When a wireless device is connected to wireless networks such as Wi-Fi and GSM, annoying noise in audible frequency range, named buzz noise, can appear in the audio system. The characterization and quantification of buzz noise provide the theoretical fundamental for solving this problem. It has been discovered that the buzz noise is converted from the radio frequency (RF) signal through the unexpected square-law demodulation in the microphone. Based on the buzz noise generation mechanism, this paper developed a two-port network model to quantify the RF noise coupling path and the conversion from RF noise to buzz noise. The results have been validated by repeating the measurements with different RF coupling path.