Adhesion testing of film-on-substrate structures by surface acoustic waves is a complex issue. Indeed, the fluctuations of some parameters like the film thickness can lead to misinterpretation of the experimental results. Additionally, in laser-ultrasonics, the positions of the generation and detection sources influence the excited and detected parts of the Rayleigh modes as well as the behavior of these surface acoustic waves when the adhesion decreases. While most studies published are focused on the generation of these waves on the film surface, we use an excitation at the interface between the film and the substrate in order to study the adhesion of the structure. To that end, a transparent PVC film with a quasi-constant thickness is placed in direct contact with an aluminum substrate and the laser pulses used are focused through the film at the interface. Finite element simulations are first presented to study the influence of the source position for several adhesion degrees then experimental results complete this work.