Romain Boulandet

University of Applied Sciences and Arts Western Switzerland · Institute of Industrial Science and Technology

Semi-anechoic rooms are used for the acoustic characterization of noise sources. They involve heavy infras-tructures and thick absorbent lining. The purpose of the ongoing project "DADA" (Dôme Anti-Diffraction Acous-tique) is to demonstrate a lower-cost alternative by supplementing a thin passive lining with active technology. This project targets...

In recent decades, smart building has received considerable research attention due to the increased demand for connected and integrated technology. Based on data collected by sensors, alarms, lighting, access control, heating and cleaning can be adjusted according to human activity and the actual needs of the occupants, resulting in efficient energ...

Room modes are known to alter the low frequency response of electrodynamic loudspeakers and are one of the biggest obstacles to accurate sound reproduction in listening rooms. The characteristics of the room may therefore influence the response of the loudspeaker at low frequencies due of the strong modal acoustic coupling. In this presentation, we...

Long-established industries in rural areas are now creating noise issues for new communities that have developed nearby. Proactive control of noise emission has therefore become a priority for industries concerned with respecting the tranquillity of residents. The traditional method of noise monitoring utilizes a sound level meter (SLM) which must...

This research focuses on the acoustic coupling between a bass-reflex loudspeaker and a room, in order to both make the positioning of a speaker less critical and to optimize the sound reproduction at low frequency. We present numerical results from multi-physics simulation involving a lumped parameter model for the transducer and a finite element m...

This paper presents an experimental approach for estimating the front-side radiation impedance of a loudspeaker. This acoustic load impedance is the reaction of the sound field on the radiating diaphragm which may affect the loudspeaker response, particularly in the low frequencies due to the coupling with the room modes. In general, this impedance...

This communication proposes an electromechano-acoustic absorber model that couples three physical domains using plate vibration and sound radiation theories. The mechanical system is an elastically suspended plate specifically developed to favor the piston-like movement thereof. An electromechanical transducer is attached to the plate in order to t...

Abstract This paper deals with active sound attenuation in lined ducts with flow and its application to duct modes damping in aircraft engine nacelles. It presents an active lining concept based on an arrangement of electroacoustic absorbers flush mounted in the duct wall. Such feedback-controlled loudspeaker membranes are used to achieve locally r...

This paper presents a local control approach to generate remote quiet zones. To deal with situations where global control can hardly be achieved, it is proposed to use an arrangement of spot-type sound reducers as originally suggested by Olson and May. Assuming that cross-coupling between control units is weak, each can be controlled independently...

Acoustic liners are a widespread solution to reduce turbofan noise in aircraft nacelles, due to lightweight and relatively small dimensions for integration within nacelles. Although conventional liners might be designed so as to target multiple tonal frequencies, their passive principle prevents the adaptation to varying engine speeds and therefore...

This paper presents a concept of sensorless electroacoustic absorber for damping the low-frequency modes in a cavity such as a duct or a room. Taking advantage of the reciprocity of the voice coil transducer, it is shown that a synthetic electrical admittance can be designed so that the loudspeaker diaphragm is matched to a target specific acoustic...

This paper presents a convenient and cost-effective experimental tool for measuring the mobility characteristics of a mechanical structure. The objective is to demonstrate that the point mobility measurement can be performed using only an electrodynamic inertial exciter. Unlike previous work based on voice coil actuators, no load cell or accelerome...

Le cas d’un panneau plan avec des conditions aux limites simplement supportées sur tous ses bords est utilisé dans de très nombreux articles ou ouvrages de référence en vibro-acoustique, car une résolution simple et exacte du problème posé est alors obtenue. Contrairement à de nombreuses études théoriques, la mise en oeuvre pratique d’un panneau av...

L’analyse des principaux modes vibratoires d’une structure mince, et notamment de ses caractéristiques de mobilité , permettent de prédire son comportement dynamique lorsqu’elle est soumise à une excitation mécanique ou acoustique, et de définir un contrôle vibroacoustique adapté pour réduire le bruit rayonné ou transmis. Que ce soit pour évaluer l...

Le contrôle actif vibratoire des structures peut être obtenu avec des méthodes de contrôle actif de vibration décentralisées. Le principe consiste à répartir plusieurs unités actives sur la surface de la structure afin de créer autant de ports Hamiltonien. Chaque port est composé d'une variable commandée dite « d'effort » (force) co-localisée avec...

A technique to setup a simply supported rectangular plane panel for laboratory vibroacoustic tests is described and validated. For a given panel fixed to thin vertical supports, a dimensionless parameter is proposed to size these supports following a desired frequency precision compared to theoretical eigenfrequencies of a panel with such boundary...

