Delphine Chadefaux

A model of harp plucking

In this paper, a model of the harp plucking is developed. It is split into two successive time phases, the sticking and the slipping phases, and uses a mechanical description of the human fingers behavior. The parameters of the model are identified through measurements of the finger/string displacements during the interaction. The validity of the model is verified using a configurable and repeatable robotic finger, enhanced with a silicone layer. A parametric study is performed to investigate the influence of the models parameters on the free oscillations of the string. As a result, a direct implementation of the model produces an accurate simulation of a string response to a given finger motion, as compared to experimental data. The set of parameters that govern the plucking action is divided into two groups: Parameters controlled by the harpist and parameters intrinsic to the plucking. The former group and to a lesser extent the latter highly influence the initial conditions of the string vibrations. The simulations of the strings free oscillations highlight the large impact the model parameters have on the sound produced and therefore allows the understanding of how different players on the same instrument can produce a specific/personal sound quality.

Gestural Strategies in the Harp Performance

This paper describes an experimentally-based analysis of the interaction between musician and instrument in the case of the classical concert harp. The study highlights gestural strategies used by three harpists while performing a short musical excerpt. As a result of years of practicing, a trained musician has developed the ability to deal with a number of trade-offs among simultaneous objectives while playing. She/he has obviously to set the instrument into vibration, but also to convey some musical intention to the audience and to communicate with other musicians, while keeping a safe posture with respect to articular and muscle pain. In order to precisely describe the motion strategies carried out by trained harpists, an experiment has been designed using a motion capture system and corresponding video and audio recordings. This provides accurate three-dimensional positioning of several markers disposed on the harpist and on the harp, within the execution of a musical piece. From the acquired gestural and acoustical signals, a set of kinematic and dynamic descriptors were extracted. The investigation shows that while each musician uses their own specific and repeatable upper-limb movements, the global sound-producing gesture is mostly controlled by the shoulders. Sound-facilitating hand gestures are highlighted for their supporting role to the musician throughout the musical piece.

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.

Investigation of the Harpist/Harp Interaction

This paper presents a contribution to the field of the musician/instrument interaction analysis. This study aims at investigating the mechanical parameters that govern the harp plucking action as well as the gestural strategies set up by harpists to control a musical performance. Two specific experimental procedures have been designed to accurately describe the harpist motion in realistic playing contexts. They consist in filming the plucking action and the harpists gestures using a high-speed camera and a motion capture system, respectively. Simultaneously, acoustical measurements are performed to relate the kinematic investigation to sound features. Results describe the musical gesture characteristics. Mechanical parameters governing the finger/string interaction are highlighted and their influence on the produced sound are discussed. Besides, the relationship between non sound-producing gestures and musical intent is pointed out. Finally, the way energy is shared between harpist arm joints according to various playing techniques is analyzed.

Dynamical analysis of stroke induced vibrations in tennis racket

Tennis rackets are mostly designed disregarding the boundary condition managed by the players hand on the handle. This process leads to a lack of accuracy in the mechanical parameters the manufacturers provide to their rackets in order for them to be reliable and comfortable to the player. Our work aimed at providing a better understanding of the effect of the tennis players hand on the rackets dynamical behavior. For this purpose, a dedicated experimental procedure involving 14 tennis players and 5 tennis rackets has been carried out. Vibrations propagated from the racket toward the upper-limb have been collected synchronously with kinematic and electromyographic data during forehands of various intensities. Additionally, an analytical model of the hand/racket interaction has been designed based on operational modal analyses. This model provides a straightforward tool to predict changes in the dynamical behavior of a tennis racket under playing conditions. Results indicated that tennis players adjust ...

How runners deal with the shock induced vibrations propagating through their body

Runners experience numerous shocks leading to vibrations propagating from the foot toward the entire body. These repetitive shocks are related to musculoskeletal injuries. Consequently, runners tend to adapt their running patterns according to the ground surface to cushion the impact. However, the way runners manage precisely the three-dimensional components of the vibrations, especially in the frequency domain, is not well understood. The present study investigated which biomechanical parameters runners adapt to tune the shock induced vibrations according to different running conditions. A specific experimental procedure was designed, based on simultaneously collecting kinematic, dynamic, vibration, and electromyographic data during running barefoot or shod and at various velocities. Using 10 non-specialist runners, energetic and spectral analyses of the three-dimensional foot impact induced vibrations occurring at the third metatarsal bone, the tibial plateau, the knee joint, the hip joint, and the 7th ...

Influence of the instrumentalist on the sound of the concert harp

The sound of musical instruments comes from a subtle mix between its mechanical behavior and its interaction with the instrumentalist. For the concert harp, the instrumentalist defines the initial conditions which determine the vibratory contents of the strings. This vibration is then radiated through the soundboard and the sound-box over a range of 7 octaves. Besides, this radiation may be affected by the instrumentalists physical presence next to the instrument. The aim of the talk is to show, thanks to ten years of research on the physics of the concert harp, how the instrumentalist and the instrument act in the sound from the instrumentalist gesture to the radiated sound. For that, specific set-up and models are carried out in order to carefully analyze each important step of the sound production : plucking, strings coupling, dynamical behavior of the soundboard and radiated sound. These studies are performed when the instrument is isolated, without the harpist, or in playing situation in a musical c...