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Figure 1. Control window of aim2006. The upper left area contains the play function and the modules corresponding to each stage in AIM. Right to that is the MOVIE column and below are various functions for controlling the appearance of the plots. See text for details.

Aim2006 has a graphical user interface (GUI) for constructing auditory images. The GUI is composed of a control window and a graphics window. The control window in Figure 1 shows the stages of processing required to construct an auditory image (the columns PCP, BMM, NAP, SP, SAI, MMI) and contains a number of functions for customizing the image in the graphics window. The graphics window shows the result of a particular stage. For example, in Figure 2 the result of the PCP and BMM stages is shown (using maf and dcgc pre-processing, see next section for details).

Figure 2. The main graphics window with the output of the current stage of auditory processing. In this case it shows basilar membrane motion for the vowel /a/. The top panel shows the waveform of the vowel.

Standard menus are located at the top of the control window. They enable the user to load wave files, save the results of an analysis in a file, save the parameter set used to perform an analysis, and access additional tools such as the FFT.

A sound file is loaded by selecting either the load or substitute entry in the File menu. The function load reads the sound file and any associated project files into aim2006. The function substitute applies the parameters of the current model to a new sound file; this is useful when a particular model is applied to several sound files. Once loaded, the sound can be played-back by pressing the Play button at the top right of the control window.

The auditory image is constructed by simulating a series of processing stages (Table 1) in the auditory system. The computations pertaining to each processing stage are explained in detail in the next section. Below is a brief introduction to how to operate each stage with the GUI. Each processing column (i.e. module) contains three functions:

  1. At the top is an execute button that causes the output of that particular stage of processing to be computed or recomputed, and the output at that stage to be displayed in the graphics window.
  2. A drop-down menu with the different algorithms available to simulate that stage of auditory processing.
  3. A tick box indicating that the module will be calculated or recalculated if the parameters of earlier modules have been changed.

The six modules are: pre-cochlear processing (PCP), basilar membrane motion (BMM), neural activity pattern (NAP), strobe point identification (SP), stabilized auditory image (SAI) and a development module (Developement) whose default is currently the Mellin transform (mt). The contents or each module are explained in the next section.

The lower left-hand panel of the control window contains two sliders which enable the user to select the start time and the duration of the segment of the wave to be analysed. The three lower panels to the right control the appearance of the image in the graphics window:

The Movie function at the top right allows the user to construct a film composed of a series of images calculated from segments of the sound file. This can be useful to illustrate the perceptual salience of dynamic sounds.

The results produced by a module are displayed in the main panel of the main graphics window as illustrated in Figure 2. In this window, there are optional panels to display:

  1. The segment of the wave on which the analysis was based (top),
  2. A spectral, or tonotopic, profile showing the average over time (right),
  3. A temporal profile showing the average over frequency channels (below).

These subpanels can be added or removed as appropriate by toggling the switches in the Display panel as explained above. So, for example, in the Figure 2, for the BMM, the temporal profile is not particularly useful and so it is turned off for this stage.

The windows are standard MATLAB windows and so the properties of the graphical objects can be changed by clicking on the relevant axes in the usual way. The images can be exported in standard graphics formats (wmf, eps, bmp, etc.) by using the Copy entry in the Edit menu or the Save As option in the File menu in the main graphics window.

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