Multiscaled randomness: A possible source of 1/fnoise in biology

We evaluate the possibility that the 1/f fluctuations observed in many biological time series result simply from the fact that biological processes have many inputs with differing time scales. We present a stochastic model whose output is the summation of multiple random inputs (i. e. , different regulatory mechanisms). We derive the conditions under which the model reproduces the complex fluctuations and 1/f scaling observed in biological systems. Simulations demonstrate that if model parameters are unconstrained, the likelihood of generating 1/f noise is quite small. Thus, while the model can be used to generate 1/f^ noise with various scaling exponents, it is unlikely that the 1/f behavior observed in many biological systems is due only to the fact that these systems are regulated by many different inputs acting on different time scales. 1996 The American Physical Society.