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Using the Basilar Membrane Filter Modules

The decomposition of stimuli into different frequency channels is an important stage in auditory processing. It is generally visualised as occurring at the basilar membrane. Accordingly the modules which simulate this processing stage are called the basilar membrane filter modules. Within the LUTEar library, these modules are distinctive because it is at this point that the number of channels representing a signal can be increased.

There are several different basilar membrane filter models implemented in the LUTEar library, ranging from the simple gamma-tone model to the more complex composite models, made up of multiple filter components. There are two important requirements which are common to all of the basilar membrane filter modules, even though each particular model has its own specific parameters. The first of these is the centre frequency for each filter of the model producing an output channel, and the second is the respective bandwidth at each centre frequency. The LUTEar library provides a simple interface which is used by all of the basilar membrane modules to control these two requirements. This interface can be accessed from the basilar membrane module parameter files. This mode of use is described below, and an example parameter file is given in figure [27] below.

Figure [27]: Examples of parameters files for the "BasilarM_GammaT" basilar membrane filter module: (A) the parameter file for a single filter at 1000 Hz; (B) the parameter file for a filter-bank with 20 filters ranging from 80-4500 Hz, equally spaced on a logarithmic scale. Both parameter files specify the equivalent rectangular bandwidth (ERB) bandwidth mode.



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