Vibetec Inc.

The study of whole body vibration (WBV) is a relatively new phenomenon, it is the study of how vibration effects the human body. This type of survey is particularly useful in environments such as sawmills work stations, were low frequency vibrations are in evidence.

Principle effects of vibration are:

• Degraded Health
• Impaired activities such as hand control and vision
• Impaired Comfort
• Motion sickness
• Fatigue

Frequencies in the range of 0.5Hz to 80 Hz are significant in terms of body response. Every object (or mass) has a resonant frequency for example when a bell is rung it will resonate at its natural frequency. When an object is vibrated at its resonance frequency, it will vibrate at maximum amplitude, which is larger than the amplitude of the original vibration. (You have probably seen the old film clip of a suspension bridge that is twisting back and forth until it self destructs - this is a good example of a small amount of force having a devastating effect, in this case the wind blowing over the bridge excited its natural/resonant frequency). In the human body individual members and organs have their own resonant frequencies and do not vibrate as a single mass. This causes amplification or attenuation of input vibrations by certain parts of the body due to their own resonant frequencies. The most effective exciting frequency for vertical vibration lies between 4 and 8 Hz. Vibrations between 2.5 and 5Hz generate strong resonance in the vertebra of the neck and lumbar region with amplification up to 240%. Between 4 and 6 Hz resonances are set up in the trunk with amplification up to 200%. Vibrations between 20 and 30 Hz set up the strongest resonance between the head and the shoulders with amplification up to 350%. In a human body, this unwelcome situation may create chronic stresses and sometimes even permanent damage to the affected organs or body parts.

Frequency Effects:

Symptoms	Frequency (Hz)
General feeling of discomfort	4 - 9
Head Symptoms	13 - 20
Lower jaw symptoms	6 - 8
Influence on speech	13 - 20
"Lump in throat"	12 - 16
Chest pains	5 - 7
Abdominal Pains	4 - 1
Urge to urinate	10 - 18
Increased muscle tone	13 - 20
Influence on breathing movements	4 - 8
Muscle contractions	4 - 9