There is provided a method of operating a hearing assistance system comprising a hearing device (10, 110, 210), which comprises means (24) for stimulating a user's hearing and which is worn at one of the user's ears, and a remote device (12, 30, 40) spaced apart from the hearing device. The method comprises: establishing a wireless link (26) between the hearing device and the remote device for transmitting signals from the remote device to the hearing device, and operating the system in a base mode; detecting whether a source (28) of radio frequency signals interfering with the wireless link and having a transmission power changing according to a predictable scheme between low power regimes and high power regimes is present in the vicinity of the hearing device; and operating the system in an interference mode as long as the presence of such source of periodic signals interfering with the wireless link is detected, in which interference mode the transmission of the signals from the remote device to the hearing device is synchronized to the detected power scheme of the interfering signals in such a manner that the signals are transmitted only during the low power regimes.