The Robustness of Hearing Aid Microphone Preferences in Everyday Listening Environments

Abstract

Automatic directionality algorithms currently implemented in hearing aids assume that hearing-impaired persons with similar hearing losses will prefer the same microphone processing mode in a specific everyday listening environment. The purpose of this study was to evaluate the robustness of microphone preferences in everyday listening. Two hearing-impaired persons made microphone preference judgments (omnidirectional preferred, directional preferred, no preference) in a variety of everyday listening situations. Simultaneously, these acoustic environments were recorded through the omnidirectional and directional microphone processing modes. The acoustic recordings were later presented in a laboratory setting for microphone preferences to the original two listeners and other listeners who differed in hearing ability and experience with directional microphone processing. The original two listeners were able to replicate their live microphone preferences in the laboratory with a high degree of accuracy. This suggests that the basis of the original live microphone preferences were largely represented in the acoustic recordings. Other hearing-impaired and normal-hearing participants who listened to the environmental recordings also accurately replicated the original live omnidirectional preferences; however, directional preferences were not as robust across the listeners. When the laboratory rating did not replicate the live directional microphone preference, listeners almost always expressed no preference for either microphone mode. Hence, a preference for omnidirectional processing was rarely expressed by any of the participants to recorded sites where directional processing had been preferred as a live judgment and vice versa. These results are interpreted to provide little basis for customizing automatic directionality algorithms for individual patients. The implications of these findings for hearing aid design are discussed.

Evaluation of A “Direct-Comparison” Approach to Automatic Switching In Omnidirectional/Directional Hearing Aids

“…To be included in the study, HI listeners had to demonstrate a directional advantage of at least 15% (i.e., a 15% improvement in speech recognition performance for DIR processing re OMNI processing) under laboratory testing where speech was presented from the front and competing noise originated from 90u, 180u, and 270u azimuths (see Walden et al, 2007). The 30 HI listeners formed three groups of ten listeners.…”

“…The methods used in making the recordings of realworld listening situations are described in detail in Walden et al (2007). In brief, each field rater was fit with a modified version of the manually switchable Canta 770D hearing aid (GN Resound Corporation).…”

“…Since, for most HI listeners, directional processing is beneficial in some listening situations and omnidirectional processing is preferable in others (Walden et al, 2004;Walden et al, 2007), current directional hearing aids generally provide both processing modes, and switching between microphone modes is either done manually by the user or automatically by the device based on an analysis of the incoming sound. Under manual switching, the user selects the currently preferred mode by flipping a toggle on the hearing aid or a remote control.…”

“…In a recent report, Walden et al (2007) made recordings of OMNI-and DIR-processed speech produced in a range of everyday listening environments. Walden et al reported preference judgments (OMNI, DIR, or No Preference [NoPref]) made ''in the field'' at the time the recordings were made and laboratory judgments based on comparisons of the recorded, OMNI-and DIR-processed signals.…”

“…Walden et al reported preference judgments (OMNI, DIR, or No Preference [NoPref]) made ''in the field'' at the time the recordings were made and laboratory judgments based on comparisons of the recorded, OMNI-and DIR-processed signals. The laboratory stimuli from Walden et al (2007) were based on monaural field recordings and were presented monaurally in the laboratory. The authors reported close agreement between original field preferences and laboratory preferences based on these recordings.…”