Apparatus and methods for attenuating environmental interference are described. A wearable monitoring apparatus includes a housing configured to be attached to the body of a subject and a sensor module that includes an energy emitter that directs energy at a target region of the subject, a detector that detects an energy response signal - or physiological condition - from the subject, a filter that removes time-varying environmental interference from the energy response signal, and at least one processor that controls operations of the energy emitter, detector, and filter.
