Customer wants a home office wall that actually blocks noise from the kids' playroom.

Best bang for the buck: Add resilient channel + double-layer drywall (5/8" Type X) on the office side. This typically jumps STC from ~33 (standard) to ~45-48.

• Resilient channel decouples drywall, breaking sound paths.
• Double-layer drywall adds mass (mass law: +5 STC per doubling).
• Type X adds density.

What kills it:

1. Flanking paths – Sound bypasses walls through ceilings, floors, shared studs. Seal gaps with acoustical caulk.
2. Single stud wall – Limited decoupling. For major gains, rebuild as staggered or double-stud wall (STC 50+).
3. Recessed lights or outlets – Penetrate the air gap. Use IC-rated, airtight fixtures and sound gaskets on outlets.
4. Not addressing the source – Carpet/playroom side needs treatment too. Add mass-loaded vinyl (MLV) or acoustic panels there.

Quick upgrade path:

• Remove existing drywall on office side.
• Install resilient channel (RC-1 or RC-2) at 24" o.c.
• Hang two layers of 5/8" Type X drywall with staggered seams.
• Seal all joints with acoustical caulk.

Code note: Check local building codes—some jurisdictions require fire-rated assemblies when adding layers. Resilient channel must be installed per manufacturer specs to maintain fire rating.

For maximum performance, consider adding insulation (R-13 mineral wool) in the cavity if not already present.

Biggest STC jump per dollar: Decoupling + Mass + Damping (in that order).

1. Decouple (STC +10–15): Remove existing drywall on one side only. Install resilient channel (RC-1) or, better, hat channel + sound isolation clips (e.g., Kinetics, GenieClip) perpendicular to studs. Clips outperform channel; channel is cheaper but fails if screws hit studs. Code: IRC R702.3.3 (fastening schedule).
2. Add Mass (STC +5–8): Hang 2 layers of 5/8" Type X drywall on the new channel/clips. Stagger seams. Use Green Glue (or generic viscoelastic damping compound) between the two layers. This adds mass and constrained-layer damping.
3. Seal Everything (STC +3–5, but kills flanking): Acoustic caulk (not silicone) at perimeter, outlets, penetrations. Putty pads on back of outlet boxes. This is where cheap jobs fail. A 1% gap kills 10+ STC points.

Total assembly (one side treated): ~STC 55–60. Cost: ~$3.50–$5.50/sq ft (clips + 2x 5/8" + GG + caulk).

What kills it:

• Screws hitting studs through resilient channel (shorts the decoupling).
• Recessed lights/outlets back-to-back without putty pads or offset boxes.
• HVAC ducts sharing the cavity (use lined flex duct + soffit).
• Door: Hollow core = STC 20. Must use solid core + automatic door bottom + perimeter seals. Wall STC means nothing if door is weak.

Don't bother: Fiberglass batts alone (STC +3–4), MLV alone (expensive, hard to seal), double stud wall (too late, framed).

Pro tip: If ceiling is open, treat it same way. Flanking over the top wall plate is the #1 complaint.