Sound Insulation Testing for Buildings in Quebec

The acoustic performance of a building depends on the performance of its individual components. The performance of a separating wall, for example, is expressed by how much sound is transmitted through it from one room to the next. For most building components today, such as walls, ceilings, doors, and windows, the sound insulation measured in a laboratory is known and published as a sound transmission class (STC) rating, which architects and designers use for the initial design. Relying on STC ratings alone is incomplete, because the true performance achieved between two spaces also depends on the quality of the adjoining construction, through which a part of the sound travels. Acoustic testing in the finished building remains the only way to establish the performance actually achieved, and it is used to verify a design, to identify deficiencies after construction, and to evaluate the sound insulation of components in service.

How Sound Insulation Is Measured in a Building

The test measures the sound insulation of the separation as it was built, adjoining construction included, and the result is therefore reported as an apparent rating: the apparent sound transmission class (ASTC) for airborne sound, and the apparent impact insulation class (AIIC) for impact sound. The method differs with the type of sound to be assessed.

Apparent ratings (ASTC, AIIC) and laboratory ratings (STC, and the impact insulation class, IIC) are directly comparable numbers, although the apparent rating is normally expected to be somewhat less than the laboratory rating of the same element. For example, the Quebec Construction Code considers a laboratory rating of STC 50 to be equivalent to a measured rating of ASTC 47, accepting that a small degradation occurs in practice due to sound being transmitted via the adjoining construction. About 3 points is therefore the difference normally accepted. Where the measured difference is substantially greater, it points to a deficiency either in the separating assembly or in the adjoining construction, through which sound travels by a flanking path such as the floor or ceiling junctions, the ductwork, or small gaps around electrical conduits. Specialized diagnostic measurements can identify that path, so that the correction is directed at the actual deficiency.

Sound Insulation Testing Service

A test typically includes the following work:

• Airborne sound insulation measurements — a loudspeaker generates the test signal in one room and sound levels are measured in both rooms, together with the background noise and the reverberation of the receiving room, following the ASTM field test standards
• Impact sound insulation measurements, where required — a standard tapping machine is operated on the floor above and sound levels are measured in the room below
• Façade sound insulation measurements, where required — a loudspeaker outside the building, or the road traffic itself, serves as the source, and sound levels are measured at the façade and inside the room
• Diagnostic measurements, where a result falls short — additional measurements identify the path by which the sound is transmitted, so that the correction is targeted at the actual deficiency
• Rating and statement of results — the measured data are rated according to the standard and compared with the target, in a signed report

The result is a report that states the sound insulation the building provides, compared with the specified target rating, and ready for the occupancy file, the project’s quality documentation, or the product’s technical file.