When to call a pro

DIY seals and masking are enough for many mild cases. Call a specialist when:

You have already sealed obvious gaps and still cannot sleep
You are about to spend thousands on windows and want apples-to-apples quotes
Noise enters through walls/roof (not just glass) — may need an acoustical consultant
You need documentation for a landlord, HOA, or legal matter

Bring your noise log, photos of windows, and budget range. Ask every vendor for OITC/STC data and flanking-path honesty.