A generic time-frequency analysis-based signal processing and imaging approach for air-coupled ultrasonic testing

The utilization of air-coupled ultrasonic technology is crucial for examining objects that are challenging to establish contact with or cannot endure coupling. Nevertheless, air-coupled ultrasonic is susceptible to various factors such as impedance mismatch, sound wave attenuation, and environmental noise, consequently leading to a diminished signal-to-noise ratio of the received signal. This reduction in signal quality amplifies the complexity of analysis and imaging processes. In this study, a generic air-coupled ultrasonic signal processing and imaging procedure for ultrasonic inspection is proposed, which capitalizes on time-frequency analysis. This methodology attains a heightened level of stability and superior signal-to-noise ratio imaging through a series of procedural steps, encompassing feature extraction, denoising, and the reconstruction of the A-scan signals. The efficacy of the proposed approach is quantitatively assessed in terms of signal-to-noise ratio, probability of detection, robustness, and generality. This innovative method presents a newfangled resolution for automated air-coupled ultrasonic testing.