The noise fluxes of the cavity Langevin force in the case of three longitudinal modes with the different damping rates are investigated for a class –A laser. The Maxwell-Bloch equations of motion are thus solved in the presence of three cavity Langevin forces associated with the simultaneous oscillations of cavity central mode and its left and right adjacent modes. The notion of correlation function is implemented to calculate the noise fluxes of stimulated and spontaneous emission radiations to gather with that of laser pumping. The results indicate that the cavity Langevin force of each of three oscillating modes makes a direct contribution in producing the noise fluxes of other two oscillating modes. It is finally demonstrated that by increasing the damping rate of cavity mirrors, the noise fluxes of laser radiation and spontaneous emission are increased