LTS2 is a team of researchers led by Prof. Pierre Vandergheynst working within the Institute of Electrical Engineering of the EPFL, one of the two Swiss federal institutes of technology. The main part of our research activities focuses on modern challenges in data processing.
The joint expertise of the acoustic group extends the LTS2 research landscape to audio engineering and electroacoustics.
— Christophe Ballif, director of the Phototovoltaics and Thin Film Electronics Laboratory (PV-Lab) at the Institute of Microengineering in Neuchâtel, was selected for the project, "Ultimative Photovoltaics" along with Stefan Glunz of the Albert Ludwigs University Freiburg (Germany) and Stéphane Collin of the National Center for Scientific Research (CNRS) (France). Pierre Vandergheynst, head of the Signal Processing Laboratory (LTS2), was selected for the project, "Generative machine learning for combined process control and materials design" along with Cyril Aymonier of the National Center for Scientific Research (CNRS) (France) and Gian-Marco Rignagnese of the Catholic University of Louvain (Belgium).
— In the parable of the blind men and the elephant, several blind men each describe a different part of an elephant they are touching – a sharp tusk, a flexible trunk, or a broad leg – and disagree about the animal’s true nature. The story illustrates the problem of understanding an unseen, or latent object based on incomplete individual perceptions. Likewise, when researchers study brain dynamics based on recordings of a limited number of neurons, they must infer the latent patterns of brain dynamics that generate these recordings.
— Nonlinear distortions are not favored in audio systems, except in the cases where they contribute to the DNA of music genres (eg. heavy metal or electronic music). However, nonlinear membrane sound absorbers are known to allow absorbing acoustic energy through a physical phenomenon known as Targeted Energy Transfer. When triggered by high enough sound pressure levels, energy can be transferred from the incident sound pressure to higher harmonics vibration components of the membrane, leading to a net loss of energy in the acoustic domain, as thoroughly described in the literature on Nonlinear Energy Sinks. This is exactly the aim of the Nonlinear ElectroAcoustic Resonators (NEAR) presented in our paper, published in Physical Review Applied [1], where a loudspeaker is used as an active membrane absorber, through an hybrid active impedance control scheme. Such device tweaks the loudspeaker to act as an “active” nonlinear membrane resonator, mimicking the behavior of a cubic stiffness, exhibiting Target Energy Transfer phenomena even for excitation levels that are 1’000 times lower than the one reported in the literature. This study paves the way to a new generation of Active Nonlinear Energy Sinks, outperforming the existing concepts so far, for better sound absorption at low frequencies.
