Can You Hear Me? Optimizing Learning through Sustainable Acoustic Design

Understanding acoustic design, surface materials and services will provide optimal educational environments.
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Sponsored by Ceilings Plus, Meyer Sound Laboratories, Inc. and Serious Materials
Celeste Allen Novak, AIA, LEED AP

Soundproofing Lightweight Gypsum Meets ANSI School Criteria

To point out the long history of acoustical concern by professionals, Brandon Tinianov, CTO of Serious Materials and current Chair of the Acoustical Society of America's Technical Committee on Architectural Acoustics, quotes Vitruvius: "Sound moves in an endless number of circular rounds, like the innumerably increasing circular waves which appear when a stone is thrown into smooth water." Long after this first- century explanation for sound, professionals continue to examine the complex interactions between architecture and sound waves.

When analyzing the sound transmission of wall components in schools, acoustic experts focus on three main characteristics of sound: level (or sound pressure level), frequency and reverberation. Sound pressure level measures the loudness of a sound, which can be affected by the numerous and complex interactions of sound waves with materials and background noises. The intensity of a sound is measured by the decibel level (dB) and in learning environments, the signal-to-noise ratio of the teacher to background noise is critical. Background noise can be transmitted through the walls from classroom to classroom and from hallways to classrooms. The frequency of sound refers to the pitch or vibration of a sound wave. Reverberation, as defined later in this article, can degrade comprehension of sounds, not just when one or more people are speaking, but also when competing mechanical noises or highway noises disrupt the listener.

Sound pressure level, frequency and reverberation can hurt or benefit speech intelligibility and affect learning. That is why the American National Standard Institute (ANSI) Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools (ANSI S12.60-2002) set maximum standards for reverberation time for different room sizes as well as for Sound Transmission Classifications (STC) and decibel levels for classrooms. ANSI also recommends minimum STC ratings for single or composite wall, floor-ceiling, and roof-ceiling assemblies that separate an enclosed core learning space from an adjacent space. (See ANSI standards in online version of this course.)

Traditionally, professionals specify multiple layers of sheetrock or drywall, or mass to adjoining walls with masonry or staggered studs. All of these solutions add weight, labor and materials to the project. A recent development in lightweight gypsum meets or exceeds the recommended noise attenuation levels for walls while reducing the materials required to achievehigh acoustic performance goals. When compared to other assemblies, soundproofing gypsum drywall provides higher STC values/labor and materials as seen in this 2009 chart using RS Means Building and Construction Cost Data. (See table at end of article.)

Acoustic energy comes in contact with the wall. Constrained layer, damped panel converts acoustic energy to heat energy (in tiny amounts) which is absorbed.

Graphic courtesy of Serious Materials

Soundproofing gypsum drywall allows the designer to provide the auditory learning environment as recommended in ANSI/ASA S12.60-2002, as well as meet sustainability design goals. Depending on the wall assembly, and design application, the designer can choose between several types of soundproofing and moisture resistant materials. Although similar to sheetrock, these 5/8 inch drywall panels have a thin innerlayer that adds soundproofing to the wall system without adding the weight of additional layers of wallboard panels. This soundproofing drywall is screwed in place and does not need to have a resilient channel. Gypsum drywall can be perforated by screws without any loss to its soundproofing capacity. This drywall can be specified to be load bearing, or Type X, have a one hour fire-rating, can be specified as abuse-resistant, and can provide an STC 55 rating on single steel stud construction. The materials are as follows:

  • For wood construction: a laminated or damped drywall designed for school applications that have a calcium silicate back face.
  • For masonry construction: the same drywall as above but placed on one-inch wood furring strips. This application can be used for both interior and exterior walls.
  • For metal studs: a gypsum face drywall with magnesium back.

Installation of soundproofing lightweight gypsum used to absorb sound transmission

Graphic courtesy of Serious Materials

Sustainability - more acoustic performance with less material

The soundproofing material inside of a 5/8-inch gypsum wallboard is less than one-thirtieth of an inch thick. Lightweight and soundproof, gypsum wallboards deliver soundproofing with many fewer layers of drywall - often less than half of the materials typically used in wall construction - while achieving the same acoustical performance values. Typical soundproofing wall construction used in school projects can use as much as four to six layers of traditional drywall. Other options include the design of walls with double studs to achieve higher performance values. Professionals specifying this product will use less material, less labor and will have less waste on the construction site, as well as gaining additional square footage. With this improved soundproofing technology, professionals can reduce drywall material useage in these situations or applications by up to 75 percent. Moreover, the primary and most sustainable reason to use soundproofing drywall is to enhance human performance and create a "high performance acoustic learning classroom." Soundproofing lightweight gypsum wall boards reduce noise from 70 to 97 percent and can result in STC ratings from 46 to 80 for walls - depending upon the wall assembly.

 

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Originally published in Schools of the 21st Century
Originally published in January 2010

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