José A. Bea¹ and Pedro C. Marijuán²

¹ Mechanical Engineering Department, CPS-University of Zaragoza; María de Luna, 3. E 50018, Zaragoza, Spain.
E-mail: [email protected]
² Fundación CIRCE, CPS-University of Zaragoza, Zaragoza 50018, Spain.
E-mail: [email protected]

Received: 10 January 2003 / Accepted: 12 February 2003 / Published: 30 June 2003

Abstract: Laughter is one of the most characteristic -and enigmatic- communicational traits of human individuals. Its analysis has to take into account a variety of emotional, social, cognitive, and communicational factors densely interconnected. In this article we study laughter just as an auditive signal (as a 'neutral' information carrier), and we compare its structure with the regular traits of linguistic signals. In the experimental records of human laughter that we have performed, the most noticeable trait is the disorder content of frequencies. In comparison with the sonograms of vowels, the information content of which appears as a characteristic, regular function of the first vibration modes of the dynamic system formed, for each vowel, by the vocal cords and the accompanying resonance of the vocalization apparatus, the sonograms of laughter are highly irregular. In the episodes of laughter, a highly random content in frequencies appears, reason why it cannot be considered as a genuine codification of patterned information like in linguistic signals. In order to numerically gauge the disorder content of laughter frequencies, we have performed several "entropy" measures of the spectra -trying to unambiguously identify spontaneous laughter from "faked", articulated laughter. Interestingly, Shannon's entropy (the most natural candidate) performs rather poorly.

Keywords: Information, Laughter, Sonograms, Plosives, Entropy of Laughter, Power Spectral Density.