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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.

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.