Wind noise in hearing aids: II. Effect of microphone directivity

Objectives: The objectives were: (1) to examine the effects of a directional microphone with different directivity patterns and different microphone combinations on wind noise levels at the hearing aid output; and (2) to derive strategies appropriate for hearing aid selection and future designs. Design: The in-situ frequency responses of a behind-the-ear hearing aid (BTE1) were matched when the hearing aid was programmed to dipole, hypercardioid, cardioids, or adaptive microphone mode. The in-situ frequency responses of another hearing aid (BTE2) were matched among an omnidirectional microphone (OMNI), an adaptive directional microphone (ADM), and a combination of an omnidirectional microphone at low frequencies and an adaptive directional microphone at high frequencies (MIXED). Flow noise was recorded at flow velocities of 0, 4.5, 9.0, and 13.5 m/s. Measurements were repeated for the hypercardioid pattern of BTE1. Study sample: Flow noise recorded using directional microphones with four directivity patterns and using OMNI, ADM, and MIXED. Results: Directional microphones with different directivity patterns generated similar flow noise levels. ADM yielded higher overall levels than OMNI and MIXED, which had similar overall levels. Conclusions: The adaptive directional microphone is the most versatile microphone for use in wind. The mixed microphone mode is a viable wind noise reduction option.