All current iOS devices include built-in microphones. These mics tend to be very consistent from one unit to the next, and are wide-range. However, Apple does include a very steep high-pass filter (which cuts low frequencies), presumably as a wind and pop filter. The low-frequency roll-off for the internal mic in these devices is very steep, on the order of 24dB / octave starting at 250Hz.
However, we are able to turn off the low-frequency rolloff filter, thereby resulting in fairly flat response. Of course this is still basically a cell phone mic, and the performance is limited. Also, often we find that real-world mics get dirty or damaged in usage and performance degrades over time.
Also, in most of the later models, there is a limiter — making SPL measurements, as well as more sophisticated measures such as Impulse Response difficult to make accurately. Again, we can disable this limiter, so we can work around this.
We test all new iOS devices as they are released, and design custom frequency compensation files that are applied automatically. This can be disabled on the Settings-Global Audio page, but we recommend that you leave it turned on.
You can also create your own microphone calibration file, if you would like to override the default compensation in AudioTools.
And, check out our generic Audio Devices page.
Changes in iPhone Analog Hardware
Although we disable the limiter, some years ago Apple stopped giving us the ability to control the input gain of the built-in mic. For all modern devices, this limits the maximum possible SPL to around 104 dB, flat.
In the cases where we can control the microphone gain, two ranges will be are present on the Input Select screen for each module.
Select Low Range for the best performance in the 30 – 90 dB SPL range, and select High Range for the best performance in the 45 – 120 dB SPL range. This does vary a bit by device, but in most cases works very well.
Using the Headset Output Signal
All recent iOS devices have removed the audio i/o connector (headset jack). If you have a device with one, this section applies to you.
The headset connector is a 4-pin TRRS 1/8″connector on the iOS device. The additional pin is for the mic input. If you want to use the output from the headset jack (for example as a pink noise source) while still using the internal mic, make sure your cable has a 3-conductor plug. This will tell the iOS device to leave the internal mic operational.
There are also splitters available, for example by SoniTalk, that provide a 3-pin headset output and also include a mic similar to the Apple mics.
Lightning Input – Analog or Digital?
All Lightning connectors allow digital audio only. The USB C connector also supports digital audio.
Digital Audio Input Devices
Starting with iPhone 4, Apple implemented a digital audio link in the 30-pin connector, and then in the Lightning and USB C connectors. This provides a way to get high-quality professional audio into and out of iOS devices. All current iOS devices use this audio interface method.
Our iAudioInterface2 connects to the iOS device using digital audio, and provides a phantom-power microphone input with up to 50dB of gain, a second balanced line input, a balanced line output, and a Toslink digital audio output. It includes a built-in li-ion battery system, and can charge the attached iOS devices when the charger is plugged in.
iAudioInterface2 also is tightly connected to our AudioTools app, providing gain control, mode control, and access to advanced features such as impedance measurement.
iTestMic2 uses the same digital audio link, and also avoids all Apple analog electronics.
Over time, more iOS digital audio devices will become available.
Type 1 & 2 Microphones
See our Microphone Type 1 & 2 Certification page for information about ANSI and ISO specification compatibility.