1. Sound reduction is evaluated by two different indexes:
- The Sound Transmission Class (STC) that includes airborne sounds such as television, music and discussions. To give an example, a normal voice is perceived at an STC of 50, but only a person screaming will be heard at an STC of 60.
- The Impact Insulation Class (IIC) refers to the reduction of impact noises such as furniture being moved, someone walking on a wooden floor, etc. With an IIC of 50, it is possible to hear muffled steps in a construction with a wooden frame, like it would be possible to hear a high heel through an 8-inch concrete floor. At level 63, these impact noises are no longer perceivable.
2. Only the National Building Code - that falls under federal jurisdiction - is authorized to rule on the matter.
Up to this day, the Code has established norms, but only regarding the STC against airborne sounds. Section 9.11 of the National Building Code of 2005 stipulates that: "Every dwelling unit will be separated from every other space in a building in which noise may be generated by a construction providing a sound transmission class rating of at least 50 . . . the construction separating a dwelling from an elevator shaft or a garbage chute will have a sound transmission class rating of at least 55." The future editions of the Code will likely will recommend a minimum IIC also.
3. Even if it has no judicial power, the Canada Mortgage and Housing Corporation (CMHC) has made recommendations in its Acoustic guide.
They recommend a minimum IIC of 55 for ceiling/floor partitions made of hard materials (wood or ceramic), of 60 for constructions of high quality and of 65 if the rating is determined from theoretical data (the real conditions on the work site may reduce the rating by a few points).
4. The two acronyms FSTC (Field Sound Transmission Class) and FICC (Field Impact Insulation Class) refer to tests made onsite and not in a laboratory.
In a condominium, these evaluations would prove more representative.
5. A new sound classification system is on the rise: the Noise Criteria (NC) that could also be called the background noise index.
To get an idea, just think about the noises produced by plumbing, garage doors, toilets and transformers. According to Robert Ducharme, acoustician at Acoustilab, the background noises should not be louder than ambient noises. Even if there are no recommendations in this matter, many condo owners are pushing for action.