3M eg4 Leq Equivalent Level, Logging, Maximum Level Lmax, Measurement Range, Minimum Level Lmin

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Appendix B

Glossary of Terms

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.

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.

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