For the purposes of this Section, the following terms are defined:

Frequency
A "frequency" is the number of oscillations per second of a vibration.

Impact vibrations
"Impact vibrations" are earth-borne oscillations occurring in discrete pulses at or less than 100 pulses per minute.  

Steady state vibrations
"Steady state vibrations" are earth-borne oscillations that are continuous. Discrete pulses that occur more frequently than 100 times per minute shall be considered to be steady state vibrations.

Three-component measuring system
A "three-component measuring system" is a device for recording the intensity of any vibration in three mutually perpendicular directions.