3M NoisePro Series, Быстрый старт

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Common Noise Dosimeter Terms
Criterion Level (CL) - expressed in decibels (dB), it is the maximum allowable accumulated noise
level that results in 100% dose. Regional noise standards specify criterion level.
Dose - expressed in percent, it is the percent of the maximum exposure that has accumulated
over the run time. 100% is the maximum allowable exposure. 100% dose occurs for an average
sound level equal to the criterion level for an 8 hour period.
Exchange Rate (Doubling Rate) (ER)- the decibel level that would or halve the sound exposure.
For instance with a 3 dB exchange rate the sound exposure doubles with every 3 dB increase,
and the sound exposure is halved every 3 dB decrease. Regional noise standards specify the
exchange rate.
Lavg - stands for “level average” and is the average sound level measured over the run time.
Leq - stands for “level equivalent” and is the average sound level measured over the run time but
is calculated with a 3 dB exchange rate with no threshold.
Max Level - the highest weighted sound level that occurred, also allowing for the response time
that the meter is set to. If the meter is set for A weighting with Slow response then the Max level is
the highest A weighted sound that occurred applying the Slow response time.
Peak level - the highest instantaneous sound level that the microphone detects. Unlike the Max
Level, the peak is detected independently of the slow or fast response time the unit is set for.
Response Time (Fast, Slow, Impulse) - how quickly the circuitry responds to changing noise
levels. These are ANSI/IEC defined response times. Most occupational noise standards require
slow response time.
Threshold Level (Cut Off) - noise levels below the threshold are integrated as zero decibels.
This will affect Lavg, Leq, TWA, and Dose values. Most regional noise standards specify the
threshold level, if any.
TWA (Time Weighted Average) - takes the noise exposure accumulated in the run time and
applies an eight hour time period. If the meter was in run for 5 minutes, the TWA takes that 5
minutes of noise input and averages it into an 8 hour run time. The TWA in this case would be
much lower than the Lavg.
Weighting (A,C,Z) - frequency filters that cover the frequency range of human hearing. A
weighting greatly attenuates high and low frequency noise to mimic how the human ear hears
noise. C weighting also attenuates high and low frequency noises, but not nearly as much as
A weighing. Z weighting does not apply any attenuation, or weighting, to any frequency. Most
regional noise standards require a weighted measurements.