A hearing device comprising an implantable prosthetic system comprising a receiver coil and a vibrator; a memory and an external audio processor device comprising a microphone configured to transform a received sound into an electrical input signal, a signal processor configured to process the electrical input signal into a processed electrical data signal, a transmitter coil configured to inductively transmit data signals and/or power, across the skin of a hearing device user, to the receiver coil, and a detection device configured to detect if the external audio processor device or the transmitter coil is within a predefined distance from the implantable prosthetic system or to detect if a coupling coefficient between the transmitter coil and a receiver coil is within a predefined value range; characterised in that the detection device comprises a parameter measuring circuitry, wherein the parameter measuring circuitry in response to a controlled signal of predefined characteristics applied to the transmitter coil is configured to measure a quantity value associated with the transmitter coil and/or the external audio processor device for determining the distance or coupling coefficient between the transmitter coil and the receiver coil, and furthermore, the detection device is configured to I) access a characteristic quantity value stored in the memory and the characteristic quantity value being defined in accordance with frequency curve parameters of the vibrator of the hearing device, wherein the frequency curve parameters defining force output of the vibrator as a function of frequency; II) compare the measured quantity value with the accessed characteristic quantity value; and III) generate a compared result based on the comparison, representing the determined distance or coupling coefficient between the transmitter coil and the receiver coil. an implantable prosthetic system comprising a receiver coil and a vibrator; a memory and an external audio processor device comprising a microphone configured to transform a received sound into an electrical input signal, a signal processor configured to process the electrical input signal into a processed electrical data signal, a transmitter coil configured to inductively transmit data signals and/or power, across the skin of a hearing device user, to the receiver coil, and a microphone configured to transform a received sound into an electrical input signal, a signal processor configured to process the electrical input signal into a processed electrical data signal, a transmitter coil configured to inductively transmit data signals and/or power, across the skin of a hearing device user, to the receiver coil, and I) access a characteristic quantity value stored in the memory and the characteristic quantity value being defined in accordance with frequency curve parameters of the vibrator of the hearing device, wherein the frequency curve parameters defining force output of the vibrator as a function of frequency; II) compare the measured quantity value with the accessed characteristic quantity value; and III) generate a compared result based on the comparison, representing the determined distance or coupling coefficient between the transmitter coil and the receiver coil.