When it comes to sound traveling from room to room, it primarily traverses through the densest materials initially and then through any voids within the walls or floors. To break it down more precisely, sound moves through materials like drywall or plywood, followed by wall studs or floor joists, and finally reaches the other side of the drywall. Additionally, sound tends to reverberate within these voids, creating a drum-like effect.
My wife often reminds me that we can hear sounds from the family room below our bedroom. As the saying goes, "The cobbler's shoes are never mended," and indeed, my construction oversight about 12 years ago didn't adequately anticipate sound transmission. Placing speakers in the family room ceiling inadvertently allowed the sound to carry to our room above, despite using batt insulation within the joist spaces. This scenario underscores a common architectural issue where the primary bedroom sits directly over a potentially noisy space like the family room. While it's logical to position the primary suite over the family room for spaciousness and better views, it can lead to sound-related challenges.
Within the industry, the effectiveness of sound mitigation is gauged by STC ratings. Sound Transmission Class (STC) ratings indicate how well a wall or floor assembly reduces airborne sound traveling between rooms. Higher STC numbers signify better sound transmission reduction.
In the case of a bedroom situated above a family room; there are several ways to minimize sound transmission. However, the most effective methods can be financially daunting. A wood-framed floor assembly might boast an STC range of 40 – 43. An affordable option involves installing soundboard on the ceiling, potentially using two layers of drywall, and filling the joist cavity with blown-in cellulose. This combination could elevate the STC to a range of 49 – 52, significantly improving sound reduction but not achieving absolute sound-proofing. This option tends to be practical for most homes, but individual clients have varying tolerance levels for noise.