viola_c.gif The Visual Input/Output Locator Algorithm Program (VIOLA)



The VIOLA program is a graphical approach to determining a best-fitting input/output (I/O) function for choosing and fitting linear or non-linear hearing aids. It is a 32-bit Microsoft Windows application that can run on most systems with Microsoft Windows. The rationale behind using the VIOLA program is to select a hearing aid based on consideration of its gain, maximum output, and I/O functioning. The user must provide loudness perception data from the Contour Test or, at the least, audiometric thresholds. In the absence of loudness data, threshold data is used by the program to predict these values. This information is used by the program to generate a hearing aid prescription. A screen is displayed which includes an interactive table of hearing aid parameters at the top and adjacent graphs for two I/O functions at the bottom. The user then specifies values for compression parameters and observes the goodness of fit between the prescription targets and the performance of the specified hearing aid. Parameter values may be varied until an acceptable match is seen between targets and hearing aid performance. For additional information see Cox, 1995.

VIOLA is a free-standing program which was a module within the IHAFF Suite software. We no longer support nor distribute the original DOS-based IHAFF software.


Free Download:

Obtaining the VIOLA software:

The VIOLA program is somewhat dated, and is not used for modern hearing aid fittings. However, it can be a useful teaching tool.The VIOLA software is available for free download at right.

Format: Version 1.0 of the VIOLA for Windows software is currently available.


Information about the development and research regarding the VIOLA may be found in:

Cox, R.M. (1995). Using Loudness Data for Hearing Aid Selection: the IHAFF Approach. The Hearing Journal 47(2), pp. 10,39-42.Cox, R.M., Alexander, G.C., Taylor, I.M., Gray, G. (1997).

Cox, R.M., Flamme, G.A. (1998). Accuracy of predicted ear canal speech levels using the VIOLA I/O-based fitting strategy. Ear & Hearing 19(2), pp. 139-148.

Cox, R.M. (1999). What has happened to the IHAFF protocol? The Hearing Journal, 52 (9): 10-18 (1999).