Electroacoustic Enhancement Systems Research Articles

SAFE Credit Union Performing Arts Center audio enhancement to support architecture

Opened in 1976 and without a major renovation since, the 98,000-sf SAFE Credit Union Performing Arts Center was in dire need of transformation. The building’s aging infrastructure needed a comprehensive modernization to meet accessibility requirements, the escalating requirements of contemporary performance, and to present a new face to the public as the premier cultural institution in the state capital. The existing theater’s acoustics represented a challenge to effectively accommodate the wide range of performance types including Broadway roadshows, the Sacramento Choral Society, and the Sacramento Philharmonic and Opera. Major renovations work included a complete exterior renovation; new mechanical, plumbing, electrical, and theatrical systems; and substantial updates to the interior finishes throughout the building. Providing an accessible venue to all patrons and performers was the primary goal of the project. Significant modifications to the external and internal circulation included removal of the entire audience chamber floor and new seating and aisle ways throughout. An electro-acoustic enhancement system was designed to provide an acoustically tunable audience chamber and electronic shell on stage to meet all the needs of the resident companies. Design and implementation of the electro-acoustic enhancement system will be discussed, including challenges of performer buy-in and audio orchestra shell integration.

The fictional environment meets acoustic reality—Simulating and creating acoustical conditions in for laboratory testing

In recent years, we have installed electro-acoustic enhancement systems in specialized acoustic laboratories. These labs incorporate sound isolating environments with loudspeakers that enable multi-channel playback of soundscape recordings that reproduce acoustical conditions of a variety of spaces. In addition, the systems use electronic architecture to carefully match the acoustics of the soundscape recordings to enable live sources in the lab to interact with these environments in real time.

Perceptual relevance of location of reverberation in a concert hall.

Standard reference texts as well as the International Organization for Standardization (ISO) standard on room acoustic quality (see, e.g., Beranek, 2004; Barron, 2010; and ISO3382-1:2009) focus on temporal distribution of energy [e.g., reverberation time T, G, and C80] and binaural aspects [lateral energy]. Kahle (2013) suggested that this description is insufficient when working with concert halls and that spatial aspects of sound fields need to be taken into consideration beyond binaural aspects. Furthermore, spatial aspects should be considered independently and separately for the (source presence) and the (room presence; see, e.g., Kahle, 1995, for details on source presence and room presence). For source presence, lateral reflections have different effects than ceiling reflections; this difference is taken into account by the objective criterion of lateral energy and the subjective factor of apparent source width. For room presence, listeners prefer to be fully enveloped by room sound; when talking to musicians and experienced listeners it is clear that this must not be limited to the frontal hemisphere and the question of lateral energy. All of the room around the listener should be active and this includes the parts of the room above us and behind us. Finally, when accepting the concept of segregation into a foreground source stream and a background room stream, a generalization of the cocktail party effect suggests that segregation is facilitated when the center of gravity (or direction of arrival) of the source is spatially separated from the center of gravity (or direction of arrival) of the room stream. Room reverberation should hence ideally be spatially homogeneous or come from a different direction than the source stream. In this paper, case studies are examined that show how spatial aspects of late sound can influence the perception of early sound and how frontal noise can influence the perception of both source presence and room presence. This suggests that spatial direction of arrival can strongly influence the perception of room acoustic quality.Case Study: Electro Acoustic Enhancement System Stockholm Concert HallThe Stockholm Concert Hall (Konserthuset, see Figure 1 for a photo of the hall) had been plagued with acoustic problems for decades (Dahlstedt, 1974) and has undergone several renovations. During the 1972 renovation, an electro-acoustic enhancement system was installed the hall, but apparently decommissioned after few months of use (Dahlstedt, 1974). The reasons for the decommissioning of the system are unknown, but probably the increase of natural reverberation during the renovation was at the time considered as being sufficient. Further renovations 2000 and 2005 decreased reverberation time and as a consequence the audibility of the late room response was significantly below optimum after 2005.As already indicated, it was found that one of the main reasons for the insufficient reverberance (what musicians described as lack of bloom) was the presence of a semitransparent technical ceiling installed under the lighting bridges for practical and esthetic reasons. The semitransparent expanded-metal ceiling (which can be seen at the top of Figure 1; Figure 2 shows a more detailed side view) created a slight transmission loss both on the way in for sound into the volume under the roof and on the way out. As a consequence, no reverberation could be heard coming from the top of the room and the ceiling was felt as being acoustically absent.First as a tryout and then as a final solution, an electro acoustic enhancement system based on the multiple channel amplification of reverberation (MCR) principle (de Koning, 1983-1984; Mulder, 2001) was installed the volume above the semitransparent ceiling, with microphones picking up the sound under the stretched-metal ceiling and loudspeakers enhancing the sound above the stretched metal ceiling. …

