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• <br />r5 <br />5.3.2. Checking the Microphone <br />Sensorcheck tests the microphone's operation by sending a signal to the microphone and <br />measuring its frequency and amplitude response. If the resulu of the test fall within specified <br />ranges, the microphone is within calibration. <br />5.3.3. Sensorcheck Report <br />Tate Sensorcheck report appeazs on the BlastMate III display. The massage "All Channels <br />Working. Press Print to Print" indicates the Blastavlate III sensors have passed the Sensorcheck. <br />5.4. Antialias Filters <br />Aliasing occurs when ahigh-frequency signal appeazs as an erroneous low frequency because the <br />waveform was sampled at too ]ow a sampling rate. An antialiasing filter solves this problem by <br />removing the high-frequencies. <br />5.5. Data Analysis Techniques <br />7'he following sections define the BlastMate III data analysis techniques. The first section, ground <br />vibrations, discusses calculations applied to event data recorded by a vansducer. The second <br />section, sound pressure, describes the microphone event data calculations. <br />• 5.5.1. Ground Vibrations . <br />The BlastMate III calculates the Peak Particle Velocity, Zero Crossing Frequency, Peak <br />Acceleration, and Peak Displacement Cor each of the transverse, vertical, and longitudinal axes. <br />The B1astMate III calculates Peak Vector Sum using data from all three axes. <br />a. Peak Particle Velocity (PPV) <br />Peak Particle Velocity indicates the maximum speed particles travel resulting from an event's <br />ground vibrations. The BlastMate III calculates the PPV for each geophone. <br /> <br /> Psak Panfde Vei~ry <br />MVM. <br />~M, O.wY,~ <br /> T~ <br /> <br />Figure 5.9 Calculating Peak Particle . <br />Velocity. <br />b. Zero Crossing Frequency (ZC Freq) <br />The Zero Crossing Frequency calculates the event waveform's frequency at the lazgest peak. <br />(1) Calculating Zero Crossing Frequency <br />7o calculate the Zero Crossing Frequency, we need to determine the period of oscillation of the <br />waveform. Convenient wave[otm positions for measuring period, the time Cor one complete cycle, <br />occur between two successive peaks, troughs, or zero crossings. The BlastMate III measures <br />• between zero crossings. Frequency is the number of periods tha[ occur in one second calculated by <br />the formula: Frequency = 1/period. <br />Blas[Mate III Operator Manual <br />