FIR_READ.DOC

How to pass the recruitment input waveform through a filter of a given transmission characteristic before carrying out the recruitment simulation and then passing the simulation waveform through the inverse of the same previously transmission characteristic.

Three transfer functions with their inverses are provided FF, DF & ERP
Each file consists of a title, number of taps (257), then the same number (257) of coefficients. The naming convention is for the inverse function to be the same as the forward function but with an 'I' on the front, this is only for convenience in using the batch file do_rec1.bat.

Provided filter coefficient files are:
FF	Frontal free field to cochlea
IFF	Inverse frontal free field to cochlea
DF	Diffuse free field to cochlea
IDF	Inverse diffuse free field to cochlea
ERP	Ear reference point to cochlea (ITU P.58 Telephone)
IERP	Inverse ear reference point to cochlea (ITU P.58 Telephone)


Run the simulation using do_rec1.bat, e.g.

do_rec1 asl1 asl1 ff

This will take the speech file asl1, put it through the 'frontal free field to cochlea' transform, do the recruitment simulation as specified in do_rec1.bat by filtering into 13 channels etc and doing  'n.r2' flat 50dB loss simulation (as currently defined) then carry out the inverse transformation to give asl1.r2, the output file.

do_rec1 asl1 asl1 erp

This will take the speech file asl1, put it through the 'ITU P.58 transform' etc

The FIR filtering program can be run from the DOS prompt, DOS filename restrictions apply.

fir_corr -i input_file -o output_file -f filter_coeff_file [-g gain_scaling]
e.g. fir_corr -i asl1 -o asl1.erp -f erp

N.B. the -g flag is optional, default is 1.0, if there is too much gain in the fir filter overflows (>32767) and underflows (<-32767) are reported at the end of the program run.


MAS, BG & BCJM 6/6/2001

