Directivity Pattern Measurement of Ultrasound Transducers

Both diagnostic and therapeutic ultrasound applications require an understanding of the directivity patterns on the transducers to design ultrasound equipment and faithfully characterize the acoustic output from medical ultrasound devices. Since each ultrasound transducer has its own specific directivity pattern, the measurement of the directivity pattern is necessary. The objectives of this work were to determine directivity patterns analytically and measure directivity patterns experimentally. An experimental method was developed to obtain the directivity patterns for circular ultrasonic transducers. The implementation of the experimental method utilizes a pulse-echo technique using a set of acoustic transducers with three different resonance frequencies, 2.25 MHz, 3.50 MHz, and 5.0 MHz, to measure the beam patterns of the transducers. The results of the measurement are presented in comparison with the theoretical results as a function of spatial angle on both linear and logarithmic scales. Comparison between experimental and theoretical results indicates similar general behavior. However, our comparison also indicates some differences between experimental and theoretical plots, and possible reason for this behavior is due to the reflection of the ultrasound waves within the water tank.