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The generalized ultrasonic inspection method harnesses piezoelectric transducers and ultrasonic resonance spectroscopy to detect sub-500-micron defects in batteries. By analyzing the resonance behavior of high-frequency sound waves and employing novel data processing techniques, subtle structural changes in batteries can be identified. Two hardware setups were developed: one employing direct transducer contact and another utilizing ultrasonic measurements through a captured water column. Both configurations incorporate a scanning technique that captures spatial degradation data – rather than a single point measurement – enabling structural insights even in layers too thin for time-domain c-scan resolution. Processing of the data includes converting the measurements and reference time domain signals to the frequency domain, then normalizing the measurement signal in the frequency domain to determine the frequency dependent reflection coefficient. As a result, resonance behavior between the test specimen and apparatus can be isolated. This resonance-based approach is ideal for delicate materials unsuitable for high-powered laser excitation or full immersion testing, and the associated data-analysis allows the battery defects to be detected more efficiently. This NASA invention offers significant potential for highly sensitive, nondestructive enhancements of battery safety and quality control in industries such as automotive, aerospace, additive manufacturing, and composites.