Music and outdoors: are they meant to work together?
Outdoor spaces, or very large venues for that matter, often offer a seducing way of hosting large events without undue complications regarding security and fittings. However, they usually do not provide the audience and the performers with as high a level of comfort than enclosed venues. More to the point, community noise control of such facilities can really be tricky. What can be expected of such facilities? This paper intends to submit a few hints, looking at recent projects and developments.
Acoustique active et acoustique passive: approches complémentaires ou opposées ?
Certains architectes sont souvent tentes de soigner l'apparence de leur bâtiment ou de leur salle de spectacles, quitte a ce que la qualite acoustique du lieu soit impactee. A cet egard, l'acoustique active peut apparaitre comme une solution miracle permettant toutes les adaptations de volumetrie. De plus, elle laisse envisager une utilisation de la salle pour tous types d'usages, pouvant aller de la musique au theâtre et peut etre meme au sport ! Mais, dans la pratique, qu'en est il reellement, et quels sont les avantages et inconvenients par rapport a des approches plus conventionnelles, telles que les dispositifs sceniques mobiles ? A travers quelques exemples de projets, le present article se propose d'aborder ces points.
Carmen: A physical approach for Room Acoustic Enhancement System
It is very common that the acoustic of ancient performing halls or musical spaces cannot be improved by refurbishment works, because of the high cost or because of the registered building. Even for high standing performing halls, demand of multipurpose hall, which require variable acoustic, is also growing. A new Acoustic Enhancement System has been developed and experienced in several halls. The physical statements on which Carmen is based are presented, as well as objective and subjective assessment of the enhanced acoustic. Introduction Each type of music requires specific acoustic conditions characterised by several objective criteria such as the reverberation time. It is well known that the required reverberation time (RT) for opera is shorter than for symphonic music. For practical and economical reasons, more and more concert halls plan performances that need variable acoustics in the auditoria impossible to achieve with a unique architectural design. The acoustic correction of architectural defaults is another reason for installing reverberation enhancement systems (RES). There are two distinct types of RES: regenerative and nonregenerative systems [1]. In regenerative systems the reverberation enhancement is produced by the acoustic feedback between loudspeakers and microphones spread over the walls and ceiling of the hall. Non-regenerative systems use microphones placed relatively close to the stage to lower the acoustic feedback from the system loudspeaker relative to the direct sound. Reverberation enhancement is created by electronic delays and reverberators. The most inconvenient side effect of this method is very often a change in the colouration of the hall. The Active Virtual Wall Principle Considering that the acoustics of a hall originate basically from the reflections of sound from the walls and ceiling, the virtual wall principle corresponds best to the desired behaviour, without introducing electronic reverberators. The active virtual wall principle was first proposed by Guicking [2]. An acoustic virtual wall consists of several independent active cells, each one comprised of a microphone, an electronic unit, a power amplifier and a loudspeaker placed very close to the microphone (cf. Fig. 1). The acoustic feedback from the loudspeaker to the associated microphone is controlled acoustically and electronically. To fulfil the virtual wall a high cell density is expected but in practice having only a few cells readily permits the desired effects. The system cells act as diffuse reflecting elements. Having only two opposite virtual walls and a virtual ceiling increases the natural reflectivity so that an enhanced reverberation builds up from acoustic energy exchanges between the virtual walls. Each cell is made of : • a loudspeaker • an electronic processing unit • a microphone insensitive to the acoustic radiation of the loudspeaker D/A PROCESSEUR NUMERIQUE Pi Pr = r.(Pi Pc) A/D