ISO 21984:2018 gives guidelines for the measurement, evaluation and reporting of vibration with regard to habitability for all persons on board ships satisfying one or both of the following conditions:

a) 2-stroke cycle, long-stroke, low-speed diesel engine directly coupled to the fixed-pitch propulsion propeller is installed.

b) length of deck house (L) is limited as compared with its height (H) (i.e. deck house of around 1,0 and above in slenderness ratio of H to L). An example of length of deck house (L) and its height (H) for slenderness ratio is shown in Annex A.

Overall frequency-weighted r.m.s. vibration values in the frequency range 1 Hz to 80 Hz are given as guidance values for different spaces on ships.

ISO 21984:2018 is applicable to specific ships with intended voyages of 24 h or more.

ISO 21984:2018 specifies requirements for the instrumentation and the procedure of measurement in normally occupied spaces. It also contains analysis specifications and guidelines for the evaluation of ship vibration with respect to habitability.

This document is not applicable to machinery spaces, other than engine control rooms, where persons do not stay for prolonged periods of time.

ISO 20283‑5 is generally applicable to all ships. Requirements for measurement, evaluation and reporting of vibration with regard to habitability for all persons on board passenger and merchant ships, including specific ships to which this document may also be applicable can be found in ISO 20283‑5. This document is neither complementary nor additional but supplementary to ISO 20283‑5. The shipbuilder can select either this document or ISO 20283‑5 to apply to any specific ship upon due consideration to individual design conditions of the ship and, if any, experience in building sister or similar ships, and that particular selection is intended to be agreed on by the shipowner.

The evaluation of low-frequency ship motion which can result in motion sickness is covered by ISO 2631‑1. For the evaluation of the global structural vibration of a ship, however, see ISO 20283‑2.