Recently, an increased interest has been demonstrated in evaluating hearing aids (HAs) inside controlled, but at the same time, realistic sound environments. A promising candidate that employs loudspeakers for realizing such sound environments is the listener-centered method of higher-order ambisonics (HOA). Although the accuracy of HOA has been widely studied, it remains unclear to what extent the results can be generalized when (1) a listener wearing HAs that may feature multi-microphone directional algorithms is considered inside the reconstructed sound field and (2) reverberant scenes are recorded and reconstructed. For the purpose of objectively validating HOA for listening tests involving HAs, a framework was developed to simulate the entire path of sounds presented in a modeled room, recorded by a HOA microphone array, decoded to a loudspeaker array, and finally received at the ears and HA microphones of a dummy listener fitted with HAs. Reproduction errors at the ear signals and at the output of a cardioid HA microphone were analyzed for different anechoic and reverberant scenes. It was found that the diffuse reverberation reduces the considered time-averaged HOA reconstruction errors which, depending on the considered application, suggests that reverberation can increase the usable frequency range of a HOA system.

It can be concluded that the considered VSEs can be used for testing directional HAs, but the provided sensitivity is reduced when compared to a real environment. This can result in an underestimation of the provided directional benefit. However, this minor limitation may be easily outweighed by the high realism of the acoustic scenes that these VSEs can generate, which may result in HA outcome measures with a significantly higher ecological relevance than provided by measures commonly performed in the laboratory or clinic.

The accurate reproduction of acoustic real-world environments is becoming of increasing importance in hearing device research and development. It is thereby often required to accurately predict the sound pressure at the microphones of ahearing device in asimulated or recorded acoustic environment. Forthat reason, an extensive set of head-related transfer functions (HRTFs)w as measured in free-field with ap air of behind-the-ear (BTE) hearing aids placed on aHead and Torso Simulator (HAT S).Transfer functions to the in-ear HATS microphones were also measured. As pherical head model wasa pplied to extend the useable frequencyr ange towards low frequencies. Special care wasgiven to preservethe phase properties of the measurements so that the HRTFs could be widely used in phase-sensitive technical applications, including the evaluation of spatial signal processing algorithms (i.e. directional microphones, beamformers)i nh earing devices and the evaluation of sound field resynthesis methods. The extended HRTF set can also be used for research in psychoacoustics. It is available for download at: http://www.nal.gov.au/download/HATS_BTE_hrirDatabase.zip.

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