An experiment is conducted in which plate vibration is used to successfully cancel a sound‐excited Tollmien–Schlichting wave. With sound excitation, transition to turbulence in the boundary layer occurs at a streamwise Reynolds number (Rx) of 1.2×106. The addition of plate vibration delays the transition toRx=1.8×106. In the laminar region of the boundary layer (atRx=0.97×106) the addition of plate vibration reduces the level of streamwise velocity fluctuations from more than 100 times to only two times the particle velocity of the sound excitation.