Charles Darwin once wrote, “I cannot doubt that language owes its origin to the imitation and modification, aided by signs and gestures, of various natural sounds, the voices of other animals, and man’s own instinctive cries”.
The link has long been established and many different accounts of this exist, as also stated by Walden et al (1993), Munhall et al (2004),and P. Erber, (1975) when he states in the Journal of Speech and Hearing Disorders, “Hearing-impaired persons usually perceive speech by watching the face of the talker”. What is of importance to us in this study is the idea that “signs and gestures” are at the roots of modern language.
In the field of respiratory protection, speech intelligibility is perceived to be the quality of sound transmission through a respiratory interface. The paper given here aims to explore how speech intelligibility is a complex issue in part comprising of sound transmission, as well as other more subtle but no less important aspects, such as the visual cues gained from lip movement.
The data and results gathered from this investigation of respiratory interfaces aims to demonstrate how the interaction between hearing and vision is perceived in speech intelligibility and how this phenomenon may be used to advantage manufacturers of Respiratory Protective Device systems.
With an understanding of this phenomenon, a manufacturer may create a respiratory interface that helps persons with impaired hearing who need to wear respiratory protection in their chosen occupation, be useful members of the workforce. It may also help completely able bodied people to communicate if their hearing is temporarily rendered obsolete by an unforeseen event.
The following article was written while the author held the position of “Development Engineer” at “Avon Protection”. Avon Protection sponsored the research and all experiments were performed at their headquarters with the following address: Avon Protection, Hampton Park West, Melksham, Wiltshire, SN12 6NB,UK. The research was presented at the ISRP conference in 2012, Boston. The author was the recipient of the Bob Bentley Bursary Award.