407355 Datasheet, PDF (6/17 Pages) Extech Instruments Corporation. – Noise Dosimeter with PC Interface

9. Use the MODE button at any time to view the elapsed time of the test. Press the
MODE button until the TIME display icon appears. Now the elapsed time will appear in
hours and minutes. Press the RUN button again to return to the %DOSE display.
10. To end the noise survey, press and hold the RUN key for 3 seconds. Read the
accumulated noise exposure value on the LCD.
11. Testing notes:
Never shout into the microphone as this will affect the test.
To obtain reliable data, the user’s activities must reflect a typical working day.
For best results, test over the course of several days and average the %DOSE
Refer to the dosimetry parameter descriptions below:
Event Select
Press the EVENT button to enter the EVENT mode. Each time the EVENT button is
pressed the LCD increments the Event bank (E1 through E5). Each bank is a memory
location. The user can store (or write over) the data in any of these locations. Each bank
location (E1, for example) is displayed on the LCD along with the stored data. If data is
present in a bank, the bank ID blinks. To erase data in a bank, press and hold the RESET
button until the display ID stops blinking.
% DOSE
The unit of measure, % DOSE, is used to quantify noise exposure measured during a
work shift. 100% dose is the maximum allowable noise exposure in accordance with
OSHA, MSHA, DOD, ACGIH, and ISO standards. Most standards specify Criterion
Level, Exchange Rate, Response Time, and Frequency weighting for the dosimeter as
discussed next.
CRITERION LEVEL (Lc)
To take an on-site noise exposure survey in accordance with standards such as OSHA
and MSHA, the dosimeter’s Criterion Level must first be set. The 100% DOSE
parameter discussed above is determined by the following equation: 100% DOSE =
Criterion Level for 8 hours. Each country has a unique Criterion Level (most countries,
including the U.S., use 90dB). The Criterion level is selectable (80, 84, 85, or 90dB).
Select the appropriate level per the Programming section of this manual.
EXCHANGE RATE (ER)
Exchange rate is best illustrated by example; refer to the following example: Since
100% DOSE = Criterion Level for 8 hours, a person would receive 50% DOSE in 4
hours if the noise level equals the Criterion Level setting. Now consider a Criterion
Level of 90dB, a noise measurement of 95dB (5dBA higher than the Criterion Level),
and an Exchange Rate of 5dB; in this example a 100% DOSE would be received in
only 4 hours. This is because with a 5dB Exchange Rate, a 5dB increase in sound level
is considered a doubling of the DOSE. Other Exchange Rates can be selected (3, 4, 5,
or 6dB). Refer to the local regulations or standards.
FAST (F) SLOW (S) RESPONSE TIME
Set the response time to Fast (F) to capture quick bursts of sound such as discharging
firearms, fireworks, hammering, and other impulse noises. Use the Slow (S) setting if
the noise under test is more of a continuous drone or background din. The Slow setting
is typically specified by OSHA and MSHA standards for use in noise surveys. Refer to
the Programming section of this manual to set the response time.
THRESHOLD LEVEL (Lt)
The threshold level is the sound level at which the 407354 begins to integrate noise into
the exposure test. For example, if the threshold level (Lt) is set to 85dB, the meter will
integrate all noise that equals or exceeds 85 dB. Sound levels below this threshold
would not be included in the dose calculation. See the Programming section to change
the level. The Threshold Level can be set from 70 to 90dB in 1 dB steps.
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407355 Version 2.4 9/07