Demodulation-derived damage metrics for nonlinear wave modulation-based health monitoring of structures

•Proposing Modified In-Phase/Quadrature Homodyne Separation for accurate and reliable signal demodulation in nonlinear wave modulation.•Validating the M-IQHS and Hilbert transform-derived modulation indices against theoretical values.•Implementation of the M-IQHS to demodulate signals modulated by high-frequency pump actuation, even in the ultrasonic range.•Introducing the M-IQHS's potential for demodulating signals with multiple sidebands.