Multiple reference subband adaptive noise canceler for hands-free cellular phone applications

This paper presents the development of adaptive noise cancelation systems for improving the intelligibility of speech transmitted in hands-free cellular phones. Both periodic and random noise cancelation techniques are developed. A narrow band noise cancelation technique, which generates the reference signal internally, thereby achieving selective cancelation of harmonics for reducing the speech distortion is proposed. The theory and design issues of subbands are explored and their application to noise cancelation is verified. A multiple channel subband adaptive noise canceler is developed to deal with the multipath, multisource nature of the noise present in the car and its effectiveness was verified through computer simulations, which were carried out using real transfer functions estimated by an HP3563A Control Systems Analyzer.