side note my own use of these algorithms was partly due to the wife-acceptance-factor of my surround sound set, partly due to I needed newer sound card for gaming anyway and partly due its low quality compared to my headphones but thats another story
post #2 of 12
Are u talking about DSPs to create the surround sound effect?

have u heard of CMSS 3D by Creative? ..its an example of pathetic virtual surround sound.
post #3 of 12
Quote:
Originally Posted by Nocturnal310 View Post
Are u talking about DSPs to create the surround sound effect?

have u heard of CMSS 3D by Creative? ..its an example of pathetic virtual surround sound.

CMSS3D is meant for harware using Directsound 3D games, there it works really well. It isnt just spatializer. "Surround" spatializers suck anyway.
post #4 of 12
The best surround/binaural devices are your brains. Nuff said.
post #5 of 12
Thread Starter 
Well yeah I got the X-Fi elite pro as one of my PCI-interfaced DAC systems.. I Personally think the CMSS 3D with a proper 'phones in a good implemented game is up there with Dolby headphone down mix of a dolby surround track to a DVD or the like. How ever still I really like radiolab and other binaural recordings - they make my spin chill like nothing else at the moment.

The most crucial point of failure of these algorithms is of course all the different parts where the individual's binaural hearing make it so complex that your can't make system near surround quality on all areas within a realistic price tag*. Areas like central front <-> back confusion which we all take for granted as the simplest thing in surround sound system are the very hardest part for these algorithms to recreate.

Anyway going back on track: Do anyone out there have some technological knowhow about this they want to share?
I'd like to drive this of to one of 2 places: a) wealth of useful information, links and debate to bath in for all head-fi members and googlers alike. b) We find out how little head-fi's members know about this and I will take a few more weeks and make something up from papers and books I'm reading at the moment.

In fact I actually think I might do a special project about this and get some ECTS points for my degree regardless. Would give me more time for work/play with head-fi tech

*read when I get my degree in engineering done and get all your monies you are saving for a HE90 replacement we can work something out or track down the right people if you are as mad about this stuff as I am
post #6 of 12
well,

I did some research to this subject for my study a while back and concluded that the only thing that can come close to th real life experience is Binaural recording.

A computer can calculate his ass of but it'll still be digitized and not exactly life-like. It can sound stunning, but it's not that your brain automatically assumes it's hearing real life stuff.

Let me explain:

I tested this all with headphones and IEMS. Now all those digital technologies *can* sound awsome, but in an entertaining way. My brain knows that it's listening to pre-recorded stuff. It can be tricked and loose track of all the sound for a minute but it'll remember it's being tricked and that it is listening to recorder sound.

This was with all these systems (Dolby Headphone, SRS Headphone, SRS 360, SRS CSH and all the other ones out there)

Now with a Binaural recording it was as if the brain just didn't react. It thought there was no change and that the sound was perfectly live and natural. it didn't loose track and it wasn't telling me and the test person that he was being tricked and thet it was recorded. It even started sending signals to turn the head when the sound of a car passing by was auditioned. So the brain was just doing it's natural thing having no idea it's being tricked.

I did this research with the help of some doctors and professors and scientists, and the reason why the brain didn't felt tricked was simple (so explained a audiologist/doc to me):

The human ear can determine distance and placement of the soundsource by reflections in the outer earshell and the time difference of the sounds coming in betweenthe right and left ear amongst others (well, the brain actually calculate the distance and placment using this data from the ear) A headphone or IEM as soundsource cancels these 'instruments' out and so the brain only can determine the headphone membrane's position.

With these digital techniques this won't cange, the sound can be changed though but the signal (i.e. information/data the brain needs to determin the position of the sound) will never be exactly as detailled and clear, at least not with the technology of today.

With Binaural mics (inside a human ear) this neccesary 'data' from the outher earshells and differences between both ears will be added to the sound before it's being recorded. So when this sound will be heared (without sending it past the earshells again) again the brains can detect their 'data' from the pre-recorded signal and determine almost exactly where the sound comes from (at least where it thinks it comes from, 'cause it's now being tricked).

This research cost me a lot of time and efforts at the time and was well received by my profs. So I know it's no b*llsh*t :P

Bottom line is that the modern-day technology is far from being good enough to be able to generate a sound with that extra data our brain needs in such a way our brain wouldn't know it's being tricked. You can only achieve this at the moment by feeding the brain with a sound that contains that data from a human ear all ready.

Long story, hope it helps you and the NewB's

grz
post #7 of 12
Thread Starter 
Quote:
Originally Posted by ricthaman View Post
well,
............
Long story, hope it helps you and the NewB's

grz
Right on the money

That is in short what I'm getting from research papers, books etc.
post #8 of 12
Thread Starter 
I should however add that published studies have shown that you can learn to adapt to any new modified version of spatial hearing like learning a second language - it never goes away. Thought its of course limited by this new one - if it doesn't recreate spatial hearing cues as well as you normally do with your ears and body. After you take this modifications off, you also still retain your normal/old hearing perfectly. How ever it does take up to 6 weeks of no-stop wearing/using this modification to learn this new "language".

Its also the reason why a you as a child could evolve your spatial hearing so it could keep up with changes of your physical body. And why people who have been physical damaged to parts vital to creating spatial hearing doesn't just loose it or a twisted sense of spatial hearing. Their brain adapts a very long way as long as there is no or little of normal hearing impairing involved. Since I live in Denmark where large percentages of the worlds hearing aids and bluetooth headsets* are developed I just happen to have heard that some of them recently came out with sets of hearing aids for both ears that wireless synchronize their work so to minimize spatial hearing losses due to the technicals of hearing aids and even enhance spatial hearing on some people with heavy loss.

*William Demand(Oticon, Sennheiser Communications), GN Store Nord(Resound, Jabra), Widex, Brüll and Kjær and so on... In fact a scary large part of the dorms and such at the Danish Technical University are donated by the William Demand foundation alone.
post #9 of 12
Quote:
Originally Posted by ricthaman View Post
Long story, hope it helps you and the NewB's

grz
It's true that you can't recreate the 3d space of the original performance using a normal stereo music signal alone, but it could be possible to use three omni microphones at the recording studio, which would allow triangulation of the sound location. Then, using a personalised HRTF, the 3-channel audio could be reduced to 2, and this would sound (although only to that particular individual), virtually as though they were physically in the studio listening to the music.
post #10 of 12
There used to be a good explanation with pictures of their dummy head microphone on the zbs.org site. That seems to be gone, but they still have some good binaural radio drama on their list.
post #11 of 12
Thread Starter 
Yes, yes.. keep it flowing
b0dhi >> Actually didn't think about a 3 channel recording only.
Kicksonrt66 >> thanks for the link
post #12 of 12
This is good stuff. More links to technical/medical documents that can be found online!!!
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