I performed computer and laboratory experiments modelling avalanches on a "sandpile" to investigate the theory of self-organized criticality. The experiments consisted of a one-dimensional cellular automaton on the computer and a "continuous hourglass" of glass beads in the laboratory. Each was maintained at the critical slope and the flowing particles were studied. The automaton exhibited self-similar behavior with a power spectrum of S ~ f t, where t = -0.0±0.1, which coincided with the findings of Bak, Tang, and Wiesenfeld. The noisy signals obtained from the laboratory experiment did not exhibit power-law spectra and did not yield results similar to the cellular automaton.