• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1260-1264
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• 2006

Shock-type vibrations are usually experienced in vehicles excited by impulsive forces. Fifteen subjects used magnitude estimation to judge the discomfort of vertical shock-type vibration generated on a rigid seat. The shocks had different frequencies and magnitudes and were produced from the response of a 1 degree-of-freedom model to a half-sine force input. The magnitudes of the shocks, expressed in terms of both peak-to-peak value and un-weighted vibration dose values, VDVs, were correlated with magnitude estimates of the discomfort. In this study, equivalent comfort contour of shock-type vibration were obtained. From the contour, it was investigated that shock-type vibration at frequency below 0.8 Hz and between 4.0 Hz and 10.0 Hz is highly sensitive to the discomfort than at other frequencies.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.108-113
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• 2007

This study aims to find equivalent comfort contours, reciprocal of frequency weighting curves, for vertical steering wheel vibration. Psychophysical responses were measured from twelve male subjects by using magnitude estimation of relative discomfort due to vertical steering wheel vibrations of magnitude of 0.1 to 1.58 $m/s^2$ in the frequency range of 4 to 250 Hz. Relative discomfort were estimated with a reference vibration of 0.4 $m/s^2$ at 31.5 Hz. Equivalent comfort contours were produced from the median of sensation magnitudes judged by twelve subjects, which showed variation in the shapes with increase of vibration magnitude. A shape of the contour came close to the perception threshold curve with decrease of vibration magnitude. When the vibration magnitude increases, the shape changed close to those in the references of Hong and et al (2003). It is also recommended frequency weighting curves for vertical steering wheel vibration must be expressed as a function of vibration magnitude as well as frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.658-664
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• 2006

Shock vibrations are usually experienced in vehicles excited by impulsive input, such as bumps. The frequency weighting functions of the current standards in ISO 2631 and BS 6841 are to help objectively predict the amount of discomfort of stationary vibration. This experimental study was designed to develop frequency weighting shape for shock vibration having various fundamental frequencies from 0.5 to 16Hz. The specks were produced from the response of single. degree-of-freedom model to a half-sine force input. Fifteen subjects used the magnitude estimation method to judge the discomfort of vertical shock vibration generated on the rigid seat mounted on the simulator. The magnitudes of the shocks, expressed in terms of both peak-to-peak value and un-weighted vibration dose values (VDVs) , were correlated with magnitude estimates of the discomfort. The frequency weighting shapes from the correlation were developed and investigated having nonlinearity due to the magnitude of the shock.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.50-57
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• 2007

Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.