Benoit Fabre

SOUND PRODUCTION IN RECORDERLIKE INSTRUMENTS. I. DIMENSIONLESS AMPLITUDE OF THE INTERNAL ACOUSTIC FIELD

Data on the internal acoustic pressure signals in an experimental recorderlike flue organ pipe are presented. A dimensionless representation appears to be a powerful basis for the analysis of these data. The dimensionless amplitude of the fundamental is, for a given geometry, a function of the Strouhal number only. For the first hydrodynamic mode of the jet, this amplitude is independent of the acoustic mode involved. The dimensionless amplitude of the second harmonic displays two different behaviors, depending on whether the jet is laminar or turbulent. This specific Strouhal number dependency implies a strong influence of the distance W from the flue exit to the labium on the timbre of recorderlike instruments. In recorders the ratio W/h, where h is the height of the flue exit, is adjusted by craftsmen to a value close to 4. This specific ratio ensures an optimal harmonic content to noise ratio in the produced sound. Increasing the distance W yields a more powerful sound but at the expense of additional...

Predicting the decay time of solid body electric guitar tones

Although it can be transformed by various electronic devices, the sound of the solid body electric guitar originates from, and is strongly linked with, the string vibration. The coupling of the string with the guitar alters its vibration and can lead to decay time inhomogeneities. This paper implements and justifies a framework for the study of decay times of electric guitar tones. Two damping mechanisms are theoretically and experimentally identified: the string intrinsic damping and the damping due to mechanical coupling with the neck of the guitar. The electromagnetic pickup is shown to not provide any additional damping to the string. The pickup is also shown to be far more sensitive to the out-of-plane polarization of the string. Finally, an accurate prediction of the decay time of electric guitar tones is made possible, whose only requirements are the knowledge of the isolated string dampings and the out-of-plane conductance at the neck of the guitar. This prediction can be of great help for instrument makers and manufacturers.

Regime change and oscillation thresholds in recorder-like instruments

Based on results from the literature, a description of sound generation in a recorder is developed. Linear and non-linear analysis are performed to study the dependence of the frequency on the jet velocity. The linear analysis predicts that the frequency is a function of the jet velocity. The non-linear resolution provides information about limit cycle oscillation and hysteretic regime change thresholds. A comparison of the frequency between linear theory and experiments on a modified recorder shows good agreement except at very low jet velocities. Although the predicted threshold for the onset of the first regime shows an important deviation from experiments, the hysteresis of threshold to higher regimes is accurately estimated. Furthermore, a qualitative analysis of the influence of different parameters in the model on the sound generation and regime changes is presented.

Analysis of Flute Control Parameters : A Comparison Between a Novice and an Experienced Flautist

The sound produced by flutes depends not only on the physical characteristics of the instrument but also on the control exerted by the musician. The latter is very important in some instruments of the flute family, especially in those where the air jet is shaped with the lip of the player. Some of the most relevant parameters controlled by the flautist, such as the distance from the lips to the sharp edge, the shape of the lips hole and the speed of the jet, are experimentally measured in this paper. Data produced by an experienced and a novice flautist are collected, analyzed and compared. Subjects are studied under normal musical playing conditions, playing phrases made out of simple musical intervals with subjective dynamics. Images of performers lips are taken together with measurements of the blowing pressure and the sound radiated by the instrument. Data analysis shows remarkable differences between the two subjects. The optimized coordination of several parameters in order to obtain a desired musical response, coupling between performers mouth and the instrument, as well as the efficient use of the available resources are some of the differences observed.

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.

Scaling of Flute-Like Instruments: An Analysis from the Point Of View of the Hydrodynamic Instability of the Jet

The scaling of a family of five baroque recorders is studied considering two aspects: the compass of each instrument and the control parameters. The observations are interpreted in terms of the homogeneity of the timbre. The control parameters are measured on an experienced player performing a simple scale task on each of the instruments, and are described in the frame of the hydrodynamic jet behaviour. On the family studied, the geometrical parameters appear to be adjusted so that the control parameters are similar on all the instruments. Low-pitched instruments present an enrichment of their spectra in high frequencies.

Influence of the Electric Guitar's Fingerboard Wood on Guitarists' Perception

The sound of a solid body electric guitar comes from the loudspeaker transducing into sound the string velocity. Because of mechanical string-structure coupling, the string vibration, and therefore the sound, substantially depends on the lutherie parameters. This study focuses on the comparison between ebony-fingerboard and rosewood-fingerboard guitars: is a change in the fingerboard wood perceived by the guitar players? In order to test the hypothesis that it is actually perceived, a psychological investigation is carried out. Two experimental methods are used: a free sorting task with recorded stimuli from the guitars (listening test) and a free verbalisation task where the guitarists play the guitars. In the listening test, the guitarists perceive differences between guitars, but the resulting clusters do not show an ebony/rosewood dichotomy. A linguistic analysis of the verbalisations exhibits psychological descriptors that are relevant for the discrimination of the wood of the fingerboard: PRECISION (referring to how each note stands out from others), and to a lesser extent ATTACK (referring to the guitars response to musicians gesture) and BALANCE (referring to the frequency content). This study is part of a broader project aiming at establishing an explicite relation between mechanics, perception, and lutherie. A physical interpretation of the psychologically-relevant descriptors is eventually proposed in order to use them as hypotheses in a further hypothetico-deductive approach starting from physics and using psychophysical methods.

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.

From Breath to Sound: Linking Respiratory Mechanics to Aeroacoustic Sound Production in Flutes

This paper combines measurements from two different experimental set-ups (Montreal and Paris) in order to provide a global view, from breath to sound, of one flautist playing the flute. The main goal of the Montreal experiment was to provide data on the flautists respiratory behavior during flute playing while the aim of the Paris experiment was to gather data for hydrodynamical and aeroacoustical analyses of the flute playing control parameters. The same professional standard player was studied in both experiments. Both locations included sound and mouth pressure recordings. In addition, Montreal measurements included: chest wall compartment volumes (with optoelectronic plethysmography) and the main respiratory muscle electrical activation. In Paris, additional direct measurements included lip opening area and the lip distance to the blowing hole of the flute. Global descriptions of flute playing, from the respiratory to hydrodynamical perspectives, are given. The results show that the blowing patterns are very similar, especially during performance of musical excerpts. Merging the data from the two experiments shows that the hydrodynamical control parameters are directly linked to the melodic structure of the music, independently of the pulmonary volume. This is interpreted as the result of the players training to produce the muscular activation that is highly adapted to the pulmonary volume.

Time-domain simulation of flute-like instruments: Comparison of jet-drive and discrete-vortex models

This paper presents two models of sound production in flute-like instruments that allow time-domain simulations. The models are based on different descriptions of the jet flow within the window of the instrument. The jet-drive model depicts the jet by its transverse perturbation that interacts with the labium to produce sound. The discrete-vortex model depicts the jet as two independent shear layers along which vortices are convected and interact with the acoustic field within the window. The limit of validity between both models is usually discussed according to the aspect ratio of the jet W/h, with W the window length and h the flue channel height. The present simulations, compared with experimental data gathered on a recorder, allow to extend the aspect ratio criterion to the notion of dynamic aspect ratio defined as λ/h where λ is the hydrodynamic wavelength that now accounts for geometrical properties, such as W/h, as well as for dynamic properties, such as the Strouhal number. The two models are found to be applicable over neighboring values of geometry and blowing pressure.