Today at PAC

Does good STC on a wall equal good STC and IIC on a ceiling?

I have been reading online about high performing STC wall noise control products. How much added noise control do I get when add them to my RSIC-1 ceiling system?

The short answer is, It has not been fully tested. The current belief is that if something works on a wall, it must work on a ceiling. Unfortunately in the world of acoustics, that logic does not always apply. There are conflicting reports online and published that may be addressed here.

Lets start with the basics of noise. Mass, Resiliency and absorption controls noise. This is an oversimplification of noise control.The best systems apply all 3 of these methods.

Walls are unique in the way that the gypsum board is held compared to the how the noise acts on the gypsum board. Typically the weight of the gypsum board is being held up, and the noise is applied to the broad side of the board. Imagine setting a piece of gypsum board on end then holding it up with 1 finger. That is totally possible. Now move that gypsum board slightly back and forth. This is how noise (vibrations) are applied to the gypsum board on a wall. Because the weight is being balanced, the amount of isolation/decoupling needed is low. All the noise control product has to do is manage the light back and forth of the gypsum board. This is why you see some success with RC-1 channel, Visco elastic products, Visco elastic gypsum boards, and isolation clips. The performances here have some large variables from STC 46 to 64. There is a large range of wall systems that can be effective for your projects.

Ceilings are different. Lets look at the same type of example we used above. Take the gypsum board that was resting all its weight on the ground (edge), and now hold it over your head. Unless you are quite the workout buff, this is fairly hard to do. Now imagine the degree of energy needed to hold and move that same board. Gravity has changed how that same piece of gypsum board reacts to the same/similar energy. That gypsum board that you so easily moved with one finger in our wall example, now is an immovable object, not really but its very heavy. All the weight is loaded on the same plane that the noise is trying to pass through. The entire weight of the ceiling has to be fully decoupled and isolated for any chance at a good acoustical result. This is where we see some separation in products. If you were to rate the options, best first: 1. Spring isolation 2.Rubber isolation 3. Channel Isolation 4.Mass and or Visco elastic products. The mass and visco elastic products are listed even here, only due to a lack of real test data for those products on ceilings. More testing is needed on the visco products to warrant a true placement in this short evaluation. By no means am I discounting the visco elastic products, only stating that there needs to be more testing.

Isolation clips with mass is currently the least expensive, highest performing option for a successful noise control ceiling system. The implementation of increased mass along with the correct isolation system, whether it be a rubber, or spring based isolation is where you see the best gains in acoustical performance.

I am sure there are plenty of arguments to this online. Here at PAC we rely on test data. When new test data is available we can revisit this.

Do I need a perimeter gap around Ceilings

The RSIC installation guide calls for a 1/4″ gap between the ceiling gypsum board and the perimeter of the ceiling. This gap should then be filled with acoustical caulking. The corner then can be taped and finished like a regular ceiling / wall intersection. The caulking provides 2 functions. It allows fills the void and bonds the ceiling top the wall with a flexible material ensuring an air tight ceiling. This air tight ceiling stops noise from flanking around the gypsum board and through what may be a weak area of the ceiling. The second function ensures that in the event of a movement the corner will remain sealed. Typically mud is pushed into the corner and tape is placed over the mud. This drywall mud creates an initial hard bond between the wall and ceiling. If there is any movement that bond can be broken, resulting in a gap that lets noise leak through.

RSIC-Joist Isolators and Floating Floors

The RSIC-Joist isoaltor is designed to support a 2×4,6,8,10,12 on end. This allows you to build a floating stage/floor to separate the floor from the floor. It also allows you to build bass traps in the floor to control noise within your space. The RSIC-Joist Isolator typically is spaced at 24″ intervals on every stud/joist for your floating floor. The RSIC-Joist Isoaltor is made form a TPE type rubber ensuring consistent performance over the life of the isolator. You might see these used in home theaters, Band stages, performing arts theaters, private voice over, or vocal booths. Click here to go to the product page.

Retrofit Ceilings

A question came across my desk today asking if you can retrofit RSIC-1 over an existing ceiling? The simple answer is no, you can not achieve the desired acoustical results when the RSIC-1 is installed directly under an existing ceiling. You can physically install the RSIC-1 Retro under an existing ceiling, but with substantially handicapped results. Below is a ceiling that has the RSIC-1 installed under an existing ceiling. This creates what’s called a triple leaf ceiling. These types of ceilings typically have not performed well acoustically.

The Correct way to build an acoustical ceiling with minimal impact to the bottom line is to tear off the existing gypsum board, add insulation if needed, and install a new ceiling using the RSIC-1 clips. This has shown to increase the acoustical performance of ceilings by up to 15 IIC points. That means you ceiling will transmit 70% less noise. I have attached an image below, for a reference. The difference can seem daunting, but the increased cavity above the gypsum board helps the RSIC isolator increase performance.

RC-1 Boost on ceilings

The RC-1 Boost is the new resilient product in the game of noise control focused primarily wood framed on multifamily construction. The made in USA innovative design allows the RC-1 Boost to be used on all brands and types of Resilient channel.

The RC-1 Boost with one layer of 5/8″ gypsum board achieves a 7 IIC point increase over RC-1 channel alone, and a 5 IIC point increase when added to RC-Deluxe channel.

How to decouple one wall from another?

The RSIC-CWB and the RSIC-DC04 can both be used to isolate one framed wall from another. Both the RSIC-CWB and RSIC-DC04 items are available in 36 Lb and 72 Lb acoustical load ratings. The RSIC-DC04 X2 HD has an acoustical load rating of up to 144 Lbs.

For more information please visit the RSIC product page, email, or call our staff for additional information.