3M eg3 用户手册
61
Appendix B
Glossary of Terms
053-644, Rev E
Page 61
eg4 & eg3
Leq (Equivalent Level)
The true equivalent sound level measured over the run time. The term LEQ is functionally the same as
LAVG except that it is only used when the Exchange Rate is set to 3 dB and the threshold is set to
none.
none.
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
(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.
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
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.
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
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
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.
be careful of placing too much emphasis on the reading.