In this paper, we propose a speech enhancement method by exploiting masking properties of human auditory system. The masking properties are exploited to calculate a masking threshold. The spectral components which lie above the threshold are audible to human listeners. These audible spectral components in the proposed method are suppressed as a predefined attenuation factor of the original noise. The evaluation is conducted in the experiments. The experimental results show that the proposed method provides significant performance compared to the conventional approaches.