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14 June 2001 Lightweight low-frequency woofer for active sound control in payload fairings
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A low-mass sound generator with particularly good performance at low audio frequencies (i.e. 30 to 300 Hz) has been developed. The actuation component is a Thunder actuator (Face Int. Corp.). This actuator is coupled to a resonant compliant diaphragm to increase output in the low frequency band. The modal response of various 28 cm diameter prototypes was monitored using laser Doppler vibrometry and nearfield acoustic holography. The first mode appears near 40 Hz, with a maximum displacement of 3.4 microns per volt. Sound pressure levels measured in the farfield using 200 volts peak drive found nominal levels of 74+/- 6 dB(at 25 cm) over the band from 38 to 330 Hz. Near 45 and 100 Hz the SPL reaches 80 dB. (Above 330 Hz the output is higher, but remains well behaved to at least 2 kHz.) Higher outputs can be obtained by using a higher drive voltage and multiple devices. Because of its low mass, this device is particularly interesting for aerospace applications. This work was developed in the NRL/ONR Smart Blanket program, which is exploring the use of active controlled surface covers for reducing sound levels in payload fairing regions.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robert D. Corsaro "Lightweight low-frequency woofer for active sound control in payload fairings", Proc. SPIE 4332, Smart Structures and Materials 2001: Industrial and Commercial Applications of Smart Structures Technologies, (14 June 2001);

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