Electronic architecture—Recent developments in the design, implementation, and performance of time variant acoustic enhancement systems

When an electro-acoustic enhancement system is integrated with architectural surfaces in an enclosed volume, the acoustical conditions experienced throughout the venue result from the interaction between the two. Over two decades, we have encountered performance venues with a variety of sizes, shapes, and configurations. Each venue presents unique challenges in configuring architectural elements, as well as the makeup of the electro-acoustic enhancement system, in order to meet the expectations of the users and the audience. This paper describes important elements germane to a successful outcome—from the essential qualities of system components, to the physics and physiology that enable humans to perceive sonic quality. Examples of performance spaces with unique physics and system integration will be discussed.

A new third generation time variant electro-acoustic enhancement system

This paper describes the hardware and software implementation in a new generation of time variant electronic acoustic enhancement systems designed for use in medium and large sized venues. Examples of currently installed systems and applications will be discussed, as well as capabilities for sound file storage and playback, multi-channel film surround sound, 2D effects panning, and 3D live tracking.

Acoustic enhancement in the Aylesbury theatre with the CARMEN® electroacoustic system

The 1200 seat Aylesbury Waterside Theatre opened in October 2010 in the UK. The theatre needed to be flexible enough to accommodate events and performances from pop to classical music, as well as opera and theatre. To host the different performances in the best acoustic conditions, it has been decided to design an acoustics adapted to amplified music (RT = 1,1s at mid frequencies) and to install an acoustic enhancement system in order to adapt it for other music events. The CARMEN® electroacoustic enhancement system, designed by CSTB, has been chosen and installed. This paper presents the design and results of the installation of the Carmen system in the Aylesbury Waterside theatre. It details the CARMEN® electroacoustic design and explains the tuning and fine-tuning session with musicians. Detailed explanations are given for the use with orchestral music. Measurement results and the subjective evaluation with the feedback of acousticians and musicians are finally presented.

A new active acoustics system for enhancing musician's environment on concert and recording stages

The necessity of variable acoustics in modern performance spaces is widely acknowledged; particularly, there has been a growing interest in active acoustics enhancement systems. Many different systems have been developed and installed in concert halls, public venues, and research facilities worldwide. However, further improvements are required to provide musicians with a desirable acoustic on-stage support equal in quality to the best rooms. An innovative electro-acoustic enhancement system, based on measured high-resolution impulse responses, is developed at the Virtual Acoustics Technology (VAT) lab, in McGill University. The first model is installed in Multi-Media Room (MMR), a large rectangular space (80 ft. × 60 ft. × 50 ft.) designed as a film scoring stage. The system uses an array of omni-directional radiators and its signal processing includes 24-channel low-latency convolution at 24 bit/96 KHz, three separate stages of matrix mixing, equalization, and time variation. The objective measurement of the system adjusted to improve on-stage acoustics verifies the enhancement of parameters such as inter-aural cross-correlation coefficient (IACC), early stage support (ST1), and early decay time (EDT) without excessively increasing the overall acoustic energy in the room. The subjective evaluations collected from multiple recording sessions with professional musicians using the system will be presented. [Work supported by NSERC, JMP.]

Successfully merging architectural and electronic acoustical treatments

In enclosed volumes, the integration of electronic acoustical components with architectural surface treatments forms a hybrid system that produces the perceived acoustical conditions. Since the underlying operating principles for electro-acoustic enhancement systems differs considerably between manufacturers, the requirements for system infrastructure are not germane, nor is the optimum integration of architectural treatments. As a result, the nature of the work performed by the acoustical consultant changes to accommodate optimum performance of the specific “hybrid” system, which may also include other forms of variable treatments.

