FUNDAMENTAL STUDY ON EVALUATION METHOD OF HORIZONTAL TRAFFIC VIBRATION FROM THE VIEWPOINT OF HABITABILITY

Abstract

 Traffic vibrations causes problems from a viewpoint of habitability. In recent years, due to the densification of the city and the development of the transportation network, it is difficult to take enough distance between living space and road or railway which are vibration source. Therefore, the problems due to traffic vibration are increasing. The characteristic of traffic vibration is nonstationary vibration whose amplitude changes randomly. Therefore, it is necessary to study the applicability of previous study using sine waves.

 In this study, we developed sensory evaluation tests using 18 vibration waveforms which was measured in the housing, and search a physical index that is relative to a human’s vibrations sense while comparing with the previous study.

 The investigated procedure is described as follows;

 1) 18 traffic vibration waveforms measured at the upper floor of a wooden house near a road or railroad were selected.

 2)the samples were exhibited to examiner randomly, and we obtained one answer from each of them about their feeling of amplitude, annoyance and discomfort for each sample.

 3)We constructed psychographic scales of feelings of amplitude, annoyance and discomfort against various vibrations using a method of successive categories.

 4)Several physical index candidates were set referring to previous research and vary in the degree of frequency reflecting characteristics, duration, and amplitude undulation. And we searched for the index of the most relative to a human’s vibratory senses and evaluations.

 The results are described follows;

 1) We found that VL_max which is maximum value index of a vibration level has relatively good correspondence with the psychological scale, whereas A1/3oct.eq.max which is calculated from only the amplitude of the dominant frequency component has a poor correspondence. This is because feeling and evaluation of vibration were influenced by the amplitude of all frequency range.

 2) Comparing A1/3oct.eq.max with A1/3oct.eq.max plus duration time, we observed that A1/3oct.eq.max plus duration time has a good correspondence than A1/3oct.eq.max. Similarly comparing VL_max and VL_max plus duration time, we observed that VL_max plus duration time has a good correspondence than VL_max. Therefore, feeling and evaluation of vibration were observed to be influenced by the duration of vibration.

 On the basis of the study, we found that the relation between the feeling of annoyance scale and VL_max plus duration time described as “VLT＝VL_max(630ms)＋20･log₁₀T^1/4” has overall good correspondence. Where “VL_max(630ms)” is the maximum value of vibration level (time const.=630ms) and “T” is the duration level over 60dB. This result is consistent with previous studies.