Visualization of temperature elevation in ultrasonic beam from circular piston

The temperature elevation due to ultrasound was investigated in a dissipative medium using gelatin with the thermochromic particle. As the ultrasonic source, a plane circular piezoelectric transducer was used. A thermochromism layer of 100 μm was inserted between two gelatin layers. The 670 kHz-ultrasound irradiated the medium for less than 1 min. The discolored area due to the ultrasound increased as the exposure time increases. Through the image processing, the temperature increasing tendency along the acoustic axis was confirmed experimentally.