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. Author manuscript; available in PMC: 2016 Aug 3.
Published in final edited form as: Curr Biol. 2015 Jul 16;25(15):2051–2056. doi: 10.1016/j.cub.2015.06.043

Figure 1.

Figure 1

The modulation power spectrum (MPS): examples and ecological relevance.

(A) Representations of a 1000 Hz tone amplitude modulated at 25 Hz. Top, waveform. Middle, spectrogram. Bottom, MPS: power modulations in the spectral (y-axis) and temporal (x-axis) domains. 25 Hz modulation highlighted.

(B) As in A. for a spoken sentence.

(C) Modulations in human vocal communication. Perceptual attributes occupy distinct areas of the MPS and encode distinct categories of information. Modulations corresponding to pitch (blue) carry gender/size information [6, 11]. Temporal modulations below 20 Hz (green) encode linguistic meaning [13, 15]. Orange rectangles delimit ‘roughness’ [16, 17]. This unpleasant attribute has not yet been linked to ecologically relevant functions. We hypothesize that this part of the MPS space might be dedicated to alarm signals.