Comments on “Particle gathering and microstreaming near ultrasonically activated gas-filled micropores” [J. Acoust. Soc. Am. 84, 1378-1387 (1988)]

It is suggested that surface forces on small particles may be important in particle gathering experiments. These forces may explain the observations of Miller [J. Acoust. Soc. Am. 84, 1378-1387 (1988)] that particles accumulate on the surface of a membrane containing ultrasonically activated gas-filled micropores, whether the particles are more or less dense than the fluid medium.