Noise Reduction Analysis of an Underwater Decoupling Layer

Abstract

Based on the vibro-acoustic coupled model of an infinite bare plate, using the impedance transfer matrix, the analytical model predicting the noise reduction performance of a void decoupling layer covered on an infinite plate under mechanical excitation is presented. The void decoupling layer, especially containing periodically distributed cylindrical or conical holes, can be approximated as a homogenous material described by several parameters, including the effective density, the effective propagation constant, and the effective attenuation. Analysis shows that (1) the primary mechanism of noise reduction is the vibration attenuation of the decoupling layer from the “front” interface between the decoupling layer and the plate to the “back” interface between the decoupling layer and the water, rather than the plate vibration reduction, (2) the plate vibration is increased with the decoupling layer at low frequencies and the increased amount of plate vibration is more than the attenuated amount of the decoupling layer vibration, so the radiated pressure is increased at low frequencies, and (3) at high frequencies, the pressure insertion loss, which quantitatively describes the noise reduction performance of the decoupling layer is estimated by the general sound transmission loss through a simple expression. Finally, good agreement between analytical calculations and experimental results validates that the developed model is useful to predict the noise reduction performance of the void decoupling layer.

An exact elasticity model for rib-stiffened plates covered by decoupling acoustic coating layers

“…Previously published researches have mainly focused on the unreinforced plates coated by decoupling acoustic coating layers [1][2][3][4][5][6][7]. There are also numerous researches regarding with the reinforced structures [12][13][14][15][16][17][18][19][20][21][22], while which are not covered by decoupling acoustic coating layers.…”

“…As an effective passive control approach, the addition of decoupling acoustic coating layers on resonant structures is commonly applied to reduce the vibration and noise radiation by the structures immersed in fluids [1][2][3][4][5][6][7]. The purpose of this treatment is to isolate the vibrating structure from the surrounding fluids.…”

Underwater sound radiation from an elastically coated plate with a discontinuity introduced by a signal conditioning plate

“…The coating investigated by Tao et al 5 contained periodically distributed cylindrical or conical holes. Their goal was to understand the mechanism involved in noise reduction.…”

“…Attaching an elastic coating to the outside surface of an underwater structure has become a common practice for reducing a structure's self-noise [1][2][3][4][5][6] and the reflection of incoming signals from active sonar. 7,8 The coating is usually acoustically soft and decouples the fluid in contact with the coating from motion in the base structure.…”

Experimental and Theoretical Analysis for a Fluid-Loaded, Simply Supported Plate Covered by a Damping and Decoupling Composite Acoustic Coating

“…Three types of dynamic models have been applied to decoupling coatings. The first of model is based on the theory of wave propagation in a layered media [9] and is derived using an impedance transfer matrix [10][11][12], which just regards the tensile stresses and longitudinal waves in the decoupling material. The second type is the locally reacting model [13][14][15][16], which assumes that the decoupling material behaves as a set of evenly distributed massless springs on the plate.…”