Interpreting the efficacy of frequency-lowering algorithms
The Hearing Journal®
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
... ributors 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. WHAT IS AN ADEQUATE EVALUATION? Any evaluation must begin with the assumption that the optimal settings have been verified. That is, the hearing aid settings are indeed providing the potential for the added audibility. Verification does not guarantee that the Audibility Extender (AE) algorithm is helpful and/or produces meaningful changes. It simply verifies that the algorithm results in "optimal" acoustic changes that are needed for improved performance. If the settings are not optimal, one cannot draw any conclusion on the efficacy of the processing algorithm. See Kuk et al. 3 for a brief description on how to verify the AE settings using the SoundTracker. An adequate evaluation informs the clinician (and patient) how changes in the acoustic condition (i.e., from using the AE) affect the patient's performance. However, performance is not an all-or-nothing phenomenon. While one may not notice any substantive changes on one task, changes may occur on other tasks. Indeed, one lesson we have learned is that a battery of tests varying in the cognitive/integrative demand is necessary to evaluate the efficacy of the AE.