ISO 21940-31:2013规定了确定机器振动对不平衡敏感度的方法，并提供了作为相关共振转速与工作转速接近度函数的评估指南。ISO 21940-31:2013仅涉及不平衡引起的每转一次振动。它还就如何在某些特定情况下应用数值灵敏度值提出了建议。 它包括一个分类系统，可应用于与不平衡变化敏感性相关的机器。机器分为三种灵敏度和五种灵敏度范围。灵敏度值适用于简单的机器系统，最好是转子在其整个工作转速范围内只有一个共振转速。 如果共振速度相差很大（例如超过20%），则灵敏度值也可用于在其工作速度范围内具有更多共振速度的机器。 给出的灵敏度值并非用于任何机器组的验收规范，而是用于指示如何避免严重缺陷，以及指定夸大或无法达到的要求。它们还可以作为更深入调查的基础（例如，在特殊情况下，需要更准确地确定所需的灵敏度）。如果适当考虑给出的值，在大多数情况下，可以预期令人满意的运行条件。 仅考虑灵敏度值并不能保证不超过运行中给定的振动幅度。 可能会出现ISO 21940-31:2013范围之外的许多其他振动源。

ISO 21940-31:2013 specifies methods for determining machine vibration sensitivity to unbalance and provides evaluation guidelines as a function of the proximity of relevant resonance rotational speeds to the operating speed. ISO 21940-31:2013 is only concerned with once-per-revolution vibration caused by unbalance. It also makes recommendations on how to apply the numerical sensitivity values in some particular cases. It includes a classification system that can be applied to machines which is related to their susceptibility to a change in unbalance. Machines are classified into three types of susceptibility and five ranges of sensitivity. The sensitivity values are intended for use on simple machine systems, preferably with rotors having only one resonance speed over their entire operating speed range. The sensitivity values can also be used for machines that have more resonance speeds in their operating speed range if the resonance speeds are widely separated (e.g. by more than 20 %). The sensitivity values given are not intended to serve as acceptance specifications for any machine group, but rather to give indications regarding how to avoid gross deficiencies as well as specifying exaggerated or unattainable requirements. They can also serve as a basis for more involved investigations (e.g. when in special cases a more exact determination of the required sensitivity is necessary). If due regard is paid to the values given, satisfactory running conditions can be expected in most cases. The consideration of the sensitivity values alone does not guarantee that a given magnitude of vibration in operating is not exceeded. Many other sources of vibration can occur which lie outside the scope of ISO 21940-31:2013.