Welcome to another edition of Frequently Asked Questions about Noise, Vibration, and Acoustics. In this video series, we answer the questions we hear most often from clients or through inquiries via our website. My name is Simon Edwards, an acoustical engineer with HGC Engineering, and today’s question is: What do property managers need to know when addressing a noise complaint from neighboring suites?
We get a lot of calls from residential property managers and condo boards about these types of noise complaints, asking about the steps required to determine if there’s some type of deficiency and of course, if so, what can be done? During those calls, we’ll often start by asking about the nature of the noise complaint – do the residents hear voices or music, or maybe they hear footsteps or furniture being moved? The purpose of these questions is to classify the noise complaint under airborne noise, structure-borne noise, or both.
Airborne vs Structure-Borne Sound
Airborne noise is likely how you’re hearing this video from your speakers, it’s also how you would hear someone speaking to you from across the street – it’s sound travelling through the air from the source of the noise to the listener. Typical airborne noise complaints in condos are things like voices and music, or other high frequency sounds. Structure borne noise is how you might hear a weight dropped in the gym several floors away – it’s sound travelling through the structure from the source to the listener’s room, and radiating off the structure to the listener. Typical structure borne noise complaints in condos are things like footsteps, furniture moving, and items dropped on the floor. Note that these types of sound transmission are totally separate from one another – a floor/ceiling assembly may have a very low amount of airborne sound transmission between two spaces, while at the same time have a very high level of structure-borne sound transmission between the same two spaces.
Sound Transmission Class (STC) vs Impact Insulation Class (IIC) Sound Testing
We measure airborne sound transmission with a standardized test called an STC test, or Sound Transmission Class test. This test is conducted by placing a speaker on one side of the demising assembly and measuring sound on both sides, as well as ambient and reverberant levels. The result of the test is called an STC rating for the demising assembly, and a higher STC rating means that the demising assembly is better at preventing airborne sound transmission between two spaces. Similarly, the standardized test to measure structure-borne noise transmission is called an IIC test, or Impact Insulation Class test, and measures the IIC rating of an assembly by placing a standardized tapping machine on the floor above and measuring several different tapping machine positions in the space below, as well as ambient and reverberation levels – as with STC ratings, higher means better. These two ratings are not linked to one another, so an assembly can have both performance ratings be high or low, or alternatively have one high and the other low.
Apparent Sound Transmission Class (ASTC) vs
Apparent Impact Insulation Class (AIIC) Sound Testing
Now an STC or IIC rating describes the sound transmission through just that demising assembly, such as the wall, and is typically measured in a lab. When you’re measuring in the field, you’re measuring not only sound through the demising assembly, but also sound around the demising assembly, such as through the floor, through common ductwork, through holes in the caulking, or other indirect sound transmission paths. These type of tests and subsequent performance ratings are called ASTC and AIIC ratings, and again describe sound transmission not only through the demising assembly, but around the demising assembly too. It’s the total amount of sound in the field that travels from one room to another, through all the different transmission paths combined.
To give you an example, you could have a wall between two suites with a very high STC rating, normally very good at reducing sound between suites, but maybe the drywall contractor forgot to caulk the wall. All the sound will travel through the top and bottom of the wall through the junctions, and the result will be a very low ASTC rating. You can think about it using a light analogy, where even a small crack in the wall between two spaces can be a path for plenty of light to travel through and light up the adjacent room.
Sound Transmission Criteria in Building Codes
It’s important to understand that just because a resident can near noise from their neighbour’s suite, it does not mean that the level of sound transmission is excessive or in violation of building code. Some people are surprised to learn that the noise they hear is unfortunately for them considered acceptable in standard construction.
In Canada and the US, airborne sound transmission, STC and ASTC, are requirements in the National or International Building Code, depending on where you are. Different provinces in Canada may also have their own building code with similar sound transmission requirements. The International Building Code, used in the US, also includes similar requirements for IIC and AIIC ratings; however, in Canada, the National or various provincial building codes only quote an IIC recommendation, and not a requirement. This can introduce a bit of a grey area when assessing structure-borne performance in Canada, which can sometimes be sorted out via an IIC requirement in the Condo Documents, or just assessed subjectively based on other international standards by the acoustical engineer.
Acoustical Consulting Next Steps
In the event that a resident is complaining about hearing noise from their neighbour, an acoustical engineer can conduct sound transmission testing, either an ASTC test or an AIIC test, or both, to measure the sound transmission performance of the demising assembly. The ASTC and AIIC ratings can be compared to building code requirements or recommendations, or other relevant criteria for the geographical area.
When ASTC or AIIC Sound Test Results are Lower than Expected
In terms of next steps, in limited scenarios where the test performance is lower than expected, the mode of failure can be gauged from experience with similar assembly types and frequencies of failure – such as typical frequencies for large gaps in lamination between drywall and a poured concrete wall, or where caulking was not included in the wall. Otherwise, in order to investigate why an assembly performed lower than expected, we would need to open up the demising assembly to see exactly what was built and how it compares to the design drawings.
If you are a property manager with noise issues between neighboring suites and have questions, please reach out to us.