Towards Augmentative Speech Communication

Speech is the most natural form of communication for human beings and is often described as a unimodal communication channel. However, it is well known that speech is multimodal in nature and includes the auditive, visual, and tactile modalities. Other less natural modalities such as electromyographic signal, invisible articulator display, or brain electrical activity or electromagnetic activity can also be considered. Therefore, in situations where audio speech is not available or is corrupted because of disability or adverse environmental condition, people may resort to alternative methods such as augmented speech. In several automatic speech recognition systems, visual information from lips/mouth and facial movements has been used in combination with audio signals. In such cases, visual information is used to complement the audio information to improve the system’s robustness against acoustic noise (Potamianos et al., 2003). For the orally educated deaf or hearing-impaired people, lip reading remains a crucial speech modality, though it is not sufficient to achieve full communication. Therefore, in 1967, Cornett developed the Cued Speech system as a supplement to lip reading (O.Cornett, 1967). Recently, studies have been presented on automatic Cued Speech recognition using hand gestures in combination with lip/mouth information (Heracleous et al., 2009). Several other studies have been introduced that deal with the problem of alternative speech communication based on speech modalities other than audio speech. A method for communication based on inaudible speech received through body tissues has been introduced using the Non-Audible Murmur (NAM) microphone. NAM microphones have been used for receiving and automatically recognizing sounds of speech-impaired people, for ensuring privacy in communication, and for achieving robustness against noise (Heracleous et al., 2007; Nakamura et al., 2008). Aside from automatic recognition of NAM speech, silicon NAM microphones were used for NAM-to-speech conversion (Toda & Shikano, 2005; Tran et al., 2008). 15