This paper presents an analysis of the gated Gaussian impulsive noise and its effects on M-ary Quadrature Amplitude Modulation (M-QAM) schemes. In the approach, both amplitude variation and noisy pulse duration can be characterized as a modulation of the impulsive noise component by a discrete (binary or m-ary) random process. New exact expressions are presented for the probability density function, autocorrelation function and power spectral density of the noise, as well as for the bit error probability of M-QAM, considering the maximum a posteriori probability optimum receiver. An important aspect of the proposed approach is the fact that the discrete random process incorporates the main parameters of the impulsive noise, such as amplitude, duration, instants in which the noise is added and time intervals between instants in which the noise is added.