Application of photoplethysmogram for detecting physiological effects of tractor noise

This study sought to investigate the effect of tractor noise on the cardiovascular system of farm workers by the photoplethysmographic technique, which was used to derive signal reflecting features of cardiovascular system performance. Fourier transform and nonlinear time-series analysis methods, such as time-delay embedding and the Wayland test, were applied to the photoplethysmogram signal to analyze differences in cardiovascular system performance arising upon exposure to levels of tractor noise corresponding to low, medium and high tractor engine speeds. Results showed that the ratio of two significant component frequencies obtained by Fourier analysis and Wayland test translation error can distinguish differences in photoplethysmogram signal arising under noise exposure. Additionally, the translation error was less dependent on the subject than the frequency ratio, which may make it useful index for application to real-time health monitoring of farmers.