Speech enhancement apparatus and respirator masks including speech enhancement apparatus, as well as methods of enhancing speech transmission for the wearer of a respirator mask are described herein. In one or more embodiments, the speech enhancement apparatus and methods described herein detect acoustic energy within a first frequency range in the clean air envelope of a respirator mask and deliver compensating acoustic energy outside of the clean air envelope using a speaker. The compensating acoustic energy is, in one or more embodiments, delivered in one or more predetermined attenuated frequency ranges that cover less than all of the detected first frequency range. In one or more embodiments, the compensating acoustic energy may be delivered with an attenuated amplitude profile that uniform or that is non-uniform over the one or more attenuated frequency ranges.