DECOUPLING

One of the primary objectives of decoupling is to separate objects. This can be achieved through various methods, such as using resilient clips, resilient channel, double stud, or staggered stud framing. By creating space between materials, sound transmission can be significantly reduced, as sound transfers through vibrations and minimal contact between materials inhibits the transfer. Decoupling is an effective way to isolate a wide range of frequencies in walls and ceilings, from low to high, and is also key in isolating impact footfall in ceilings. To learn more about decoupling, you can read Concept of Decoupling or explore products that facilitate decoupling.

DAMPING

Many products can be dampened, including walls, ceilings, floors, pipes, sheet metal, doors, and isolation boxes. Damping compound such as Green Glue Compound is commonly used to reduce vibrations between layers of drywall or wood. Pipe and Duct Wrap can also be used to dampen lightweight plastic or metal surfaces, such as pipes, sheet metal, and the inside of automobiles. The goal of sound damping is to convert sound vibrations into non-perceptible amounts of heat. Damping is effective at isolating sound across all frequencies, with the most significant gains in the mid to high frequency range. When applied to the floor or ceiling, damping can also help with isolating impact sound transfer, assuming the assembly is resilient, such as with resilient clips, resilient channel, or independent joists. To learn more about damping concepts or to view damping products, visit enosh wall damping.

MASS

Sound transmission occurs through vibration. Heavier partitions are more difficult to vibrate, while lighter partitions are more easily vibrated. Minimal increases in mass do not result in significant improvements in sound isolation. To increase noise isolation in a wall with two layers of drywall on each side by five STC points, you will need to add four more layers on either side. To achieve an additional five STC points of noise isolation, you will need to add eight more layers on either side, effectively doubling the mass in the assembly. Increasing mass is effective for low, mid, and high frequency sound transfer, with low frequency isolation benefiting the most from added mass. Consider using TotalMass MLV Barrier for a low-profile way to add more mass to any assembly without resonating like other building materials.

ABSORPTION

Insulation is a crucial component in meeting the sound absorption requirements of walls, ceilings, and floors. The type of insulation is not as important as the thickness, with R-13 recommended for 2×4 walls and R-19 for 2×6 or resilient clipped walls, as well as any depth of ceiling joist cavity. While absorption can improve isolation in the mid to high frequency ranges, it does not have the same effect on low frequencies and footfall impact noise. However, when the assembly is decoupled, the value of absorption is significantly increased.

RESONANCE

Issues with resonance are typically encountered when attempting to separate materials or using the same type of material in multiple layers. To resolve resonance issues when decoupling, it is simple. To avoid creating more than one air space in any assembly, simply insulate the one air space with the proper amount of insulation. If additional air spaces are created, such as by installing resilient clips over existing drywall or building a new wall in front of an existing wall, then insulating this newly created air space can help reduce resonance issues. It is recommended to have only one air space per wall or ceiling cavity in any sound isolation assembly.

When it comes to using the same type of sound isolation material in multiple layers, it is best to avoid it by using varying thicknesses of drywall or plywood in an assembly. Each building material has a specific resonance point, which is the weakest frequency point for that material in terms of sound transmission loss. Using two materials of the same type in the assembly will exacerbate the weak performance of that material at that frequency point. To mitigate this issue, use different thicknesses of drywall or plywood on each side of the assembly. For example, if one side of the assembly has 1/2” drywall, use 5/8” drywall on the other side. If multiple layers of drywall or wood are being added to one side of the assembly, use a different thickness for each layer. Additionally, including a damping compound like Green Glue Compound in the layering can reduce resonance issues enough that multiple layers of the same material thickness are no longer considered a problem.

CONDUCTION

Flanking is a fundamental concept that refers to the transmission of sound vibrations through conductive materials, such as wood framing, plumbing pipes, and sheet metal, into other conductive materials. This type of sound transmission is indirect, which makes it difficult to predict the degree of loss that may occur. However, it can be substantial. To prevent the transmission of sound through conduction, two approaches can be taken: decoupling the materials or damping the materials. A variety of products available on our website can help accomplish these goals.