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Piezoelectric ultrasonic transducers are used in many situations, including system and structural health monitoring and for non-destructive testing. For this, a piezoelectric resonator is used to actuate a structure and produce the sound waves that interact with the system under investigation and are then analysed. The behavior of such transducers is dependent on their environment, e.g., on the temperature. The mechanical parameters of the metals can be significantly changed if the temperature modification is large. Furthermore, the piezoelectric materials have their coefficients and losses modified by temperature changes. While the temperature behavior of the piezoelectric and metal can be independently determined experimentally, the role of the temperature change on the transducer performance and generated sound level is not well understood. In this paper, a simple transducer intended for high-temperature applications is investigated using Finite Element Analysis. A piezoelectric disc resonator is glued under a fixed stainless steel membrane, with parameters for the glue considered as those of gold. Effects of losses on the fundamental resonance of the admittance of the transducer and on the sound level it produces are investigated between 20°C and 300°C. Increasing the temperature reduces the resonance frequency of the transducer while maintaining the sound level at resonance. An error of one order of magnitude in input elastic losses of the piezoelectric material will have a stronger effect on the transducer admittance at every frequency than a similar error in the input dielectric and piezoelectric losses.

International audience; A mute is a device that is placed in the bell of a brass instrument to alter its sound. However, when a straight mute is used with a brass instrument, the frequencies of its first impedance peaks are slightly modified, and a mistuned, extra impedance peak appears. This peak affects the instrument's playability, making some lower notes difficult or impossible to produce when playing at low dynamic levels. To understand and suppress this effect, an active mute with embedded microphone and speaker has been developed. A control loop with gain and phase shifting is used to control the damping and frequency of the extra impedance peak. The stability of the controlled system is studied and then the effect of the control on the input impedance and radiated sound of the trombone is investigated. It is shown that the playability problem results from a decrease in the input impedance magnitude at the playing frequency, caused by a trough located on the low frequency side of the extra impedance peak. When the extra impedance peak is suppressed, the playability of the note is restored. Meanwhile, when the extra impedance peak is moved in frequency, the playability problem position is shifted as well.

L’usage de sourdines est courant pour modifier le timbre des instruments de la famille des cuivres. Cependant, ces sourdines peuvent également modifier la jouabilité de l’instrument. Ainsi, il devient plus difficile de jouer certaines notes pédales d’un trombone équipé d’une sourdine sèche,voire impossible à la nuance pianissimo.Des mesures précédentes ont montré que l’utilisation d’une sourdine sèche provoque principalement l’apparition d’un mode de résonance supplémentaire dans l’instrument, qui se traduit par un pic d’impédance d’entrée supplémentaire, de faible amplitude, entre le premier et le secondpic. Un dispositif de contrôle actif, ajouté à une sourdine sèche permet de supprimer ce pic d’impédance parasite sans modifier le timbre de l’instrument. De plus l’expérience a montré qu’un trombone équipé de cette sourdine permet aux trombonistes de jouer le Sib pédale sansdifficulté particulière.Ce travail propose une analyse de la dégradation de la jouabilité du Sib pédale par un trombone équipé de sourdines sèches passive et active. L’approche consiste à réaliser une analyse de stabilité linéaire de la solution non oscillante d’un modèle de trombone. Le modèle retenu couple une valve en dehors à un degré de liberté au résonateur de l’instrument représenté par la décomposition modale de son impédance d’entrée. Il est ainsi possible de réaliser l’analyse de stabilité du trombone avec sourdine sèche, avec sourdine active « allumée » ou « éteinte », et d’évaluer la pertinence du modèle physique utilisé pour interpréter les résultats expérimentaux décrits par les publications antérieures.

International audience; This paper reports the experimental results of modifying the resonances of wind instruments using modal active control. Resonances of asimplified bass clarinet without holes (a cylindrical tube coupled to abass clarinet mouthpiece including areed)are adjusted either in frequencyorindamping in order to modify its playing properties (pitch, strength of the harmonics of the sound, transient behaviour). This is achievedusing acontrol setup consisting of ac o-located loudspeaker and microphone linked to ac omputer with data acquisition capabilities. Software on the computer implements an observer (which contains am odel of the system)a nd ac ontroller. Measuring and adjusting the transfer function between the speaker and microphone of the control setup enables modifications of the input impedance and the radiated sound of the instrument.

For large-scale woodwind instrument makers, producing instruments with exactly the same playing characteristics is a constant aim. This paper explores manufacturing consistency by comparing five Howarth S10 student model oboes. Psychophysical testing involving nine musicians is carried out to investigate perceived differences in the playing properties of the two Howarth oboes believed to be most dissimilar. Further testing, involving one musician and combinations of the five oboes, provides information regarding the relative playabilities of the instruments at specific pitches. Meanwhile, input impedance measurements are made on the five oboes for fingerings throughout the playing range and their bore profiles are measured. The main findings are (i) the two instruments used in the preliminary psychophysical testing are perceived as identical by most of the musicians, although differences are identified by two players when playing the note F6 and by one player when playing in the lowest register, (ii) a variation in the playability of F6 across the five oboes is due to differences in the elevation of the C key, and (iii) variations in the playing properties in the lowest register are related to input impedance differences which, in turn, appear to be at least partly due to bore profile differences.

Active control is widely used in industry. However, there have been relatively few applications to musical instruments, particularly wind instruments. The aim of this study is to attempt to control the sound quality and playability of wind instruments, using active control. Active control makes it possible to modify the input impedance (amplitude and frequency) of an instrument and to modify the instrument's quality. Simulations and first experiments on a cylindrical tube, which is considered to be a simple wind instrument, with embedded microphone and speaker are presented. Finally, the effects on the sound and the input impedance of the instrument are studied.

Ferroelectric ceramics and crystals are the main component of many acoustic transducers based on piezoelectric effect. These materials exhibit different types of losses (dielectric, mechanical or coupled, piezoelectric “losses”) which may have strong effect on the resonances of its impedance.