F.W. Grosveld

Forced response sound radiation experiments were conducted in the NASA Langley Transmission Loss Apparatus equipped with two anechoic rooms. Modal frequencies and mode shapes of a 0.3810 m by 0.3048 m clamped aluminum plate were measured, yielding good agreement with predicted modal frequencies from a finite element analysis and the results from an approximated closed form solution. Sound radiation was memmred in terms of noise reduction of the plate to include the acoustic excitation field. Noise reduction was measured at 15 locations behind the plate and showed good agreement with predictions using the SYSNOISE numerical rumlysis system for acoustic-structure interaction. The modal frequencies and sound radiation of an aluminum plate with free boundary conditions along one or two of its edges was also studied. These plate arrangements were mechanically excited by a piezoelectric actuator. Good agreement was found between the measured and predicted modal frequencies. Measurements showed that the freely vibrating edges radiate less sound than the clrunped edges. The effects of added mass, stiffness, damping and directional material properties on the noise reduction of a clrunped plate were experimentally investigated. The fundmnental resonru1ce frequency, the increased mass and the characteristics of the forcing function need to be considered to obtain the most reduction over the frequency range of interest.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 11 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.106-116; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1992