Experimental investigation on finite-amplitude standing waves: Ⅰ. the properties of second harmonic

Experimental investigations on onedimensional finite-amplitude standing wave field are carried out comprehensively. The system of experiment is introduced. Emphases are placed on the discussion of second harmonic properties. Experimental results show that:the magnitude of second harmonic is a function of driving frequency at a constant fundamental frequency sound pressure level (L_p1). The curve of second harmonic sound pressure level (L_p2) can be approximately described by a harmonic function. The standing wave field in the closed tube can be divided into four regions in the frequency domain. In what is called "steady region", the theories proposed by Prof. MAA Dab-You predict the magnitude of second harmonic satisfactorily. The theory agrees well with experimental results. The trend of L_p2 can be explained qualitatively by further theories⁸.