Objective and subjective validation of an active control approach to reduce the occlusion effect in hearing aids
The occlusion effect refers to the altered perception of one's own voice when the ear canal is fully or partially obstructed. Conventional countermeasures include the use of large vent bores or open fittings on the one hand and fittings reaching as deep as the bony part of the ear canal on the other hand. A more recent approach is the use of active control where the disturbing own-voice sounds originating from bone conduction are sensed with a microphone in the ear canal and then attenuated by means of destructive interference. This paper describes a prototype implementation of this approach along with an objective and subjective validation of the occlusion effect reduction in N = 10 normal-hearing subjects. As regards the objective evaluation, the average active occlusion reduction achieved within the two octaves from 125 Hz to 500 Hz over all subjects was Sm = -8.2 dB (+- \sigma = 2.2 dB). As regards the subjective evaluation, all subjects reported satisfaction with the naturalness of their own voice when a combination of aided sound and active control was presented. The subjective rating of this combined effect was significantly larger than the sum of the individual effects when only aided sound or only active control was presented (p<0.004). These findings indicate that active control has the potential to substantially improve the acceptance of the perception of a hearing aid user's own voice, especially when only minimal venting is applied.