Vibration Ride Comfort Criteria

Abstract

This paper presents results obtained from a test program being conducted at Langley Research Center to develop an empirical model for predicting passenger comfort responses to multiaxis vibrations. The specific results contained in this paper are restricted to a description and understanding of human response to complex vertical axis vibrations. The approach to multifrequency vibration includes a separate consideration of the discomfort associated with each frequency component or band of the total spectrum, and a subsequent empirical weighting of the discomfort components of these frequency bands when in various random combinations. Mathematically, this may be represented as: [Formula: see text] The discomfort (DISC) represents the subjective discomfort associated with the acceleration level of a particular frequency band. The F value, or masking factor specifies the fashion in which the discomfort of different frequency bands are added together. Fundamental to this approach is a detailed understanding of human response to discrete frequency inputs. A study has been recently completed that included 186 subjects, exposed to frequencies of 1 to 30 Hz, and ranging in acceleration level from 0.05 to 0.50 peak g. The F value was derived in a second set of tests that systematically explored the passenger discomfort response as a function of various random spectra. The results are in the form of equal discomfort curves that specify the discomfort associated with discrete frequencies between 1 and 30 Hz, of varying acceleration levels. These results, in addition to being necessary for the above equation, provide detailed information of the human discomfort response to increases of acceleration level, for each frequency investigated. More importantly, the results provide a method for adding the discomfort associated with separate frequencies for a total typification of the discomfort of a random spectrum of vibration.