Subject: Re: HRTF Question From: =?ISO-8859-1?Q?Sergio_Rodr=EDguez_Soria?= <sergio(at)LPS.USP.BR> Date: Wed, 17 Aug 2005 12:09:08 -0300Dear Chris, As far as I am concerned, there is not a particular study about the influence of the torso in the HRTF when the head is moving or when all the body moves together. But, in fact, the HRTFs will be different... the question is whether this difference will have a great perceptual impact (of course the head movement HAS a great perceptual impact by itself). As you should know, Algazi and Duda made several geometrical models for the torso (the snowman, an elliptic torso, numerical analysis, etc) and they concluded that the Torso may provide (but DON'T necessarily provides, it depends on the individual, on the type of sound event, etc) cues for elevation localization ONLY far from the median plane. The simple snowman model could be added to an HRTF system in order to improve the elevation localization performance in low frequencies, always problematic. This was done in: V.R. Algazi, R.O. Duda, D.M. Thompson, "The use of head-and-torso models for improved spatial sound synthesis", Proc. 113 AES Convention, 2002, preprint 5712 D.Zotkin, J. Hwang, R.Duraiswami, L.S.Davis, "HRTF personalization using anthropometric measurements", Proc. 2003 IEEE WASPAA, pp 157-160. By intuition, given the symmetry of an spherical torso, the reflection provided by it won't depend on the head position related to the torso position (at least when the head rotates in azimuth), it will only depend on the source position. Then, the entire HRTF will just change for the new relative positon of the sound source. Maybe if the head rotates in elevation... but it probably won't be significative. Anyway, this is only for the snowman. Other studies including torso influence are: G.F. Kuhn, R.M Guernsey, "Sound pressure distribution about the human head and torso" JASA, 73, 1983, pp. 95-105 K. Genuit, "A model for the description of out-ear transmission characteristics", PhD thesis, Reinisch-Westfaelischen Technichen Hochschule Aache, Germany, 1984 C.P. Brown, R.O. Duda, "A structural model for binaural synthesis", IEEE Transactions on Audio Processing, 6(5), 1998, pp. 476-488 A good summary if provided by Algazi et al. in: V.R. Algazi, C. Avendano, R.O.Duda, "Elevation Localization and Head-related Transfer function analysis at low frequency", JASA 109 (3), 2001, pp 1110-1122. Maybe you should see also: P. Mackensen, "Auditive Localization, Head Movements, an additional cue in Localization", PhD Thesis, Technische Universitat Berlin, 2004. David, Regarding to the question about "Generic HRTFs", maybe you should read an interesting paper of Martens where several concepts about HRTFs are discussed, like Individual, Customized, Averaged and Generalized HRTFs. Following his definition, a generic public set of HRTFs would be the MIT KEMAR one, and the CIPIC one could serve for customized HRTF systems. See: W. Martens, "Perceptual Evaluation of Filters Controlling Source Direction: Customized and Generalized HRTFs for Binaural Synthesis", Acoustical Science and Technology, 24 (5), 2003, pp 220-232 My best, Sergio On Tue, 16 Aug 2005, Chris Share wrote: > Date: Tue, 16 Aug 2005 15:44:35 +0100 > From: Chris Share <cshare01(at)QUB.AC.UK> > To: AUDITORY(at)LISTS.MCGILL.CA > Subject: HRTF Question > > Hi, > > I'm currently doing some research into head-related transfer functions. > > In the articles that I've looked at so far, it's mentioned that the > torso plays a role in the creation of the perceptual cues that enable > sound source localization. > > I'm curious as to whether there has been any research comparing > whole-body rotation (i.e. where the head and body move as one unit) as > opposed to head-only rotation (where the body remains fixed as in > sitting in a chair and turning the head to look sideways). > > It seems that the HRTFs for these two cases would be different as the > ears' positions with respect to the shoulders/torso is not the same? > > Is that correct? > > Are there any articles that examine this issue? > > Cheers, > > Chris Share >