Abstract: Generally,conventional anti-noise transmitters and receivers have limited low-frequency capability of noise reduction,while more and more sound energy of the modern high-intensity noise environment converges in the middle-and low-frequency range.Active anti-noise transmitter and receiver,developed from the active ear defender,supply these devices not only with the benefit of advanced low frequency anti-noise capability,but also a selectivity in the reduction of sound.This later virtue ensures a high speech intelligibility at the time while the signal-noise ratio of speech communication is highly raised in a middle-and low-frequency noise environment.On the basis of ref.1,a detailed discussion on the principle,structures and experimental results of active antinoise transmitters and receivers is given in this paper.