Soundproofing Basics: 8 Reasons Why Sound May Be Leaking Between Adjacent Rooms

1. Insufficient sound insulation

The first and foremost cause for sound leakage, of course, is thin walls. If the walls are not acoustically sound, they will not effectively insulate noise, which is why one should avoid thinner walls or materials with low sound insulation. Brick and block walls usually provide sound insulation around the range of 35dB to 38 dB (considering a 100 mm wall). On the other hand, gypsum-based drywalls provide a range of 40 to 60 dB depending upon configuration and thickness, with the right modifications, this number can go even further.

2. Incomplete height

Another reason for sound leaking through could be that the wall of the room is not taken up to the true ceiling but instead, ends at the false ceiling level itself. This leaves a gap between the true ceiling and the false ceiling, forming an unobstructed path for sound to travel. Since the defect will not be visible to residents, it can be hard to identify the root of the problem in such a case.

3. Cracked walls

As a building settles over time, it is not unusual for cracks to appear on the walls. These cracks are not only visually unappealing, they can also form a significant cause of sound leakage. Even small cracks, as thin as 0.2 mm, can reduce the sound insulation of a partition to up to 10 dB. As the size of the crack increases, the sound insulation will keep deteriorating.

4. Common AC ducts

Usually, buildings are built in a way that adjacent rooms have common AC ducts passing through them. Since these ducts have an opening in both rooms, they can be a common medium of sound to travel from one room to the other.

One way to reduce the leakage of sound through AC ducts can be to keep the opening of the AC vent as far as possible from the common wall. Another option is to accommodate a zig-zag shaped path for the AC duct above the false ceiling. This increases the overall length of the duct, forcing any sound to die out before it can reach the other room, thus reducing inter-room disturbance.

5. Gaps along the edges

If there are gaps left between the walls or between the wall and ceiling in any room, sound may be permeating through these gaps. These are typically installation-related flaws that might have gone unnoticed during construction. Ideally, gaps should be avoided at the very nascent stage itself by adopting appropriate measures while installing the wall. However, if you do find gaps after the installation process, they can still be sealed, simply by using a suitable acoustic sealant.

6. Misshapen cut-outs

Usually, the area above the false ceiling is where most of the services are present, such as pipes, AC ducts, wires, etc. To allow these services to pass from one side of the wall to the other, the walls are usually punctured and cut to a suitable size. However, if these cut-outs are too large, the additional area cut out beyond the duct size becomes a leakage point. Hence, cut-outs should be fit to size, with just enough room for the pipes and ducts to pass through. The remaining area can be sealed by using appropriate sealants or other encasing materials as per the site’s requirement.

5. Back-to-back installations

Within the wall cavity, there are numerous services such as switch boxes, wiring and cables, or pipes and fittings. A lot of these services are metallic in material. For example, switch boxes are usually required on both sides of a common wall, to serve the requirements of both the rooms. When these switch boxes are installed back-to-back and their metallic surfaces touch each other, it creates a path for sound waves to travel through, from one room to other. This can be avoided by installing switch boxes in a staggered manner as shown below.

8. Combinational partitions

Sometimes, for aesthetic purposes, it is preferred to have a combination of gypsum-based drywall partitions and glass partitions combined. This gives an optimum blend of opacity and transparency, and uplifts the look and feel of the space. Although aesthetically it is a smart choice, it is imperative to seal the joints between these 2 different materials properly. Often, there are gaps observed between the two which turn into a major source of sound leakage.