Non linear frequency compression with particular reference to helium speech.

Abstract

Helium speech is a term used to denote the speech produced by a deep sea diver breathing a Helium Oxygen mixture. The replacement of nitrogen in normal air by Helium solves some of the physiological problems associated with diving under pressure. However, it introduces severe distortion in diver's speech. The principal distortion is the nonlinear frequency expansion in the formant frequencies. A real time enhancement system has been constructed and partially tested. The design specification for this unscrambler has been generalised to enable the system to correct most of the Helium speech distortions. The system operates in the frequency domain and is based on the wide band analysis-synthesis technique. The system's algorithm for correcting the Helium speech distortion, is flexible and could be easily changed to satisfy different diving conditions. The possible use of the system to study Helium speech characteristics has also been considered.

Date of Award	1984
Original language	English
Awarding Institution	University of Bath