Vibrometry - Fundamentals and Assessment Tools for Occupational Ergonomics - page 651

33
Vibrometry

33.1 Introduction . ............................. 33-1
33.2 Vibration Basics ........................... 33-1
33.3 Vibration Measurements Basics . .............. 33-4
33.4 Occupational Vibration Standards

Donald E. Wasserman
D.E. Wasserman, Inc.
David G. Wilder
University of Iowa

Guides ....... 33-7

/

Whole-Body Vibration Standards / Guides Used in the U.S.

†

Hand-Arm Vibration Standards / Guides Used in the U.S.

33.5 Summary . . . ............................. 33-12

33.1 Introduction

There are some 8 million workers 1 in the U.S. exposed to occupational whole-body vibration (WBV) or
hand-arm vibration (HAV) with resulting severe medical consequences of WBV or HAV exposures (see
text Chapter: Occupational Vibration and Cumulative Trauma Disorders). The ability to measure, quan-
tify, and evaluate the vibration impinging on the human body and relating these results to the disease
processes it produces is essential to understanding both dose-response relationships and methods for
controlling human vibration exposure. The purpose of this chapter is thus threefold: (1) To provide
an introduction to the occupational vibration measurement process; (2) to provide a basic understand-
ing of the occupational WBV and HAV health and safety standards guides currently in use in the U.S.;

and (3) to demonstrate the interrelationships between these measurements and their respective WBVand
HAV standards

/

guides.

/

33.2 Vibration Basics 2,3

Vibration is a description of motion. As such, this motion is characterized by its direction and a corre-
sponding magnitude; thus, by definition vibration is a vector quantity. A total of six vectors are needed to
describe vibrating motion measured at any one point; three of these vectors portray “linear motion” and
are situated mutually perpendicular to each other; the remaining three vectors portray the rotational
motion around each of these linear vectors and are called pitch, yaw, and roll. Currently pitch, yaw,
and roll are not measured; only the three perpendicular linear vectors are measured and evaluated in
human vibration work. Figure 33.1 shows the mutually perpendicular measure coordinate system
used for WBV measurements. Similarly, Figure 33.2 shows the two coordinate systems used to
measure HAV. We define the directions of motion as follows: The “Z axis” motion is in the long
(head-to-toe) WBV direction, and for HAV measurements the motion is a direction parallel to the
hand arm long bones. Similarly, the “Y axis” motion is in the direction across the shoulders for WBV

measurements, and for HAV measurements the motion is across the knuckles of the hand. Finally, the

/

33-1