Source: https://jmrplens.github.io/phonometry/vibration/human/ # 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](https://jmrplens.github.io/phonometry/vibration/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)](https://jmrplens.github.io/phonometry/vibration/multiple-shock-vibration/) 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](https://jmrplens.github.io/phonometry/signals/) section. ## Pages in this section - [Human Vibration](https://jmrplens.github.io/phonometry/vibration/human-vibration/): ISO 8041-1 weightings, ISO 2631-1 r.m.s. and dose measures, ISO 5349 daily exposure A(8) and the Directive 2002/44/EC values. - [Multiple-shock whole-body vibration (ISO 2631-5)](https://jmrplens.github.io/phonometry/vibration/multiple-shock-vibration/): the spinal-response model, acceleration dose and probability of lumbar injury. ## 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.