The use of thermistor probes to measure energy distribution in ultrasound fields

The use of small thermistors coated with absorbing material for the measurement of ultrasound fields is discussed. Equilibrium temperature rise gives a rough measure of intensity, but is affected by convective cooling due to streaming. The initial rate of temperature rise provides an accurate parameter for use in assessing energy density in all types of ultrasound field. Measurements made in standing wave fields show that the thermistor response is related to the pressure component of the sound wave, and is determined by absorption throughout the coating material.