Time delay spectrometry for hydrophone calibrations below 1 MHz

Area of Science:

• Acoustics
• Medical Ultrasound
• Transducer Technology

Background:

• Accurate acoustic pressure pulse measurements are crucial for medical ultrasound.
• Miniature ultrasonic hydrophones require precise characterization below 1 MHz.
• Existing calibration methods may lack efficiency or accuracy in this frequency range.

Purpose of the Study:

• To develop an efficient system for measuring miniature ultrasonic hydrophone sensitivity below 1 MHz.
• To assess the accuracy of acoustic pressure pulse measurements in medical ultrasound.
• To compare different piezoelectric ceramic source transducer designs for optimal performance.

Main Methods:

• Development of a time delay spectrometry (TDS) system.
• Utilizing a swept-frequency signal and a tracking receiver to distinguish arrivals by propagation delay.
• Employing two piezoelectric ceramic source transducers: a standard planar disk and a disk with varying thickness.
• Calibration using a reference hydrophone via a substitution technique.

Main Results:

• The developed TDS system provides an efficient means to measure hydrophone sensitivity below 1 MHz.
• A piezoelectric transducer with varying thickness demonstrated a more uniform response without significant sensitivity loss.
• The TDS method, while not absolute, proved capable of accurate hydrophone calibration.

Conclusions:

• Time delay spectrometry is an effective method for calibrating miniature ultrasonic hydrophones.
• The varying thickness transducer design is advantageous for uniform hydrophone response.
• Accurate hydrophone calibration is essential for reliable medical ultrasound applications.