24. The apparatus of claim 15 , wherein said post-suppression coefficient calculator determines a plurality of lower limit values of noise suppression coefficients based on said speech-versus-noise relationship, compares said vector of noise suppression coefficients with said lower limit values of noise suppression coefficients, and determines said vector of post-suppression coefficients by using said plurality of lower limit values or said noise suppression coefficients depending on a result of the comparison.
24. The apparatus of claim 15 , wherein said post-suppression coefficient calculator determines a plurality of lower limit values of noise suppression coefficients based on said speech-versus-noise relationship, compares said vector of noise suppression coefficients with said lower limit values of noise suppression coefficients, and determines said vector of post-suppression coefficients by using said plurality of lower limit values or said noise suppression coefficients depending on a result of the comparison. 25. The apparatus of claim 24 , wherein said post-suppression coefficient calculator determines said plurality of lower limit values of noise suppression coefficients further based on a first correction factor lower limit value and a second correction factor lower limit value.