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. Author manuscript; available in PMC: 2015 Oct 1.
Published in final edited form as: Trends Cogn Sci. 2014 Jul 18;18(10):543–553. doi: 10.1016/j.tics.2014.06.004

Figure 2.

Figure 2

A. Speech and macaque monkey calls have similar rhythmic structure in their acoustic envelopes. Modulation spectra for human speech and long duration (>400 ms) macaque monkey calls. X-axes represent frequency in log Hz; y-axes depict power deviations from a 1/f trend. B. Mouth motion and auditory envelope for a single sentence produced by human (top panel). X–axis depicts time in seconds; y–axis on the left depict the area of the mouth opening in pixel squared; y-axis on the right depict the acoustic envelope in Hilbert units. Bottom panel shows mouth motion and the auditory envelope for a single coo vocalization produced by a macaque monkey. X–axis depicts time in milliseconds; y–axis on the left depict the distance between lips in pixels; y-axis on the right depict the acoustic envelope power in Hilbert units.