Disturbances in the freestream, such as sound or vorticity, enter the boundary layer as small fluctuations of the basic state and excite unstable modes. The receptivity stage of the transition to turbulence process is the least understood, but is extremely important because it provides the initial conditions on the disturbance amplitude. Here we consider disturbances consisting of only plane acoustic waves and we ignore freestream turbulence and artificial disturbances within the boundary layer. Moreover, in order to compare with theory and computations, the main objective of this experiment is to isolate the influence of the leading edge on the initial amplitudes of TS waves. Pitfalls of the experiment are discussed in a critical manner. The theory and DNS are described and compared with the measurements with good results.