Step order
- Confirm the dominant noise type and where it leaks.
- Seal obvious air gaps first (trim, outlets, penetrations).
- Decouple where possible (resilient channel, isolation clips, or separation layers).
- Add mass strategically (second layer where it matters).
- Treat flanking paths (vents, shared framing, doors).
Context notes
- Noise focus: Bass. Low-frequency energy transfer.
- Room focus: Apartment. Shared walls, limited modifications.
- Assembly focus: Doors. Solid core, seals, thresholds.
Common failure modes
- Sealing the visible gap but missing flanking paths.
- Adding absorption without sealing/decoupling.
- Blocking ventilation to chase silence.