gtf — Apply a gammatone filter to an audio signal.
idecay -- rate of decay
iorder -- (optional) Order of filter in rangs 1 to 10 defaulting to 4.
iphase -- (optional) Phase output, defaulting to zero.
asig -- audio signal to be filtered.
kfreq -- central frequency of filter in Hertz.
The gammatone filter is commonly used in models of the auditory system. The algorithm is based on Martin Cooke's Ph.D work (Cooke, 1993) using the base-band impulse invariant transformation. See http://staffwww.dcs.shef.ac.uk/people/N.Ma/resources/gammatone/