Jean-Loïc Le Carrou

Categorization of seismic sources by auditory display

Recordings of the Earths surface oscillation as a function of time (seismograms) can be sonified by compressing time so that most of the signals frequency spectrum falls in the audible range. The pattern-recognition capabilities of the human auditory system can then be applied to the auditory analysis of seismic data. In this experiment, we sonify a set of seismograms associated with a magnitude-5.6 Oklahoma earthquake recorded at 17 broadband stations within a radius of ~300km from the epicenter, and a group of volunteers listen to our sonified seismic data set via headphones. Most of the subjects have never heard a sonified seismogram before. Given the lack of studies on this subject, we prefer to make no preliminary hypotheses on the categorization criteria employed by the listeners: we follow the free categorization approach, asking listeners to simply group sounds that they perceive as similar. We find that listeners tend to group together sonified seismograms sharing one or more underlying physical parameters, including source-receiver distance, source-receiver azimuth, and, possibly, crustal structure between source and receiver and/or at the receiver. This suggests that, if trained to do so, human listeners can recognize subtle features in sonified seismic signals. It remains to be determined whether auditory analysis can complement or lead to improvements upon the standard visual and computational approaches in specific tasks of geophysical interest. HighlightsSeismic data is sonified.The resulting sounds are presented to subjects in a listening task.Subjects are sensitive to some geophysical features.

Harp plucking robotic finger

This paper describes results about the development of a repeatable and configurable robotic finger designed to pluck harp strings. Eventually, this device will be a tool to study string instruments in playing conditions. We use a classical robot with two degrees of freedom enhanced with silicone fingertips. The validation method requires a comparison with real harpist performance. A specific experimental setup using a high-speed camera combined with an accelerometer was carried out. It provides finger and string trajectories during the whole plucking action and the soundboard vibrations during the string oscillations. A set of vibrational features are then extracted from these signals to compare robotic finger to harpist plucking actions. These descriptors have been analyzed on six fingertips of various shapes and hardnesses. Results allow to select the optimal shape and hardness among the silicone fingertips according to vibrational features.

Nonsmooth contact dynamics for the numerical simulation of collisions in musical string instruments

Collisions in musical string instruments play a fundamental role in explaining the sound production in various instruments such as sitars, tanpuras, and electric basses. Contacts occurring during the vibration provide a nonlinear effect which shapes a specific tone due to energy transfers and enriches the hearing experience. As such, they must be carefully simulated for the purpose of physically based sound synthesis. Most of the numerical methods presented in the literature rely on a compliant modeling of the contact force between the string and the obstacle. In this contribution, numerical methods from nonsmooth contact dynamics are used to integrate the problem in time. A Moreau-Jean time-stepping scheme is combined with an exact scheme for phases with no contact, thus controlling the numerical dispersion. Results for a two-point bridge mimicking a tanpura and an electric bass are presented, showing the ability of the method to deal efficiently with such problems while invoking, as compared to a compliant approach, less modelling parameters, and a reduced computational burden.