Dear Filippo, all friends, According to your comments, we have processed the binaural sound by performing headphone equalization and adding reverberation. The processed data can be downloaded from https://proself2.jaist.ac.jp/public/pVFAAA0MP8dAqTcB6R4w7AJKMfhlt8TlYUr-IojOpP-Z (test_src: the original sound; test_synthesis: the processed sound) Could you listen to them and give me your own ideas on the synthesized data? Of course, the headphone that you will use is different from mine, while its effect should be not so significant, i think.
We are now studying head-tracking which is expected to be added in the near future. And the individualization of HRTFs is quite difficult in real situation, therefore, I cannot do it currently. Thank you so much for your comments on our data and our research. Best regards, Junfeng > > > On Thu, May 26, 2011 at 10:09 PM, f...@libero.it <f...@libero.it> wrote: > >> Dear Junfeng >> >> decorrelation is a term quite loosely used in the audio community, I >> believe. >> >> You can find a definition of correlation in any good signal processing >> book. It is the convolution of a signal with the time reversed version of >> another signal. >> If this function is a delta, then the two signals are perfectly >> correlated, if it is similar to noise, they are uncorelated. >> >> You can think about white noise: if you generate a burst of white noise >> and you correlate with itself, you'll get more or less a delta function. If >> you plat these two identical throug a stereo system, you will preceive a >> virtual acoustic image between the speakers. >> >> If you now correlate the previous noise with a different burst of white >> noise, you'll get noise again (namely, the two signals are not correlated). >> If you play these two diffrent signals through the same stereo system, I >> believe you will perceive two separate noise sources. >> >> >> If you think about a binaural signal obtained by convolving a mono signal >> with an HRTF for 0 elevation and 0 azimuth, the left and right signals are >> going to be the same (assuming symmetry of the head/torso). >> >> Decorrelating the two signals mainly means to add some randomization of >> the phase of teh two signals, so that they are not exactly the same. >> >> In practice, this correspods to convolving the signals with two diffrent >> all-pass filters. Usually, these filters are chosen to be short bursts of >> white noise with and exponential decay. >> >> You might argue that this is more or less the same as adding some >> reverberation, and I would indeed agree with you... in fact a binaural >> reverberation (with IACC smaller than 1) decorrelates the right and left >> signal and gives apparently an idea of spaciousness and helps greately with >> the externalization. >> >> >> I think some suggestions on how to decorrelate signals can be found in >> Laitinen' s thesis. >> >> >> I hope this helps... >> >> Filippo >> >> >> >> ----Messaggio originale---- >> Da: junfeng.li.1...@gmail.com >> Data: 26/05/2011 15.28 >> A: "f...@libero.it"<f...@libero.it>, "Surround Sound discussion group"< >> sursound@music.vt.edu> >> Ogg: Re: [Sursound] Sound Externalization Headphone >> >> >> Dear Filippo, >> >> Thanks a lot for your quite valuable comments. >> >> >>> Apparently, as Akis and Joern mentioned, the following items often are >>> used to >>> achieve externalization: >>> - decorrelation/reverberation >>> - head tracking >>> - individualized HRTF >>> - headphone equalization >>> >> >> >> What I am now confusing is what you mean by "decorrelation/reverberation"? >> >> How to do decorrelation? for What? >> >> Thank you so much in advance. >> >> Cheers, >> Junfeng >> >> >> >> >>> >>> We believe that the order of the items above reflects their relevance (in >>> decreasing order). >>> >>> At the London AES, I discussed this with some researchers from Aalto Uni >>> (they gave me an extremely impressive demo when I visited their lab in >>> Helsinki). They stressed the fact that a visual reference to the virtual >>> sound >>> source location is an extremely important localization cue... >>> >>> I should mention that interpolation of HRTF is not the only possible >>> technique; you can use for example a virtual loudspeaker array... >>> >>> Does the Dolby product implement head tracking? >>> >>> Hope this helps >>> Filippo >>> >>> >From: Archontis Politis <deadflagb...@gmail.com> >>> >Subject: Re: [Sursound] Sound Externalization Headphone >>> >To: sursound@music.vt.edu >>> >Message-ID: <4ddbca43.20...@gmail.com> >>> >Content-Type: text/plain; charset=ISO-8859-1; format=flowed >>> > >>> >Hi, >>> > >>> >I would add to J?rn'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 >>> >>> _______________________________________________ >>> >>> Sursound mailing list >>> Sursound@music.vt.edu >>> https://mail.music.vt.edu/mailman/listinfo/sursound >>> >> >> >> >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20110601/5f226aae/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
