Usability of hydrophone as a contact microphone to measure sound pressure level on steel structure

Abstract

This study investigated the problem of variable ultrasonic sound pressure level measurement in solid substrates because such measurements matter for marine antifouling applications. Contact microphones demonstrate two fundamental flaws when operating in ultrasonic frequency ranges and produce measurement variations based on environmental conditions and placement positions. The system used hydrophones for measurement with a redesigned magnetic holder containing internal clearance and filled with ultrasonic coupling fluid to achieve better impedance match-up and minimize measurement resonance. The testing took place in two setups: The ultrasonic signal producing box produced shaky frequency outputs while the piezo drive demonstrated reliable performance through steady frequency inputs. The experiment took place in two setups where the ultrasonic signal producing box exhibited irregular frequency patterns before the Piezo Drive achieved stable frequency output for accurate measurements. New testing data showed that the redesigned magnetic holder performed better than the original design by decreasing measurement variations according to statistically evaluated results. A comparative frequency analysis agreed between the laser doppler vibrometer, but this device operates through a non-contact method of vibration assessment. The hydrophone system demonstrates excellent precision in ultrasonic vibration capture which makes it a suitable industrial and marine alternative. The research lays down reliable methods for hydrophone acoustic measurements which present useful solutions for structural inspections, underwater technology and marine growth avoidance. The implementation of controlled frequency generation practices along with mechanical optimization and coupling fluid integration tools creates enhanced accuracy levels in ultrasonic SPL systems which may apply to both laboratory and field deployment.