SP395 SoundPro Audio Integrator
Form7492
Operation Manual
100
SPL Calibration
The Audio Integrator has been fully factory calibrated and should not require in-the-field
calibration. However, you can check and recalibrate the microphone SPL calibration with a
known accurate SPL calibrator.
The SPL Setup & Calibration feature permits microphone calibration
.
Calibrating a microphone using an SPL calibrator
If you have access to an SPL calibrator you do not need the calibration value, nor do you need to
know the units. You will just connect the microphone to the calibrator and change the Cal value
until you read the correct value on the screen.
1.
Connect microphone -
Connect the microphone(s) and turn on phantom power, if
required.
2.
Turn on the calibrator -
Attach the calibrator to the microphone and turn it on.
3.
Set gain -
Set the input gain to the highest value that does not result in a clip indication
(Clipping results in blinking gain field in the top tool bar)
4.
Calibration Values -
Adjust the Cal fields until the value shown on the screen matches the
calibrator output level.
5.
Exit function -
Exit the function to store the values into non-volatile memory.
When you click on the “<” to return to the menus, the new calibration constants are stored in
non-volatile memory.
Calibrating a Microphone – Entering Calibration Constants
A second method of calibrating a microphone is to enter the microphone’s known calibration
constants into the SPL calibration screen on the SP395. When purchasing a microphone, such as
the Sencore Precision Low Noise Microphone ANSI Type 1 (#SP-PMIC1), the mic is supplied
with the calibration constants values. These are values typically specified in units of dBV/Pascal
(dBV/Pa).
The calibration constant values may also be specified in dBV/ubar. If so, you need to convert
these values to dBV/Pascal for entry into the SP395 SPL calibration display screen. To convert
dBV/ubar to dBV/Pascal, add 20 dB to the dBV/ubar value. For example: If you are provided a
reading of -60 dBV/ubar, adding 20 dB results in -40 dBV/Pascal.
Formula:
dBV/ubar + 20 dB = dBV/Pascal
Note: If the specification is rated in mV/Pascal you will need to convert it to a dBV/Pascal
value. Use the following formula.
dBV = 20 x log (mV/1000)
