When a device is communicating through wireless connections such as GSM or Wi-Fi, noise in audible range, called buzz noise, is often generated in an audio system and disturbs the audio signal quality. While the buzz noise problem has been found in wireless devices for a long time, there is little understanding of the buzz noise generation mechanism. In this paper, a buzz noise model is proposed considering demodulation and transfer function of the microphone IC front-end. The proposed model is verified through several experiments using recorded audio data in a tablet. Especially, the buzz noise caused by real Wi-Fi signals is reproduced by using the model and compared to recorded buzz noise.