Active Acoustic Enhancement Systems (AAES) are rapidly becoming essential for venues that accommodate a variety of events, spanning different styles of musical performance through to speech. It is rarely viable for venues to be dedicated to a single use, with the economics of hosting only classical music or corporate conferences just not stacking up. Modern multi-purpose venues can not be designed to be acoustically perfect for every application, with the physics of what makes a good acoustic for traditional jazz very different from the acoustic required for a keynote address.
An AAES is an integrated system of specially placed microphones, multiple loudspeakers, and a central processor that enables a venue to alter its acoustic performance properties at will. An ideal installation sees the loudspeakers hidden in the walls, the microphones invisible, and a simple touch screen interface deployed behind the scenes for venue staff to change the settings from ‘opera’ to ‘amplified band’ or ‘drama’ as required.
While the first AAES date back to the late 1980s, implementing them was prohibitively expensive until recently. Technological innovations in processing power, cabling, and amplification have made AAES an affordable reality for venues such as small or regional performing arts centres, and schools.Consulting engineers Hanson Associates, who specialise in both architectural acoustics and electro acoustics, are currently working on multiple projects that involves AAES.“Most of the projects we’re working on involve some variable acoustics,” explains director Mark Hanson. “These are usually venues that are presenting spoken word events as well as recitals, musical theatre, opera etc, each requiring distinctly different auditorium acoustics. In addition, many performances will use amplification where it is less desirable to impart the sound of a room and its reflections must be carefully controlled.”
In traditional architectural acoustics, there are two fundamental ways to adjust a room’s reverberation time. The first is to change the room volume through physical manipulation of architectural elements, such as mechanically raising the ceiling. The second is to introduce sound absorption into the room, typically in the form of acoustically absorptive banners and drapes that can be flown in and out as required. The smaller the room volume or the greater the absorption, the lower the reverberation time.“There are a few problems with these approaches,” continues Mr Hanson. “Architectural features like altering the room shape can prove prohibitively expensive to construct. Banners and drapes may be more affordable, but it can be challenging to find enough suitable wall space to make sufficient difference, particularly when retrofitting an existing venue. Another issue is that banners and drapes typically absorb mid and high frequencies without really affecting low frequencies. When deployed to reduce the reverberation time for spoken word and amplified performances, the resulting reverberation time tends to remain extended at low frequencies which is contrary to achieving the linear frequency response that is so desirable for speech or amplified music.”
Due to its small footprint and versatility, an AAES offers a compelling alternative to the traditional physical variable acoustic solutions. “By capturing the acoustic signature of an auditorium, and enhancing it with additional electronically-generated reflections, the audience’s perception of the acoustic can be changed,” outlinesMr Hanson. “Whilst an AAES can not necessarily correct inherent acoustic faults in a venue, its ability to improve performer conditions and audience experience are virtually endless. And changeover times between performances are as short as the push of a button.”In surveying the market of AAES solutions, Hanson Associates have come to admire the technology behind German firm Müller-BBM’s Vivace system.Scalable, flexible and capable of implementing object-oriented immersive mixing as well as acoustic enhancement, Vivace impressed both Mark Hanson and his colleague AV and electroacoustic consultant Mark Thompson when they visited a system being commissioned in Norway’s Lillestrøm Cultural Centre. “The Lillestrøm system was running with a combination of hidden 6” and 8” Fohhn cinema speakers installed around the auditorium,” relates Mark Thompson. “Ingeniously, Fohhn steerable line array columns mounted to balcony fronts in the auditorium and concealed within the stage wings provided pattern-controlled reflections back to the stage for the benefit of the performers. This ability to modify the degree of acoustic support for performers clearly caught the imagination of the professional musicians and singers that took part in the commissioning process.We listened to several settings through the commissioning process and I couldn’t nit-pick Vivace; it just sounded natural.It was a unique and educational opportunity for us to gain technical insight to the system, work closely with the performers and client, and contribute to the tuning processing a truly multipurpose venue.”
Müller-BBM’s expertise in AAES has evolved out of 60 years of room acoustics engineering, grounding their work in the language and goals of working venues and acousticians. “Müller-BBM’s approach to AAES allows us to adopt the same technical language and objective design parameters we use when designing acoustical constructions in the built environment,” observes Mr Hanson. “To be able to identify a desirable change to a specific auditorium acoustic metric and effect those adjustments electronically is quite exciting.”AAES opens up spaces to encourage creativity in new and different ways. A school may now be able to have a real music performance space without having to pay for the ceiling height that’s usually necessary. AnAAES can be set to reinforce speech to a level where a presenter doesn’t have to be tied to a lectern or wear a radio microphone. Venues can offer their spaces to more types of performances, filling their seats more often. With a simple license upgrade, a Vivace system can be used for creative multimedia and immersive sound art.So how does a company like Hanson Associates shepherd a venue through the process of selecting, installing, and implementing AAES? “We take an integration role in the AAES process,” saysMr Hanson. “Once a decision has been made to incorporate an AAES as part of the acoustic solution, our job is to prioritise the customer’s needs for performance, functionality, ongoing support etc, and develop an impartial technical specification. While the electroacoustic system design remains the responsibility of the AAES supplier, we ensure every aspect of the system will be properly integrated, technically, acoustically, and architecturally into the project. The Müller-BBM approach aligns well with our independent consulting approach as they are willing to provide guidelines on the performance of individual components that they don’t necessarily supply, such as speakers and microphones. They’re flexible enough that many components can be selected on the basis of greatest technical suitability or ready local support, for example through Australian distributor CMI Music and Audio, who support Vivace as well as Fohhn loudspeakers.”
Written by Jason Allen