dB-3 ™ Sound, Air and Moisture Barrier – Professional Series can:

• Help you Achieve STC results > 56
• Reduce Sound Pressure levels by more than 75%
• Reduce Sound Pressure Levels by more than 10dB throughout most of the frequency range when used in conjunction with typical R-13 insulation.

United Plastics Corporation has been around since the mid-1940s.

• Over 15 years experience of conducting and managing acoustical laboratory measurements (Transmission Loss testing, Absorption Testing, Automotive testing, et al).
• Over 20 years of product development experience bringing multiple innovative products forward to many different industries.
• All OEMs use the EVA barrier technology to control their vehicles acoustic performance. It handles the toughest acoustical situations in the highest quality vehicles… Let it work for you!
  

Definitions:

• Sound Transmission Class (STC) rates a partition’s resistance to airborne sound transfer at the speech frequencies (125-4000 Hz). The higher the number, the better the isolation.
• Noise:  Quite simply is “Unwanted Sound”

dB-3™ Sound, air and moisture barrier can help you achieve STC levels in excess of 50, however there are many design considerations that need to be addressed in order for you to achieve these results.  Test results show conclusively that the addition of dB-3™ and a layer of R-13 insulation can reduce Sound Pressure Levels in excess of 10 dB throughout most of the frequency range above 200 Hz (see Figure 1 below).   This is exceptional performance!  But simple design techniques can dramatically help you achieve your results, or conversely, help you miss your intended sound quality target.

CAUTION: Be Careful of websites promoting their barrier products as the ONLY way to achieve STC results greater than 50, you will be greatly disappointed and will not meet your design criteria.  Understand which factors in the wall system play a role in noise transfer and you will easily understand how to build a wall system that meets your needs – every time.

dB-3™  Sound, Air and Moisture barrier will help you achieve your desired results – but it cannot achieve these results on its own without making sure the entire wall design is efficient.  Each of the following design criteria can and do have a critical affect on the ability to reduce noise.  A brief description of each along with an order of importance and ease to change / add in a wall system follows along with optimal design recommendations.

1. Mass of wall system
2. Types of studs used (wood versus metal)
3. Types of fasteners used (isolators versus screws)
4. Radiation efficiency of the system
5. Spacing between studs
6. Number of fasteners used to connect the drywall to the frame

Mass:  The heavier the mass of the wall system, the more is ‘reflected’ back and the less is transmitted.  dB-3™ Sound, air and moisture barrier increases the overall weight of the wall system by 1 lb/ft2 for every layer used.  By itself, dB-3™ reduces the Sound Pressure Levels by more than 3 dB throughout most of the frequency range above 200 Hz – which is essentially like reducing the transmitted sound by 50% (every 3dB of reduction is halving the sound pressure levels of a system).  Recommendation:  Use dB-3™ as an in-expensive solution to significantly reduce transmitted noise
Stud types:  Independent laboratory testing shows that metal studs can achieve STC ratings 8 points higher than wood studs (both placed 16” on-center apart).  Steel studs transmit much less energy as compared to the wood studs which significantly reduces noise through the wall system.  Metal Studs are highly recommended.
Types of fasteners:  There are two main methods of attaching drywall to framing:  screws and resilient channel (RS).  Resilient channel is a way to isolate the vibration of the drywall to the framing, significantly reducing the amount of energy from the wall – to the frame – to the other wall.  The use of RS channel can further increase STC rating points up to 11 more points – as compared to typical screw attachments methods (Note:  isolation techniques such as rubber pads help reduce mid-frequency noise transmission, however the overall effect to STC ratings is only additional 1 or 2 points).  Recommendation is to use Resilient Channels whenever possible.
Radiation Efficiency:  Think of a wall system as a drum cymbal, the stiffer the surface, the more easily it radiates noise.  dB-3™ is a limp, homogenous barrier layer that quickly dissipates any incoming energy and does not allow it to ‘radiate’ out the other side.  This is an extremely important factor in the field of acoustics and goes along with all of the isolation techniques talked about above…if the part does not transmit noise, than there is NO noise out the other side!  Recommendation:  Use dB-3™ as an in-expensive solution to significantly reduce transmitted noise.
Stud Spacing:  The fewer amount of studs in a wall system, the less contact points between walls and therefore the less noise is transmitted out the other side.  STC ratings can be increased an additional 4 points by spacing the studs 24” apart as compared to the traditional 16” on-center.   Recommendation:  whenever possible, use metal studs and space them apart > 16”apart to reduce the surface area contact points.
Screw Spacing:  Not as significant in metal stud systems (due to the lower transmissibility in the metal studs system as discussed in the ‘stud type’ section above).  However, for wood studs, screws spaced 32” apart versus 8” apart indicate an increase in STC ratings by up to 7 more.  The more the drywall is secured to the wooden frame, the more noise is transmitted out the other side.  Recommendation is to use steel studs, but if wood studs are used, space screws a minimum of 16” apart.
 

The following Transmission Loss data was measured as Riverbank Acoustical Laboratories. The wall construction and test sample size are the following:

Note that the test sample size is critical when measuring low-frequency data.  Be careful of test data that is measured in smaller window sizes – the low-frequency data is inaccurate and cannot and should not be presented or used as it skews real world measurements.

Graph and diagram of one layer of dB-3™ PRO versus baseline

Graph and diagram of two layers of dB-3™ versus baseline

Graph and diagram of one layer of dB-3™ PRO and R-13 insulation

Graph and diagram of one layer of dB-3™ PRO on each side plus R-13 insulation

Graph and diagram of one layer of dB-3™ PRO with R-13 insulation on baseline of metal studs

There are two ways to examine the performance of limp homogeneous barrier layers. First is to examine the noise reduction properties of the product by itself (single wall) — and then test the barrier layer within certain wall assemblies to be able to best approximate noise reduction potential as it would be used in its environment. Since so many factors effect the overall noise reduction performance (leaks, structure borne noise/isolation), absorption characteristics, only general guidelines can be offered to allow architects to use the most educated data possible.

Performance of single layer, homogeneous limp layers can be calculated by the Mass Law Equation, which states the following:

Transmission Loss (TL) = 20*Log (w) (f) – constant
where, w=density of the layer and f = frequency

Note that the ONLY determining factor that effects the performance of the barrier layer is the density of the barrier layer. Thus, the heavier the barrier layer, the higher the transmission loss = less noise through the other side. If one doubled the layers (went from 1 lb/ft2 to 2 lb/ft2), this equates to an increase of 6dB reduction (= 20*log(2) = 6 dB) throughout the frequency spectrum.

Note that this performance and calculation ONLY works for single wall LIMP homogeneous layers — which is what dB-3™ is. Conversely, drywall of equal weight will not perform the same because drywall in inherently stiffer — which means it radiates sound more efficiently at many frequencies. (Of course drywall does reduce noise, but due to its stiffness characteristics, it does not perform as well as a limp barrier layer). Think of a drum cymbal, when noise strikes this, what happens? It radiates noise very efficiently. This does not happen with limp, acoustical barrier layers like dB-3™. Rather, the noise strikes the dB-3™ layer and dissipates most of its energy laterally passing on only a small percentage of noise to the other side.