Issam Kheirallah
Todd Schneider
Donald G. Jamieson
Hear. Health Care Res. Unit, Univ. of Western Ontario, Elborn College, London, ON N6G 1H1, Canada
The electroacoustic properties of many modern hearing aids change as a function of the input stimuli. One consequence is that electroacoustic measurements obtained using commercial hearing aid test systems may differ from those made with important, ``real-life'' signals. As speech is the most important real-life signal for most hearing aid users, tests using speech stimuli have been proposed. This paper describes one approach to such testing, using spectrograms to display speech signals in a three-dimensional representation. Dual spectrogram displays prepared using the computerized speech research environment (CSRE) software allow speech signals at the input and output of a hearing aid to be compared. Such spectrograms are computed for a set of important phonemes extracted from running speech. The results of these analyses are evaluated for individual hearing aid users using a display which includes the user's thresholds and loudness discomfort levels (LDLs), together with the target amplification levels specified by the individual's hearing aid prescription. Such displays provide concise representations of the audibility of aided speech tokens for particular individuals. The effects of time-varying processing are addressed with additional tests which measure how specific, putative speech cues are affected by hearing aid processing. [Work supported by grants from NSERC and OMH to D. G. Jamieson.]