I have been wanting to say exactly what richard lee says, for many days now. Only I could not figure out an unambiguous way of putting it down.
umashankar Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Richard Lee<mailto:rica...@justnet.com.au> Sent: Friday, January 29, 2016 5:39 PM To: 'Surround Sound discussion group'<mailto:sursound@music.vt.edu> Subject: Re: [Sursound] Never do math in public, or my take on explaining B-format to binaural Just to bring everyone down to earth .. There are two easily reproduced experiments first carried out by prominent members of this group which put these effects into perspective. They are the Greene/Lee Neckbrace and Malham/Van Gogh Experiment The first shows 'real life' Fixed Head Localisation (which matched HRTFs address) is TERRIBLE. Many people can't even distinguish back/front with perfect (measured on their own noggin) HRTFs ... or even in 'real life' with a Greene/Lee neckbrace. Anyone who has done fixed head localisation experiments finds this out real quick. The second shows that even the tiniest amount of head movement improves localisation immensely and any ambiguity due to mismatched Pinnae etc (and YES, the pinnae colouration effects are chaotic) are INSTANTLY resolved. No 'training' is necessary with head movement. Even vertical localisation, for which Fixed Head HRTFs have the most benefit, require a priori knowledge of the source spectrum. I've done a small amount of work involving victims ... I mean subjects ... blindfolded and tied up face down on anechoic chamber floors which show the first pin drop is impossible to localise. Second and subsequent pin drops are much easier. I'll point out that Gerzon had Fixed and Moving Head versions of all his Localisation Theories. The infamous Energy and Velocity vector 'magnitudes', rE & rV, are in fact a measure of the correspondence of Fixed with Moving. His Energy and Velocity models incorporate (give the same results as) ALL the existing Localisation models except for the HF interaural delay (Transient) and Colouration ('HRTF') models. One of Gerzon's most important contributions is that he shows the equivalence of the full Moving Head models like Makita, which assume the listener will fully turn to face the sound ... with the models that only assume small involuntary head movements. See "General Metatheory ... " for the nitty gritty. ____________________ If you make some B-format recordings with a properly aligned Ambisonic mike like TetraMic, you can test some of this for yourself. Have lots of things happening all around including up & down. Use headphones and the crudest possible Binaural decoding ... slightly hyper cardioids at about 150. You will find about 10% of the population have difficulty with front/back. But let these guys twiddle the Azimuth & Elevation controls on VVMic themselves and they immediately become happy with the scene ... even before they work out VVMic's slightly quirky interface. ____________________ CONCLUSIONS If you have Head Tracking (ie Moving Head Localisation), don't bother with fancy HRTFs. Eric Benjamin found that you get most of the benefits from just getting head size right but even this isn't necessary if you have Head Tracking. Blumlein shuffle probably worth doing as you essentially get it free with your simple IIR implementation. Fancier HRTFs will need EVIL FIRs to be of use. You will lose any chance of 'real time' and muck up the experience for 'mismatched' listeners. Expect only small (if any) 'improvement' for the huge extra.computing load to interpolate between HRTFs. If you haven't got Head Tracking, GOTO Head Tracking This covers all the Virtual Reality applications. The Video Game people like Simon Goodwin of Codeworks have been doing it for at leas a decade with 3rd Order HOA IIRC. If you insist on fancy HRTFs and Fixed Head ... do you seriously think you can improve on the listening experience of present & past generations of listeners, who have listened to 'music' over ear buds for more than a decade ... with fancy HRTFs ? GOTO Head Tracking. ____________________ SPECIAL OFFER Send $500 in used bank notes to me at Cooktown Recording and Ambisonic Productions mentioning Sursound, for a sample Greene/Lee Neckbrace and Diamond Encrusted Malham/Van Gogh cap. Golden Pinnae are an extra cost option on the last item. No Confederate money please. _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on. -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20160129/23bf36cb/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.