Noise glitches can cause functional errors or failures if they are latched into sequential cells. Thus it is very important to determine or characterize noise failure criteria of sequential cells. However, characterizing noise failure criteria of sequential cells is very computationally expensive because it often requires multiple transient simulations with different clock waveform shapes and alignments, known as clock sweeping. In this paper, we propose a new technique that eliminates the clock sweeping by using the metastable point of sequential cells. Our experiments with industrial circuits have shown that the proposed method is on average 58X faster than the conventional clock sweeping method and its average error is only 2.4%.