The engineering community often discusses and implements various practices in the field of vibration, recognizing it as a significant factor affecting machinery, equipment, and structures. However, unlike noise, the impact of vibrations on humans and the potential for causing immediate or persistent health problems is not as widely considered.

 

However, the broader term 'NVH' essentially covers this aspect; while the Noise and Vibration terms and their analogy are much understood, the Harshness part of it is less practiced or interpreted to be of any sense or use.

 

The human interaction with any equipment wherein either the hand, feet or the major part of the body comes in contact during equipment operation will induce vibrations into the human body through the point/s of contact. Depending on the vibration severity, corresponding frequencies and duration of exposure, the person involved will have a variety of ill effects on his / her health.

 

This is one such phenomenon that could be grouped under Harshness.

 

The terms Hand-Arm and Whole Body Vibrations (HA and WBV) are central in evaluating human exposure to vibrations, whether through hand-held devices or operational equipment that emits vibrational energy during use. Specific testing methods and established standards are utilized to understand and measure this exposure to vibrations.

 

Typical HA and WBV adapters

 

ISO 2631 guides through all the terminologies, prescribed HA and WBV adapters, sensors and instrumentation, testing methodology and more. This standard further guides on the frequencies to be accounted for, data processing and weightings to be used and finally the result presentation.

 

WBV and HA assessment directions

 

The assessment of human exposure to vibrations is becoming increasingly relevant and legally binding with stricter SHE (Safety, Health and Environment) requirements. The civil and construction based industry in particular are enforcing these practices considering the multitude of equipment and long hours of exposure to a variety of operations that induce severe vibrations and cause short time fatigue to long time ill effects on the health of the user.

 

Some of the most known effects of Hand-Arm vibrations are:

  1. White finger (also known as "dead finger" ) - damage to hands causing whiteness and pain in the fingers
  2. Carpel tunnel syndrome (and other symptoms similar to occupational overuse syndrome)
  3. Sensory nerve damage
  4. Muscle and joint damage in the hands and arms, like tennis elbow.
 
WBV and HA - some of the effects on Human

 

Whole Body vibrations are likely to cause

 

- Lower back pain (damage to vertebrae and discs, ligaments loosened from shaking)
- Motion sickness
- Bone damage
- Varicose veins/heart conditions (variation in blood pressure from vibration)
- Stomach and digestive conditions
- Respiratory, endocrine and metabolic changes
- Impairment of vision, balance or both
- Reproductive organ damage
 

In a nut-shell, longer the human is exposed to HA and WBV, the greater the risk of health effects and muscular disorders.

 

NV Dynamics offers its full fledged consulting and services to both assess, mange and advice its clients in this specific area of Vibration Harshness. With qualified resources and standardised procedures, we have implemented the HA and WBV testing practices in many industries across the Indian sub-continent. The whole methodology is being considered by many industry as a part of their health compliance requirement and as a routine annual practice.