This paper presents results of experimental and theoretical studies of the plasma wave and the drum effect in the photoacoustic (PA) spectra of CdSe and CdMgSe samples. The PA experimental amplitude and phase frequency characteristics of these samples have been shown. The experimental results have been interpreted in two different PA models: in the model of a drum effect and in the plasma wave model. The obtained results have been discussed and presented in this paper. They indicate that the values of extracted parameters depend on the model of the PA signal. To distinguish between the plasma and the drum model the aluminium foil test is proposed. From the results obtained one can conclude that the plasma model used for interpretation of the PA characteristics yields overestimated values of the thermal diffusivity and poor PA phase fittings. The results obtained using the drum model agree well with other measurements conducted on the investigated samples. (C) 2016 Elsevier B.V. All rights reserved.