Growth of Loudness Assessment in Children Using Cross-Modality Matching (CMM)

Loudness judgments play an important role in the selection and fitting of the electroacoustic characteristics of hearing aids such as the maximum output or the compression ratio (Fabry and Schum 1994). To aid in this process, subjective judgments of loudness are often obtained to define regions of comfort or discomfort (i.e., most comfortable loudness level [MCL]; loudness discomfort level [LDL]). This procedure is frequently used in the clinical setting. Another method is to obtain loudness judgments over a range of stimulus levels, providing information on how the listener perceives the growth of loudness. The plotted values of stimulus level by loudness magnitude are referred to as loudness growth functions. The recent popularity of non-linear hearing aid circuits as found in digital or wide-dynamic range compression (WDRC) instruments has necessitated new fitting strategies that could incorporate information about loudness over the range of intensities modified by the amplification circuitry (Kruger and Kruger 1994). A common approach to the fitting of non-linear circuits involves the concept of normalization of loudness growth, where hearing aid characteristics would be adjusted for the individual listener with hearing loss in order to normalize his/her perception of loudness (Dillon 2001). For example, insertion gain would be calculated for each input level by the amount needed to restore normal loudness for the individual hearing aid user.