What does STC mean? FSTC?

Julie Leduc

Monday, 16 April 2018

Noise transmission problems arise mainly from floor/ceiling assemblies (complete structure between floor and ceiling of the above unit) and through the party walls, that is to say between the adjacent units. Noise problems associated with these assemblies come mainly from transmission of impact or airborne noises. The latest will be treated in this article and are caused by television, voice and music. These are noises that, when the unit is poorly soundproofed, disrupt the comfort of the occupants. But how do we measure these types of noises?

First, airborne noises come mainly from radio, television, voice, crying or cries of children. It is a vibratory airborne wave that vibrates the surfaces and structures of floors, ceilings, and walls. They spread through all the small openings in the building walls (around doors, ventilation grids, electrical outlets, etc.). Finally, where air can pass so can sound. It is therefore important to seal as much as possible all small openings to minimize the spread of airborne noise. Furthermore, the higher the mass of materials used in a building structure, the more they will contribute to reducing the airborne noise circulation.

In acoustics, there are two measurement units of airborne noises:  STC (Sound Transmission Class), result of tests carried out under controlled laboratory conditions, and FSTC (Field Transmission class), result of tests carried out in the field. Laboratory tests results are generally higher than those performed on site. In terms of airborne noise, the National Building Code requires a minimum acoustic performance of FSTC 50. At this level, we are talking about an acceptable level of soundproofing. However, if your neighbor snores loudly, you may hear it! At FSTC 55, we start to be much more comfortable, however, the desired acoustic comfort is rather around FSTC 60.

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