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Comparative studies between competing engineering techniques are complex, since the comparison depends upon the application. This paper focuses upon periodic vibration and noise in regional turboprops and in fuselage-mounted twin-jets. The vibrations under discussion are propeller harmonics of the turboprop and unbalance tones of the turbojet. Broadband noise (wind noise and combustion noise) is not discussed since no mature active technology is applicable to this type of noise. A large body of both active and adaptive/passive technology is applicable to periodic noise. Much of this technology is proprietary and unavailable to the public. Competing approaches are not openly compared; rather each technology is selectively promoted by its marketing team. This paper attempts a comparison. The authors of this paper are members of an engineering team that has recently finished the development of some adaptive/passive technologies.