Power-law behavior in the power spectrum induced by Brownian motion of a domain wall.

We show that Brownian motion of a one-dimensional domain wall in a large but finite system yields a omega(-3/2) power spectrum. This is successfully applied to the totally asymmetric simple exclusion process with open boundaries. An excellent agreement between our theory and numerical results is obtained in a frequency range where the domain wall motion dominates and the discreteness of the system is not effective.