Broadening the Range of Variable Reverberance


In 1991, Artec was acknowledged as one of the most important acoustic firms in the world. Bob Essert was Russell Johnson’s principal acoustician at the time.

This paper by Johnson and Essert was presented at the 122nd meeting of the Acoustical Society of America, 6 November 1991. Houston, Texas.

Broadening the Range of Variable Reverberance

“Today social politics and operating economics dictate that the owners keep the hall as busy as possible. And since today’s concertgoers and theatregoers have increasing attractive alternatives in audio and video home entertainment, we as hall designers have to provide a truly special experience for today’s audience.”


Variable sound absorbing banners, curtains and panels have been incorporated into many performing arts facilities over the past three decades. These passive systems allow the building users to reduce the level and/or length of the reverberance from what would be the basic decay of the room. These systems are typically used to provide a dry acoustical environment for sound system use and some portions of the classical repertoire. Recently several halls have been completed that make use of partially coupled reverberation chambers to increase the level and/or length of reverberance without changing the basic shape, dimensions or materials in the audience chamber. With operable shutters at the boundary between the audience chamber and reverberation chamber and with sound absorbing curtains in the reverberation chamber, the overall reverberant decay can be tailored to provide a long decay without significant decrease in clarity. Issues of volume, surface area, coupling area, materials, shape, and location of the reverberation chamber will be discussed.

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Broadening the Range of Variable Reverberance – Johnson / Essert