Development of a voice shutter (Phase 1: A closed type with feed forward control)

摘要

Telephone voice is annoying in public spaces like trains and cafes. The speaking voice was tried to be attenuated by using an active noise control technique. It is called 'Voice Shutter'. Two types of voice shutter, which are open type and closed type, were supposed to be possible. In this paper, a closed type voice shutter with a small vent hole controlled by a feed forward active noise control method was manufactured and tested. In order to develop a small handy type of voice shutter, the distance between the reference microphone and the control speaker should be as short as about 20 mm. The causality law was satisfied by using very high sampling frequency (100kHz) and a high speed signal processor with FPGA. In order to follow the rapid change of voice, partitions with a hole was successfully installed in the voice shutter for the primary path and the secondary path not to be affected by the configuration of a mouth. As the results, the handy scale voice shutter was proved to be feasible.