Objectives: Facilitating the fine-tuning of advanced hearing aids requires information about the acoustic environment. The concept of a "trainable" hearing aid may provide a more direct approach to hearing aid fine-tuning if the aid user is allowed to control the most important fitting parameters in his/her own acoustic environments. Design: In a laboratory study, the concept of selfadjustment of the gain-frequency response was tested by 24 hearing aid users using four different controllers

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... a limited number of control functions. Research questions focused on the reproducibility of the fine-tuned responses, the efficiency of the control configurations, and the effects of the control configuration on the end results of the finetuning process. Results: The subjects were able to provide systematic and reproducible feedback with respect to their preferences in different acoustic conditions presented audiovisually, achieving an average shortterm test/retest standard deviation value of 2.8 dB. Two of the control configurations, featuring volume/slope and volume/bass/treble keys, were found to be more time-efficient and reliable, and were also preferred by 86% of the subjects. Although the control configuration did not have a strong influence on the end result, the gain-frequency response from which the subjects started their adjustments was found to have a significant effect on their preferred settings. Conclusions: Client-based adjustments of hearing aid gain provide a reliable method of individual fine-tuning. The results also showed that a biased correction of amplification is reached via self-adjustment within one session, which reduces the effectiveness of fine-tuning in a traditional clinical setting.