去耦覆盖层降噪性能评价指标的理论探讨

去耦覆盖层是降低水下结构声辐射的一个重要措施。为了给工程上去耦覆盖层降噪性能评价指标的选择提供理论参考,建立了点激励力作用下敷设去耦覆盖层的四端简支撑矩形板水下振动和声辐射理论模型,定义了可能表征去耦覆盖层降噪性能的五项评价指标。研究结果表明:只有振动传递损失相对独立于基板的长度、宽度和点激励力位置,而且能较好地描述去耦覆盖层隔离基板振动向水层传递的性能;而湿面均方振速插入损失较振动传递损失则能更好地反映辐射声功率插入损失,尤其在低频。作为评价指标,振动传递损失和湿面均方振速插入损失分别有各自的优点和缺点。 

Theoretical discussion on evaluation indicators of noise reduction performance of flexible coating

Noise reduction by means of applying flexible coating on underwater structures is commonly used in the marine field. In order to provide theoretical references for the selection of evaluation indicators of noise reduction performance of flexible coating, a vibration and acoustics model of a simply supported underwater rectangular plate covered by flexible coating, excited by a point force, is established, and the five potential evaluation indicators are defined. Only one indicator, vibration transmission loss, is independent on the length, width of the plate and the location of point excitation force, and vibration transmission loss can describe well the performance of flexible coating to isolate the fluid from the vibration of the base plate. Another indicator, wet surface quadratic velocity insertion loss, compares better with sound radiation power insertion loss than vibration transmission loss, especially at low frequency. Thus, as evaluation indicators, vibration transmission loss and wet surface quadratic velocity insertion loss have respectively their own advantages and disadvantages.