Overview

This simulation model is designed show the influence of cochlear transduction parameters on distortion. It is intended to allow researchers to simulate experiments and also makes a good teaching tool to show students how different types of distortion originate

Copyright of this program is retained by the author. It may be freely distributed but must not be modified in any way without written permission from the author.

Recommended System Requirements
Display : Super VGA (800 x 600) or higher, At least 16 bit color
Operating System: Microsoft Windows 95 or higher
PC language must be set to English. Comma delimited decimals as used in Europe will give errors

Downloading and Installation

1) Clicking on the link will download the file Dmodel11.msi and start the installation procedure if you tell the browser to run the file immediately.
The installation will not work with some versions of Netscape, so Internet Explorer should be used if you have problems.

Running the Program.

The installer will put a start Icon on both your start bar and on the desktop.Double click on the icon to start the program.
If you do not want either of the icons you can move or delete them

First test the program by hitting the <Start> button.

This demonstrates the program in "slow" mode. The input sine wave (red) is calculated with time. The input is shown on the transducer response curve (graphed at the upper left) as a red ball that moves according to the input stimulus. The calculated output from the transducer is shown as a blue waveform. The moving red ball shows how the dependence of the output on the input relies on the nonlinear transducer curve.

The green ball on the Transducer Response curve indicates the operating point, i.e. the point on the curve on which the incoming sine wave is centered. Try entering different values for operating point (0, 0.5 or -0.5) and see how it changes the output waveform.

As the output waveform accumulates, the spectrum of the output wave is calculated. The spectrum is only valid when a complete buffer of 42 msec of data is calculated.

If you don't want to watch as the waveform is generated, stop the stimulus and check the "Fast Calculate" box. Pushing the button will now calculate a 2048 point waveform instantaneously
The program allows the effects of transducer parameters (Operating point, Saturation Voltage and Transducer slope) to be evaluated on the output waveform.

A second tone can be included by entering a numeric frequency value in the "Tone 2" box .

The influence of a bias tone can also be included by entering a numeric bias frequency (e.g. 5 Hz). A time offset, to allow comparison of different bias phases, may be entered. In slow calculation mode, the green ball on the transducer curve shows the influence of the bias tone.

The influence of filtering can be observed by entering a numeric value in the filter box (only available in fast calaculation mode).

Transducer curves based on a first-order Boltman function and a second-order Boltzman function are available. The two functions differ in their symmetry, with the first order curve being symmetric in voltage, while the second order curve is asymmetric. Although the hair cell response is known to be asymmetric, we have found the first-order curve to closely predict cochlear microphonic measurements. Differences between these two approaches are still ongoing.

Each calculation causes the results to be added to the table at the bottom of the page (up to 100 results). Calculated values can be copied to other programs by copying them to the clipboard. Another button clears the data.

If you have Microsoft Excel on your machine, you can save waveform data as an excel spreadsheet. The saved data has 6 columns.
Columns 1 and 2 are the time and calculated output waveform.
Columns 3 and 4 are the displacement and voltage values for the transducer curve.
Columns 5 and 6 are the frequency and level (dB) for the calculated spectrum

Exiting the Simulator

The simulator is exited by clicking on the "X" box at the top right corner of the window.