Report on the Acoustic Transmission and Vibration Damping Characteristics of Materials for Use on Sonar Domes.

摘要

Although instrumentation for sonar detection has progressed to a fairly advanced stage, the presence of interference noise still remains the fundamental controlling factor in establishing sonar range and accuracy. Some of the interference noise is transmitted to the sonar transducers as a result of vibrations due to hydrodynamic or structure-borne excitations in the hull-mounted sonar dome itself. One of the methods currently used to reduce the the vibrations in the AN/SQS-23 sonar dome is to fill its lower section, below the acoustic 'window', with approximately 5-6 inches of Ottawa sand and to blanket this sand with foamed-in-place, high density polyurethane foam. However, field reports have indicated that the foam blanket loosened and permitted water to penetrate the sand. This water penetration, coupled with movement of the sand, resulted in both corrosion and erosion degradation of the dome and decreased damping efficiency. In order to overcome this difficulty, and in view of the successful development of the ML-D2 viscoelastic vibration damping tiles at the NAVAPLSCIENLAB as described in reference (j), the Laboratory was authorized to develop a sprayable viscoelaastic vibration damping material for use in sonar domes. Such a sprayable material, designated as ML-SD15 and which is described in reference (d), was developed.