Directional microphone system for hearing aids - has at least two spaced microphones on spectacles frame with opposite output voltages

摘要

The two microphones are mounted on one arm of a spectacles frame and their output voltages are connected in opposition, and with the negative feedback between them of 50 to 90% of the sound received from the forward direction. A propagation time delay of approximately half the wavelength of the mean speech frequency within the system range affects the rear microphone, but this delay for sounds coming from the side is less than half of this wavelength. The rear microphone is connected to its entry hole by a tube at the most 4 cm long, pref. 3.5 cm. The rear microphone may be in front of its entry hole at the end of the spectacles arm horizontal part.