This paper presents the design and characterization of an intensity modulated optical lever microphone. Optical microphones (OM) have an inherent immunity to environments hostile to electronics due to the spatial separation of the electronics and the acoustic field under test. Theoretical equations for the sensitivity, minimum detectable signal, and frequency response are presented. Physical phenomena responsible for limiting the microphone minimum detectable signal (MDS) are identified, and a model is developed for use with a laser diode as the light source. The characterization of the microphone indicates an overall sensitivity of 0.5 mV/Pa, a linear response up to 132dB ref. 20 uPa, and an overall noise floor of 70dB measured at 1kHz over a 1Hz bin.