Low frequency acoustic test cell for the evaluation of circumaural headsets and hearing protection

David A. Cartes, Laura R. Ray, Robert D. Collier

Abstract


Active noise reduction (ANR) technology, based on feedback signal processing, is being applied in commercial communication headsets and provides noise reductions up to 10-20 dB between 50 Hz and 400 Hz. There are, however, many acoustical designs and computational difficulties associated with feedback designs which limit their performance. Current research in feedforward design offers the opportunity for significant improvement in ANR performance. To support this current research in ANR feedforward algorithm development and evaluation, a low frequency acoustic test cell (LFATC) has been designed to provide a uniform and precisely controlled low frequency acoustic measurement environment. The LFATC design is based on the original work of E.A.G. Shaw and G.J. Theisson at the National Research Council of Canada and a prototype LFATC developed by J.G. Ryan, E.A.G. Shaw, A. J. Brammer, and T.G. Zang. The design analysis of the LFATC is based both on a lumped parameter model and a one-dimensional standing wave model. The acoustic performance of this test cell, including a simple floor vibration isolation system, is evaluated experimentally over a wide range of sound pressure levels. A representative set of measurements with a prototype ANR headset illustrates the application of the LFATC.

Keywords


Acoustic noise; Acoustic signal processing; Algorithms; Attenuation; Bandwidth; Mathematical models; Signal to noise ratio; Active noise reduction (ANR); Low frequency acoustic test cells (LFATC)

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