For the purpose of this subchapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
AMPLITUDE. The maximum displacement of the earth from the normal rest position. Displacement is usually reported as inches or miles.
DISCRETE IMPULSES. A ground transmitted vibration stemming from a source where specific pulses do not exceed 60 per minute (or one per second).
FREQUENCY. The number of times that a displacement completely repeats itself in one second of time. Frequency may be designated in cycles per second (cps) or Hertz.
IMPACT. An earthborn vibration generally produced by two or more objects striking each other so as to cause separate and distinct pulses.
NIGHTTIME HOURS. The hours of 10:00 p.m. to 7:00 a.m. local time.
PARTICLE VELOCITY. A characteristic of vibration that depends on both displacement and frequency. If not directly measured, it can be computed by multiplying the frequency by the amplitude times the factor 6.28. The particle velocity will be in inches per second, when the frequency is expressed in cycles per second and the amplitude in inches.
SEISMOGRAPH. An instrument which measures vibration characteristics simultaneously in three mutually perpendicular planes. The SEISMOGRAPH may measure displacement and frequency, particle velocity or acceleration.
STEADY STATE. A vibration which is continuous, as from a fan compressor or motor.
VIBRATION. A reciprocating motion transmitted through the earth, both in horizontal and vertical planes.
(1980 Code, § 93.093) (Res. 94-229, passed 1-19-1995; Res. 99-210, passed 5-20-1999)