Light drywall on studs reflects mid and high frequencies strongly, but flexes at low frequencies, so it absorbs a little bass and lets a lot of it through.
Absorption by the numbers
A single-layer drywall surface absorbs about 5% of the sound that hits it at 500 Hz (coefficient 0.05). A fabric-wrapped 2 in panel absorbs about 100%. Covering even a fifth of the wall with panels changes the room dramatically.
| Surface | Approx. absorption at 500 Hz |
|---|---|
| Single-layer drywall | 0.05 |
| Carpet on pad | 0.30 |
| Heavy curtains | 0.50 |
| 1 in panel | 0.79 |
| 2 in panel | 1.14 |