This application describes a noise reduction apparatus (800) for a microphone device (100) having an acoustic port (110). The apparatus has a spectrum peak detect block (301) for receiving a microphone signal (SMIC) and determining, from the microphone signal, at least one characteristic of a resonance peak (202) associated with the acoustic port of the microphone. The at least one characteristic may comprise a resonance frequency (fH) and/or quality factor (QH). A noise reduction block (801) is configured to process the microphone signal based on the resonance characteristic so as to reduce noise in the processed microphone signal due to said resonance. The noise reduction block may apply a function which is the inverse of the determined resonance characteristic.