A crucial step in acoustical flow estimation is determining the correct breath phase (inspiration/expiration). Determining breath phases from the lung sounds is a relatively easy task as the breath sound intensity during inspiration is significantly higher than that during expiration; hence, it results in very high accuracy in respiratory phase identification [2, 11, 12]. However, this characteristic is not exhibited in tracheal sounds; thus making phase detection from only tracheal sounds a challenging task. Therefore, the current flow estimation method requires two channel recording: tracheal sounds for flow estimation and lung sounds for breath-phase identification.