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SEMINAR ANNOUNCEMENT: Scaling laws in speech processing.

October 6, 2021

Date and place:

Wednesday 6th October, 13:00h.
Aula Torres Quevedo, ETSI Aeronáutica y Espacio.


This talk presents evidence of new scaling laws found in the human voice, originating at temporal scales below the phoneme, where the underlying mechanisms are not cognitive but only rely on the physiology of voice production.
We first show that during speech, the energy is unevenly released and power- law distributed, reporting a (language independent) Gutenberg–Richter-like law in speech. We further show that such ‘earthquakes in speech’ show temporal correlations and are invariant under a renormalization group transformation, suggesting that the process of voice production is indeed operating close to a critical point. 
These results are put in contrast with current paradigms in speech processing, which usually invoke low dimensional deterministic chaos as the origin for nonlinear traits in microscopic voice fluctuations. As these latter fluctuations are indeed the aspects that humanize synthetic speech, these findings may have an impact in future speech synthesis technologies. Finally, we find that common linguistic laws reported in written texts (Zipf, Heaps and the brevity law) are already present in the microscopic fluctuations of voice. This suggests the provocative idea that the complexity of human communication might be after all just a byproduct of a complex physiological -rather than cognitive- system.


Dr. Lucas Lacasa studied Physics at Universidad Complutense and Technical University of Madrid, graduating with a PhD in Physics of Complex Systems in 2009. He has been an invited researcher at several universities including the University of Oxford and UCLA. He was an Assistant Professor at Technical University in Madrid (UPM) before moving to London in 2013 to accept a tenured position at the School of Mathematical Sciences, Queen Mary University of London (QMUL). At QMUL, he is a Reader in Applied Mathematics, as well as an EPSRC fellow and a visiting research fellow at King’s College London. At the end of 2021 he is moving back to Spain to take a tenured position at CSIC at the Institute for Cross-Disciplinary Physics in Complex Systems (IFISC) in Mallorca.

His research spans several areas of complexity science where he has published over 70 papers that have received over 4000 citations to date. Currently, he develops methods for data analysis and works at the interface of network theory and time series analysis, a topic for which he was awarded an EPSRC fellowship and has been recently awarded the international USERN prize in Formal Sciences.