TSI Quest EDGE EG-4P, Руководство пользователя

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Glossary of Terms B-3
Dose Related to the Criterion Level, a dose reading of 100% is the maximum allowable
exposure to accumulated noise. For OSHA, 100% dose occurs for an average
sound level of 90 dB over an 8 hour period (or any equivalent exposure). By using
a TWA reading rather than the average sound level, the time period is no longer
explicitly needed. A TWA of 90 dB is the equivalent of 100% dose. The dose will
double (halve) every time the TWA increases (decreases) by the Exchange Rate.
Example: OSHA uses an Exchange Rate of 5 dB. Suppose the TWA is 100 dB.
The dose would double for each 5 dB increase over the Criterion Level of 90 dB.
The resulting dose is therefore 400%. If the TWA was instead equal to 80 dB then
the dose would halve for each 5 dB below the Criterion Level. The resulting dose
would be 25%. When taking noise samples less that the full workday, dose is an
easy number to work with because it is linear with respect to time. Example: If a
0.5-hour sample results in 9% dose and the workday is 7.5 hours long, then the
dose for the full workday would be a 135% dose (7.5 / 0.5 x 9%). This is computed
making the assumption that the sampled noise will continue at the same levels for
the full 7.5-hour workday.
Exchange Rate
(ER
– also known as
the Doubling Rate )
Exchange rate refers to how the sound energy is averaged over time. Using the
decibel scale, every time the sound energy doubles, the measured level increases
by 3 dB. This is the 3 dB exchange rate that most of the world uses. For every
increase of 3 dB in the time weighted average, the measured DOSE would double.
Some organizations such as OSHA in the U.S. have argued that the human ear
self-compensates for changing noise levels and they felt that the 3 dB exchange
rate should be changed to more closely match the response of the human ear.
OSHA currently uses a 5 dB exchange rate, which would mean that the reported
DOSE would double with every 5 dB increase in the time weighted average. The
exchange rate affects the integrated reading Lavg, DOSE, and TWA but does not
affect the instantaneous sound level.
Field Calibration
(vs. Factory
Calibration), pre-
calibration, post-
calibration To be sure the dosimeter is functioning within specified tolerance limits, it should
be returned to the factory annually for a factory calibration. To verify that the
dosimeter is measuring properly during normal use, field calibrations should be
performed. Pre-calibration is performed prior to any data being recorded by the
dosimeter. During a pre-calibration, the dosimeter level may be adjusted to match
the calibrator output level. Post-calibration is a simple verification that the
instrument has remained in calibration throughout the measurement period.
Free field setting
(microphone) Measurements made in an area without sound reflections, diffractions and
absorptions caused by nearby objects (including the operator). Sound waves are
free to spread out continuously, like ripples on a pond, without reflection. When
making free field measurements with a dosimeter set up for use as a sound level
meter, the microphone is typically pointed directly at the sound source.
Hearing
Conservation (HC) The Occupational Safety and Health Administration (OSHA) and Mine Safety and
Health Administration (MSHA) provide regulatory standards for hearing
conservation programs. In addition, the American Conference of Governmental
Industrial Hygienists (ACGIH) provides industrial standards for hearing
conservation programs.
http://www.osha.gov/ , http://www.msha.gov/ ,
http://www.acgih.org/home.htm .
Hertz (Hz) Unit of vibration frequency in cycles per second.