20
Views on the Edge
Definitions of data log values and views
| Views on the |
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| Explanation |
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| Edge |
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| LTWA |
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| with its average level computed over an |
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| Slow response, and a 5 dB exchange rate. |
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| All sound levels at or above the threshold level (cutoff level) are averaged into the |
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| calculations relating to noise exposure. TWA is calculated with no cutoff, with cutoff 1 (typically 80 |
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| dB), or with cutoff 2 (typically 90 dB). |
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| If the time period is less than 8 hours, the TWA will be less than the Lavg/Leq. |
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| If the time period is more than 8 hours, the TWA will be more than the |
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| Lavg/Leq. |
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| LAE |
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| Sound Exposure Level (SEL) – The sound exposure level averages the |
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| sampled sound over a one second period. Assuming the sampled run time to |
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| be greater than one second, SEL is the equivalent |
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| would be equal in energy to the noise that was sampled. SEL is typically |
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| measured using a 3 dB exchange rate without a threshold. (LAE is not used by |
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| OSHA.) |
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| Dose |
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| Dose - Related to the Criterion Level, a dose reading of 100% is the maximum |
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| allowable exposure to accumulated noise. For OSHA, 100% dose occurs for |
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| an average sound level of 90 dB over an 8 hour period (or any equivalent |
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| exposure). (Please see Glossary of Terms for more details, page 59). |
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| UL |
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| Upper Limit - is the amount of time that the sound level exceeds a preset |
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| level (the Upper Limit). |
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| Response Level |
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| Typically, noise is not constant. Using a response of Slow or Fast simply |
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| (Fast, Slow) |
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| flattens the noise fluctuation and makes the sound level easier to work with. |
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| Slow: 1 second (1,000 milliseconds, or msec) |
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| Fast: 0.125 second (125 milliseconds) |
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| RT |
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| Run Time - The overall time of your noise study. |
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| Weighting |
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| A and C weighting are types of frequency filters that cover the frequency range of human hearing |
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| (20Hz to 20 kHz). |
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| (A, C) |
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| ∙ “A” weighting: The “A” weighted filter attempts to make the dosimeter respond closer to |
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| the way the human ear hears. It attenuates the frequencies below several hundred hertz as |
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| well as the high frequencies above six thousand hertz. “A” weighted measurements are |
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| often reported as dBA. |
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| ∙ “C” weighting: provides a fairly flat frequency response with only slight attenuation of the |
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| very high and very low frequencies. “C” weighting is intended to represent how the ear |
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| perceives sound at high decibel levels and is often used as a “flat” response when LINEAR |
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| is not available. “C” weighted measurements are often reported as dBC. |
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| Table |
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Page 20 | eg4 & eg3 |