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85 dB for 8 Hours = 1 Pa
2
H
FAST
:
Fast Response
A Measurement Time Constant, or averaging time, of 125 milliseconds. When Fast is used, SPL will closely track a
fluctuating noise source.
LAVG
:
Average Level
The average sound level, in decibels, for the measurement period based on either a 4, 5, or 6 dB Exchange Rate (ER).
If the Exchange Rate (ER) is 3 dB, then LAVG becomes LEQ.
LEQ
:
Equivalent Continuous Sound Level
The average sound level for the measurement period based on a 3 dB Exchange Rate (ER).
If the Exchange Rate (ER) is 4, 5, or 6 dB, then LEQ becomes LAVG.
MAX
:
Maximum Level
The highest sound pressure level, in decibels, that occurs during a given time period.
MIN
:
Minimum Level
The lowest sound pressure level, in decibels, that occurs during a given time period.
PEAK
:
Absolute Unweighted Peak
The highest instantaneous sound pressure, in decibels, that occurs during a given time period.
PDOSE
:
Projected Dose
A percentage computed by measuring dose for some time period and extrapolating it to a different time period.
(Example: 50% Dose / 4 hrs = 75% Projected Dose / 6 hrs)
SEL
:
Sound Exposure Level
The constant sound level in decibels which, if lasting for one second, would deliver the same amount of acoustical
energy as that delivered over the entire measurement period.
SEL is usually measured with a 3 dB Exchange Rate. However, the dosimeter will also allow SEL to be measured with
4, 5, or 6 dB Exchange Rates. On a printout, the exchange rate is shown in parenthesis.
SLOW
:
Slow Response
A Measurement Time Constant, or averaging time, of 1 second. When Slow is used, SPL will not track a quickly
fluctuating noise source, but will produce an averaged reading.
SPL
:
Sound Pressure Level
A quantity in decibels equal to the sound pressure divided by 20 uPa (0.00002 N/m
2
), times 20. The word "Level"
indicates that the sound pressure is a certain level above the reference level. The SPL is displayed each second as the
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maximum value (Slow or Fast Response) for the previous 1 second period.
STATISTICS
:
% Time Statistical Distribution
For a given run time, the percentage of time that a sound level occured at a specific dB level.
TIME HISTORY
:
Time History
A Printout list (and Graph) showing how levels were accumulated over time. A printout can be made for each of the
following: Lavg, Lmax, and Peak.
TL
:
Threshold Level
A preset level in decibels below which sound is not accumulated or averaged into LAVG, LEQ, or Dose.
TWA
:
Time Weighted Average
The sound level in decibels that is accumulated for any time period but with its average level computed over an 8 hour
time period.
#
If the time period is less than 8 hours, the Time Weighted Average will always be less than the Average Sound
Level (LAVG).
#
If the time period is more than 8 hours, the Time Weighted Average will always be more than the Average
Sound Level (LAVG).
TWA is usually measured with A Weighting, Slow Response, and a 5 dB Exchange Rate. However, the dosimeter will
allow A or C-Weighting, Slow or Fast Response, and a 3, 4, 5, or 6 dB Exchange Rate.
UL
:
Upper Limit Time
The total time that the sound level exceeds a preset level.
Typical Setups
OSHA NOISE COMPLIANCE
Threshold = 90dB
Exchange Rate = 5dB
Weighting = A
Response = Slow
OSHA HEARING CONSERVATION
Same as above except with Threshold = 80dB
DEPARTMENT OF DEFENSE NOISE COMPLIANCE
Threshold = 80dB
Exchange Rate = 4dB
Weighting = A
Response = Slow
IEC NOISE MONITORING
Threshold = OFF
Exchange Rate = 3dB
Weighting = A
Response = Slow