Head-Baffle Effect for Different Hearing-Aid Microphone Locations

Abstract

Using a small magnetic microphone, the response at four selected microphone sound‐entrance locations in the vicinity of the ear was compared with the freefield response at the center head position. The four positions of the microphone sound entrance were immediately behind the ear, at the top of the ear, immediately in front of the ear, and at a point some 2 1 2 in. forward of the last‐mentioned position. Response curves were made for sound‐incidence angles of 0°, 90°, 180°, and 270° over the frequency range 200–7000 cps. While baffle effects are materially different for different angles of incidence, results indicate only minor differences due to microphone location, except for sound approaching the head from the opposite side. For this situation, the top and forward locations appear to reduce the head‐shadow effect some 6 or 8 dB compared to the behind‐ear location. Direction of the microphone opening, checked at the top‐of‐ear position, had no significant effect on response, as would be expected.