Acoustic enhancement

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Acoustic enhancement is a subtle type of sound reinforcement system used to augment direct, reflected, or reverberant sound. While sound reinforcement systems are usually used to increase the sound level of the sound source (like a person speaking into a microphone, or musical instruments in a pop ensemble), acoustic enhancement systems are typically used to increase the acoustic energy in the venue in a manner that is not noticed by the audience. The correctly installed systems replicate the desired acoustics of early reflections and reverberation from a room that is properly designed for Acoustic Music. An additional benefit of these systems is that the room acoustics can be changed or adjusted to be matched to the type of performance. The use of Acoustic Enhancement as Electronic Architecture offers a good solution for multi-use performance halls that need to be "dead" for amplified music , and are used occasionally for acoustic performances. These systems are often associated with acoustic sound sources like a chamber orchestra, symphony orchestra, or opera, but have also found acceptance in a variety of applications and venues that include rehearsal rooms, recording facilities conference rooms, sound stages, sports arenas, and outdoor venues.

Contents

Design and application

Acoustic enhancement systems use microphones, amplifiers, and loudspeakers interconnected with some form of processing. The number, type, and placement of microphones and loudspeakers varies according to both the application, as well as the physics limitations that are imposed by the inherent operating principles associated with each manufacturer's equipment. In most instances, however, these systems employ at least one array of loudspeakers that are distributed throughout the venue.

As concertgoers have become aware of the use of these systems, debates have arisen, because "...purists maintain that the natural acoustic sound of [Classical] voices [or] instruments in a given hall should not be altered." [1] When employed properly, however, acoustic enhancement can improve listening quality in ways that would be impossible for architectural treatments to accomplish, and deliver sound quality that the concertgoer desires to experience.

At the Vienna Festival in May, 1995, a LARES system was used outdoors to augment the Vienna Philharmonic's performance of Beethoven's Symphony No. 9 conducted by Zubin Mehta. "This was the first time on this location with classical music that we were not criticised for spoiling the music by amplifying it. "Alfred Toegel, Sound Department, Vienna Festival. Commenting on a performance by the Grant Park Orchestra at the Jay Pritzker Pavilion at Millennium Park Chicago IL, Senior V.P. of WFMT Radio Steve Robinson stated "I have never in my life heard sound projected so faithfully and beautifully over such a great distance; it was an ethereal experience"

Kai Harada's article Opera's Dirty Little Secret [2] states that opera houses have begun using electronic acoustic enhancement systems "...to compensate for flaws in a venue's acoustical architecture." Despite the uproar that has arisen amongst operagoers, Harada points out that none of the major opera houses using acoustic enhancement systems "...use traditional, Broadway-style sound reinforcement, in which most if not all singers are equipped with radio microphones mixed to a series of unsightly loudspeakers scattered throughout the theatre."

Instead, most opera houses use the sound reinforcement system for subtle boosting of offstage voices, onstage dialogue, and sound effects (e.g., church bells in Tosca or thunder in Wagnerian operas). Acoustic Enhancement systems are most often employed in traditional opera houses to improve the sound of the orchestra and have little if any effect on the sound of the voices. In a review of the State Opera of South Australia's performance of Wagners' Ring cycle at the Adelaide Festival Center Theatre, Michael Kennedy of The Sunday Telegraph, London, wrote: “The balance between the orchestra and the voices has been ideal.” The live recording of "Wagner: Die Walküre", the world's first 6 channel SACD "blitzed the 2005 Helpmann Awards, winning ten of its eleven nominations and earning critical accolades." - and the recording of "Wagner: Götterdämmerung" was nominated for a 2008 Grammy award. " [3]

Types

There exist different types of acoustic enhancement systems: In-line and feedback systems with or without electronic reverberators.

In-line systems are also called non-regenerative (i.e. no feedback). Feedback systems are also called regenerative. Electronic reverberators can be added in addition using various methods such as convolution and FIR filtering.

In-line systems with electronic reverberators: In-line acoustic enhancement systems include E-coustic LARES (Lexicon Acoustic Reinforcement and Enhancement System), SIAP, the System for Improved Acoustic Performance and ACS, Acoustic Control Systems. These systems use microphones, digital signal processing "with delay, phase, and frequency-response changes," and then send the signal "... to a large number of loudspeakers placed in extremities of the performance venue." The Deutsche Staatsoper in Berlin and the Hummingbird Centre in Toronto use a LARES system. The Ahmanson Theatre in Los Angeles, the Royal National Theatre in London, and the Vivian Beaumont Theater in New York City use the SIAP system. [2] [4] [5] [6]

