水声材料横波声速和衰减系数参量源法测量系统

提出了测量10-100 kHz频段水声材料平均横波声速和衰减系数的测量系统,系统具有低频、小尺寸、窄波束的特点。测量装置应用截断参量源作为声源,结合了精密的坐标系统。在对平板声压透射系数的平面波模型进行理论修正和实验研究的基础上,测量平板样品的透射系数(插入损失)的频谱和角谱,并采用曲线拟合方法来估计样品在测量频段的平均横波声速和衰减系数。在2 m×1 m×1.5 m消声水槽中,对一些典型样品(尺寸500 mm×600 mm)进行了测量实验,结果表明,水声材料样品在声波不同入射角时的声学性能有较大差异,不能用声波垂直入射时的声学性能数据代替;横波声速和衰减系数是评定水声材料声学性能的重要参数,尤其在声波斜入射情况下;在研究材料构件或复杂器件的声学性能时它们也是必不可少和不能不考虑的。实验还验证了测量方法和系统的可行性,也表明仅在这一频段的测量还远不能满足水声工程的实际需求,有必要将测量方法应用扩展到更低或更高的频段。

A system for measuring the transverse wave velocity and attenuation coefficients of underwater acoustic materials in parametric source method

A measurement system was provided for measuring an average transverse wave velocity and attenuation coefficients of underwater acoustic materials in the frequency range 10-100 kHz, with the characteristics of small size and narrow wave beam in the low frequency range. In the facility, a truncated parametric source was used as a testing sound source, together with a precision coordinate system. Based on theoretical modification and experiments for the plane wave model of sound pressure transmission coefficients of panels, the frequency and angle spectra of transmission coefficients (insertion loss) of panels were measured at first, then the average transverse wave velocity and attenuation coefficients were estimated using a curve-fitting means, an anechoic water tank, with a size 2 m×1 m×1.5 m, was used to measure some typed samples (500 mm×600 mm in size). The results showed that sound properties of underwater acoustic material samples were quite different at different incident angles of sound wave, and couldn't be replaced by the properties at an angle of vertical incidence. The transverse wave velocity and attenuation coefficients were important parameters for assessing sound properties of underwater materials, especially at an angle of oblique incidence. For investigations of material structures or complex parts, they were necessary and must be considered. The experiments had verified the measurement method and feasibility of the system. And it also showed that measurements in wider frequency band should be carried out to satisfy the actual need for the underwater acoustic engineering, so the measurement method should explored so that the facility can be used in the lower or higher frequency range.