There is described a method for evaluating a level of noise in a biosignal the method comprising receiving a time signal representative of a biological activity, the time signal comprising a biological activity component and a noise component； determining a modulation spectrum for the time signal, the modulation spectrum representing a signal frequency as a function of a modulation frequency； from the modulation spectrum determining a first amount of modulation energy corresponding to the biological activity component and a second amount of modulation energy corresponding to the noise component determining an indication of the level of noise using the first and second amounts of modulation energy； and outputting the indication of the level of noise.
