The receptivity of laminar boundary layer flow to leading edge vibrations has been studied experimentally. The experiments reported on in this paper include (1) a stable case and (2) an unstable case. These experiments identify the forcing field imposed by the vibrating leading edge and track the subsequent development of the unstable Tollmien-Schlichting waves. Detailed velocity measurements around the leading edge help in the identification of the source of such unstable boundary layer waves. The near-singular nature of the response of the fluid around the vibrating leading edge is found to be responsible for the generation of unstable boundary layer waves.