Sound transmission loss improvement by a viscoelastic material used in a constrained layer damping system
Keywords:Viscoelasticity, Acoustic power, Constrained layer dampers, Constrained layer damping systems, High frequency, Loss factor, Modal density, Parallel plates, Resonant mode, Sound transmission loss, Total loss, Transmission loss, Vibration energies, Visco-elastic material
AbstractA constrained layer damper is a viscoelastic material that is embedded between two parallel plates. The vibration energy in the first leaf creates shear strain in the viscoelastic material which dissipates kinetic energy into heat. A CLD is an effective way to maximize transmission loss through a partition by increasing its damping. SEA is a method for estimating the acoustic power flow through a system. The method subdivides the system into smaller elements, the so-called subsystems, that support a group of resonant modes and have a sufficient modal density and modal overlap. The measurement of the loss factors on the wall specimens with and without the viscoelastic material was done as part of a parallel paper by J.G. Richter. The reverberation method was used to measure the total loss factors on one side of the installed wall. The addition of a viscoelastic material between the leaves improves the TL significantly by more than 10 dB in the mid- and high frequency range increasing the STC rating by 8 points from 44 to 52.
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