Leping Feng

Constrained polymer layers to reduce noise: reality or fiction? An experimental inquiry into their effectiveness

Abstract The frequency and temperature dependent noise radiation properties of constrained polymer layered oil pans are examined through mobility and intensity measurements. Four metal/polymer/metal sandwich composites of varied thermo-plastic elastomer systems of polystyrene–polybutadiene–polystyrene triblock copolymers are investigated within a wide frequency range covering 1000–5000 Hz, and over a wide temperature range covering 20–100 °C, with results compared to those of an ordinary steel oil pan. The mobility and intensity are found to be strongly frequency and temperature dependent, displaying a substantial mobility reduction as compared to that of the ordinary pan, while using the constrained layer damping configurations at their maximum loss factor temperatures. However, the reduction of noise radiation is smaller than that of the mobility at those temperatures, mainly due to the increased radiation efficiency while adding damping materials.

Experimental study of structure-borne sound transmission loss of mechanical joints.

A mechanical joint is one of the most effective ways to reduce the transmission of structure-borne sound. In order to increase the transmission loss, heavily damped joints are often used, which, in many cases, will reduce the structure integrity and hence can only be used in limited cases. In this study attention is focused on a type of resonant joint, i.e., a joint which will increase the transmission loss but will not reduce the structure integrity. The study is based on experiments in a one-dimensional structure. It is found that by adjusting the overlap of the joint, the transmission loss of 30 dB can be obtained at a certain frequency range without adding any dissipative materials. The mechanism of this high transmission loss is the cantilever-type resonance. The resonant frequency can be predicted precisely. The influence of extra dissipative material is investigated. The performance of the same joint in a finite structure is also examined by using the concept of vibrational insertion loss. When there is a certain damping in a finite system, a rather high insertion loss can still be achieved by using the above-mentioned joint, but the resonant frequency is shifted to higher end. It seems that the effective length of the cantilever is shortened by the finiteness.

Predicting the sound transmission loss of honeycomb panels using the wave propagation approach

The sound transmission properties of sandwich panels can be predicted with sufficient degree of accuracy by calculating the wave propagation properties of the structure. This method works well for ...

Sound Transmission Through Double Leaf Partitions: A Criterion for Quick Convergence Using Space Harmonic Analysis

Space harmonic expansion has been used successfully to model sound transmission through infinite, periodically rib-stiffened double leaf partitions. Since the solution to this method is obtained in ...