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phonometry

Human vibration

Vibration transmitted to a person is evaluated with a measurement chain deliberately parallel to a sound level meter’s: the acceleration is frequency-weighted to reflect how the body responds at each frequency, reduced to a weighted r.m.s. value or a dose, combined across axes, and normalised to a daily exposure that regulation can act on. The two pages of this section cover the general chain and the special case that breaks it.

Human Vibration is the general chain. It covers the whole-body and hand-arm frequency weightings of ISO 8041-1, the weighted r.m.s. acceleration and the running and dose measures of ISO 2631-1 (MTVV, VDV, MSDV, crest factor) that flag shocks a plain r.m.s. would hide, the direction-independent Wm weighting that ISO 2631-2 prescribes for building occupants on every axis, the hand-arm vibration total value and daily exposure A(8) of ISO 5349-1/-2, and the exposure action and limit values of Directive 2002/44/EC that make A(8) legally meaningful.

Multiple-shock whole-body vibration (ISO 2631-5) handles exposures the r.m.s. philosophy underestimates: repeated mechanical shocks from off-road vehicles, high-speed craft or earth-moving machinery, which load the lumbar spine far beyond what their energy average suggests. ISO 2631-5:2018 models the seat-to-spine transfer explicitly, accumulates a dose from the response peaks, and converts it into compressive stress on the vertebral endplates and a probability of lumbar injury over a working life.

Use the ISO 2631-1 metrics first, and let two numbers decide when to move on. A crest factor above 9 says the basic weighted r.m.s. method is no longer adequate for that record, which is the ISO 2631-1 trigger for reaching for the running and dose measures. A band-limited vertical peak acceleration above 9.81 m/s² — 1 g, the free-fall threshold — puts the exposure in ISO 2631-5’s clause 5 regime, the severe shocks with possible loss of contact with the seat that this library implements, rather than in its Annex A finite-element model for exposures in which the occupant stays seated. The measurement front-end (weighting filters, band analysis) is shared with the core signal analysis section.

Pages in this section

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What this section does not cover

Section titled “What this section does not cover”

  • No meter is type-tested. ISO 8041-1’s own subject — the design and type-testing of general-purpose human-vibration meters — is not implemented; only its frequency-weighting definitions are taken from it, so nothing here assigns a class to an instrument.

  • Building vibration stops at the weighting. Of ISO 2631-2 the library implements the direction-independent Wm curve and nothing else, and that is closer to the standard than it looks: the 2003 edition deliberately deleted its predecessor’s guidance values, so there are no acceptable magnitudes for building vibration to compare against. A reader looking for a limit will not find one here, and will not find one in the standard either.

  • Of ISO 2631-5, the clause 5 model only. The Annex A finite-element model for less severe seated exposures is distributed separately by ISO and is not implemented, which is what makes the 1 g delineation above a routing decision rather than a preference.

  • And the verdict stops at the directive itself. An A(8) is assessed against the action and limit values of Directive 2002/44/EC — each marked exceeded or not, the exposure zone named, and a PASS/FAIL verdict issued against the limit value — but the library applies no national transposition of the directive, and the conclusion of a workplace risk assessment is not a number this section produces.

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