A standing wave tube method for measuring acoustic and vibration characteristics of underwater acoustic materials

A measurement method based on standing wave tube is proposed to get the acoustic and vibration characteristic parameters of underwater acoustic materials under hydrostatic pressure. A low-frequency emission transducer with pneumatic compensation is designed as the sound source for standing wave tube. Through a water column, the planar piston vibration of the transducer is coupled to the sample under the water surface. An accelerometer is installed on the backing of the tested sample to measure the vibration velocity of the sample backside. Meanwhile, a pair of hydrophones embedded in the tube wall is used to measure the sound pressure of the water column. Based on the measured data, the vibration velocity and sound pressure of the sample surface of incidence are derived. The vibration velocity transfer coefficient (decoupling coefficient) between the front and back surfaces of the sample, the input impedance, and the sound pressure reflection coefficient of the sample are then calculated. A low-frequency standing wave tube test system is constructed with a tube size of 300 mm inner diameter, 600 mm outer diameter, and 3 m in height, with a frequency range of 100 Hz to 1000 Hz. The experimental studies are conducted using water layer samples and multi-layer perforated rubber samples. The results show good agreement with the simulation data, thus validating the effectiveness of the measurement method.