Further questions about the acceptable noise level test.

I appreciated the October special issue on acceptable noise level (ANL), edited by Anna Nabelek. It is a fascinating test, and I agree that the test may help us identify those at greatest need for noise-reduction technology (Nabelek et al, 2006), and perhaps it will help us in setting hearing aid algorithm levels. Adding to their conjecture, I wonder if those with good (low) ANLs would be intolerant of distortion in speech concomitant with aggressive noise reduction, whereas those with high ANLs may find that trade-off desirable. The Nabelek et al article raises additional questions, and I wonder if the authors could provide insight. The most compelling data are provided by the logistical regression analysis, where ANLs predicted successful/unsuccessful use with 85% accuracy. Although the full-time users had 8 dB poorer pure tone averages, they reported that adding pure tone average to the logistic regression equation did not improve predictive accuracy. That is a fascinating finding, as the greater the loss, the greater the need for amplification, yet loss severity is not related to full-time use. I am wondering if the authors entered other variables into a forward, stepwise regression equation as well, to see if the predictive accuracy could be improved by adding variables of 500 Hz and/or 1000 Hz threshold, MCL, or hearing aid technology. Figure 1 shows about a 10 dB higher average threshold at 500 and 1000 Hz, so I wonder if that might be more sensitive than PTA. Lack of those thresholds improving the prediction of hearing aid " use when needed " would further strengthen the concept that tolerance of noise, rather than need, is the stronger predictor of hearing aid use. The role of MCL in predicting hearing aid acceptance is particularly intriguing, as other cited literature indicates that for normal hearers, the higher the presentation level, the poorer the ANL. The full-time user group had an average MCL that was slightly higher, which is expected from the poorer hearing thresholds for the group. However, higher MCLs being associated with lower (better) ANLs in the full-time user group run counter to the trend seen with normal hearers. Perhaps MCL, or the sensation level of the MCL above the SRT or PTA, might be related to the ANL, or it may be a predictor of hearing aid acceptance used along with the ANL. Again, lack of finding such an association would also be informative. …