On 1 April 2006, the National Institute of Industrial Safety (NIIS) and the National Institute of Industrial Health (NIIH) were amalgamated into a single, administrative institute known as the National Institute of Occupational Safety and Health, Japan (JNIOSH). Of all research institutions under the Japanese Ministry of Health, Labour and Welfare, JNIOSH is one of the top institutes in terms of total number of research workers and overall size. JNIOSH is the only comprehensive research institute for occupational safety and health in Japan and actively conducts scientific research to eliminate industrial accidents and diseases, promote workers’ health and create a safe and comfortable working environment.
JNIOSH has a strong connection with universities and research organisations worldwide including Loughborough University in the UK with whom they have written joint papers. Working mainly on pure research and collaboration projects funded by customers, JNIOSH undertakes two to three paid projects a year. Among their particular interests are psycho-vibration, comfort evaluation and how vibration affects health and safety issues.
The Human Engineering and Risk Management Research Group is part of the Institute of Industrial Safety. The research activities of this group cover two main areas. One relates to health hazards in work environments, and the other involves occupational accidents. The group is currently conducting health studies relating to dust, harmful gases, noise, sound (including low frequency), vibration and low back-pain; as well as safety studies relating to human errors or organisational errors that result in workplace accidents.
Human vibration is defined as the effect of mechanical vibration on the human body and it has long been recognised that the effects of direct vibration on the human body can be serious. It can can lead to blurred vision, loss of balance, loss of concentration, etc. In some cases, certain frequencies can permanently damage internal body organs. However, during our normal daily lives we are exposed to vibration of one kind or another, for example, in buses, cars and trains.
Human vibration can be pleasant or unpleasant and we try to avoid exposing ourselves to unpleasant vibration such as travelling on bumpy roads. There are two main types of human vibration – whole-body vibration and hand-arm vibration. A person driving a vehicle is subjected to whole-body vibration which can disturb the central nervous system. Symptoms of this disturbance usually appear during, or shortly after, exposure in the form of fatigue, insomnia, headache and shakiness. Many people have experienced these nervous symptoms after they have, for example, completed a long car journey. However, the symptoms usually disappear after a period of rest.
Realising the Multi-modal Sensation
To evaluate the effect and perceptible limits of whole-body vibration, some experiments have been carried out with multi-degree-of-freedom (DOF) shakers. However the real environment consists of not only the vibration but also other stimuli, especially visual and audio. Human response to the vibration is almost certainly affected by the visual and audio information, which means it is very important to reproduce the visual and sound stimuli combined with the vibration to investigate the subjective impression of whole-body vibration using the psychometric methods, such as magnitude estimation method, paired comparison, category judgment method and so on.