Installing Acoustic Panels for Walls
In this day and age fabric-wrapped, fiberglass acoustic panels for walls have become generic in nature. The primary element that will dictate the panel’s acoustic performance is its thickness. The chances of repeating the exact acoustic performance achieved in the test laboratory is about 28 million to 1. Therefore one should not be lulled into the false notion that one manufacturer of acoustic panels is better than the next, assuming that the various manufacturers use the same material compositions.
What Materials Are Acoustic Panels Made From?
The most prevalent fabric used to cover the fiberglass is woven polyester, which is acoustically transparent and extremely easy to work with. The acoustic panel edges will frequently be specified to be hardened by impregnating the edge with a polyester resin or be framed with an aluminum edge molding. In today’s market this is redundant and only serves to increase the cost and at the same time reduce the potential acoustic performance of the soundproofing panel.
When fiberglass acoustical panels were first introduced into the market several years ago, the fiberglass acoustical core was produced principally by Fiberglass of Canada and had an in-line sanding capability to produce a smooth face surface to which decorative fabrics could easily be bonded to. Unfortunately, the fiberglass board produced in Canada was a very short fibered board, which was subject to edge damage during the fabrication process.
To solve this problem, the edges were impregnated with a polyester resin which when cured produced a hardened edge to prevent crushing of the edge. New technology used by fiberglass manufacturers in the US is now able to provide a flat smooth face surface suitable for the lamination of fabric finishes to the soundproofing panel surface.
When fabric lamination is not desirable and when more custom sizes or longer lengths are required, a track system can be used which allows any size or length of fabric to be stretched over a framework.
This also allows for the use of more desirable and environmentally friendly sound absorption material made from recycled, “Green” or “LEED” credit contributing products such as Echo Eliminator™ recycled cotton or Sound Silencer™ PEPP rather than fiberglass. Echo Eliminator, Sound Silencer and the track system are available from Acoustical Surfaces Inc.
The fiberglass cores used in the US today are long-fibered resilient fiberglass mats that are sufficiently resilient to withstand abuse and crushing while still being able to be machined to produce a variety of edge profiles.
The “Edge Effect”
The soft panel edges also have the ability to improve the acoustical performance due to what is termed the “edge effect”; that is to say the soft edges will also allow acoustical absorption where the panels are separated with a space between the panels. A 1″×24″×48″ soundproof panel in effect measures 26″×50″ of absorptive surface but the cost is still only for a 24″×48″ panel, thus for the same amount of cost the client is getting 11% more sound absorption.
Architectural specifications frequently specify that the sound panels need to be mounted with male/female zee clips so that the panels can be relocated. Except in very rare cases, if ever, the fact of the matter is, acoustical wall panels are not generally relocated. The primary-reason for acoustical panel use is to reduce the reverberation time and unwanted noise build up in a room or recording studio. Thus acoustical wall panels are a part of the room’s architectural environment.
Mounting Acoustic Sound Panels on a Wall
The most cost effective way of mounting acoustic wall panels is through the use of impaling clips that are permanently mounted to the wall and then impaled into the back of the panel where they are locked into place with adhesive that wicks into and binds the glass fibers together. If by chance the wall mounted acoustic panels for any reason do have to be removed, careful removal will pull some of the fiberglass from the panel back. When relocating the panel, simply locate the impaling clips in a different location. Impaling clips provide a more cost-effective approach in both materials and labor to install the sound absorbing panels.
If acoustical panels are being used to reduce reverberation and background noise buildup that can interfere with speech intelligibility, the most cost-effective thickness is one inch. At 500 Hertz the absorption value of a 1″ thick panel is in the order of 90 to 95%, which is right in the voice frequency range. Since the absorption values are primarily based on thickness a 2″ thick panel should not necessarily be viewed as a better panel since the additional thickness only provides an additional 5-10% absorption in the voice frequency range.
At an additional cost of 30-40% a 10% increase in performance does not make economic sense. On the other hand if the background noise problem lies in the low frequency range, then a 2″ thick panel makes more sense since the thicker panels do provide better absorption at the low frequencies. Band rooms or recording studios are a good example of the need to use thicker sound absorbing panels.
Acoustical Panel performance is based on it’s average absorptive values in the 4 center frequencies to the nearest 0.5 number. This is called the NRC (Noise Reduction Coefficient) The absorptive values indicate the percentage of sound waves that will be absorbed at the various frequencies. An acoustical soundproof panel with a 84.5 NRC will be classified as having an NRC of 85 and a panel with an NRC of 82.4 will be classified as having an NRC of 80. The 5-point difference in published NRC is meaningless since in reality, the point spread could be no more than 2.1 actual, which is too close to detect.