L’analyse des principaux modes vibratoires d’une structure mince, et notamment de ses caractéristiques de mobilité, permettent de prédire son comportement dynamique lorsqu’elle est soumise à une excitation mécanique ou acoustique, et de définir un contrôle vibroacoustique adapté pour réduire le bruit rayonné ou transmis. Que ce soit pour évaluer la...

In aircraft cabins, the use of composite materials leads to a reduction of the sound-insulating capability to external noise, particularly at low frequencies. Moreover, in the case of flexural structures with a high inherent structural damping like composite panels, it has been shown that adding active damping does not allow the noise transmitted t...

This paper presents a method for synthesizing digital electrical load impedances with a view to achieving broadband electroacoustic absorption. Connected to a loudspeaker used as a membrane absorber, an electrical load can be designed so that the diaphragm acoustic impedance matches a desired impedance. Such device may be used to attenuate modes ef...

The paper addresses the practical implementation of active vibration control using self-sensing actuators, intending to equip smart structures. The control objective is to reduce the structural vibration of a simply-supported plate subject to time-harmonic excitation. The key challenge is to use a self-sensing actuator instead of a sensor-actuator...

This paper addresses an active structural acoustic control (ASAC) approach to reduce sound transmission through an aircraft trim panel. The focus is on the practical implementation of the virtual mechanical impedance approach through self-sensing actuation instead of using sensor-actuator pairs. The experimental setup includes two sensoriactuators...

Abstract This paper presents a methodology for the design of broadband electroacoustic resonators for low-frequency room equalization. An electroacoustic resonator denotes a loudspeaker used as a membrane resonator, the acoustic impedance of which can be modified through proportional feedback control, to match a target impedance. However, such impe...

The problem of Active Structural Acoustic Control (ASAC) is to attenuate the radiated sound power by energy injection using structural actuators to modify deflection shapes. Collocated and dual actuator-sensor pairs allow the feedback problem to be formulated as the implementation of virtual mechanical impedances. The approach is based on a two-ste...

The paper focuses on the design of a built-in electroacoustic resonator for active noise reduction purposes. This concept basically encompasses a loudspeaker connected to a synthetic electrical load that enhances the ability of the transducer to dissipate a certain part of the incoming acoustic energy. The strategy is therefore to control the dynam...

At low frequencies in listening rooms, standing waves cause large frequency-response variations within the whole space. These unwanted phenomena have a significant impact on the sound quality of an audio system rendering. Unfortunately, state-of-the-art soundproofing solutions cannot efficiently handle such low-frequency sound energy. To alleviate...

The current trend for multipurpose rooms requires enhanced acoustic treatments capable to meet ever more demanding specifications in terms of performance, compactness and versatility. The reason is the variety of activities to be hosted and the corresponding requirements in terms of acoustic quality which may be very different and even conflicting....

The control of low-frequency sound fields can be addressed efficiently through acoustic impedance matching. Basically, the diaphragm of electroacoustic transducers are used as refracting surface that controls the reaction of the boundaries in any surrounding sound fields. The general idea is to absorb the incident sound energy or to contain it, sim...

Sound absorption can be achieved in a relatively simple manner with passive or active electroacoustic absorbers. Electroacoustic absorbers are basically loudspeakers, the membrane of which is used as an absorber/reflector of sound, and the electric terminals of which are connected to a dedicated electric load. This electric shunt can be a simple el...

Nowadays, requirements for acoustic treatments in rooms are ever more demanding in terms of performance and compactness. A recurring issue in closed spaces is the occurrence of standing waves and acoustic interferences at low frequencies. These unwanted phenomena are likely to affect the frequency response of rooms such as offices, concert halls or...

This presentation describes how to practically implement a digital controller using the compactRIO real-time platform in order to use of a loudspeaker as an electroacoustic absorber for better sound control in listening rooms.

In small to medium size rooms, natural room modes may severely strengthen the annoyance of low frequency noises, such as traffic or equipment noise. Moreover, there is an actual technological gap in the state-of-the-art concerning low-frequency treatments, and the only potential solutions basically take the form of heavy and bulky bodies. With a vi...

In closed spaces, standing waves occur at low frequencies, thus creating annoying acoustic resonances. Such unwanted phenomena are likely to affect the annoyance of noise sources in the low frequency range. Up to date, low-frwquency treatments are mainly based on bulky devices, such as heavy enclosures. To alleviate this problem, electroacoustic ab...

Un des problèmes majeurs rencontrés dans des situations de correction acoustique de petites salles destinées à l’écoute de système de diffusion sonore (type « home audio ») réside dans le traitement des basses fréquences. Le problème résulte de mauvaises propriétés d’absorption et d’isolation des matériaux de construction à ces fréquences. Face à c...

Ce poster présente les "matériaux acoustiques intelligents", qui sont des haut-parleurs actifs dont l'impédance électrique peut-être changée de façon contrôlée, soit de manière passive, ou semi-active.

