I built acoustic panels (haven't hung them yet :)) following a tutorial on youtube. Total cost ~$30 : r/BudgetAudiophile
How to Easily Make DIY Soundproof Panels - Noting Grace
HOW TO BUILD A SOUND ABSORBING PANEL IN 5 EASY STEPS<br/> — Full English Post
How To Build High-Performance DIY Acoustic Panels | Working from home? Let's build some high-performance acoustic sound absorption panels that look SUPERB. | By DIY PerksFacebook