Abstract
OBJECTIVES: When using ecological momentary assessment (EMA) to compare different hearing aid programs, it is usually assumed that for sufficiently long study durations similar situations will be experienced in both programs. However, conscious or subconscious adaptation of situations to one's hearing ability (e.g., asking a conversation partner to speak up, increasing TV volume)-which might be different across the time spent in different hearing aid programs-may challenge this assumption. In the present study, we investigated how test participants modify their acoustic environment and if these modifications depend on the hearing program. DESIGN: Twenty-nine experienced hearing aid users were provided with hearing aids containing two hearing programs differing in directionality and noise reduction (NR). The hearing programs called NR-on and NR-off changed each day automatically. Over the course of 3 weeks, participants were asked to answer a questionnaire every time they encountered an acoustic situation they modified or would have liked to modify to improve the listening situation. Objective data on sound pressure level and classification of the acoustic situation were collected from the hearing aids. At the beginning of the study participants recollected modifications of the acoustic environments they typically do when using their own hearing aids and reported on the frequency of this behavior. RESULTS: During the field trial, participants reported on average 2.3 situations per day that they modified or would have liked to modify. Modifications were usually performed quickly after the onset of the situation and significantly improved the pleasantness of the listening situation. While the number of the reported situations did not differ between the programs, modifications increasing the volume of the target signal and increasing the hearing aid volume were more frequent for the NR-on hearing program. Changes in the objective data at the time of the modification were consistent with the reported modifications. Further, the usage time as well as the distribution of the acoustic situations over the entire study period differed between the two hearing programs. CONCLUSIONS: The large improvement in pleasantness due to the modification might explain the generally positive ratings observed in EMA studies. Furthermore, the results found here suggest that caution is needed when comparing ratings of audiological attributes in EMA, because the different modification behavior across hearing programs may lead to an underestimation of hearing problems and reduced sensitivity when comparing two technologies.