Sound shielding by a piezoelectric membrane and a negative capacitor with feedback control

Sound shielding by a piezoelectric membrane and a negative capacitor with feedback control

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Unformatted text preview: IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, VOL. 55, NO. 8 AUGUST 2008 1859 Sound shielding by a piezoelectric membrane and a negative capacitor with feedback control Tom´aˇs Sluka * , Hidekazu Kodama † , Eiichi Fukada † and Pavel Mokr´y * * Institute of Mechatronics and Computer Engineering, Technical University of Liberec, CZ-46117 Liberec, Czech Republic † Kobayasi Institute of Physical Research, Kokubunji, Tokyo 185-0022 Japan Abstract —The design and realization of an adaptive sound- shielding system based on a method to control the effective elastic stiffness of piezoelectric materials are presented in this paper. In this system, the sound-shielding effect is achieved by a sound reflection from the piezoelectric curved membrane fixed in rigid frame and connected to an active analog circuit that behaves as a negative capacitor. The acoustic transmission loss through the curved membrane was measured for the incident sound of frequency 1.6 kHz and of acoustic pressure level 80 dB. When the negative capacitor in the system was properly adjusted, the acoustic pressure level of the transmitted sound was reduced from the initial 60 dB to 15 dB by the action of the negative capacitor. Then the system was exposed to naturally changing operational conditions and their effect on sound-shielding efficiency was studied. It is shown that the acoustic transmission loss of the system dropped by 35 dB within 30 min from the moment of negative capacitor adjustment. Therefore, a self-adjustment of the system has been implemented by appending an additional digital control circuit to the negative capacitor. It is shown that the aforementioned deteriorating effect has been eliminated by the adjusting action of the control circuit. The long-time sustainable value of 60 dB in the acoustic transmission loss of the adaptive sound-shielding system has been achieved. Index Terms —Piezoelectric membrane, PVDF, Noise control, Negative capacitor, Elastic stiffness control, Computer controlled circuit I. INTRODUCTION I N recent years, researchers in the field of acoustics have paid much attention to piezoelectric materials. The reason for a gradual increase in the interest in piezoelectric ceramics and polymers is a unique possibility to construct simple and low-cost electroacoustic transducers with superb functional properties, including high sensitivity, high precision, and fast response [ 1 ], [ 2 ], [ 3 ], [ 4 ]. These are the features that can be profitably used in noise- and vibration-suppression devices. Although the piezoelectric elements within active noise and vibration control (ANVC) systems require additional complex control and sensing electronics, Forward and Swigert [ 5 ], [ 6 ] and Edwards and Miyakawa [ 7 ] presented, for the first time, the possibility of damping vibrations of resonant structures using piezoelectric elements connected to passive electrical circuits....
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This note was uploaded on 07/10/2011 for the course MECHANICAL 24175 taught by Professor Hosseini during the Spring '11 term at University of Toronto- Toronto.

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Sound shielding by a piezoelectric membrane and a negative capacitor with feedback control

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