TS-96
Structure-Borne Noise Reduction Measures in Cabins
Katsuhiro HARANO*, Motonobu IMASATO** and Osamu MIYATA**
ABSTRACT
Recently noise levels in cabins have been reduced remarkably owing to inventions of low vibration propellers such as high-skewed ones and the development of high damping panels for walls. Few papers concerning the resilient lining system of a cabin have been published recently. However all technical problems concerning how to design a low noise cabin have not been settled yet. For example the ceiling of a cabin is hard to isolate well from ship structure. In this study, experiments were carried out to obtain the vibration features of a ceiling structure by using a cabin model, which was made to improve resilient lining system. The reducible vibration level of a ceiling by a well designed isolation hanger is at most 12dB in all frequency ranges.
Key Words: Floating Lining System, Vibration Isolation Hanger, Vibration Reduction Effect.
1. INTRODUCTION
Floating lining system of a cabin is adopted to reduce noise level in the room by isolating all lining surfaces from the vibrating ship structures. The ceiling is the most difficult surface to isolate well because it is composed of the lightest and the most flexible panels of the lining materials. A full floating lining system of a cabin was conducted in a training ship, the vibration isolation effect of the ceiling hangers was found only in the frequencies above 800Hz1). The effect was not enough. This paper describes experimental results to investigate the vibration features of a ceiling structure by using a cabin model, which was made to improve resilient mount lining system of a cabin.
2. EXPERIMENTAL METHOD
The experimental apparatus is shown in Fig. 1. A floating floored cabin is set on a steel deck, which is fixed to a steel bed and steel frames are bolted to the bed to attach ceiling hangers. The steel bed is excited by an electric shaker. As illustrated in Fig. 2, the ceiling of the cabin model is composed of five cassette panels; type SR-C2 of 2.4m × 0.3m; manufactured by ASK Ltd.Co., Japan. The panel has lapels on both side with which they are connected each other.
Fig. 1 Experimental Apparatus of a Vibration Isolation Hanger.
