Single precision gammatone filterbank - help needed :(

[Piotr Holonowicz <piotr.holonowicz@xxxxxxx>]

Dear Colleagues,

I am currently working on analysing music using Gammatone filters instead of 
the FFT. Due to the fairly large number of the concurrent filters I needed to 
implement it using Graphics Processing Units (Nvidia CUDA), but my 
implementation uses double precision numbers, which are only available with 
decent and powerful, thus expensive graphic cards. 
I would like then to change the implementation to a single precision, however, 
it returns garbage if the center frequency is below 200 Hz. 
Has someone an implementation of the Gammatone / Gammachirp filter bank that 
does not require double precision? I am more interested in how it works than 
just the code as I need to rewrite it to make it working on GPU. 

For any suggestions/ help I'll be very grateful.

Best

Piotr Holonowicz
Music Technology Group
Universitat Pompeu Fabra,
Barcelona
Spain