Subject: Question about Vocal Tract Modeling From: Tarun Pruthi <tpruthi(at)GLUE.UMD.EDU> Date: Wed, 1 Dec 2004 14:05:37 -0500Hi all, I have been working on vocal tract modeling for nasalized vowels using the computer simulation program (VTAR) developed in our lab. It is usually said in these cases that the poles of the system occur when Bp + Bn + Bo = 0 where Bp, Bn and Bo are the susceptances for the pharyngeal cavity (Bp), oral cavity (Bo) and nasal cavity (Bn) (from the branching location). I am using detailed vocal tract areas from MRI recordings. During my simulations I have observed that the zero crossings of Bp+Bo+Bn do not correspond to the resonances observed in the vocal tract transfer function (computed by the same computer program). However, the resonances correspond exactly to the zero crossings of Bi (where Bi is the total susceptance of the vocal tract, looking into the vocal tract at the glottis). My question is: Should the zero crossings of Bp+Bo+Bn correspond to the resonances of the transfer function when I am using the transmission line model with multiple short tubes (modeling the detailed area function)? Or is this valid only when the pharyngeal, oral and nasal cavities are modeled as single uniform tubes? (My simulations show that the zeros of Bp+Bo+Bn and the resonances of the transfer function do correspond to each other when I model the cavities as simple tubes). Is there a reference proof somewhere which proves that the zero crossings of Bp+Bo+Bn should give the resonances of the transfer function even when I am using a detailed area model? Or if it is not true is there a reference which proves it the other way? I am just wondering whether there is something wrong with the program (although I have checked hard and don't seem to find anything wrong) or is it theoretically incorrect to say that? Thanks in advance, Tarun ----------------------------------------- Tarun Pruthi Graduate Research Assistant, ECE Room 3180, A V Williams Building University of Maryland, College Park MD 20742 USA Email: tpruthi(at)glue.umd.edu Web: www.ece.umd.edu/~tpruthi Ph: 301-405-1365 ----------------------------------------