Quantitative evaluation of distortion in sketching under mono and dual axes whole body vibration.

Performance of sedentary activities such as reading and writing, in trains is known to be affected by the vibrations. An experimental study was therefore initiated to investigate the interference perceived in sketching task under low frequency random vibration in both mono and dual axes. Thirty healthy male subjects participated in the study. Random vibration stimuli were excited in various axes in frequency range of 1-20 Hz at magnitudes of 0.4, 0.8 and 1.2 m/s(2). The task required the subjects to sketch the given geometric figures such as circle, rectangle and triangle under vibration environment in two subject postures (sketch pad on lap and on table). Three performance methods were used to measure the effect of vibration stimuli and posture. They consisted of two specifically designed objective methods for percentage distortion measurement and one subjective method using Borg CR10 scale. The results revealed that the percentage distortion and difficulty in sketching increased with an increase in vibration magnitude and was found to be higher for vibration in Y- and Z-axis. Similar trend was observed for percentage distortion and difficulty in sketching for dual axes also. The perceived difficulty and impairment in sketching performance was greater while sketching on lap for X-axis, while the effect was just the reverse for other axes.