ICC Permit Technician Practice Exam

Walls separating dwelling units must have a sound transmission class of not less than ___ for airborne noise.

1. 50

2. 100

3. 25

4. 75

The correct answer is: 50

The correct answer indicates that walls separating dwelling units must have a sound transmission class (STC) rating of not less than 50 for airborne noise. An STC rating of 50 signifies that the wall is designed to significantly reduce the transmission of sound, providing a sufficient barrier against noise from adjacent units. This is critical in multifamily housing settings to ensure a reasonable level of privacy and comfort for residents. STC ratings are a standard measure determining how well a building element can block sound. A higher STC rating means better sound insulation. An STC rating of 50 effectively prevents the transmission of normal conversation and other typical household noises, promoting a more peaceful living environment. This rating is often required by building codes to maintain quality living conditions in multifamily dwellings. In contrast, ratings below 50—like the one associated with 25—are insufficient in providing the necessary sound privacy. Higher numbers, such as 75 or 100, exceed typical requirements for most residential applications and may not be practical or necessary for all dwelling unit separations. Therefore, the specified STC rating of 50 balances sound attenuation with construction practicality, making it the appropriate standard for separating dwelling units.