Preliminary studies on respiratory activity in speech

Abstract

Work at Edinburgh University in the 1950s, summarized by Ladefoged [Three Area of Experimental Phonetics (Oxford University Press, Oxford, 1967)] claimed that (1) the mean power for speech was provided by actions of the respiratory muscles. The external intercostals check the outgoing airflow when speaking with high lung volumes, and the internal intercostals, rectus abdominis, and other muscles become more active as lung volume decreases. (2) Stressed syllables are produced by increases of respiratory power above the mean, usually by further activity of the internal intercostals. Hixon and Weismer (1995) pointed out technical limitations of these early studies, but wrongly indicated that they were of little value. These studies have been replicated with modern methods to measure intramuscular EMG and airflow and pressure. The two subjects studied to date follow the pattern previously described. In addition the improved techniques indicate that speakers exercise further control by bringing in stabilizing antagonistic muscles. These results are consistent with the general hypothesis that the central nervous system is able to control subglottal pressure by using various combinations of passive elastic and active muscle forces, thereby achieving motor equivalence and acoustic invariance over a wide range of lung volumes.