Variable acoustic properties can be obtained at the diaphragm of a loudspeaker, with the help of very basic control strategies, among which is the simple electrical shunting of the transducer. These shunt techniques have been demonstrated to present singular similarities with active acoustic feedback strategies, dedicated to the control of the acou...

The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The form...

This paper discusses a time-domain technique for synthesizing acoustic impedance at the di-aphragm of a loudspeaker using a proportional-plus-derivative output feedback. The dynamics of electroacoustic transducers such as moving-coil loudspeakers can be readily controlled ei-ther by direct feedback principle on acoustic quantities, or by plugging a...

This paper discusses the implementation of a synthetic electrical admittance for performing active sound absorption at the diaphragm of electroacoustic transducers. The dynamics of electroacoustic transducers such as moving-coil loudspeakers can be readily controlled either by applying a direct feedback on acoustic quantities or by plugging some sh...

Variable acoustic properties can be obtained at the diaphragm of an electroacoustic transducer, with the help of very basic control strategies, among which is the simple electrical shunting of the transducer. These shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic trans...

In multivariate systems, when it comes to identifying actual operating conditions ranges, or optimal settings, the use of constrained optimization is often required. Among the different tools for the engineer to perform such optimization, designed experiments offer accurate performances. In this paper, the optimization process of “electroacoustic a...

Le comportement modal des salles est une des causes d'inconfort acoustique, dans l'habitat et dans les salles destinées à accueillir du public, dans le domaine des basses fréquences. Les solutions techniques de l'état de l'art ne permettent par ailleurs pas de traiter efficacement ces spécificités acoustiques des espaces clos. Afin de surmonter ces...

Dans cet article le processus d'optimisation d'absorbeurs électroacoustiques est étudié à l'aide de la méthode des surfaces de réponses. Un absorbeur électroacoustique est un système haut-parleur dont l'impédance acoustique peut être ajustée électriquement, de manière passive ou bien active. Un modèle mathématique est établi par plans d'expériences...

De plus en plus souvent, les espaces d'écoute sont amenés à accueillir des spectacles autres que ceux pour lesquels ils ont été conçus et dimensionnés. C'est le cas d'un auditorium classique devenant le temps d'un festival une salle de concert pour musique amplifiée, ou d'une cathédrale se prêtant occasionnellement à des concerts de musique chorale...

Modal acoustics is one of the main sources of annoyance in the low frequency range in rooms. Active noise control techniques can be deployed to reach sufficient acoustic benefit, but limited to a single frequency, whereas broader efficiency would require complex systems with a large number of transducers. This paper introduces the semi-active/activ...

Le comportement modal des salles est une des principales causes d’inconfort acoustique, dans l’habitat et dans les salles destinées à accueillir du public, dans le domaine des basses fréquences. Les solutions techniques de l’état de l’art ne permettent par ailleurs pas de traiter efficacement ces spécificités acoustiques des espaces clos. Afin de s...

Engineers dealing with noise reduction in habitations close to transportation traffic or indus-trial facilities encounter several problems to decrease noise level in rooms at low frequencies. Passive materials and current building construction knowledge enable to avoid noise trans-mission in habitations at medium and high frequencies and the regula...

We present a concept of "active material" with variable acoustic properties, being constituted of an electroacoustic transducer which acoustic impedance can be changed by an active mean. Among the different ways to obtain variable acoustic properties on an electroacoustic trans-ducer's voicing face is the shunting of the transducer's electrical inp...

We present a concept of "active material" with variable acoustic properties, being constituted of an electroacoustic transducer which acoustic impedance can be changed by an active mean. Among the different ways to obtain variable acoustic properties on an electroacoustic transducer's voicing face is the shunting of the transducer's electrical inpu...

The poor acoustic comfort of usual commercial products is often perceived as annoying. Today, more and more companies have realized that sound can be an important component of product attributes and image. They are interested in having acoustic guidelines for enhancing their products sound quality. The objective of this research is to quantify the...

Nowadays, customers have legitimate requirements as regards quality that marketing and consumers departments attempt to satisfy. The sound is well-known to enhance or detract from our pleasure in possessing or using a product. Sound quality engineering is consequently more and more requested by companies in order to have acoustic guidelines to deve...

In this paper, an active electroacoustic absorber [1] is designed with the help of COMSOL Multiphysics® Acoustics Module. An "electroacoustic absorber" is a loudspeaker, used as an absorber of sound, which acoustic impedance can be varied by electrical means. This can be achieved either by plugging passive shunt electric networks at the loudspeaker...

This paper describes the modal equalization of a room by actively controlling the reaction of electroacoustic elements embedded into the walls. Generally speaking, the control of low-frequency acoustic resonances is difficult and expensive, and in many cases inefficient. In this frequency range, the wavelengths of interest, of the order of magnitud...