One of the most common noise complaints from residents is sound transfer from neighbours, including in condos, apartments, townhomes, and semi-detached homes. Soundproofing is also an issue in many multi-family homes, for example where the main floor and basement of a house are occupied by different tenants. 

Below, we summarize two common measures of noise transmission between units – sound transmission class (STC) and impact insulation class (IIC). STC is a measure of airborne sound transmission between spaces sharing a common wall or floor-ceiling. This includes many of the common sounds that cause disturbance, including speech, TV, and music. IIC is a measure of vibration borne sound transfer from one floor to the space directly beneath it. This refers to how well the floor-ceiling assembly protects against impact noise transfer. 

Hearing conversations, music, the TV, and many other miscellaneous sounds from a neighbour sharing a common wall or floor-ceiling is caused by poor sound isolation between your unit and theirs. In particular, sounds such as speech that transfer from one room to the next are known as airborne sounds. This is because these sounds travel through the air from the source, through the separating wall or floor-ceiling, and then through the air to the where the receiver is. “Sound transmission class,” or STC, is the standard measure used to quantify the airborne sound isolation between units. 

The STC rating is a single number that quantifies the airborne sound isolation of a wall or floor-ceiling separating two rooms. It targets the noise spectrum for speech sounds. The higher the number, the better the sound isolation. Importantly, STC is a laboratory rating, which means that an STC rating assigned to a certain wall composition, for example, only considers the wall itself under ideal conditions, without taking into account flanking or construction deficiencies. 

In practice, flanking noise transmission and construction deficiencies are inevitable. This is why the “apparent” sound transmission class, or ASTC, is used when doing field measurements of sound transmission. The ASTC is essentially a field measurement of STC, and represents the airborne sound isolation from the entire construction, including the partition and all flanking paths. 

The STC and ASTC ratings are the most commonly used in North America for evaluating airborne sound transmission. Importantly, the Ontario Building Code (OBC) has requirements for ASTC and STC ratings for partitions separating dwellings in the same building. These requirements are in line with the National Building Code of Canada. 

Many owners and landlords prioritize acoustical privacy in multiple-unit dwellings, where different tenants live in adjacent spaces. Sound isolation can also be a priority in single-family residences, where the noise isolation of a home office, gym, or workshop is beneficial to everyone at home.

Noise from road traffic, planes, the playground across the street, or the generator in your neighbour’s backyard can all be disturbing.

Spaces such as home studios, home theatre rooms, and recreation rooms all have special acoustical requirements