Experimental Evaluation of High Intensity Ultrasound Source System using Acoustic Waveguide and Concave Transducer with 100 mm Diameter for Calibration of Hydrophone

Recently, equipments using high intensity ultrasound have been increasing in medical and industrial fields. A high intensity ultrasound source for calibrating a hydrophone to evaluate a high intensity ultrasound field is required. Especially, to calibrate the receiving sensitivity of the membrane type hydrophone as the primary standard, it is necessary to vibrate the required area of acoustic receiving surface on the primary standard hydrophone uniformly. We proposed and developed a high intensity ultrasound source system using a cylindrical acoustic waveguide and a concave transducer. In this system, the output ultrasound wave forms main beam similar to that formed by a flat type transducer and is expected to increase the ultrasound power acoustically by using of the concave transducer with larger diameter. We constructed an experimental system using an 1 MHz concave transducer with an effective diameter of 40 mm, and confirmed the peak acoustic pressure of 670 kPa at the position of 10 mm from the transmitting aperture. Furthermore, we constructed an experimental system using a concave transducer with an effective diameter of 100 mm, and measured the acoustic pressure distribution on the lateral axis at distances of 10, 20, and 30 mm from the transmitting aperture. As the result, it was confirmed that the -6 dB beam width become almost equal to the conventional source system with the effective diameter of 40 mm and the transmitting sensitivity increased about 2-fold with that.