The noise generated by thermal agitation of electrons in a conductor. The noise power, P, in watts, is given by P = kTf, where k is Boltzmann's constant in joules per kelvin, T is the conductor temperature in kelvins, and f is the bandwidth in hertz. Note 1: Thermal noise power, per hertz, is equal throughout the frequency spectrum, depending only on k and T. Note 2: For the general case, the above definition may be held to apply to charge carriers in any type of conducting medium. Synonym Johnson noise.