A new generation of time variant electro-acoustic enhancement systems

In 1991, Dr. David Griesinger presented a paper at the 90th AES convention [preprint 3014] describing a new method for improved electronic acoustic enhancement, and hundreds of these systems have been installed throughout the world. This paper describes a new approach to both hardware and software that comprises a third generation system. The new system retains the essential features of multichannel time variance with low pitch alteration, but updates the algorithms to utilize the superior DSP power of modern computers. Multiple reverberators, equalization, and matrix distribution can be combined into a single, reliable, and easily replaceable piece of hardware. Overall system gain and equalization can be calibrated automatically anytime; parameters in the hall have changed. The new algorithm combines the efficiency of infinite impulse response filters with direct convolution to produce a time-variant structure with extremely low coloration. The algorithm also includes a novel 32 band antifeedback circuit...

Altering stage acoustics using time variant electro-acoustic enhancement

Time variant electro-acoustic enhancement systems have been successfully installed in a variety of venues and applications since 1990. Many of these systems have included electro-acoustic support for performers on stage, as well as increased direct sound from virtual reflectors, in both indoor and outdoor venues. Examples of these systems and venues are described, including: The Mormon Tabernacle Choir, Vienna Philharmonic Orchestra, and Arnold Schoenberg Choir, Grant Park Symphony, Adelaide Symphony Orchestra, Midland Symphony Orchestra, and Stonebriar Community Church.

Trends in contemporary theater design: Arup Acoustics.

This presentation will describe the design process for a quartet of drama theaters completed by Arup Acoustics over the past decade. While the theaters addressed include both US and UK facilities, in this paper we will largely focus on the two US venues: The Las Vegas Academy Theater and the Tempe Center for the Arts. Along with the discussion regarding the room acoustics aspects of geometry, finish materials, and sound isolation, the integration of electroacoustic enhancement systems to provide acoustic variability will also be described. This presentation is being given in association with the publication of an ASA book on the subject of drama theaters, which will include the facilities mentioned here.

The measurement of coloration in electroacoustic enhancement systems

The use of electroacoustic systems to enhance the acoustics of concert halls is becoming increasingly prevalent. Regenerative systems are often used for obtaining a source position independent enhancement of reverberation time. However, these systems can produce unnatural acoustics due to the unequal enhancement of the response at different frequencies, a phenomenon termed coloration. Coloration alters the natural Rayleigh statistics of the transfer function magnitudes, and the variation in statistics can be used as a method for quantifying it. This approach avoids the difficulties of examining only the peaks in the transfer function magnitude. A method is developed for measuring the deviation of room transfer functions from Rayleigh statistics. Variance measures are derived. The underlying probability density function is modeled by fitting a three-parameter density termed the generalized gamma function. The maximum deviation of the modeled cumulative distribution from the Rayleigh distribution provides an alternative measure of coloration. The sensitivity of the measures is improved by eliminating the dominant early part of the impulse response, which is largely unaffected by non-in-line systems. An assisted reverberation system simulator is used to simulate the VRA system, which includes a unitary multichannel reverberator in the feedback loop to provide room volume expansion. The simulations show that the coloration measures increase with loop gain as expected, and are independent of other parameters in the system such as the secondary room reverberation time.

Concert hall research: Balancing complexity and practicality

An approach that has carefully balanced complexity and practicality has led to several new developments in concert hall research. These new developments are reviewed and their practical implications are explored. The two separate dimensions of spatial impression, apparent source width and listener envelopment, are each related to different physical parameters. The relationship between these acoustical parameters and the design of halls will be explored. For example, listener envelopment is related to the relatively late arriving lateral sound energy. Measurements in a number of halls will be used to explore how this and other acoustical measures of spatial impression are related to hall design. This same new understanding of spatial impression can also further enhance our understanding of sound fields under balconies and help us to design improved electroacoustic enhancement systems. Spatial impression is also influenced by sound level and especially by lower frequency levels. The importance of levels and the balance between high- and low-frequency levels has often been neglected. New work relating the perception of bass and treble sound to different factors will be reviewed. Previous studies and new analyses will be used to explore how hall design can influence perceptions of tonal balance in concert halls.