Lukas Jürgensen1,2, Hendrik Husstedt2, Florian Denk2
Universität zu Lübeck, Lübeck, Germany
2German Institute of Hearing Aids, Lübeck, Germany

As medical devices, hearing aids compensate for a hearing loss but also include several interacting features such as directional microphones, noise reduction or feedback reduction. Detailed knowledge and access to these features would be beneficial for researchers. However, the amount of insight and control into the signal processing strategies of commercially available hearing aids is often quite limited. One approach that could possibly be used as a research hearing aid, is the open Master Hearing Aid (openMHA), which has recently been made available as an open-source tool. In combination with the Portable Hearing Lab (PHL), a portable miniature computer with the opportunity to connect realistic hearing aid headsets, the openMHA can be seen as a full hearing aid prototype. In this contribution, the frequency dependent gains, latencies, the performance of the feedback reduction and the characteristics of the hearing aid channels of the PHL equipped with BTE-RIC headsets running a standard openMHA configuration, were measured in a test box setup, and partly in a KEMAR setup as well. The results measured in the test box setup were also compared to those achieved with two technology levels of a recent commercial hearing aid series. The results show functional feedback reduction for both the prototype and the commercial hearing aids. The latencies of the prototype were 4 ms longer, and the maximum provided gain was 10 dB higher compared to the commercial devices. The results regarding the hearing aid channels show different strategies used in the tested devices without indicating a better or worse performance in either of them. All in all, the hearing aid prototype performed on a comparable level as the commercial hearing aids for the assessed metrics and thus can be viewed as a fully functional hearing aid for research purposes.