An offshore wind farm can include at least two wind energy installations for generating electrical power from wind, at least two acoustic warning devices, and a visibility measuring device for detecting visibility. After detection of a visibility below a visibility limit value, an activation signal can be applied to the at least two acoustic warning devices. One or more synchronization modules can be provided which determine the points in time of the acoustic signals to be emitted by at least one of the acoustic warning devices in relation to the acoustic signals of the other acoustic warning devices. Accordingly, this facilitates the navigation along an offshore wind farm and enables safe circumnavigation. Also, the impression of a contiguous area can be conveyed to the ships by the synchronized emission of the warning signals.