An anomalous photoacoustic effect is produced when a suspension of carbon particles in water is irradiated by a high-power, pulsed laser. The photoacoustic effect has an amplitude on the order of 2000 times that produced by a dye solution with an equivalent absorption coefficient and gives a distinctly audible sound above an uncovered cell. Transient grating experiments with carbon suspensions show a doubling of the acoustic frequency corresponding to the optical fringe spacing of the grating. The effect is thought to originate in high-temperature chemical reactions between the surface carbon and the surrounding water.