Reduction of Structure-Borne Sound by Damping Treatment

—2nd Report, Prediction of Dynamic Characteristics of Damping Materials—

Abstract

To attain the quietness of vehicles such as automobiles, ships and airplanes, which are mostly composed of plate elements, the reduction of structure-borne noise is important, and for which the damping treatment by using viscoelastic materials is effective.
In adoption of this treatment, difficult problems are the systematic design of damped structures and the prediction of damping effects, taking the damping material properties into acount.
To develop a systematic design tool for damping treatment, 1st report has already revealed the prediction procedure of the damping effects of structures attached viscoelastic materials of which dynamic properties are known, and this paper presents a estimation method of damping properties of viscoelastic materials from vibratory characteristics of a sandwiched beam.
The discussions of this paper are as follows.
1) To obtain the dynamic properties of viscoelastic materials as shea modulus and loss factor, the symmetric sandwiched beam method is applied, and their properties are estimated from measured data of modal frequency and loss factor of sandwiched beam.
2) To ensure the estimated result by this method, the effective range of the modal loss factor and the natural frequency ratio of the sandwiched beam in reference to the undamped beam is shown.
Dynamic properties of a damping material estimated by using this technique shows a good result.