Hearing aid with directional properties - relies on combination of electrical filtration and acoustic processing by using directional effect of higher frequencies

摘要

In a conventional hearing aid, the microphone has wide-angle sensitivity, an undesirable feature when attention is to be given to particular speech against conversation noise coming from many directions. Frequencies below 1500 Hz are dispensible for speech intelligibility and accordingly the aid eliminates frequencies between 30 to 1500 Hz which have poor directionality by electrical filters in the amplifier system; on the other hand, acoustic impedances and delay lines passing frequencies between 1800 Hz and 5000 Hz to the microphone are provided. These have directional characteristics. In one embodiment the device is integrated with a spectacle frame (B) having lenses (G) and mounted on it a microphone (M) exposed to sound waves coming in front at (OV) and from the back through ducts (L) and orifices (OR) turned towards a source. The annex duct (marked D), serves to increase the effective propagation delay in the ducts (L). The arrangement can be chosen to provide for the frequency range contributing most to intelligibility a phase shift of 180 deg. thus reinforcing microphone action by 6 decibels directionally.