Acoustic performances of silicone foams for sound absorption

Abstract

The aim of this study is the investigation of the link between the elaboration process, the microstructure and the acoustic behaviour of silicone foams obtained using a two-component silicone. Different parameters are varied such as the ratio of components, the addition of a thinning agent and the curing temperature, with the objective of understanding the influence of each parameter in the foam's acoustic absorption. The microstructure is analysed using SEM and acoustic properties are measured. Two non-acoustical properties of the porous material are also investigated, namely the porosity and the flow resistivity. Pore cell size and interconnected porosity have great impact on acoustical properties. Significant enhancements of the absorption properties could be obtained in the low frequency band by increasing the rate of agent B through an increase in the amount of interconnected porous cells. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. Representative models of the foam for acoustic simulations are obtained allowing estimation of the tortuosity, viscous and thermal characteristic length from acoustic measurements. These models are able to simulate the acoustic behaviour of the silicone foams when embedded in sound packages.

Recent progress in micro‐/nano‐fibrillar reinforced polymeric composite foams

“…First impressions of the foam are usually lightweight, energy‐saving, and low cost. In fact, the capability of foams includes various advantages in terms of thermal insulation, [ 1, 2 ] sound barrier, [ 3 ] energy absorption, [ 4 ] and specific mechanical properties. [ 5 ] Nowadays, polymer foams, as the most commonly used foam products, are widely used as building and construction materials, automotive parts, medical equipment, packaging, and upholstery.…”

Carbon Capture Utilization for Biopolymer Foam Manufacture: Thermal, Mechanical and Acoustic Performance of PCL/PHBV CO2 Foams

“…Similarly, the dip in absorption coefficient recorded between 1000 Hz and 2000 Hz was suspected to be due to an increase in the imaginary part of the impedance. However, at frequencies beyond 3000 Hz, the wavelength became close in magnitude to the foam thickness, leading to higher energy losses and increased absorption as a result of greater interaction between the incident sound waves and the internal structure of the foams [ 76 ]. At about 4000 Hz, it was observed that the sound absorption coefficients recorded for the foams were directly related to their characteristic acoustic impedance ( Figure 7 b).…”

“…Each of the tests was repeated three times to obtain consistent and representative results. Average and standard deviation were then computed from the readings [ 76 ]. While microstructural and non-acoustic properties of polymer composites foams do not depend on the size of the sample, sound absorption coefficient and surface impedance mainly depend on the sample thickness [ 77 ].…”

Progress of low-frequency sound absorption research utilizing intelligent materials and acoustic metamaterials

“…3(a). [56][57][58] Those porous materials usually present excellent sound absorption properties in the middle and high frequencies but inherently show much weaker sound dissipation in the lower-frequency range because the thickness of the absorber is limited by the quarter working wavelength, making it difficult to achieve effective absorption of lowfrequency sound waves in a limited space. 59 In previous works, efforts have been devoted to modulating the pore size and increasing the mesh rate, which ensures the absorption peak shis toward the lower frequency band, [59][60][61] but this achievement was rather limited.…”