A study of the travelling-wave parametric amplification mechanism in non-linear acoustics

Abstract The possibility of obtaining parametric amplification by the use of the non-linearities inherent in acoustic wave propagation has been mentioned by many authors. In this paper, an assessment is made of the factors which may contribute to the existence of negative-resistance effects in the case of freely travelling acoustic waves; such effects would lead to amplification at the signal frequency itself, as opposed to the “up-converter” mechanism used in previous proposals.