MM310 - The Implementation of Bilateral Beamforming in Current Hearing Aid Technology

Array microphones, including bilateral beamforming, have been available for several years. Although their effectiveness compared to unilateral beamforming is somewhat mixed, a recent evidence-based review suggests that bilateral beamformers offer some degree of signal to noise ratio improvement for many wearers relative to other commercially available directional microphone systems.

This mini-module examines some of the more recent updates to bilateral beamforming technology, describes how it works and how when it is paired with noise reduction (process-based) algorithms, wearer performance in noise significantly improves.

Summary: A key challenge for hearing aids to provide appropriate support when the wearer wants to actively participate in a conversation. Increased social interaction has a positive effect on neurological function and mental wellbeing. The hearing aid processing approaches traditionally applied to improve speech-in-noise performance often fall short in group conversations. Even though use of directional microphones can be applied to capture all talkers in the group conversation, this will typically require the use of more aggressive noise reduction algorithms to remove disturbing surrounding noise. This is not always effective in improving speech perception, and such algorithms may add a considerable amount of distortion to the sound and create an overall poor listening experience when speech and noise is processed together. Even though use of a directional microphone with a narrow beam may provide a benefit when the wearer listens to a person just in front of them, it will cut out simultaneous talkers from other directions, and it will typically not allow the wearer to turn their head to look in other directions (away from the active talker). 

Considerable progress has been made through the release of new technologies that highlight speech and suppress noise via the use of advanced signal processing schemes, such as binaural processing, directionality, and noise reduction. One unique characteristic of these advances is using advanced directional technology to split incoming sounds into two streams, which are processed separately. This approach has been shown to offer significant benefits in a wide range of situations. In more advanced sound analysis, separate focus streams are added to split-processing within the front hemisphere resulting in improvements in situations where the wearer engages in conversations with one or multiple talkers in background noise. By applying this advanced sound analysis, new bilateral directional beamforming technology can detect the locations of relevant conversation partners. The multi-stream architecture creates an auditory space where the conversation partners are enhanced, making it easier for the wearer to participate in and contribute to the conversation. 

Analysis of the sound sources constantly scouts the acoustic environment to identify number of talkers and their location. In order to sketch a virtual conversation layout, it is essential to also know the dynamic behavior over time during the conversation. Sometimes people are just listening for a while in between speaking – it is important that the hearing instruments know that there is still a conversation partner in order to keep the virtual layout stable. Thus, dynamics of the conversation including turn-taking and timing, plus the level of diffuse noise, any transient noise sources, and the locations of pure noise without speech are constantly calculated and monitored. Furthermore, separate analyses of the front hemisphere focus and back hemispheres as well as surrounding sound streams are enabled by the split processing of the auditory space.
Speed and processing power of this new technology adapts to any changes in the conversation layout, e.g., when talkers move or when the wearer turns their head.