like Mr Optimist has stated, the excitation of natural frequencies in the cabin and wing can create such buzzing sounds. I recall some issues with an airline, I think Air France, who had complaints over buzzing sounds on the A330 ( I think), it turned out that the frequency of the EDP at high RPM (e.g. during take-off) excited resonant frequencies which lead to 'buzzing' sounds in the cabin. I think this was rectified by increased number clamps and potentially an attenuator.