Mapping the phonetic structure of humpback whale song units

The striking similarities of time-frequency spectrograms of voiced human speech and humpback whale vocalizations suggested a common targeted frequency-modulated phonetic basis. To map the sub-unit structure of humpback whale song units, a time-frequency contour segmentation, extraction, and classification procedure was developed and tested on streaming voiced human speech. When the procedure was applied to humpback vocalizations and the tone-pairs of the two most energetic “vocal fold” harmonic frequencies were plotted in x-y coordinates, the plot exhibited properties of an optimally structured Shannon “modem symbol constellation” diagram of 14 distinct sub-regions and 60 acoustically distinct sub-unit symbols. The humpback symbol constellation is structurally comparable to the tone-pair symbol constellations of English and Asian language vowels. The information entropy and plot of the humpback sub-unit symbol set’s cumulative probability vs. ranked frequency distribution function are nearly identical to the entropy and Zipf power law profile of the English language phoneme set. The precise specification of the sub-unit structure of more than one hundred song units analyzed to date has resulted in a three-fold expansion in the number of unique units identified in previous studies, suggesting that the “lexicon” of humpback song units is potentially much larger than cited in the literature.