Download aim2006
AIM2006 v1.40 (Released 10 November 2009, 1.2Mb ZIP Archive) - Adds the Pole-Zero Filter Cascade (PZFC) filterbank and assorted bugfixes
AIM2006 v1.20 (Released 11 June 2008, 1.2Mb ZIP Archive)
System requirements: aim2006 should run on all operating systems supporting MATLAB 6.5 and upwards (Windows NT, 2000, XP; GNU/Linux; Solaris; MacOS X). The graphical user interface will not run on versions of MATLAB before 6.5. The signal processing toolbox is required for the basilar membrane modules included in this release.
Authors
Core programming: Tom Walters, Stefan Bleeck (aim2003)
Module contributors: Tim Ives, Ralph van Dinther, Richard Turner, Toshio Irino
Documentation: Martin Vestergaard, Stefan Bleeck (aim2003)
A guided tour of AIM
The auditory image model (AIM) is a time-domain, functional model of the signal processing performed in the auditory pathway as the system converts a sound wave into the initial perception that we experience when presented with that sound. This representation is referred to as an ‘auditory image’ by analogy with the visual image of a scene that we experience in response to optical stimulation (Patterson et al., 1992). Aim2006 is a complete implementation of AIM in which the processing modules, the resource files and the graphical user interface are all written in MATLAB, so that the user has full control of the system at all levels. It is an updated version of aim2003 which is described in Bleeck et al. (2004).
AIM
The principle functions of AIM are to describe and simulate:
1. Pre-cochlear processing (PCP) of the sound up to the oval window of the cochlea,
2. Basilar membrane motion (BMM) produced in the cochlea,
3. The neural activity pattern (NAP) observed in the auditory nerve and cochlear nucleus,
4. The identification of maxima in repeating neural patterns, that can be used as strobe points (SP) to construct auditory images,
5. Stabilized auditory images (SAI) that form the basis of auditory perception,
6. A size invariant representation of the information in the sound at the syllable level, referred to as the Mellin Magnitude Image (MMI).
Table 1 shows the architecture of AIM and its relationship to the physiology and signal processing of the auditory system.
Table 1. The relationship between the auditory processes simulated in aim2006 (top row), the physiological structures associated with the process (middle row) and the corresponding aim2006 modules (bottom row).
| Auditory process |
Bandpass filter |
Frequency analysis |
Sharpening |
Feature detection |
Temporal integration |
Normalization |
| Physiological structure |
Middle ear |
Cochlea |
Brainstem/IC/Thalamus/MGB |
Cortex |
||
| aim2006 module |
PCP |
BMM |
NAP |
SP |
SAI |
MMI |
There are typically several alternative algorithms for performing each stage of processing. The default options represent the most advanced version of AIM, as we currently understand auditory processing (e.g., the dynamic compressive gammachirp filterbank for simulating basilar membrane motion). In each case, there is also one of the previously standard options for comparison (e.g., the traditional, linear gammatone filterbank for simulating basilar membrane motion).
New features in aim2006
Aim2006 includes a number of new features:
1. The default spectral analysis module (dcgc) uses a dynamic, compressive GammaChirp (dcGC) filterbank, which has fast acting compression in the filter, after the module that simulates the passive motion of the basilar membrane, as part of the module that simulates the active process in the cochlea (Irino & Patterson, 2006).
2. The default form of neural transduction module (hl) is reduced to half-wave rectification and low-pass filtering, since there is now fast-acting compression in the auditory filter itself (i.e., in the dcGC filterbank).
3. The default strobe finding mechanism is currently sf2003. It will eventually be replaced by sf2006 which is two dimensional and adaptive; the cross-channel constraints are implemented with a Bayesian statistical network.
4. The default temporal integration module is currently ti2003 from aim2003. It stabilizes repeating neural patterns as required in AIM (e.g., Patterson et al., 1995). It will eventually be replaced by ti2006 which will produce separate auditory images for pitch information and resonance information. This is because the time-like dimensions of the Auditory Pitch Image (API) and the Auditory Resonance Image (ARI) are fundamentally different. The abscissa of the pitch image is time interval as in the original auditory image. The abscissa of the resonance image is time-interval X channel-centre-frequency, that is, the h dimension of the Mellin transform (Irino & Patterson, 2002). The ARI is a scale-covariant representation of the information in the sound.
5. There is a new module (mellin) for converting the auditory resonance image into a Mellin Magnitude Image (MMI) and a Mellin Phase Image (MPI). The MMI is a scale-invariant representation of the information in the sound (Irino & Patterson, 2002).
There are parameter files for all of the modules in aim2006 where the user can control the operation of the module.
Input signals
All standard wave files can be used to input sounds into aim2006. The sampling rate of the sound file determines the sampling rate of all subsequent calculations, and all sampling rates are supported.
Acknowledgements
This development of aim2006 was supported by the European Office for Airforce Research and Development under reward number IFT-053043. The development was also supported by the UK Medical Research Council (G990369, G0500221).