Reducing the Sound Transmission Between Suites, One Conduit at a Time

Michael Kundakcioglu – mkundakcioglu@hgcengineering.com

HGC Engineering, 2000 Argentia Road, Plaza One, Suite 203, Mississauga, Ontario, L5N 1P7, Canada

Jessica Tinianov
Adam Doiron

Popular version of 1aAA9 – Sound flanking through common low-voltage electrical conduit in multi-family residential buildings
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0026642

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Residents living in an apartment or condominium expect a certain amount of privacy, especially when it comes to noise intrusions from neighbours. In fact, there are Building Code requirements in most jurisdictions which outline minimum requirements for the design of suite-demising architectural assemblies, to limit the allowable amount of sound that can go directly through (or in some cases, around) walls, floors, and ceilings. Despite this, sometimes, noise finds a way to travel through the building in unexpected ways, sometimes bypassing these assemblies. One such “sneaky” path is through the electrical conduits – those tubes that carry electrical wires between suites.

These conduits can act like a highway for sound, especially if they’re not sealed properly at certain points, like where they connect to fire alarms. This can allow noise from one suite to easily travel to another, even if the walls are properly designed to block sound. It’s a bit like having string from one suite to another, tied to a foam cup on each side, like those makeshift telephones we used to make as children.

This isn’t just a minor annoyance; it can be a big problem. In fact, this conduit issue has been found in multiple buildings in recent times, and it can reduce the effectiveness of the walls that are meant to keep sound in – by quite a bit. In many cases, this simple flaw in construction can cause the sound transmission between suites to fail Building Code requirements mentioned above, depending on the local requirements.

The good news is that this can be prevented. Sealing the open holes at the end of the conduits with simple flexible caulking on both sides of the tube greatly reduces the amount of noise from traveling through them (see Figure 1 below). It’s a simple solution that can make a big difference in the level of noise intrusion between suites.

Figure 1: Unsealed Conduit Opening in Fire Alarm Junction Box (Left), and Conduit Opening after Applying Sealant (Right). Image Courtesy of HGC Engineering

Standard sound transmission testing (known as Apparent Sound Transmission Class or ASTC testing) has shown that sealing these conduits can reduce the amount of sound travelling through the conduit so much that the amount of sound transmitted from suite-to-suite returns to the expected design values. In Figures 2 and 3 below, we plot the amount of sound transmitted between two adjacent suites as tested in four different real-world buildings with three different wall types separating the suites (double steel stud walls in Figure 2, and poured concrete walls in Figure 3); the dotted lines represent the amount of sound blocked by the wall when the conduit routed between the suites is left unsealed, while the solid lines represent the amount of sound blocked when the conduit has been sealed with caulking.

Figure 2: Steel Stud Walls Transmission Loss Results, as Tested by HGC Engineering

Figure 3: Poured Concrete Walls Transmission Loss Results, as Tested by HGC Engineering

In the above tests, we see the ASTC rating increase by 5 to 10 points once the conduits are sealed, which is a significant and very noticeable difference. In conclusion, if you are a developer, builder, architect, or engineer, it might be worth looking into whether the conduits in the suites in your buildings are properly sealed. It’s a fix that can help everyone get back to enjoying their own space in peace.