Spatial Acoustic Scenarios in Multichannel Loudspeaker Systems for Hearing Aid Evaluation

Field tests and guided walks in real environments show that the benefit from hearing aid (HA) signal processing in real-life situations is typically lower than the predicted benefit found in laboratory studies. This suggests that laboratory test outcome measures are poor predictors of real-life HA benefits. However, a systematic evaluation of algorithms in the field is difficult due to the lack of reproducibility and control of the test conditions. Virtual acoustic environments that simulate real-life situations may allow for a systematic and reproducible evaluation of HAs under more realistic conditions, thus providing a better estimate of real-life benefit than established laboratory tests.

To quantify the difference in HA performance between a laboratory condition and more realistic conditions based on technical performance measures using virtual acoustic environments, and to identify the factors affecting HA performance across the tested environments.

A set of typical HA beamformer algorithms was evaluated in virtual acoustic environments of different complexity. Performance was assessed based on established technical performance measures, including perceptual model predictions of speech quality and speech intelligibility. Virtual acoustic environments ranged from a simple static reference condition to more realistic complex scenes with dynamically moving sound objects.

HA benefit, as predicted by signal-to-noise ratio (SNR) and speech intelligibility measures, differs between the reference condition and more realistic conditions for the tested beamformer algorithms. Other performance measures, such as speech quality or binaural degree of diffusiveness, do not show pronounced differences. However, a decreased speech quality was found in specific conditions. A correlation analysis showed a significant correlation between room acoustic parameters of the sound field and HA performance. The SNR improvement in the reference condition was found to be a poor predictor of HA performance in terms of speech intelligibility improvement in the more realistic conditions.

Using several virtual acoustic environments of different complexity, a systematic difference in HA performance between a simple reference condition and more realistic environments was found, which may be related to the discrepancy between laboratory and real-life HA performance reported previously.