Single burst acoustic streaming

A new type of acoustic streaming is reported. It was first observed near a needle hydrophone while mapping the sound field of a focusing ultrasound transducer, when it resulted in unstable amplitude measurements of the field. The streaming was subsequently detected with tracer dye injected in the water near the needle probe. When the hydrophone probe is removed from the sound field, the streaming can no longer be detected. If the repetition frequency of the bursts—about 80 cycles at 1 MHz—is reduced to 1.1 Hz, the streaming can still be detected. This implies that even a single burst can cause observable streaming.