The decrease in intensity of a signal, beam, or wave as a result of absorption of energy and of scattering out of the path to the detector, but not including the reduction due to geometric spreading. Note 1: Attenuation is usually expressed in dB. Note 2: "Attenuation" is often used as a misnomer for "attenuation coefficient," which is expressed in dB per kilometer. Note 3: A distinction must be made as to whether the attenuation is that of signal power or signal electric field strength.