An apparatus and a method for computing a Speech Absence Probability (SAP), and an apparatus and a method for removing noise by using the SAP computing device and method are provided. The provided SAP computing device for computing the SAP indicating probability that speech is absent in a m<th> frame, from a first through Nc<th> posteriori (Nc means the total number of channels) Signal to Noise Ratios (SNR) calculated with regard to the m<th> frame of a speech signal and a first through Nc<th> predicted SNRs predicted with regard to the m<th> frame, includes: a first through Nc<th> likelihood ratio generators for generating a first through Nc<th> likelihood ratios from the first through Nc<th> posterior SNRs and the first through Nc<th> predicted SNRs, and outputting them; a first multiplying unit for multiplying the first through Nc<th> likelihood ratios by a predetermined a priori probability, and outputting the multiplication results; an adding unit for adding each of the multiplication results received from the first multiplying unit to a predetermined value, and outputting the added results; a second multiplying unit for multiplying the added results received from the adding unit and outputting the multiplication result; and a inverse number calculator for calculating inverse number of the multiplication result received from the second multiplying unit and outputting the calculated inverse number as the SAP. Therefore, since the accuracy of the calculated SAP is high, noise can be efficiently removed from the speech signal that may have noise and an enhanced speech signal with an enhanced quality can be provided. <IMAGE>
Speech absence probability estimation and noise removal