terça-feira, 2 de fevereiro de 2010

Information Rate

(Lawrence Rabiner)

(...) Here we see the steps in the process laid out along a line corresponding to the basic information rate of the signal (or control) at various stages of the process. The discrete symbol information rate in the raw message text is rather low (about 50 bps [bits per second] corresponding to about 8 sounds per second, where each sound is one of about 50 distinct symbols). After the language code conversion, with the inclusion of prosody information, the information rate rises to about 200 bps. Somewhere in the next stage the representation of the information in the signal (or the control) becomes continuous with an equivalent rate of about 200 bps at the neuromuscular control level, and about 30,000-50,000 bps at the acoustic signal level.
The steps in the speech-perception mechanism can also be interpreted in terms of information rate in the signal or its control and follows the inverse pattern of the production process. Thus the continuous information rate at the basilar membrane is in the range of 30,000-50,000 bps, while at neural transduction stage it is about 2000 bps. The higher-level processing within the brain converts the neural signals to a discrete representation, which ultimately is decoded into a low-bit-rate message.

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