Flexible Space, Acoustically Controlled

There are often design conditions with client requirements that can make acoustical performance more difficult if available options are not fully understood. A great example is the common request for building spaces to be more open and more flexible in the ways that they are used. Open, vibrant spaces can be great for large groups, but small meetings or individual workstations often need some acoustical separation. The design question then becomes how to provide both the desired openness and the needed acoustical control.

A popular solution to this seeming paradox is to use opening glass walls. This intriguing product type is comprised of individually framed glass panels that can be moved into either a closed or open position. The panels fold or slide along a track to open fully, permitting a once enclosed space to seamlessly reintegrate with those around it, allowing the space to be truly multifunctional. In the closed position, the glass panels can be specified to provide the appropriate level of acoustical barrier to create a more private, separated space. Floor-supported folding glass walls are able to achieve sound control up to impressive levels. This system combines sleek acoustically separated aluminum framing and specialized gasketing with sound-enhanced glass to achieve optimal performance with an STC range of 35–45.

Other all-glass opening walls are specifically engineered for enhanced acoustical separation and a minimalistic, frameless appearance. Such high-performance systems can provide better sound buffering than many fixed all-glass partitions. These systems have been independently tested and rated to a STC 36.

When selecting and specifying operable glass walls, it is important to consider not only the configuration and usability of the space but also the acoustical performance of the product. The higher-rated framed acoustical systems have been specifically engineered for interior spaces where acoustical privacy and ease of use are of utmost concerns, such as educational or work environments. The frameless versions offer flexible space management solutions for offices, banks, schools, or other building types, providing a design solution that goes beyond what a fixed glass wall provides. With no floor track required in many cases, these systems allow for uninterrupted transitions between interior spaces.

While some sound-control products require tools to crank and seal panels when closed, quality acoustic glass walls offer the user ease of operation. Some products are engineered with roller systems and acoustic seals that do not require additional efforts when closing. It is important to note that when the STC requirements of the system go up, so does the weight of the glass used within the panel. Therefore, it is best not to overload specification requirements when the environment may not require the highest acoustical values.

Other things to keep in mind are that product cost is determined by the level of acoustical privacy and the type of opening glass wall system selected. Hence, it is important to only specify the product and acoustically enhanced glass type that is needed for any given space. Finally, as with most construction, to achieve the desired acoustical control of any room, it is important that the sound-rated opening glass wall is properly installed. It also needs to be integrated into the space so that it is matched and surrounded with acoustically comparable ceiling, walls, and flooring.

Photos courtesy of AMBICO

Acoustic doors are available in a both wood and steel with a wide variety of appearance and performance options to suit any project.

Acoustical Doors and Frames

While walls and ceilings can be treated as continuous surfaces and addressed acoustically, intentional openings in those walls require particular attention. Doors in particular are needed for access, but if they are not also addressed acoustically, then unwanted sound transfer and noise will be unwelcome intruders. It is important to note that in most commercial building applications, this means addressing not only the operable door itself but also the door frame that couples the door with the wall.

Sometimes design professionals incorrectly assume that to make doors perform and achieve desired STC ratings, aesthetic beauty has to be sacrificed for performance. A review of the available options for acoustically enhanced doors and frames quickly reveals that this assumption is incorrect. Rather, a range of both wood and steel doors are now available that maintain the aesthetic options found on other commodity door types while still providing superior acoustic design and performance.

Interior doors between rooms and spaces often require other design attributes too, such as vision lites, fire ratings, and hardware configurations. Each of these needs to meet the functional requirements that they fulfill in a door and become part of its integrated design. However, each of these attributes will also directly impact acoustical performance in one way or another. Fortunately, there are manufacturers who welcome the challenge to provide wood and steel doors and frames that meet all of the aesthetic design attributes while still providing the needed acoustical performance. Often this is accomplished by careful selection of the materials used and optimizing them for performance and appearance. It also means paying close attention to the details of the interface between the door and the frame and the frame with the wall. In some cases, this includes the use of add-on gaskets and seals that inhibit the flow of sound, just as weather-stripping on exterior doors inhibits the flow of heat and drafts.

It is worth noting that doors and frames are acoustically tested according to the same standards as other building components. There are two common tests used by independent testing laboratories to determine acoustic performance. The first is ASTM E-90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements. The scope of this test method is intended to cover the laboratory measurement of airborne sound-transmission loss of building partitions, such as walls of all kinds, operable partitions, floor-ceiling assemblies, doors, windows, roofs, panels, and other space-dividing elements. The second is ASTM E413: Classification for Rating Sound Insulation. This classification covers methods of calculating single-number acoustical ratings (i.e., STC and related acoustical ratings) for laboratory and field measurements of sound attenuation in materials. Combined with ASTM E-90, this test is useful to determine how well an acoustic door reduces the amount of sound transfer between the two sides of the door.

The way to ensure that the best performance is achieved throughout a project is to specify acoustical doors and frames as a tested assembly from a single manufacturer. Otherwise the compatibility and seal between them may come into question without a clear means of who is responsible for resolving any issues that might arise. Manufacturers of such full door and frame assemblies can work with architects and designers to provide a full and varied range of options to meet the differing needs throughout a project. There is rarely a one-size-fits-all solution for doors and frames, but standardized systems can be used to create optimized assemblies with different STC ratings as needed for different openings. This is true for both wood and steel door assemblies that can be specified or selected based on all of the other design requirements and attributes being sought.

Following are some of the specific features of steel and wood acoustical doors.

Steel Doors

Steel doors and frames are widely used in commercial buildings of all types and can be readily specified to provide a full range of acoustic performance. The preferred products are a complete system with acoustic steel frames, perimeter and bottom seals, threshold, and astragal pairs that all work together to assure reliable, tested, STC ratings. Steel door assemblies that are 1¾ inches thick offer acoustic performance ratings from STC 33–53. In greater thicknesses, ratings of STC 54–59 are readily available. If higher ratings are needed, custom-engineered solutions can be pursued. Any of the doors can be provided with factory-installed acoustic glazing to allow vision while restricting sound. In addition to acoustical performance, steel doors can be provided with needed fire labels in single or double panels for most tested classifications covered by NFPA 80. The relatively lightweight panels combined with level swing seal systems allow for easy operation and compliance with accessibility standards required by codes and ANSI 117.1. From an appearance standpoint, they can be painted or finished in any common manner comparable to any other steel door product, thus providing all of the same design freedoms in addition to the specified performance.

Wood Doors

Acoustic wood doors with steel frame assemblies provide a broad range of STC ratings up to and including STC 56. The specific door and frame assemblies matter though. Wood doors that are 1¾ inches thick are rated up STC 50, while wood frames are available up to STC 45. Wood acoustic door and frame assemblies are also available to meet fire ratings up to 90 minutes. If vision lites are required, they can be factory glazed, including accompanying sidelites and transoms. With all of these performance attributes, remember that the beauty of wood can still be maintained and enhanced. Face veneers are available in virtually every wood species, cut, and grade. Stiles and rails are typically hardwood with vertical door edges to match the face. The factory finish can be a standard or custom stain or clear coat. If preferred for any reason, laminate face veneers are also available with hardwood edges. Doors can be Forest Stewardship Council certified to contribute to LEED or other green building rating systems.

Overall, steel and wood doors can meet all of the design and appearance requirements sought for a project while being specified to achieve the most appropriate acoustical rating.

Photos (from left): courtesy of Turf Design; © Eric Laignel Photography; courtesy of Turf Design

Acoustical treatments made from PET felt can be used as hanging baffles or integrated into ceilings in other ways to provide very good performance while also acting as notable design elements of an interior space.