> 4 | Analog Audio Interfaces

> To employ audio interfaces it is recommended to use a microphone (D=6mm) with a sensitivity of at least –44 ±3 dB/Pa at 2V and 2kΩ (0dB=1V/Pa, 1kHz). As a rule, smaller microphones provide a higher noise floor than bigger ones. The microphone should be equipped with two internal EMI capacitors for GSM 900/1800Hz bands. External ESD protection is required to protect the microphone from damage. Even a high-quality microphone should be placed at least 5cm away from the antenna.
> Keep in mind that big level differences between the two audio inputs may cause cross talk from the higher level input to the lower level input.