Compensation of environmental and operational conditions in ultrasonic testing of structures

A method for detecting changes to a structure, the method performed by a system including an acoustic transmission transducer, an acoustic reception transducer, and one or more processors, the method comprising:

• transmitting, by the acoustic transmission transducer, an acoustic signal along the structure;
• receiving, by the acoustic reception transducer, the acoustic signal after the acoustic signal has traveled along at least a portion of the structure;
• generating, by the acoustic reception transducer, output signals conveying signal characteristics of the received acoustic signal;
• monitoring, by the one or more processors, the output signals for a change in the signal characteristics of the received acoustic signal from baseline signal characteristics, the change in the signal characteristics of the received acoustic signal from the baseline signal characteristics caused by a change to the structure, a change in operating temperature of the structure, and/or liquid presence within the structure, the liquid presence within the structure causing a liquid boundary effect;
• compensating, by the one or more processors, for the change to the operating temperature of the structure by phase-shifting the signal characteristics of the received acoustic signal to match the baseline signal characteristics;
• compensating, by the one or more processors, for the liquid boundary effect by excluding frequencies of the received acoustic signal dominated by the liquid presence within the structure;
• and
• detecting, by the one or more processors, the change to the structure based on the phase-shifted signal characteristics of the received acoustic signal outside the frequencies dominated by the liquid presence within the structure.