Using Dosimeter
A Dosimeter measures a persons cumulative noise exposure over time.
It was designed to help prevent hearing loss by allowing a user to monitor
the amount of noise that they have been exposed to, which over time can correlate
to hearing damage.
Typically, an 8 hour workday is
considered, and the % noise exposure is shown as a "Dose". The idea is
to keep the Dose below 100% for a day. There are several standards for
the formula for computing Dose %. All of them use an "exchange rate",
which may be 3 or 5dB, and a "criterion level".
If the user is exposed to the criterion
level (for example perhaps 85dB) for 8 hours, they would hit exactly
100% dose. If you add the exchange rate dB, to get to perhaps 88dB,
then 100% dose will be reached in 4 hours.
Different SPL filters and decay methods are specified depending on the standard.
The actual formula is somewhat more complex, and can include thresholds, below which no dose accumulates, and other factors.
Operation
Choosing the Method
Tap the wrench icon to bring up the
Setup page, and select between ISO, OSHA HC, OSHA PEL, and NIOSH. Check
your local legal requirements to see which standard you need to use.
All tests default to an 8 hour test time, which can be overridden if desired.
ISO
Criterion level 85, exchange rate 3.0, SPL Leq, A weighting. There is
no threshold, so all sound contributes to dose, although low SPL levels
do not add much.
OSHA HC
This is one of the methods used in the
USA, and
it is based on allowing 90 dBA exposure over 8 hours. It uses a 5dB
exchange rate, so as sound increases 5dB the length of time to 100%
dose is halved. It uses A weighting and Slow decay with a threshold at
80 dB.
OSHA PEL
This is another method used in the USA, and
it is also based on allowing 90 dBA exposure over 8 hours. It uses a 5dB
exchange rate.
It uses A weighting and Slow decay with a threshold at 90 dB.
NIOSH
NIOSH is used in most
EU countries. It is very similar to OSHA, although it uses an 85dBA
normal exposure level, and a 3dB exchange rate. The threshold is 80dB, SPL Slow mode, A weighted.
Dose Used / Remaining
Normally a Dosimeter will show the amount of dose used, starting at 0%
and increasing to 100%. You can opt to see Dose % remaining. In this
case it starts at 100% and decreased to 0 %.
SPL Meter
Dosimeter also includes an SPL meter, which can be setup independently
from the dosimeter settings. You can select Z/A/C wieghting (Z =
unweighted), Slow/Fast/Peak/Impulse/Leq10, where Leq10 is a rolling
linear average of the last 10 seconds.
You can also set 2 trigger levels which will cause the SPL meter to
change color if the current reading exceeds the trigger level
Running the Test
Tap the Play/Pause button on the lower left corner of the screen to
begin the test. The SPL Meter will begin showing the current SPL level,
and the dose calculations will begin.
As the dose increases, the box will start to fill up, or empty out,
depending on the Used/Remaining setting. The color will change from
green to yellow to red, as the dose gets closer to 100%.
The SPL Meter reading will also change from green to yellow red, based on the trigger level settings.
Dosimeter will continue to run in the background, so you can shut off
the display, or exit the app (the red recording bar will show on the
top of the screen), and when you return to Dosimeter you the results
will be showing.
If you need to pause the test, for example this would be used during a
break at work, tap the Play/Pause button as needed to stop and start
the test.
Tapping the Stop button will end the test. You can still save the file, until you press Play to start a new test.
Saving and Recalling Files
To save the current test results of Dosimeter, tap the folder icon on
the lower left side of the toolbar on the bottom of the screen. This
will being up the Save / Recall page.
Save the file by entering a file name and tapping Store File on the the popup that appears.
To recall a stored file, select it from the list to highlight it, and
then tap Recall to bring up the results. Note that recalling a stored
file will replace the current test data.
After recalling a test, you can continue the test, by pressing the Play/Pause button to start the test running.
To clear a recalled test, press the Stop button.
When you save the file, the app stores all of the current values, and
it also stores a list of minute-by-minute values that include the Leq
over the minute, and the Peak value reached in that minute. The filter
setting of the SPL meter (Z/A/C) is used for these calculations.
These values are saved in the .txt file, which may be opened in Excel
or Numbers.
Screenshots
Tap the screen shot button on the upper right toolbar to save an image of the test in your photo roll.
As with all iOS apps, you can take a screenshot of the entire screen by
simultaneously pressing the Home and Power buttons on the device. The
image will then be in your photo roll.