In one aspect, the present invention relates to a system for monitoring wind turbines, wherein image and acoustic monitoring, in particular, is performed. In order to further improve, for example, the maintenance, safety and efficiency of a wind turbine, it is desirable to monitor additional parameters of the wind turbine. A wind turbine is provided, wherein acoustic and optical sensors are employed to monitor the operation of the wind turbine. In one embodiment, the optical sensor images a particular location in the nacelle housing when the acoustic sensor detects a sound emanating from that location in the nacelle housing. A method for monitoring a wind turbine is described wherein when a deviation between the operating acoustic spectrum and the reference acoustic spectrum exceeds the threshold, the component that generated the operating acoustic spectrum is imaged.