Noise is tricky. It finds all sorts of pathways to travel through, some direct and others indirect. It’s those indirect pathways that are referred to as flanking noise, and it’s an important concept you need to consider when renovating or remodeling your home or office.

The diagram above illustrates how noise travels from one room to another. Direct noise is represented by the red arrows-- the straight line from the noise source through the wall to the adjoining room. But even more noise enters the adjoining room through indirect pathways like floors, air pockets in ceilings, ductwork, etc.

Noise travels as mechanical vibrations through a building, such as through studs, joists, subfloors, and walls. If you want to reduce the amount of noise traveling from one room to another, consider creating a special design just for that room. For example, you could use staggered or double studs, or decoupling such as Green Glue Noiseproofing Clips (or comparable sound clips), or resilient channel on the studs.

The most effective sound isolating design is creating a “room within a room.” This is where a double row of studs are combined with separate ceiling joists, effectively eliminating practically all mechanical connections between the room and the rest of the structure.

A critical component of reducing noise from vibration is using Green Glue Noiseproofing Compound. Just one layer of the compound between two layers of drywall or other similar building material dissipates up to 90 percent of noise.

Here are some other tips on how you can keep flanking noise from ruining your home renovation plan:

• Get Serious About Doors. Doors are often the weakest link in a noiseproofing plan. Even if doors don’t directly connect two rooms, noise can travel through doors into hallways and into adjoining rooms. Depending on your budget, you can create an oasis of quiet in your home by focusing on your doors.
  • Go Heavy. Be sure to use solid-core interior doors with exterior jams that have been weather-stripped with effective seals. The heavier the door, the better. Solid wood and steel have similar characteristics
  • Add Weight and Damping. Adding Green Glue Noiseproofing Compound and a layer of MDF to the door will boost sound isolation performance.
  • Acoustic Doors. You may want to consider specially-engineered doors with high performance sealing. When comparison shopping, don’t judge just by STC ratings and be sure to look for sound transmission loss data at low frequencies. That’s the secret to a truly well-designed acoustic door.
  • Communicating Doors. If a door connects two rooms directly, two communicating doors work much better than even the best single door. Communicating doors form an airlock that isolates noise
    effectively.
• Plugging Up. Another weak link in a sound isolation system is the electrical socket. It offers a pathway for noise to travel, so be sure to install outlets in separate stud cavities (never back to back). Outlets should be sealed properly, and consider adding some mass to the outlet like caulking or insulation.

• Deconstruct Your Ducts. Noise traveling through ductwork can be very difficult to isolate. Some tips to consider include the following:

• Be sure to use insulated ductwork. Lined ductwork absorbs sound, but the lining must be inside the ductwork to be effective.
• Make the ductwork pathways long and complex. By forcing noise to travel through complex pathways, more of it can be absorbed by the duct insulation.
• Use flexible duct in areas where the duct is not exposed to direct sound.
• If ductwork is exposed to sound, use soffits to prevent direct exposure. If you must expose ductwork,try using round ducts rather than rectangular. 

• Float Your Floors. Although these can be expensive options, using floating floors can be effective at reducing flanking noise. This is a floor that has a “floating” surface on top of a resilient layer like rigid fiberglass, rubber mats, etc. The floating surface could be layers of wood, gypsum, or other material.

• Seal the Deal. You may be using the best soundproofing material available, but if there are air cracks between two rooms, noise will get through. Be sure to use acoustic sealant; a good choice is water-based, low-odor Green Glue Noiseproofing Sealant. For caulking, use multiple caulk layers on partitions where sound isolation is important. Be careful when sealing around resilient mounts and follow manufacturer instructions