4mm Noise-Canceling Electret Condenser Microphone CUI Devices 4mm Noise-Canceling Electret Condenser Microphone (ECM) is a 4mm diameter, 1.5mm depth noise-canceling microphone sized to fit applications with a very small footprint. The CUI Devices 4mm Noise-Canceling ECM is an analog device that offers -44dB sensitivity and features a top and bottom port. This ECM operates over a -40°C to +85°C temperature range and features a 500µA current rating.