• There are different sources of vibration of vehicle i.e. road roughness, the unbalance of the engine, whirling of shafts, worn out parts, damaged chassis, bent or deformed axle, wobbly wheels etc.
• Depending upon the cause the vibration may be free or forced. The free vibration may occur when the vehicle passes over an isolated irregularity in the road surface, which may die off as a result of dissipation of energy in damping.
• Then the forced vibration may result when disturbances occur persistently such as passing over obstacles on a proving road. In this case even if there may be damping, the vibration may persist & build up an undesirable level

Some of the most common sources of vibrations are:

1. Road Roughness

   Free vibration may occur when the vehicle passes over isolated irregularities in the road surface, on the other the forced vibration may result when disturbances occur persistently such as passing over obstacles on a proving road.

2. Vibration Due To Engine Unbalance

   The reciprocating parts of the engine may cause vibration of an automobile due to the periodic disturbances.

3. Whirling of Shafts

   A rotating shafts carries different mountings and accessories in the form of gears, pulleys etc. The centre of gravity of pulley or gear is at a certain distance from the axis of rotation and due to this the shaft is subjected to centrifugal force. This force will bend the shaft and causes vibrations.

Effect of Vehicle Vibration on Human Body:

1. Mechanical Damage

   Damage is produced when the accelerative forces are of sufficient magnitude. Chronic injuries may be produced by vibration exposure of long duration. Such exposure is accepted as a risk factor in the development of low back pain minor kidney injuries are occasionally suspected & rarely to act of blood may appear in urine due to the vehicle vibration. Pathological changes have been observed in the spine of operators of cars & on the rood trucks & other occupations involving chronic exposure to whole body vibration.

2. Physiological Responses

   It is difficult to separate out effects due to vibration from effects due to sitting all-day or manual loading & unloading. The vibration of frequency range 4 to 10 Hz procures pain in
   the chest after backaches seem to occur very particularly at 8 to 12 Hz Headaches, eye strain & irritations in the intestines and bladder are usually associated with frequencies between 10 to 20 Hz.

3. Subjective Responses

   The subjective response most often assessed in the vibration studies is comfort; Comfort of course, is a state of feeling & so depends in part on a person experiencing the situation. People are most sensitive for vertical vibrations between 5 & 16 Hz & to the lateral vibration between about 1 & 2 Hz.

4. Visual Performance

   Visual performance is generally impaired most by vibration frequencies in range of 10 to 25 Hz .The amplitude of vibration seems to be key factor & the degradation in performance is probably due to movement of image on the retina, which causes image to appear blurred, for frequencies below 3 Hz.

5. Neural Processes

   Tasks that involve primarily central neural processes, such as reaction time, monitoring & pattern recognitions, appear to be highly resistant to degradation during vibration. Evidence suggests that short time exposure to vibration causes effects such as increase in heart rate, increase in muscle tension, effects on digestive system peripheral veins & the female reproductive organ.

There are different sources of vibration of vehicle i.e road roughness, the unbalance of the engine, whirling of shafts, worn out parts, damaged chasis, bent or deformed axle,wheels, etc.

Depending upon the cause the vibration may be free or forced. The free vibration may occur when the vehicle pases over an isolated irregularity in the road surface, which may die off as a result of dissipation of energy in domping. Then the forced vibration may result when disturbances occur persistently such as passing over obstacles on a proving rood. In this case, even if there may be damping, the vibration may persists build up an undesirable level.

Some of the most common sources of vibrations are:
i) Road roughness:-
Free vibration may occur when the vehicle passes over isolated irregularities in the road surface, on the other, the forced vibrations may result when disturbances occur persistently such as passing over obstacles on a proving road.
ii) Due to engine unbalance:
The reciprocating parts of engine causes vibration of an automobile due to the periodic disturbances.
iii) Whirling of shafts:-
A rotating shafts carries different mounting accessories in the form of gears, pulley etc. The Center of gravity of pulleys or gears is at a certain distance from the axis of rotation due to this shaft is subjected to centrifugal force. This force will bend the shaft & cause vibrations.

Effect of vehicle. vibration on human body:
i) Mechanical damage - Damage is produced when the accelerative force are of sufficient magnitude. Chronic injuries may be produced by vibration exposure of long duration. Such exposure is accepted as a risk factor in the development of low back pain, minor kidney injuries are occasionally suspected & rarely to act of blood may appear in urine due to the vehicle vibration. Pathological changes have been observed in the spline of operators of cars & on the road trucks & other occupations involving chronic exposure to whole body vibration.

ii) Physiological Responses:- It is difficult to separate out effects due to vibration from effects due to sitting all day or manual loading & unloading. The vibration of frequency ranges 4 to 10 Hz produces pain in the chest after backaches seem to occur very particularly at 8 to 12 Hz. Headaches, eye strain & irritations in the intestine & bladder are usually associated with frequencies between 10 to 20 Hz.

iii) Subjective Responses:- The subjective responses most often assessed in the vibration studies is comfort. Comfort of course, is a state of feeling & depends on a person experiencing the situation.

iv) Visual Performances:- It is generally impaired most by vibration frequencies in ranges of 10 to 25 Hz. The amplitude of vibrations seems to be key factor & the degradation in performance is probably due to movement of image on the retina, which causes image to appear blurred , for frequencies below 3Hz.

v) Neutral Processes:- Tasks that involve primarily control neutral process, such as reaction time, monitoring & pattern recognition, appear to be highly resistant to degradation during vibrations.