Note: A faster method of displaying this dialog is to click the button on the Standard toolbar.
In step number 2, we have selected . If you select , you first need to calibrate your sound card before calibrating your microphone (or another transducer). The calibration must be used if you do not have a calibrator but the sensitivity of your microphone is known (e.g. 20 mV/Pa). Use also if you have an external input amplifier with fixed gain steps and want to adjust the gain steps of this amplifier, or if you are using WinMLS to perform both electrical measurements and measurements using a microphone.
Note that the number shown in the figure above is updated after the calibration. It shows the maximum input level that WinMLS is able to measure (a higher level will result in digital clipping). In this case it is 130.654 dB SPL. If you want to measure SPL higher than 130.654 dB, e.g. 140 dB, you have two alternatives:
• If WinMLS is set to control the sound card mixer, and the input volume is not set to minimum during the calibration, you can measure higher input levels just by decreasing the sound card mixer input volume slider.
Type in or choose the correct settings for your calibrator. In the figure above 1000 Hz and 94 dB is selected. You will find the output level of your acoustic calibrator in the calibrator documentation (usually it is also written on the calibrator).
The WinMLS mixer dialog will pop up to give you the levels, if not, you can also find the levels on the status bar found at the very bottom of the WinMLS program . The level should be in the range -30 dBFS to -1 dBFS. If the level is less than –30 dBFS, it should be increased (a warning will be given if this is the case when you perform the calibration).
Click the button to perform the calibration. This will exit the dialog box if the calibration is successful. It takes a few seconds and afterwards the new conversion factor and date and time for the calibration is displayed as shown below.