All of our apps come pre-calibrated for the typical iPhone built-in and headset mic, but you can adjust the calibration if you have access to a professional, calibrated meter to compare it to.

See our Microphones and iOS Devices page for more microphone information.

Note that the default calibration is +7.0dB.

To adjust the calibration of SPL Meter, RTA, or any other app, follow these steps:

* For SPL or SPL Meter, first set your reference meter to the same settings as the app (choose A and Slow, for example, on both meters). For RTA or FFT, the app is reading unweighted, fast, so set your reference meter to match that.

* Now play pink noise or white noise through your system to get a reading on your reference meter in the range of 70-85dB. It is a good idea to turn down the bass, so that you are comparing mid-range frequencies.

* Go to the settings page on the app (flip the screen over by tapping the small letter i)

* Select the internal mic setting in the app

* Adjust the Trim field using the + and - buttons until the dB field on the app matches the dB reading on your reference meter.

That's it, you're now fully calibrated. But remember, we do NOT recommend the use of a Radio Shack SPL meter for reference, they are just not accurate enough.