Optical microphone assembly

A method of manufacturing an optical microphone assembly, wherein the optical microphone assembly comprises:

• a micro-electromechanical system (MEMS) component comprising an interferometric arrangement, the interferometric arrangement comprising a membrane and at least one optical element spaced from the membrane;
• at least one photo detector;
• a light source;
• and
• a housing defining an aperture, wherein the aperture is provided with an acoustically transparent cover which does not create an acoustic cavity between the acoustically transparent cover and a side of the membrane that is in fluid communication with an exterior of the optical microphone assembly;
• the method comprising:
• mounting the MEMS component such that the MEMS component is sealed to the housing with the interferometric arrangement positioned between the light source and the acoustically transparent cover such that the MEMS component closes the aperture and does not create an acoustic cavity between the acoustically transparent cover and the side of the membrane that is in fluid communication with the exterior of the optical microphone assembly;
• positioning the light source to provide light to the interferometric arrangement such that a first portion of said light propagates along a first optical path via said interferometric arrangement and a second portion of said light propagates along a second, different optical path via said interferometric arrangement such that at least one of said first and second portions is reflected by the reflecting surface of the membrane, thereby giving rise to an optical path difference between the first and second optical paths which depends on a distance between the membrane and the optical element;
• and
• positioning the at least one photo detector in a spaced relationship with the MEMS component such that the MEMS component has a displacement relative to the at least one photo detector in a direction perpendicular to a reflecting surface of the membrane and such that the at least one photo detector is arranged to detect at least part of an interference pattern generated by said first and second portions of light dependent on said optical path difference.