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|Title:||Blast-sound-absorbing surfaces : a joint project of the ERDC and the Netherlands Ministry of Defense|
Dutta, Piyush K.
Van Den Berg, Frank.
Van Der Eerden, Frits.
Van Der Weele, Pieter.
Absorption of sound
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||ERDC/CRREL ; TR-04-17.|
|Abstract:||This research investigated methods of absorbing blast sound, including the development of analytical theories, numerical simulations, laboratory experiments, and a field trial. Prior to this research, no theory existed for the design of sound-absorbing surfaces at low frequencies in a highly non-linear shock environment. The work includes developments of (1) a theory for the non-linear response of rigid-porous materials to high amplitude sound, allowing for a linear variation of flow resistivity with flow velocity (Forchheimer’s non-linearity); (2) a time-domain non-linear theory that assumes low frequencies, semi-infinite media, and weak shocks and gives explicit results for incident triangular shock waveforms; (3) an alternative time-domain formulation that enables predictions for a finite layer but requires numerical integration; and (4) a further non-linear theory that predicts the response of multiple rigid-porous layers to continuous high-intensity sound. Numerical work has been carried out to predict the surface impedance of a porous and elastic layer subject to continuous high-intensity sound and including Forchheimer’s non-linearity. Measurements have been made on the propagation constant, characteristic impedance, and reflection coefficients for finite-amplitude, low-frequency continuous sound waves incident on porous concrete, porous aluminum, sand, gravel stones, perforated panels, and open-cell polymer foams. In addition, shock tube systems based on membrane rupture have been used to look at the acoustic shock response of materials. Finally, the far-field propagation is modeled using parabolic equation method. A full-scale field test using high explosives was conducted at Ft. Drum, NY. The primary purpose was to test predictions of the blast reflection from and attenuation into a porous medium, and a secondary objective was to test the effect of plowing the ground surface over a larger area. Charges of C4 were exploded over two candidate blast sound-absorbing test surface sections filled with gravel stones. The non-linear theory for response of rigid-porous layers to continuous high amplitude sound has been found to give predictions in good agreement with impedance tube data. The most interesting behavior is that the reflection coefficient decreases at first as incident sound pressure increases. The non-linear theory for the impulse response of single rigid-porous layers has been found to give predictions in good agreement with laboratory measurements of shock wave reflection and transmission. The predictions of the plane wave non-linear theories have been found to be in reasonable agreement with reflection and transmission data from Ft. Drum.|
|Appears in Collections:||Technical Report|
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