Subject: [AUDITORY] Gammatone filter bank in MATLABr2019a From: Bastian Epp <000000a94eb56441-dmarc-request@xxxxxxxx> Date: Tue, 16 Apr 2019 09:04:23 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear list, This morning I read through the release notes of MATLAB R2019a and was happy to find that there was an implementation of a Gammatone filter bank included:=20 "Gammatone Filter Bank: Mimic the human auditory system" With the reference to (among others): Glasberg, Brian R., and Brian CJ Moore. "Derivation of Auditory Filter Shapes from Notched-Noise Data." Hearing=C2=A0Research. Vol. 47. Issue 1-= 2, 1990, pp. 103 =E2=80=93138. This made me quite happy because it is a proper description of what Gammatone filter banks most often are used for - to model the frequency selectivity of the auditory system (as measured using psychoacoustics). However, in the DOC page, they show a picture of the Basilar membrane on top with the frequency response of the filter bank - suggesting that there exists a 1:1 correspondance. Everybody needs a topic to grow old and grumpy on - mine is this:=C2=A0 From my point of view, this is only correct under the (overly strong?) assumption that the cochlear is the only place in the auditory system underlying the perceptually observed frequency selectivity. Measuring "auditory filters" means to evaluate the auditory system as a whole=C2=A0(the concept of a "neuron" also only makes sense when being embedded in its network). "Cochlear filters" are measured on/in the cochlea .=C2=A0 Besides the common critiques (linearity, coarse approximation of the actual "filter" shape, etc), the main problem in my point of view is=20 that we teach students that we can "measure" the function of a "subsystem" (the cochlea) using a method that assesses the function of the "whole" system. There are some data sets that suggest a strong link, but the "tool" of psychoacoustics simply does not allow such a statement. Even though I like the working hypothesis "The brain exists to keep the cochlea warm", I think equating cochlear frequency selectivity with auditory filters (without explicitly stating the assumption that no(!) element along the auditory pathway modifies this frequency selectivity) is a point where we could be more careful to avoid misconceptions and overly strong conclusions. In most publications and books, this point is not explicitly wrong, but not as precise as it could be in my opinion. I hope that someone from MATHWORKS follows this list and considers a more careful description in the DOCs. I would also be happy to compile all the constructive arguments that people might have for/against my point of view. Have a great day everybody! BAstian --=20 Bastian Epp Associate Professor DTU Healthtech=C2=A0=C2=A0=C2=A0=C2=A0 ------------------------------------ Technical University of Denmark =C3=98rsteds Plads Building 352, Room 118 2800 Kgs. Lyngby Direct +45 45253953 bepp@xxxxxxxx http://www.dtu.dk/english