Feedback systems with electronic reverberators: Feedback acoustic enhancement systems include Meyer Constellation (formerly VRAS) (Variable Room Acoustics System) which uses "...different algorithms based on microphones placed around the room." Yamaha's AFC3 Active Field Control system which "enhances the architectural acoustic characteristics of a room and optimizes reverberation time performance." Also XLNT's MCR system (Multiple Channel Reverberation). L-Acoustics Ambiance is also a hybrid acoustic enhancement solution that combines both in-line and regenerative acoustic technologies to transform the acoustic properties of a building or venue to meet the needs of varying desired scenarios, whether it's a small acoustic performance or a large, fully amplified event. Ambiance uses an array of strategically placed microphones to capture the existing acoustical energy of an architectural space, then processes these signals, giving the sound designer the ability to extend the Reverberation Time (RT60) of a space while also controlling additional acoustic energy in the form of early reflections. [7] [8] [9] [10] [11]


Feedback systems without electronic reverberators: CARMEN developed by CSTB comprises a number of electro-acoustic active cells (approximately from 16 to 40), each of them being composed of a microphone, an electronic filtering unit, a power amplifier and a loudspeaker. Placed around the walls and ceiling of the auditorium, the cells form virtual walls depending on the architecture and the acoustic problem to solve. They only communicate between each other by the acoustic way. [12] Another newer variant for smaller halls is CARMENCITA. [13]

Related Research Articles

<span class="mw-page-title-main">Audio feedback</span> Howling caused by a circular path in an audio system

Audio feedback is a positive feedback situation which may occur when an acoustic path exists between an audio input and an audio output. In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting howl is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them. The principles of audio feedback were first discovered by Danish scientist Søren Absalon Larsen, hence it is also known as the Larsen effect.

<span class="mw-page-title-main">Recording studio</span> Facility for sound recording

A recording studio is a specialized facility for recording and mixing of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home project studio large enough to record a single singer-guitarist, to a large building with space for a full orchestra of 100 or more musicians. Ideally, both the recording and monitoring spaces are specially designed by an acoustician or audio engineer to achieve optimum acoustic properties.

Room acoustics is a subfield of acoustics dealing with the behaviour of sound in enclosed or partially-enclosed spaces. The architectural details of a room influences the behaviour of sound waves within it, with the effects varying by frequency. Acoustic reflection, diffraction, and diffusion can combine to create audible phenomena such as room modes and standing waves at specific frequencies and locations, echos, and unique reverberation patterns.

<span class="mw-page-title-main">Echo chamber</span> Hollow enclosure used to produce reverberated sounds

An echo chamber is a hollow enclosure used to produce reverberation, usually for recording purposes. For example, the producers of a television or radio program might wish to produce the aural illusion that a conversation is taking place in a large room or a cave; these effects can be accomplished by playing the recording of the conversation inside an echo chamber, with an accompanying microphone to catch the reverberation. Nowadays, effects units are more widely used to create such effects, but echo chambers are still used today, such as the famous echo chambers at Capitol Studios.

<span class="mw-page-title-main">Acoustical engineering</span> Branch of engineering dealing with sound and vibration

Acoustical engineering is the branch of engineering dealing with sound and vibration. It includes the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the design, analysis and control of sound.

<span class="mw-page-title-main">Instrument amplifier</span> Speaker and anplifier for use with musical instruments

An instrument amplifier is an electronic device that converts the often barely audible or purely electronic signal of a musical instrument into a larger electronic signal to feed to a loudspeaker. An instrument amplifier is used with musical instruments such as an electric guitar, an electric bass, electric organ, synthesizers and drum machine to convert the signal from the pickup or other sound source into an electronic signal that has enough power, due to being routed through a power amplifier, capable of driving one or more loudspeaker that can be heard by the performers and audience.

<span class="mw-page-title-main">Royal Festival Hall</span> Multi-purpose venue in London, England

The Royal Festival Hall is a 2,700-seat concert, dance and talks venue within Southbank Centre in London. It is situated on the South Bank of the River Thames, not far from Hungerford Bridge, in the London Borough of Lambeth. It is a Grade I listed building, the first post-war building to become so protected. The London Philharmonic Orchestra, the Philharmonia Orchestra, the Orchestra of the Age of Enlightenment, the London Sinfonietta, Chineke! and Aurora are resident orchestras at Southbank Centre.

<span class="mw-page-title-main">Public address system</span> Electronic system for amplifying sound

A public address system is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution.

<span class="mw-page-title-main">Sound reinforcement system</span> Amplified sound system for public events

A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience. In many situations, a sound reinforcement system is also used to enhance or alter the sound of the sources on the stage, typically by using electronic effects, such as reverb, as opposed to simply amplifying the sources unaltered.

<span class="mw-page-title-main">Elgin and Winter Garden Theatres</span> Toronto, Ontario Theatres

The Elgin and Winter Garden Theatres are a pair of stacked theatres in Toronto, Ontario, Canada. The Winter Garden Theatre is seven storeys above the Elgin Theatre. They are the last surviving Edwardian stacked theatres in the world.

Adaptive feedback cancellation is a common method of cancelling audio feedback in a variety of electro-acoustic systems such as digital hearing aids. The time varying acoustic feedback leakage paths can only be eliminated with adaptive feedback cancellation. When an electro-acoustic system with an adaptive feedback canceller is presented with a correlated input signal, a recurrent distortion artifact, entrainment is generated. There is a difference between the system identification and feedback cancellation.

