We present the results of direct numerical simulations of power spectral densities for kinetic energy, convective entropy and heat flux for unsteady Rayleigh-Bénard magnetoconvection in the frequency space. For larger values of frequency, the power spectral densities for all the global quantities vary with frequency f as f−2. The scaling exponent is independent of Rayleigh number, Chandrasekhar’s number and thermal Prandtl number.