NOVELTY - The remote sensor (10) has a light emitting device driven by a direct current (DC)component; and a second detector responsive to the light emitting device and connected to the first detector to subtract at least a portion of the DC component from the composite signal producing a modified signal. An amplifier responsive to the modified signal detects vibrations of the surface. The first detector is responsive to electromagnetic radiation and generates composite signal including DC and alternating current (AC) components.    USE - Passive, remote sensor for remote observation of surfaces in monitoring e.g. tunnel entrances and buildings. Uses include but are not limited to walls, solar panels, window panes, floors, ceilings, auto body skin, windows, foliage and other vibration structures. Can also be used for identifying different types of automotive engines or even individual cars by their unique signature observed remotely.    ADVANTAGE - Allows clandestine monitoring and detection and recovering of voices in a room, building, vehicle, or other structure. The sensor can be deployed on the ground or in connection with aircraft or other airborne devices or a satellite to detect foliage vibrations and/or canopy monitoring of equipment operation or other interesting signatures hidden under a canopy. The sensor can be made small, portable, battery operated and still have a range of 500-1,000 feet or greater. Packages a radiometer to minimize electromagnetic pickup and uses batteries for power. Sensor vibration is eliminated to avoid sensor jitter caused by the audio and vibration signals directly moving the sensor and hence the sensor field-of-view contaminating acoustic detections. The sensor is placed on a tripod with vibration-isolated blocks used by astronomers and additional stiff foam.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method of passively and remotely measuring vibrations based on electromagnetic radiation scattered off a vibrating surface.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic three-dimensional view of a sensor system.    Remote sensor (10)    Optical subsystem (12)    Housing unit (14)    Tripod (16)