One example discloses a magnetic induction device, including: a transmitter configured to induce a magnetic signal in a structure; wherein the structure is coupled to a sub-structure; a controller configured to characterize the structure so as to identify a first frequency range of the magnetic signal that resonates with the structure; wherein the controller is configured to identify a second frequency range that resonates with the sub-structure; wherein the controller is configured to select a frequency for the magnetic signal within the first frequency range that has a harmonic frequency in the second frequency range; and wherein the transmitter is configured to transmit the magnetic signal into the structure at the selected frequency.