Membrane hydrophone phase characteristics through nonlinear acoustics measurements.

Area of Science:

• Acoustics
• Materials Science
• Electrical Engineering

Background:

• Polyvinylidene fluoride (PVDF) membrane hydrophones are crucial for acoustic measurements.
• Full characterization necessitates understanding both amplitude and phase response.
• Existing methods may not fully capture phase behavior, especially at higher frequencies.

Purpose of the Study:

• To investigate and present methods for extracting phase information from PVDF membrane hydrophones.
• To comprehensively characterize two PVDF membrane hydrophones up to 100 MHz.
• To validate a semi-empirical computer model for predicting nonlinear acoustic fields and hydrophone response.

Main Methods:

• Utilized nonlinear acoustic measurements to extract phase information.
• Employed a semi-empirical computer model with a hyperbolic propagation operator.
• Performed impedance measurements and receive transfer function simulations.
• Analyzed experimental results from two PVDF membrane hydrophones.

Main Results:

• PVDF hydrophone phase characteristics were obtained by comparing modeled and measured harmonic phase values.
• Model predictions for phase characteristics agreed within 10% with simulation results.
• Identified and distinguished cable loading effects and membrane resonances.
• Observed oscillations in the phase versus frequency plot, linked to membrane resonances and antiresonances.

Conclusions:

• Both amplitude and phase are essential for complete PVDF hydrophone characterization.
• The developed semi-empirical model accurately predicts nonlinear acoustic fields and hydrophone phase response.
• Membrane thickness resonances and antiresonances influence the phase characteristics.
• Cable length can introduce resonances, as observed at 100 MHz with a 1-m cable.