Active Noise Reduction System for Creating a Quiet Zone

摘要

The present invention provides a system to create a quiet zone by suppressing background noise near a user's head. The present invention utilizes two microphones; one microphone receives environmental noise and the other one is located close to a person's head. A parabolic dish loudspeaker creates a uniform sound field near a user's head. A high performance frequency-domain filtered-x least mean square with band selection (FD-FX-LMS-BS) algorithm is utilized to generate the anti-phase noise signals. The algorithm has high noise reduction performance and also allows selection of specific frequency bands for noise reduction. The FD-FX-LMS-BS algorithm is performed by a field programmable gate array (FPGA) chip, which has minimal delay in algorithm processing.

主权项

1. An active noise reduction system for reducing a noise level in a cabin near an occupant's head, comprising:
a first microphone, disposed adjacent to said occupant's head for measuring said noise level in said cabin near said occupant's head; a second microphone, for receiving a background noise; a speaker, configured to generate a noise-reducing field, disposed in said cabin, and directed at said occupant's head; and the active noise reduction system is to reduce said noise level measured by the first microphone; a processor, configured to perform an adaptive filtering algorithm, and electrically coupled to said speaker, said first microphone, and said second microphone, wherein said processor receives said background noise from said second microphone, and generates an anti-phase signal according to said background noise using said adaptive filtering algorithm, and transmits said anti-phase signal to said speaker; wherein, said noise-reducing field is generated according to the anti-phase signal, and said noise-reducing field reduces said noise level in said cabin near said occupant's head.