Francois Charette

Active control of sound radiation from a plate using a polyvinylidene fluoride volume displacement sensor

This paper presents a new volume displacement sensor (made of shaped strips of PVDF film) and the experimental implementation of this sensor in an active control system. A design strategy for a PVDF sensor detecting the volume displacement induced by a vibrating 2D structure is presented. It is based on the modal representation of the plate response. It actually consists in designing a PVDF sensor, composed of several shaped PVDF strips bonded to the surface of the structure, in such a way that the output signal of the sensor is directly proportional to the volume displacement. The design methodology is based on the experimental measurements of the plate mode shapes (eigenfunctions) and is valid for any type of boundary conditions. The experimental implementation of such a volumetric sensor in an active control system is then presented. The experimental results obtained validates this new type of volume displacement sensor.

Minimization of sound radiation from plates using adaptive tuned vibration absorbers

Abstract Vibration absorbers have widely been used to minimize the vibration of structures, either globally for rigid structures or locally for flexible structures. This paper presents novel experimental work by applying the use of vibration absorbers to minimize sound radiated by a simply supported plate. Experimental results are presented comparing the effectiveness of sound attenuation by an adaptive tuned vibration absorber (ATVA) using two different tuning algorithms. The first algorithm “tunes” the ATVA to the excitation frequency of the plate. The second control algorithm adapts the ATVA tuning frequency to minimize the radiated sound field. Results indicate that “tuning” the ATVA to the excitation frequency can guarantee reduction of the vibration level near the base of the ATVA, but cannot guarantee reduction of the radiated sound field. In fact, it is shown that “tuning” the ATVA can actually increase the sound levels. Using an acoustic cost function to optimize the resonant frequency of the ATVA is a more effective procedure to guarantee a reduction of the radiated sound field. As a result of using this cost function, the ATVA was “detuned”, i.e., the resonant frequency of the ATVA was not equal to the excitation frequency.

Asymmetric actuation and sensing of a beam using piezoelectric materials

The purpose of the present work is the modeling of a beam actuated by a ceramic piezoelectric on the top with a PVDF piezoelectric on the opposite side acting as a sensor. The two piezoelectric are different in types, may be of arbitrary length and can be positioned independently along the beam. Since there is only one actuator, the asymmetric excitation induces transverse and axial displacement in the beam. This asymmetric actuation contrast with the symmetric actuation normally considered in the literature. Symmetric actuation implies no axial displacement. Here, both piezos are considered perfectly bonded to the beam and the Bernoulli–Euler hypothesis is used for the displacement field. The variational approach with Hamilton’s principle is put to use in the theoretical model. Hamilton’s principle states that the definite time integral of the Lagrangian shall be stationary. This formulation, which is energy based, allows one to consider any boundary conditions and to take into account the dynamic effect...

Sound detector device

A sound detector device for locating and diagnosing sound in a motor vehicle includes a headphone and a plurality of directional microphones. The sound detector device also includes a main unit having a circuit operatively connected to the headphone and the directional microphones for allowing an operator to diagnose sound in the motor vehicle.

Control of sound radiation from panels using multiple globally detuned vibration absorbers

In this paper, the results of an investigation on using multiple globally detuned vibration absorbers to minimize sound radiation from vibrating elastic panels will be presented. The vibration absorbers consist of lumped mass–spring systems whose characteristics (i.e., resonance frequency) can be electronically varied. A fully coupled multiple‐channel control algorithm, implemented on a DSP, is used to adapt the characteristics of the multiple absorbers so as to minimize the radiated sound at selected positions in the far field. Both theoretical and experimental results are presented and are compared to those obtained using tuned (i.e., to the disturbance frequency) vibration absorbers. Improved sound attenuation is shown to be obtained using the globally detuned vibration absorbers. The results are very similar in characteristics to those obtained previously using active structural acoustic control implemented with electrodynamic shakers or piezoelectric actuators. The results thus suggest a combined act...

Active control of plate volume velocity using shaped PVDF sensor

The radiated sound power of a planar structure is related to the velocity distribution over the surface of that structure. The well‐radiating velocity distributions have in general a nonzero volume velocity. A PVDF sensor design strategy is presented for applications in active structural acoustic control (ASAC). It is based on the modal representation of the response of the studied finite simply supported plate. It consists in designing a PVDF sensor composed of several PVDF strips bonded to the surface of the structure in such a way that the output signal of the sensor is directly proportional to the volume velocity of the vibrating simply supported finite plate. This sensor detects only contributions from the odd–odd modes, being the only ones with a nonzero volume velocity as well as being the most effective radiators. Experimental implementation of such a PVDF volume velocity sensor will be discussed. The efficiency of this type of sensor in ASAC will be analytically evaluated as the far‐field radiate...

Active control of automobile cabin noise with advanced speakers

The purpose of this presentation is to demonstrate the application of active control of engine noise in the interior cabin of a sport utility vehicle with advanced, compact piezoelectric sound sources. A broadband feedforward filtered‐X LMS algorithm has been used to achieve this goal. Preliminary tests have been conducted using arrangements of up to four commercially available speakers and four microphones. Various reference signals have been studied and these configurations show good results; attenuation of 7 dB at the error sensors has been measured in the 40–500 Hz frequency band and the dimensions of the zone of quiet generated by the control has also been measured. The ultimate goal of the research is the implementation of the active noise control with a new generation of speakers. These speakers use piezoelectric devices to induce the displacement of a speaker membrane, which radiates sound. Their main advantages are weight and dimensions, which are significantly smaller than conventional speakers ...