Hearing losses caused by deficiencies in a person's outer or middle ear may be compensated for by converting received sounds to vibrations and transmitting the vibrations to the skull bone (2). Bone-conduction hearing devices (27) may transmit such vibrations transcutaneously or percutaneously. In both cases, a precise determination of the magnitude of the vibrations applied to the skull bone (2) is needed for determining the person's bone-conduction hearing thresholds as well as for calibrating the hearing devices (27). The present invention provides a device (1, 27, 37) and a method, which allow determination of the applied vibrational force with better precision than prior art devices and methods. This is achieved by placing an accelerometer (21) on the countermass (11) of the vibrator (1) that generates the vibration signal. The accelerometer (21) thus provides an acceleration signal representative of an acceleration of the countermass (11), from which acceleration signal the vibrational force may be determined precisely and reproducibly.