Determination of the seat-to-head transfer function and influencing factors on comfort under vertical random vibrations

Abstract

This study aims to determine the seat-to-head transfer function (STHT) in subjects exposed to vertical random vibrations originating from a hydraulic pulsator, measured under laboratory conditions. The main objective is to examine how various anthropometric characteristics of subjects, such as Body Mass Index (BMI), sitting height, and age, influence the body's response to these vibrations. Ten female participants were exposed to uniaxial random broadband excitations in the vertical direction across three excitation levels (0.45 m/s², 0.8 m/s², and 1.1 m/s² r.m.s.) within the frequency range of 0.1 Hz – 20 Hz. Accelerometers were placed at the seat and the head to capture six acceleration signals in the x, y, and z axes at both locations. The results indicate that body mass, sitting height, and age significantly affect the STHT response, with higher BMI and sitting height correlating with distinct resonance characteristics. Notably, heavier subjects demonstrated lower resonance frequencies but higher maximum amplitude in the STHT frequency response. This research contributes to a better understanding of how individual anthropometric factors influence vibration transmission through the body, which is crucial for assessing comfort and designing ergonomically optimized seating in various vehicular and industrial environments.