Non-contact OFL measurement for bone conductive transducers

For bone conductive headphone, whereas, the input is same in the above case but the output will be in terms of mechanical vibration measured as an vibrating force. IEC standard 118-9 defines a method of expressing the ration between input and output level as an acousto-mechanical sensitivity measured on a mechanical coupler. This paper proposes a non-contacting output force level measurement system for the place of the mechanical coupler. The proposed measurement system utilizes the Michelson interferometry for detecting the displacement of the loading mass. The acceleration of the mass can be obtained by the second order differentiation of the observed signal for time.