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Resilient channels are metal strips used to add airspace between drywall and the studs of a wall structure in order to reduce sound transmission. The metal channels are placed at right angles to the studs, and the drywall is screwed into the channel, being very careful that no screws touch a stud directly. In this way, the drywall is isolated from the studs, thus carrying less noise and vibration to the outer wall.
The ability of building materials to reduce sound transmission is typically classified according to "sound transmission class," or STC. Typical interior wall construction using wood studs sheathed in drywall has an STC rating of 30-34. When installed correctly, resilient channels can improve STC ratings by 5-7 points or more, depending on construction.
What is Soundproofing Drywall?
Soundproofing drywall is a sound isolation system designed to replace standard drywall in any wall (or ceiling) construction including wood or steel studs. Soundproofing drywall is a multi-layer laminated gypsum wall product that uses viscoelastic polymers to convert sound waves into harmless heat. The polymer kills vibration and is more effective with successive layers applied. Soundproofing drywall can easily be added to new or existing walls to achieve remarkable reductions in sound transmission.
To take an example, by adding a 5/8"-thick sheet of QuietRock soundproofing drywall to both sides of an existing wall, the STC rating jumps to 56, which translates into an 80% perceived sound reduction. In new construction, it is possible to obtain an STC rating of 70 using two layers of wood studs and a layer of QuietRock soundproofing drywall on each side.
How Do They Compare on Performance and Price?
While in theory construction with resilient channel can deliver excellent noise control results, it implies significant risks in terms of performance. The main concern with resilient channel is that it can be easily "short-circuited" during installation. Because the success of the resilient channel construction depends upon the decoupling of the frame from the drywall, if the drywall loses some of its isolation the effectiveness of the resilient channel can be compromised. Recent investigation has shown that resilient channel construction has a post-construction failure rate (STC designed value) of 90%. One of the major drawbacks of construction with resilient channel has been its high failure rate in the field.
Soundproofing drywall on the other hand, can be installed just like regular drywall but with much better results. Brands like QuietRock offer panels that are specially designed to score and snap as easily as a standard panel of drywall. This makes installation quick and easy and obviates the need for complex construction techniques. Because soundproofing drywall has the soundproofing technology built into it, the results are reliable and difficult to compromise through faulty installation.
Resilient channels imply significantly lower materials cost, and for that reason are often perceived as the most cost-effective construction option. However, because soundproofing drywall can be scored, snapped and hung like regular drywall without the added step of installing resilient channels, the installation time is lower. When you factor in the labor time for installation soundproofing drywall often makes up for higher materials costs.
Summary
Resilient channels pose a significant risk of failure in floor/ceiling and party wall assemblies. Lab specifications showing STC 43-55 often result in field-tested STCs in the 34-38 range. Soundproofing drywall can provide an easier, more reliable option with excellent soundproofing results and quick, simple installation.
