A lip-reading assessment for profoundly deaf patients

Abstract

To understand spoken sentences, first the acoustic information is processed, and secondly linguistic knowledge is applied (Fry, 1961; Kalikow et al., 1977). The more the spoken message contains linguistic redundancies in the form of lexical, syntactical and semantic constraints, the less the listener needs to rely on processing the details of the acoustic signal. For normal listening conditions there is usually enough information available to make an unambiguous decision about the spoken message. However, when the acoustic signal is degraded, more reliance is placed on the context in which the message was spoken (Miller et al., 1951). For some hearing-impaired individuals the auditory signal is permanently degraded. In addition, if people are totally or profoundly deaf, speech is usually perceived via lip-reading alone. This is usually difficult because not all phonemes can be clearly distinguished visually. For example, some phonemes form homophenous groups, i.e. they look the same on the lips; such a group would be the bilabial plosives and nasal /p, b, m/. Since the information reaching the individual is incomplete, greater reliance must also be placed on linguistic skills and on the context in which the message is spoken.