The behavior of 1/f noise effective intensity in two-phase percolation systems and percolationlike systems with an exponentially wide distribution of bond resistances is reviewed. Monte Carlo simulations on random resistor networks are performed. For a two-phase system the numerical values of noise critical exponents ϭ1.54Ϯ0.025, Јϭ0.61Ϯ0.02, wϭ6.31Ϯ0.25, and wЈϭ6.9Ϯ0.25 are found in agreement with theoretical analysis performed with the help of a hierarchical model of a two-phase percolation system. For a system with an exponentially wide spectrum of bond resistances, i.e., a system in which bonds take on resistances rϭr 0 exp͑Ϫx͒, where ӷ1 and x is a random variable, it is assumed that in the individual resistors the noise generating mechanism obeys the form ͕␦r 2 ͖ϳr 2ϩ . In this case the effective noise intensity C e ϵS⍀, where S is the relative power spectral density of system resistance fluctuations and ⍀ is the system volume, is given by C e ϳ m exp͑Ϫx c ͒, where 1Ϫx c is the percolation threshold. The exponent m is ''double universal,'' i.e., it is independent of lattice geometry and of the microscopic noise generating mechanism. Numerical simulations performed for ϭ1 and 0 give approximately mХ2.3 and confirm this ''double universality'' of the exponent m. The connections between 1/f noise effective intensity and effective susceptibility in a two-phase weakly nonlinear percolation system are also established. ͓S1063-651X͑96͒04405-4͔ PACS number͑s͒: 64.60.Ak, 64.60.Ht * Electronic address: snar@carrier.kiev.ua

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