Our very own Principal Research Physicist, Andrew Hurrell, has recently co-written two papers that have now been published;
S. Rajagopal, S. P. Robinson, J. Ablitt, P. Miloro, L. Wang, B. Zeqiri and A. Hurrell.,
“On the importance of consistent insonation conditions during hydrophone calibration and use,”
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2022
Hydrophones are generally calibrated in acoustic fields with temporally localized (short pulse) or long duration (tone burst) signals. Free-field conditions are achieved by time gating any reflections from the hydrophone body, mounting structures and surrounding water tank boundaries arriving at the active sensing element. Consequently, the sensitivity response of the hydrophone is a result of direct waves incident on its active element, free from any contaminating effects of reflections. However, when using tone bursts below 400 kHz to calibrate hydrophones, it may not be possible to isolate the direct wave from reflection artefacts. This means the sensitivity responses derived at these frequencies using short pulse and tone burst signals might not be comparable as they can be characteristic of the acoustic field interaction with either/both the hydrophone active element alone or the hydrophone active element and body.
G. Harris , S. Howard , A. M Hurrell , P. Lewin , M. Schafer , K. A Wear , V. Wilkens and B. Zeqiri
“Hydrophone Measurements for Biomedical Ultrasound Applications: A Review”
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2022
This article presents basic principles of hydrophone measurements, including mechanisms of action for various hydrophone designs, sensitivity and directivity calibration procedures, practical considerations for performing measurements, signal processing methods to correct for frequency-dependent sensitivity and spatial averaging across the hydrophone sensitive element, uncertainty in hydrophone measurements, special considerations for high-intensity therapeutic ultrasound, and advice for choosing an appropriate hydrophone for a particular measurement task.
