Daniel Royer is a Visiting Professor at the Institut Langevin (Ondes et Images) in Paris, France. His research focuses on the propagation of guided elastic waves and their generation and detection by optical methods. Tony Valier-Brasier is a lecturer at the Jean Le Rond d’Alembert Institute at Sorbonne University in Paris, France. His research focuses on the propagation of elastic waves in multiple scattering media, as well as on guided waves.