Practical considerations in evaluating directional hearing devices

Abstract

In theory, a directional hearing device could apply large attenuation to a single noise source and achieve great enhancement of signal-to-noise ratio relative to an omni-directional device. However, as observed in many clinic studies, the actual benefit of a directional device measured in typical rooms rarely exceeds 6 dB, even in conditions with a single noise source located in the direction of maximum attenuation of the device. This dramatic reduction from the theoretical benefit is a manifestation of many factors, including mismatch in the microphone responses, misalignment of the device relative to the target source, head movement, head shadow, room reverberation, and so on. In the present study, we examine the relative contributions of these factors using computer simulations and electroacoustical measurements. The results provide a basis for setting realistic expectations of the benefit of directional devices for specific listening environments.