A helium speech decoder of the type that may be used to an advantage by drs living, working, and communicating in and from deep water habitats is disclosed as including a microphone, a digital-to-analog converter, a battery of pairs of shift registers, a like battery of select gate circuits, an analog-to-digital converter, and earphones. A programmable generator produces a plurality of control signals which are timely supplied to the aforementioned components as necessary to effect the concerted operation thereof in such manner as to cause a pitch scaling, reduction, or decoding of the human speech that is spoken in a pressurized helium-oxygen environment, without substantially changing the syllabic or word rate thereof. A filtered fundamental frequency of said human speech is optionally added to the decoded portion thereof to enhance the fidelity thereof.
