Reactions of humans to vibrations of 1 to 80 Hz inside buildings are assessed in this Standard by use of degrees of perception and associated vibration levels and durations. Accelerations or velocities inside buildings may be measured to assess perceptibility and possible adverse reactions from those inside. A variety of building types and situations are covered by the use of multiplying factors applied to the basic curves. Responses are related to the event durations, frequencies of vibration, and body orientation with respect to the vibration. Adherence to the vibration magnitudes corresponding to the perceptibility threshold will insure minimum discomfort and annoyance. The "acceptability" of a given magnitude of vibration above the perception threshold will be influenced by the interference of the vibrations in the activities of individuals and by the various social, economic, and legal relationships between the source of the vibrations and the receivers. Other related factors are the degree of startle, fear of injury or structural damage, and attitudes about the source including its inevitability, duration, and necessity.