AES Section Meeting Reports

Boston - September 8, 2009

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Boston AES Meeting
September 2009
with Steve Barbar

On Tuesday September 8, 2009 the Boston Section of the Audio Engineering Society featured guest speaker Steve Barbar with his presentation — "Inside Out" -- Time Variant Electronic Acoustic Enhancement Provides the Missing Link for Acoustic Music Outdoors. His presentation was a preview of his scheduled appearance at the AES Convention in NYC in October, 2009.

Moving an acoustic ensemble from the concert hall to an outdoor stage dramatically changes the listening experience for both the musicians, and those in attendance — usually, not for the better. Using time variant electro-acoustic enhancement can improve the acoustical musical experience for outdoor performance by giving the impression of a controlled indoor environment.

Acoustic feedback limits the gain that can be achieved with acoustic enhancement. Steve reviewed the common ways in which feedback can be controlled, revealing that these methods are not used with LARES, which incorporates Time Variance Reverberation. Using more speakers allows for more gain to be used before feedback, giving a 12-18 db advantage.

Steve explained that the ratio of direct sound to reverberant sound is the most important factor in deciding if something sounds good. Critical Distance is where direct energy and the reverberant energy are equal in amplitude. Even in the best halls there are not many seats that satisfy the critical distance qualifications.

He moved onto comparing the techniques of recording in a room vs. close miking, more commonly used today, which applies digital reverb to the dry signal. Using minimal microphones and maximum speakers gives more control over the gain for using LARES outdoors. But outdoor environments offer unique challenges over indoor settings; weather, the larger scale of the venue, the power required is significantly greater, sound over distance looses intensity and you also need to make sure that the surrounding noise does not interfere with the listening experience.

Steve covered many examples of outdoor environments he has worked with and how he dealt with the specific needs of each. Installations discussed included Crystal Palace — UK, Morbisch Seefesspiele -- Austria, Vienna Fest — Austria, Mathausan -- Austria, Turandot at the Forbidden City — China, Millennium Park -- Chicago IL, and the Sun Valley Pavilion — Sun Valley, Idaho.

E-coustic Systems is the result of more than 30 years or research in the fields of acoustics, neuroscience, and digital audio. At its core is LARES processing. Dr. David Griesinger and Steve Barbar developed LARES (Lexicon Acoustic Reinforcement and Enhancement System) in 1988 while working at Lexicon Inc. With this foundation, LARES was created to overcome the fundamental physics problem of using microphones and loudspeakers together — acoustic feedback.

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