How much sound reduction can a wooden interior door actually achieve?

A hollow core door typically achieves around 20 dB; a 40 mm solid core door reaches roughly 30–32 dB, and with a dense core, perimeter EPDM seals and an automatic drop-down door bottom you can approach 38 dB. The leaf is only half the system — gaps under the door and a hollow frame will undo a good door. Always specify the seal package together with the leaf.