In general, extraneous energy, from natural or man-made sources, that impedes the reception of desired signals. 2. A coherent emission having a relatively narrow spectral content, e. G. , a radio emission from another transmitter at approximately the same frequency, or having a harmonic frequency approximately the same as, another emission of interest to a given recipient, and which impedes reception of the desired signal by the intended recipient. Note: In the context of this definition, interference is distinguished from noise in that the latter is an incoherent emission from a natural source (e. G. , lightning) or a man-made source, of a character unlike that of the desired signal (e. G. , commutator noise from rotating machinery) and which usually has a broad spectral content. 3. The effect of unwanted energy due to one or a combination of emissions, radiation, or inductions upon reception in a radiocommunication system, manifested by any performance degradation, misinterpretation, or loss of information which could be extracted in the absence of such unwanted energy. 4. The interaction of two or more coherent or partially coherent waves, which interaction produces a resultant wave that differs from the original waves in phase, amplitude, or both. Note: Interference may be constructive or destructive, i.e., it may result in increased amplitude or decreased amplitude, respectively. Two waves equal in frequency and amplitude, and out of phase by 180°, will completely cancel one another. In phase, they create a resultant wave having twice the amplitude of either interfering beam.