Voice processing technique for human cerebral activity measurement

Variations in the chaotic characteristics of the human uttered voice are strongly related to the speaker´s fatigue condition. When we define a time-local exponent to evaluate the time-local characteristics of the uttered voice time domain signal and calculate it periodically or continually, it is possible to observe changes in human cerebral activity. The time-local exponent, called the Cerebral Exponent, can be defined like the first Lyapunov exponent. If it is possible to calculate the Cerebral Exponent of uttered voice signals in real-time, the proposed chaotic voice analysis technology can be considered as a technology to install a tachometer on the brain of a speaker.