If sound waves interact with an electrode upon which a gas is being liberated by electrolysis, an alternating potential of the same frequency is developed on the electrode relative to the bulk of the surrounding solution. The effect has been studied in the case of a polarized hydrogen electrode with pulse-modulated ultrasonic waves at a frequency of 200 kc/sec. Under favorable conditions the amplitude of the alternating potentials is of the order of 10−3 volt per dyne/cm2. The effect has been found to depend on the formation of gas bubbles at the electrode surface. Although the amplitude of the effect is a function of the conductance of the solution and the current density, it is essentially independent of the hydrogen ion concentration of the solution in the range 10−4 to 10−8 molar and is also independent of the specific metal upon which the hydrogen gas is being liberated. On the basis of these results, the effect is attributed primarily to the modulation of the i-r drop in the solution immediately adjacent to the electrode surface by periodically expanding and contracting gas bubbles.