For the purposes of this Section, the following terms are defined:A "frequency" is the number of oscillations per second of a vibration. "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 systemA "three-component measuring system" is a device for recording the intensity of any vibration in three mutually perpendicular directions.