Seminar on

State of the art in human comfort in vibration environment

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Presented by:Mohd Qasim.M-Tech Machine design 1st year.Enroll. no. 14539017

Submitted to:Dr. V.Huzur Saran.Asst ProfessorM.I.E.D. IIT Roorkee

Content

1. Introduction

2. Vibration and human response

3. Literature Survey

4. Conclusion

5. Proposed work

6. References

Introduction

Vibration

• Vibration is mechanical movement that oscillates about afixed (often a reference) point. It is a form of mechanical waveand, like all waves; it transfers energy but not matter.

Comfort

• Comfort is a sense of physical or psychological ease, The useof "comfort" as a verb generally implies that the subject is ina state of no pain, suffering or affliction.

Introduction(contd.)

• Study of human comfort is a multidisciplinary topic involvingbiology, psychology, biomechanics, and engineering.

• The body does not contain a single vibration-sensing organbut combines signals from the visual, vestibular, somatic, andauditory systems.

• The frequency of vibration associated with the effects onhuman body is approximately 0.5 to 100 Hz. Low frequenciesbelow 1 or 2 Hz has most severe effects on comfort.

• Some motion can be a source of pleasure or satisfaction orgive a sense of well being or comfort, but study of relationbetween vibration and comfort mainly concerned with theextent to which motion are responsible for displeasure,dissatisfaction, discomfort.

Vibration and human response

• In real world we come across complex vibration waves, but only with sinusoidal vibration it is possible to study the response to a single frequency of motion. Many experimental studies of human response to vibration have therefore attempted to investigate the reaction to pure sinusoidal vibrations .

• The study of comfort in vibration environment is concernedwith establishing cause-effect relationship between variouseffects e.g. impaired comfort activities or health conditions.

Fig: Illustration of how a complex wave can be produced by adding a small number of simple sine waves with different frequencies, magnitudes, and phase shifts.

Vibration and human response(contd.)

Application of vibration to human body• Whole Body Vibration

Whole-body vibration occurs when a human is supported by asurface that is shaking and the vibration affects body partsremote from the site of exposure.

• Hand transmitted vibrationHand-transmitted vibration occurs whenever an individualholds a vibrating tool.

• Motion sicknessMotion sickness is caused by perceived motion or apparent motion in which a body is, the signals from four senses visual, vestibular, somatic, and auditory does not match with the expectation or memory.

Fig :Typical frequency ranges and magnitudes of interest for the study of motion sickness, whole body vibration, and hand-transmitted vibration

Some parameters studied in context of human response to vibration

Literature survey

• M.K. Bhiwapurkar et al [1]:Physiological parameters like, Pulse Rate, Respiration Rate, Galvanic Skin Response, Skin Temperature, Heart Rate, Heart Rate Variability and ECG values of passengers subjected to whole body random vibrations . All parameters adversely affected in the presence of vibration as compared to control condition when considered in noise environment.

• Rammohan V. Maikala et al [2]: Metabolic and respiratory responses on exposure to 3, 4.5 and 6 Hz of WBV resulted in responses that are similar to a light physical activity.

Literature survey(contd.)

• Prakash Kumar et al [3]: Physiological parameters like, BloodPressure, Pulse Rate, Respiration Rate, Heart Rate, Heart RateVariability and ECG values reveals that larger physiologicalchanges occur when human body goes from no vibrationcondition to vibration condition, in comparison to when bodygoes from lower vibration to higher vibration condition.Showing body adapting vibration environment.

• Al-Nashash H et al [4]: ECG response of the human bodysubjected to Whole body vibration shows either depression orelevation of the ST segment indicating heart muscle fatigue.Also maximum change is seen at 8 Hz, which is considered asnatural frequency of heart.

Literature survey(contd.)

• Mitsunori Kuboa et al [5]: They produced a synthetic vibrationmodel reproducing the relations between the physical,psychological and physiological reactions of the human bodyexposed to external vibrations using multiple regressionequations.

• Cardinale, Marco et al [6]: Electromyography (EMG) responsesof vastus lateralis muscle(is the largest part of the quadricepsfemoris) to different whole-body vibration frequenciesshowed that, in all vibration conditions, average EMG (rms)activity of vastus lateralis was higher than in the no-vibrationcondition.

Literature survey(contd.)

• A.W. Irwin [7]: Human perception thresholds, in both thepresence and the absence of visual cues, and equal sensationcontours for low frequency whole body pure yaw vibrationwere investigated. At frequencies below about 1 Hzperception of yaw motion was achieved more readily by visualcues than by body sensation but above 1 Hz the difference inperception levels with and without visual cues becamemarginal.

Conclusion

• Effect of vibration magnitudeWhen magnitude of vibration is increased there is usually anincrease in discomfort.

• Effect of vibration frequencyA constant magnitude does not produce the same discomfortat all vibration frequencies . At low frequencies (below 1-2 Hz)the force acting on the body is approximately equal to theinput acceleration. At slightly higher frequencies various bodyresonances tend to amplify the motion and overall discomfortis influenced by different parts of the body.

• Effect Vibration DurationVibration applied for very less time e.g. shock produces morediscomfort than constant application of vibration.

Conclusion

• Most of parameters that are used for measurement in humanresponse to vibration in various research papers give results inonly the situations presented in the experimentation.

• Body tries to adjust the situation, thus decreasing theresponse to further increase in the applied vibration. That’swhy, results of the experiments may not give the accurateinsight if the input changes.

• Human comfort is widely subjective and people’s responsechanges widely based on extrinsic and intrinsic variables.

Proposed work

• Some physiological parameters, like respiration rate, Galvanic skin response and vagal tone shows promising result in measuring discomfort in vibratory environment.

• The proposal is to further investigate the above physiological parameter with a large and different groups of individuals, grouped by intrinsic variables, so we could have a result that is more applicable in general.

References

1. M.K. Bhiwapurkar, V.H. Saran, V.K. Goel:”Study of humancomfort under thermal and vibratory environment usingphysiological indices.” (2009)

2. Rammohan V. Maikala, Sharla King, Yagesh N. Bhambhani:“Acute physiological responses in healthy men during whole-body vibration.” (2006)

3. Prakash Kumar, V.H.Saran, S.P.Harsha: “Effect of noise andvibration on human physiological parameters.”(2014)

4. Al-Nashash H, Qassem W, Zabin A, Othman M.: “ECGresponse of the human body subjected to vibrations.”(1996)

5. Mitsunori Kuboa, Fumio Terauchia, Hiroyuki Aokia, YoshiyukiMatsuokab: “An investigation into a mechanical vibrationhuman model constructed according to the relationsbetween the physical, psychological and physiologicalreactions of humans exposed to vibration.”(2001)

6. Cardinale, Marco; Lim, Jon: “Electromyography Activity ofVastus Lateralis Muscle During Whole-Body Vibrations ofDifferent Frequencies.”(2003).

7. A.W. Irwin: “Perception, comfort and performance criteria forhuman beings exposed to whole body pure yaw vibrationand vibration containing yaw and translationalcomponents.” (1980)

8. M. J. Griffin: “Handbook of Human Vibration.”(1996)

9. Neil J.Mansfield: “Human response to vibration.”(2004)

10. W.F. Grether: “Vibration and human performance. HumanFactors” (1971)

Thank you