A viseme is any of several

speech sound In phonetics (a branch of linguistics), a phone is any distinct speech sound. It is any surface-level or unanalyzed sound of a language, the smallest identifiable unit occurring inside a stream of speech. In spoken human language, a phone is thus ...

s that look the same, for example when

lip reading Lip reading, also known as speechreading, is a technique of understanding a limited range of speech by visually interpreting the movements of the lips, face and tongue without sound. Estimates of the range of lip reading vary, with some figures as ...

. Visemes and

phonemes A phoneme () is any set of similar speech sounds that are perceptually regarded by the speakers of a language as a single basic sound—a smallest possible phonetic unit—that helps distinguish one word from another. All languages con ...

do not share a one-to-one correspondence. Often several phonemes correspond to a single viseme, as several phonemes look the same on the face when produced, such as ; as well as and ). Thus words such as ''pet, bell,'' and ''men'' are difficult for lip-readers to distinguish, as all look like alike. On one account, visemes offer (phonetic) information about place of articulation, while manner of articulation requires auditory input. However, there may be differences in timing and duration during natural speech in terms of the visual "signature" of a given gesture that cannot be captured by simply concatenating (stilled) images of each of the mouth patterns in sequence. Conversely, some sounds which are hard to distinguish acoustically are clearly distinguished by the face. For example, in spoken English and can often sound quite similar (especially in clusters, such as 'grass' vs. 'glass'), yet the visual information can disambiguate. Some linguists have argued that speech is best understood as bimodal (aural and visual), and comprehension can be compromised if one of these two domains is absent. Visemes can often be humorous, as in the phrase "elephant juice", which when lip-read appears identical to "I love you". Applications for the study of visemes include

speech processing Speech processing is the study of speech signals and the processing methods of signals. The signals are usually processed in a digital representation, so speech processing can be regarded as a special case of digital signal processing, applied to ...

speech recognition Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers. It is also ...

, and computer facial animation.

See also

References

Further reading