Existing passive materials are inadequate to cope with many problems in the control of noise, vibration and reverberation. It is only within quite recent times that active systems have been given consideration for the control of sound. The electronic sound absorber is an example of an active‐type sound absorber. The electronic sound absorber consists of a microphone, amplifier, and loudspeaker connected in an inverse feedback manner. The electronic system reduces the effective acoustical impedance in the vicinity of the absorber. As a consequence, the electronic sound absorber may be used in the manner of a conventional sound absorber or as a zone‐type sound reducer. The electronic vibration reducer consists of a sensor, amplifier, and driver connected either in negative or positive feedback fashion. The electronic vibration reducer may be used to isolate vibrating machines or to reduce the vibration of machines.