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Appendix B
56
Logging
(Also called Data Logging.) Certain measurements, such as average level (Lavg) and maximum level (max), can be recorded
by the dosimeter at regular intervals. For example: A dosimeter is set to log Lavg and max at one minute logging intervals. If
the dosimeter runs for one hour, then it would log 60 Lavg results and 60 max levels. You would be able to see the average
and maximum levels for each minute of the one hour run time.
Maximum Level (Lmax)
The highest sampled sound level during the instrument’s run time allowing for the unit’s Response Time setting (Fast or
Slow).
Measurement Range
The decibel range within which the unit’s measurements are valid.
Minimum Level (Lmin)
The lowest sampled sound level during the instrument’s run time allowing for the unit’s Response Time setting (Fast or Slow).
Noise Floor
In a “Perfectly Quiet” room, the electrical noise produced by the microphone is approximately 35 dB on A-weighting and 45 dB
on C-weighting. These levels are known as the Noise Floor of the instrument. The Noise Floor can cause inaccurate
measurements at low measurement levels. Measurements must always be at least 5 dB above the Noise Floor to be valid.
Therefore, the lowest valid measurements of the dosimeter are approximately 40 dB on A-Weighting and 50 dB on C-
Weighting.
Peak Level
Peak is the highest instantaneous sound level that the microphone detects. Unlike the Max Level, the peak is detected
independently of the unit’s Response Time setting (Fast or Slow). Example: The peak circuitry is very sensitive. Test this by
simply blowing across the microphone. You will notice that the peak reading may be 120 dB or greater. When taking a long-
term noise sample (such as a typical 8-hour workday sample for OSHA compliance), the peak level is often very high.
Because brushing the microphone over a shirt collar or accidentally bumping it can cause such a high reading, the user must
be careful of placing too much emphasis on the reading.
PEL (Permissible Exposure Level)
The A-weighted sound level at which exposure for a Criterion Time, typically eight hours, accumulates a 100% noise dose.
Projected Time
The variable amount of time used to make a projected dose calculation from an actual dose measurement.
Random incidence (microphone)
This only applies to Class/Type 1 microphones. Measurements made in an area where sound waves are coming from all
directions, including reflections and diffractions. When the dosimeter is being used as a sound level meter in an area where
reflections and diffractions from nearby objects are present, use the Random Incidence Corrector with the microphone, and
angle the microphone at approximately 70 degrees. Most personal noise dosimetry applications do not require the random
incidence corrector, since they are not measured with a Class/Type 1 microphone.
Summary of Contents for Edge eg5
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Page 58: ...49 Appendix A Edge Block Diagram Analog Board ...
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Page 68: ...59 Appendix C Appendix C Measurement equations APPENDIX C ...