Investigation On Sound Properties Of Warp-Knitted Spacer Fabric

Warp-knitted spacer fabric has many excellent properties due to its unique structure and it also has been widely used in many fields, especially in automobiles. Nowadays people abroad have already been trying to make use of spacer fabric to replace sponge considering environmental protection. The sound absorbency properties and insulation properties of warp-knitted spacer fabric under the frequencies of 100-6300Hz were investigated in this paper. The sound absorption coefficient (SAC) and the sound insulation volume of eight warp-knitted spacer fabrics with different specifications were tested in a impedance tube by transfer function method. The effect of the fabric structural parameters on the sound absorption and insulation properties was analyzed. And also the differences in the acoustic performance between spacer fabrics and the sponge with similar thickness were compared in this paper.Throw discussion and analysis of the test results, we find that the fabric sound absorption and insulation capabilities have obvious frequency selection characteristic. The sound properties of the same fabric are different at different sound frequencies, which, generally speaking, will rise with the increasing of the frequency. And the sound performance of high-frequency is better than medium-low-frequency. We also find that the fabric structure parameters have great impact on the sound absorption and sound insulation. In most cases the sound absorption and insulation of the fabric will become better with the increase of the thickness and density as well as the decrease of the void fraction. The sound absorption and insulation properties of fabrics with dense surface are superior to those with net surface. When these two fabrics are overlapped together, there is little effect on the sound insulation property when reverse the order of superposition. However, the sound absorption of superposition with the dense fabric in front is better than that with the net-surface fabric in front. When different layers of the same fabric were overlaid together, both the sound absorption and sound insulation properties will increase. Meantime, the sound absorption peak value moves to the low-frequency and the absorption bandwidth being increasing. In addition, the fabric has better sound absorption in the low frequency, but the increase of the SAC is not obvious when the layers come to a certain number. The SAC and the sound insulation volume of two different car seat materials with similar thickness were measured. These two car seat materials are made by compounding the flannel with the warp knitted fabric and sponge separately. Then we obtained that the SAC of the spacer fabric before compounding are much higher than that of sponge while it is similar to that of sponge after compounding. But its SAC under low-frequency are much better and the absorption frequency band is much wider. As to the sound insulation, the fabric's sound insulation property is greatly higher than sponge before and after compounding with flannel. And then taking into consideration of other excellent performance of warp-knitted spacer fabric, it is obvious that the warp-knitted spacer fabrics are good alternatives of sponge as cushion materials in the automobile industry.