Hi,
I would add to Jörn's comments that apart from head-tracking, which is
crucial, you probably have to apply some decorrelation to your synthetic
binaural signals, and mix them with the normal ones. From anechoic hrtfs
only, especially if they are generic ones it is easy to get the in-head
effect. You can add decorrelation by some room simulation algorithm,
artificial reverberation or simpler by convolving your signals with
bursts of noise, passing them through allpass filters, applying varying
delays, whatever you can do that will scramble the phase but not the
magnitude of the sounds.
I have heard demonstrations with room simulated binaural responses that
were well externalised without head-tracking, adding head-tracking
should be very effective. You can check the literature for audio
decorrelation techniques or artificial reverberation. Have a look also
on the following master thesis:
Headphone Sound Externalization - TKK Acoustics
www.acoustics.hut.fi/publications/files/theses/liitola_mst.pdf
Regards,
Archontis
On 5/24/11 5:31 PM, Jörn Nettingsmeier wrote:
On 05/24/2011 03:42 PM, Junfeng Li wrote:
Dear Daniel,
Thanks a lot.
I have already read some information on Dolby and Smyth surround
headphones.
However, what I could see on these headphones is only the
introduction of
the products.
What I now need is some technical/scientific documents/articles to
explain
the principle and implementation of these products.
Could you provide some references on it?
Thank you very much.
well, if you have headphones, you have to be doing binaural synthesis.
so what happens is you take the positions of the speakers you want to
simulate, and convolve each speaker signal with the appropriate
head-related transfer functions for the left and right ear.
the next step (and a pretty important one) is to track the user's head
movements, and at the same time crossfade to another set of HRTFs.
that's not exactly trivial, but also quite well understood, and there
are some free implementations that do the job pretty well.
that's pretty much all there is to it.
in theory :)
what makes it a product is to figure out how to
a) either measure the customer's own HRTFs without annoying them too
much (because you want quite a lot of them), or
b) provide some means to select and optimize a generic set of HRTFs.
iiuc, smyth is doing a).
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