Orchestral enhancement is the technique of using orchestration techniques, architectural modifications, or electronic technologies to modify the sound, complexity, or color of a musical theatre, ballet or opera pit orchestra. Orchestral enhancements are used both to create new sounds and to add capabilities to existing orchestral ensembles.

<span class="mw-page-title-main">Microphone practice</span> Microphone techniques used for recording audio

There are a number of well-developed microphone techniques used for recording musical, film, or voice sources or picking up sounds as part of sound reinforcement systems. The choice of technique depends on a number of factors, including:

LARES is an electronic sound enhancement system that uses microprocessors to control multiple loudspeakers and microphones placed around a performance space for the purpose of providing active acoustic treatment. LARES was invented in Massachusetts in 1988, by Dr David Griesinger and Steve Barbar who were working at Lexicon, Inc. LARES was given its own company division in 1990, and LARES Associates was formed in 1995 as a separate corporation. Since then, hundreds of LARES systems have been used in concert halls, opera houses performance venues, and houses of worship from outdoor music festivals to permanent indoor symphony halls.

<span class="mw-page-title-main">Stage monitor system</span> Sound reinforcement for performers

A stage monitor system is a set of performer-facing loudspeakers called monitor speakers, stage monitors, floor monitors, wedges, or foldbacks on stage during live music performances in which a sound reinforcement system is used to amplify a performance for the audience. The monitor system allows musicians to hear themselves and fellow band members clearly.

<span class="mw-page-title-main">Audio engineer</span> Engineer involved in the recording, reproduction, or reinforcement of sound

An audio engineer helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction, and reinforcement of sound. Audio engineers work on the "technical aspect of recording—the placing of microphones, pre-amp knobs, the setting of levels. The physical recording of any project is done by an engineer... the nuts and bolts."

<span class="mw-page-title-main">Hyogo Performing Arts Center</span>

The Hyogo Performing Arts Center (HPAC) is a performing arts center in the city of Nishinomiya, Hyōgo Prefecture, Japan, next to Nishinomiya-Kitaguchi Station operated by Hankyu Corporation. The Center was opened in 2005 to mark the ten-year anniversary of the Great Hanshin earthquake which largely devastated Nishinomiya and the surrounding cities.

The Variable Room Acoustics System is an acoustic enhancement system for controlling room acoustics electronically. Such systems are increasingly being used to provide variable acoustics for multipurpose venues.

In live sound mixing, gain before feedback (GBF) is a practical measure of how much a microphone can be amplified in a sound reinforcement system before causing audio feedback. In audiology, GBF is a measure of hearing aid performance. In both fields the amount of gain is measured in decibels at or just below the point at which the sound from the speaker driver re-enters the microphone and the system begins to ring or feed back. Potential acoustic gain (PAG) is a calculated figure representing gain that a system can support without feeding back.

<span class="mw-page-title-main">Clifford A. Henricksen</span> American inventor, American musician

Cliff Henricksen is a musician, inventor and audio technologist. He is self-taught as a musician with a graduate degree in mechanical engineering at Massachusetts Institute of Technology (MIT). Throughout his career Cliff has found innovative ways to apply engineering basics to electro acoustics and to audio technology as it applies to music and in particular to live music performance. He has invented and engineered a wide variety of technologies and products well known in the world of professional audio. Today he balances work in audio and work as a performing musician.

References

  1. ↑ Sound Systems- Why?!
  2. 1 2 Entertainment Design, Mar 1, 2001 "PRIMEDIA Business Magazines & Media Inc". Archived from the original on 2013-10-31. Retrieved 2007-10-25.
  3. ↑ "Melba Recordings". Archived from the original on 2008-08-28. Retrieved 2008-08-23.
  4. ↑ http://www.acs.eu
  5. ↑ "E-Coustic Systems - Electro-Acoustic Enhancement Products".
  6. ↑ "Room Acoustics System VIVACE". Archived from the original on 2013-02-16. Retrieved 2012-08-03.
  7. ↑ "Products".
  8. ↑ AFC3: http://www.yamaha-afc.com Archived 2013-01-21 at the Wayback Machine
  9. ↑ http://www.xlnt-at.com/files/pdf/Acoustics/XLNT_Advanced_Technologies_MCR_Product_Datasheet_September_2008.pdf [ dead link ]
  10. ↑ "L-Acoustics Ambiance".
  11. ↑ "Active Acoustic Systems for the Control of Room Acoustics".{{cite journal}}: Cite journal requires |journal= (help)
  12. ↑ CSTB: http://dae.cstb.fr/en/%5B%5D and CARMEN section
  13. ↑ http://www.ee.kth.se/php/modules/publications/reports/2010/IR-SB-XR-EE-SB%202010:001.pdf%5B%5D
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