Feature Request: Automatic SPL Offset Calibration Using a Reference Calibrator

[Fernando Moraes Brasil Santos]

Dear AudioTool Development Team,

I would like to suggest an improvement to the SPL calibration process in AudioTool.

Currently, AudioTool allows the user to manually adjust the Global Offset during calibration. I believe this process could be made much easier and more reliable by adding an Automatic Calibration function.

Proposed feature

The idea is to make the calibration process similar to the procedure used by professional sound level meters and dosimeters.

The user would follow these steps:

1. Connect the measurement microphone to the device.
2. Place the microphone inside a calibrated acoustic calibrator.
3. Set the acoustic calibrator to a known reference level, for example 94.08 dB SPL.
4. Start the calibrator.
5. In AudioTool, select Automatic Calibration.

6. AudioTool asks the user:

   "What is the reference SPL level?"

7. The user enters the exact value provided by the calibrator's calibration certificate, for example:

   94.08 dB SPL

8. AudioTool measures the current SPL received from the microphone.
9. AudioTool automatically calculates the required Global Offset.
10. AudioTool applies the calculated offset so that the SPL displayed by AudioTool matches the reference level of the acoustic calibrator.

Example

Suppose the calibrated acoustic calibrator is certified at:

94.08 dB SPL

When connected to the microphone, AudioTool currently reads:

92.6 dB SPL

The application would automatically calculate the difference:

94.08 − 92.60 = +1.48 dB

AudioTool would then automatically apply a +1.48 dB Global Offset.

After calibration, the application should display approximately:

94.08 dB SPL

The user would not need to manually adjust the offset and repeatedly check the result.

Why I believe this would be useful

This would make the calibration process:

• Faster
• Easier for less experienced users
• Less prone to manual adjustment errors
• More consistent between different devices
• Easier to document and reproduce
• More similar to the calibration workflow of professional measurement equipment

It would also be useful to allow decimal values such as 94.08 dB, rather than requiring the user to calibrate only to an integer value such as 94 dB.

Possible user interface

For example, the current calibration menu could have an additional option:

Automatic SPL Calibration

After selecting it, AudioTool could display:

Place the microphone in the acoustic calibrator and start the calibrator.

Reference level:
[ 94.08 ] dB SPL

Current measurement:
92.60 dB SPL

[ CALIBRATE ]

After pressing CALIBRATE, AudioTool would calculate and apply the necessary Global Offset automatically.

It could then display:

Calibration completed

Reference: 94.08 dB SPL
Measured: 94.08 dB SPL
Applied Offset: +1.48 dB

Important consideration

I am specifically suggesting this as an automation of the existing Global Offset calibration process, rather than replacing the existing 1/3-octave microphone calibration functionality.

The purpose would simply be to establish the absolute SPL reference level automatically using a known acoustic calibrator.

For example, if the user has an acoustic calibrator with a calibration certificate stating that its actual output is 94.08 dB SPL, AudioTool should be able to use that exact value as the reference and automatically determine the required offset.

I believe this would be a relatively simple but very useful improvement to the calibration workflow, especially for users using calibrated measurement microphones and external acoustic calibrators.

Thank you for considering this feature.

Best regards,
Fernando