Interpreting the efficacy of frequency-lowering algorithms

Despite a long history of research and commercial efforts, 1 hearing aids with frequency-lowering algorithms have become popular only recently. Their lack of commercial success may be attributed in part to the immaturity of analog technology when these devices were introduced such that artifacts were plentiful. But insufficient training provided to the wearers of such devices, unrealistic expectations, and inadequate means to evaluate their efficacy are equally important contributors to the limited acceptance for this technology. Widex re-introduced the concept of linear frequency transposition in its Inteo hearing aid in 2006 under the name Audibility Extender. 2 Since then, we have explored various avenues to better understand how such a feature can be fitted 3,4 and its use facilitated. 5 Just as important, we also studied (and developed) research tools that may be optimal for evaluating such an algorithm. Our effort led us to report on the efficacy of such an algorithm in a simulated hearing loss, 6 in an open-tube fitting, 7 in children, 8 and in adults in quiet and in noise. 9 We have learned that demonstrating the efficacy of a frequency-lowering algorithm is not a straightforward matter. We would like to share our experience in this paper.