A driven diffusive lattice-gas model with stochastic dynamics is used to study, via a Monte Carlo simulation, the fluctuations in the particle density and the lifetime of the particles in the system. The scaling properties of the power spectrum S(f) and the lifetime distribution function D(t) exhibit a crossover from (1/f3)- to (1/f2)-noise behavior, with β 1.5, when the drive is sufficiently strong to induce a characteristic time scale. We argue that the scaling behavior with β 1.5 is governed by the stochastic nature of the dynamics whereas deterministic dynamics leads to β 1.