Abstract: When the non-uniformity caused by medium disturbance must be considered, the wave equation is nonlinear. A general introduction to the effects of medium disturbance on wave propagation based on Lighthill wave equation is given in this paper. The emphases are on the phenomenon of 'scattering of sound by sound', which is the problem about a sound wave in propagation modulated by the medium disturbance caused by another coexist sound wave, and especially on the theoretical and experimental researches of parametric acoustic receiving array, which is based on the concept derived from 'scattering of sound by sound'. Historically, most of the researches on parametric acoustic receiving array are about its characteristic of narrow beam-width, but the emphasis in this paper is about using parametric acoustic receiving array to achieve extremely high array gain for the detection of low frequency signals. The experiments of our own and others are introduced, and the key technical difficulties applying parametric receiving array in practical projects and the possible solution methods are analyzed. In addition, the effect of a sound wave in propagation modulated by ultra-low frequency wave flow and its applications in foreign countries are also introduced, especially about the experiment conducted by a Soviet-Union team, in which this effect was used for the so-called super-long-distance submarine detection.