scope:

General

Mechanical vibrations can be caused by a wide variety of processes and operations in industry, in trade, in handicrafts, in agriculture and forestry, as well as in traffic and transportation. Mechanical vibrations which are predominantly transmitted via the buttocks and back of the seated person, or the feet of the standing person, or via the head and the back of a person in a lying position are referred to as whole-body vibrations. These whole-body vibrations are often stochastic and contain different frequencies. They potentially show characteristics of shocks; they can be described via a cartesian coordinate system, and they vary as a function of time. Transmission of vibrations into the human body and their effects are also dependent on posture and on characteristics of the particular individual (physique, age, sex).

Whole-body vibration is a load factor which is very widespread in daily life. Occupants of land vehicles, water craft, and aircraft are exposed to mechanical vibration as drivers, pilots, crews, passengers, or as sick or injured persons being transported. It can be estimated that several million employees and users of public, private, and commercial transportation in the Federal Republic of Germany are exposed to mechanical vibration every day. Furthermore, operators of self-propelled machinery such as street-cleaning vehicles, fork-lift trucks, various kinds of earth-moving machinery, also agricultural or forestry tractors, and other machines are affected. However, even stationary machinery such as presses, forging hammers, engine test stands, vibration conveyors, or vibrating screens, for example, can be the source of vibrations which effect people as whole-body vibrations. Finally, vehicles or stationary machines can excite vibrations in buildings and parts of buildings which then transmit them to people.

As far as the physiological effects are concerned, there may exist large inter-individual variations. Whole-body vibrations may impair the general wellbeing, influence human performance, and/or be a risk to health and safety. Low-frequency vibrations of the body with frequencies below 0,5 Hz may be the cause of different types of kinetosis (motion sickness, seasickness), which is not a topic of this part of the standard. The current knowledge with respect to the possible effects of whole-body vibrations is dealt with in Section 6 in connection with their assessment.

The mechanical vibrations affecting a human being will be regarded in this part of the standard as an exposure or load upon the body. This exposure depends on several physical parameters such as the amplitude, frequency (spectrum), direction of the vibrations with respect to the individual and to gravity, the point of vibration transfer to the body, and the duration of the exposure. Knowledge of these details is, therefore, a necessity for the assessment of the effects of vibrations on individuals.

There are also some further influencing factors which have to be taken into account in the assessment, such as differences in posture when sitting, simultaneous exposure to vibration via the buttocks, the back, the feet, and the hands. The current state of knowledge about the simultaneous effects of influencing factors of this kind only permits to a limited extent their adequate quantitative assessment.

Assessing the effects of vibration exposure on the human being on the basis of the load experienced - in other words, on the basis of physically measurable quantities - requires knowledge of a strain caused by it. The strain also depends on load ability which is not constant over time. Apart from physical quantities, individual physiological and psychological factors are also important: e. g., type of physique, constitution, age, sex,disposition, and motivation. It has in some cases already been possible to clarify the relationship between exposure and strain for some aspects but not comprehensively.

The statements made in this standard are based on those reactions which are currently known, such as the biomechanical response of the body or its parts to vibration, acute physiological reactions (muscle activity, reactions of the circulatory system, e. g.), the magnitude of the individual perception of vibration, impairment of performance, and also chronic impairment of health.

Under certain working or environmental conditions the same vibration exposures may have different effects.

Note: Separate standards have been prepared for certain situations, such as vibration exposure in buildings (DIN 4150-2, VDI 2057 Part 3, and ISO 2631-2), vibrations on ships (DIN ISO 6954) or in rail vehicles (ISO 2631-4), shock-containing vibrations (ISO 2631-5, DIN SPEC 45697). Information on protective measures to be taken against vibration are given in standard VDI 3831.

Characterisation of vibration exposure

The quantitative characterisation of human vibration exposure is based in this standard on the following basic principles:

a) The instantaneous exposure in the direction l is characterised by the frequency-weighted acceleration awl (t) at the point of vibration transfer. The range of fluctuation can be seen from the time-dependent variation of the frequency-weighted acceleration awl (t).

b) The stress occurring within a specific duration T of vibration exposure is characterised by the rootmean- square value (effective value) of the frequency- weighted acceleration awl (see Section 3.9).

c) The exposure occurring during a single day in the sense of a "daily dose" is characterised by the assessment acceleration aw0l (see Section 3.17). It is calculated for a specified assessment duration T0 (see Section 3.15).

d) Long-term exposure in the sense of an accumulated vibration exposure involving continued exposure over several years is assessed via the total dose DVl on the basis of the assessment acceleration in c and the total number of days of exposure (see Section 3.20).

e) The effect of vibrations in the case of vibration curves with repeated high acceleration peaks or of vibrations with a large magnitude, even for an exposure of a short period, may require a separate assessment which does not make use of the basic principles cited in c and d (see Section 6.2).

Note 1: In contrast to ISO 2631-1, the symbols of the national standards are used in this part of the standard. The symbols awl(8) and Al(8) refer to the same quantity for an assessment duration of T0 = 8 h. In the German implementation of the EU Directive (2002/ 44/EC) the symbol Al(8) is preferred.

Note 2: The principles of this section are described for translatory vibrations and are also valid for rotatory vibrations in an analogous way.

Purpose and application

This standard provides a uniform procedure for assessing the exposure of mechanical whole-body vibrations with respect to human beings and also to give general instructions on determining the assessment quantities (see also the note to Section 1.1). On the basis of the physical data of vibration measurements and taking different frequency-dependent effects into consideration, the root-mean square value awl of the frequency-weighted acceleration awl (t) is formed as a quantity characterising vibration exposure (see Section 3.9). Taking into account the exposure duration T it is possible to estimate restrictions on well-being, performance, and the risk of health impairment. Knowledge of awl in conjunction with the exposure duration T is thus a necessary condition for formulating measures to avoid or limit the impairments mentioned.

This standard will not provide any limit values for the acceptability or admissibility of vibration exposures, but, references to the current technical and legal rules are given. However, Section 6 includes a number of guide values and some information for assessing particular exposures with respect to the expected effects on the individual. The procedure which is described in this part of the standard is applicable to any kind of translational or rotatory vibrations. But it is not suitable for evaluating single impacts of great amplitude, such as occur in vehicle accidents, for example. The frequency range extends from 0,5 Hz to 80 Hz for impairments of health, well-being, and performance, and from 0,1 Hz to 0,5 Hz for impairments due to different types of kinetosis. Mechanical vibration exposure can occur via the feet of a standing person, or via the buttocks, back, and feet of a sitting person, or the contact area of the recumbent person. The procedure can be used even for cases of alternating or unknown postures (hand arm vibration exposure via the hands is dealt with in VDI 2057 Part 2).

Note: Currently little knowledge is available about the effects on the human being of exposure to rotatory vibrations. For this reason this part of the standard will not initially provide any further information on assessing such vibrations. Information in this regard may be found in Clause 8.2 of the international standard ISO 2631-1.