# THE AUDITORY MODELING TOOLBOX

Applies to version: 1.1.0

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# HOHMANN2002 - Invertible Gammatone filterbank

## Usage

fb = hohman2002(fs, flow, basef, fhigh, filters_per_ERBaud)


## Input parameters

 fs The sampling frequency of the signals on which the filterbank will operate flow The lowest center frequency of a filter basef "base frequency". One of the filters will have exactly this center frequency. Must be >= flow fhigh The highest center frequency of a filter. Must be >= basef filters_per_ERBaud The density of gammatone filters on the ERB scale.

## Output parameters

 fb The constructed filterbank object.

## Description

hohman2002 constructs a new fb object implementing the analysis part of a gammatone filterbank as described in Hohmann (2002).

fb contains several all-pole gammatone filters; each one with a bandwidth of 1 ERB (optional: times bandwidth_factor), and an order of gamma_order.

The center frequencies of the individual filters are computed as described in section 3 of Hohmann (2002).

hohmann2002 takes the following flags at the end of the line of input arguments:

 'gamma_order' The order of the gammatone filters in this filterbank. Default is 4. 'bandwidth_factor' The bandwidth parameter of the individual filters is calculated from the Equivalent Rectangular Bandwidth (ERB) according to equation 14 in Hohmann (2002). ERB is taken from the Glasberg & Moore formula for a specific center frequency (equation 13 in Hohmann (2002)). Using this parameter, it is possible to widen or narrow all filters of the filterbank with a constant bandwidth factor. Default is 1.0 'l' Scaling factor l from Eq. 13 in Hohmann (2002). Default is 24.7. 'q' Scaling factor q from Eq. 13 in Hohmann (2002). Default is 9.265.

## References:

V. Hohmann. Frequency analysis and synthesis using a gammatone filterbank. Acta Acustica united with Acoustica, 88(3):433--442, 2002.