Physical effects of frequency-dependent acoustic attenuation on photoacoustic wave propagation in multilayered human skin

Frequency-dependent acoustic attenuation plays a central role in shaping photoacoustic wave propagation in biological media. However, its interaction with interfacial reflections and wave interference in multilayered media remains insufficiently understood. This study investigates the physical effects of frequency-dependent acoustic attenuation on photoacoustic wave propagation in multilayered human skin using a Fourier-domain semi-analytical approach. The formulation extends a previously developed lossless model by incorporating attenuation and its associated dispersion while preserving explicit interface-resolved wave interactions. Analytical expressions for the frequency-domain pressure field are obtained in each layer, and time-domain responses are reconstructed via inverse Fourier transformation. The results show that, in multilayered media, attenuation not only reduces signal amplitude but also alters the relative contributions of reflected and transmitted waves through preferential suppression of high-frequency components. This leads to systematic modification of interference patterns and corresponding changes in waveform structure and temporal broadening. Dispersion introduces additional phase variation but has a comparatively minor influence on the overall waveform under the conditions considered. These results provide a unified framework for interpreting attenuation effects in layered media, highlighting the dominant role of attenuation in shaping photoacoustic signals while retaining physically consistent wave propagation.