Perceptual entropy rate estimates for the phonemes of American English

We estimated the perceptual entropy rate of the phonemes of American English and found that the upper limit of the perceptual entropy of voiced phonemes is approximately 1.4 bit/sample, whereas the perceptual entropy of unvoiced phonemes is approximately 0.9 bit/sample. Results indicate that a simple voiced/unvoiced classification is suboptimal when trying to minimize bit rate. We used two different methods for the entropy estimation, and the results of both methods show that short segments of unvoiced speech are approximately Gaussian