Mineral wool (rock wool) batt significantly outperforms fiberglass for acoustic separation — its higher density absorbs sound energy rather than merely resisting thermal transfer. Mineral wool in interior walls, combined with resilient channel mounting for drywall and acoustic caulk at all penetrations (electrical boxes, top plates, plumbing), creates a meaningfully quieter home. Adding insulation alone without sealing flanking paths limits the acoustic improvement — RainFire Builders addresses both as part of every acoustic wall scope.