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.

If you are using iAudioInterface2, see this page.

Also, in AudioTools, you can apply a microphone calibration correction file, by following these instructions.

Note that the default calibration for the internal iOS device mic is +7.0dB.

Calibration for External Mics

AudioTools now includes a new advanced microphone calibration system. With this system, the app recognizes any new audio input source when it is first connected, identifies it, and creates a new group of calibrations for that input source.

Then the next time that input source appears, the calibrations that apply to it are recalled. For example, if you plug in one of the devices below the app will automatically switch to its calibration.

Headset mic — There are some inexpensive headset mics available that may be used with AudioTools. Although there is no big advantage to using them, still it is convenient to store a calibration for that mic. AudioTools will now see the headset mic and apply its calibration.

iAudioInterface2 — The app has always recognized iAudioInterface2 when it is plugged in, but now every iAudioInterface2 is identified by its unique serial number, so if your office uses more that one, you will get the calibrations that apply to that specific unit.

iTestMic and iPrecisionMic — Since each iTestMic and iPrecisionMic transmits its calibration when it is plugged in, there is only one calibration that will apply. This will happen automatically.

USB Audio Interface — If are are using iPad, you can connect the Apple Camera Connection Kit to use some USB audio interfaces. The app will recognize this, and switch to the calibration for that unit. Note that the app cannot distinguish between different USB interfaces, so if you use more than one you will need to select the correct one from the Microphone Calibration screen.

Calibration Procedure

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.

Calibrating the Studio Six Digital CM-125 with iAudioInterface2 

Open the included pdf on the USB drive, and find the “Sensitivity” number in dB. It should be approximately -40.

Connect the microphone to iAudioInterface2, and with iAudioInterface2 connected to AudioTools, open the Microphone Settings page.

Low Range:

Select +45 gain. Compute the using this formula.  Make sure that you get the minus signs in the formula.

Low Trim = -51 – sensitivity

The result should be within a few dB of -10.0. Enter this in the Trim field.

High Range:

Select +25 gain, and set the trim according to this formula, which is based on the Low range trim.

High Trim = Low Range Trim – 1.5

This should be within a few dB -11.5. Enter this in the Trim field.

If you have a UMIK-1 and have downloaded the calibration file for it, there will be line that looks like:
“Sens Factor =-2.200dB, SERNO: 7136249”
You will need to convert the dB value to two AudioTools Trim factors that you will enter on the Microphone Settings page. To get the Low Range Trim value, add 9.4 to the supplied value. To get the High Range Trim value, add 0.4. These values will bring the UMIL-1 into calibration in AudioTools. In this example the values to enter would be:
Low Range 7.20
High Range -1.80
To apply the frequency compensation values in the UMIK-1 file, follow the procedure explained on the Microphone Calibration Files page.

Dayton Audio IMM-6 Calibration

We find that entering -32.0 Trim for Low Range or High Range gets you pretty close.