A respirator mask comprising: a mask body configured to define a clean air envelope between the mask and the mouth and nose of wearer and exhibiting an acoustic attenuation profile over a first frequency range; and a speech enhancement apparatus (20; 120) comprising: a microphone (34; 134) configured for attachment to the mask body, the microphone (34; 134) further configured to detect acoustic energy within the clean air envelope when attached to the mask body; a speaker (36; 136) configured to produce acoustic energy outside of the clean air envelope; a controller (30; 130) operably connected to the speaker (36; 136) and the microphone (34; 134), wherein the controller (30; 130) is configured to: receive a speech signal from the microphone (34; 134), wherein the speech signal is indicative of acoustic energy detected by the microphone (34; 134) within the first frequency range; and deliver an output signal to the speaker (36; 136), wherein the output signal is configured to cause the speaker (36; 136) to emit compensating acoustic energy, characterised in that the compensating acoustic energy is emitted in one or more predetermined attenuated frequency ranges, and wherein the compensating acoustic energy comprises a predetermined attenuated amplitude profile such that the compensating acoustic energy exhibits an amplitude less than 6 dB greater than the acoustic attenuation profile of the mask body over at least 90% of each predetermined attenuated frequency range of the one or more predetermined attenuated frequency ranges. a mask body configured to define a clean air envelope between the mask and the mouth and nose of wearer and exhibiting an acoustic attenuation profile over a first frequency range; and a speech enhancement apparatus (20; 120) comprising: a microphone (34; 134) configured for attachment to the mask body, the microphone (34; 134) further configured to detect acoustic energy within the clean air envelope when attached to the mask body; a speaker (36; 136) configured to produce acoustic energy outside of the clean air envelope; a controller (30; 130) operably connected to the speaker (36; 136) and the microphone (34; 134), a microphone (34; 134) configured for attachment to the mask body, the microphone (34; 134) further configured to detect acoustic energy within the clean air envelope when attached to the mask body; a speaker (36; 136) configured to produce acoustic energy outside of the clean air envelope; a controller (30; 130) operably connected to the speaker (36; 136) and the microphone (34; 134), receive a speech signal from the microphone (34; 134), wherein the speech signal is indicative of acoustic energy detected by the microphone (34; 134) within the first frequency range; and deliver an output signal to the speaker (36; 136), wherein the output signal is configured to cause the speaker (36; 136) to emit compensating acoustic energy, characterised in that the compensating acoustic energy is emitted in one or more predetermined attenuated frequency ranges, and wherein the compensating acoustic energy comprises a predetermined attenuated amplitude profile such that the compensating acoustic energy exhibits an amplitude less than 6 dB greater than the acoustic attenuation profile of the mask body over at least 90% of each predetermined attenuated frequency range of the one or more predetermined attenuated frequency ranges.