Phonetics and Speech Science

Speech is normally used for verbal interaction between at least two persons, called interlocutors. Researchers have measured rate of information transfer by speech across languages and have found a relatively constant value across languages. Spoken language is very different from written language in a number of important ways. Speech is perceived by hearers based primarily on the acoustic information contained in the speech signal, but modified by a number of factors, including top--down processing. Perception is made more complex by factors such as the necessity of segmenting and variance in the signal caused by individual differences and conditions of the speech environment. Speaker normalization is required by the hearer. The ear and hearing mechanism play an important role in speech perception. Rapid pressure variation of sound is converted to fluctuations in the viscous fluids of the inner ear or cochlea. This conversion occurs through the middle ear in which the principle of the lever, and the principle of collecting energy over a large area and concentrating it, play roles.