Experiments with coated surfaces to generate sound waves in water

Abstract

Sources for underwater sound have a wide range of applications, such as active sonar, navigation, and underwater communication. Particularly, sources with large dimensions l, such as a coating on a boat structure, can be suitable for generating low-frequency underwater sound. In this context, low-frequency refers to wavelength λ in water that fall within the range of 40 l > λ > 1,5 l. In this study, a sample of an active surface for generating underwater sound is created by attaching an array of 18 circular piezoelectric actuators to a glass-fiber reinforced plastic (GRP) plate. The array and the plate are coated with a potting compound that possesses the same acoustic properties as water. This coating physically separates the actuators from the water. The actuators can be individually controlled to analyze different configurations. The radiation characteristics of the active surface are investigated in an underwater test range with free field conditions, specifically for low-frequencies. Additionally, the interaction among the actuators and between the actuators and the GRP-plate are analyzed.