Fast doors make two closing sounds

Beginning with the Doom II engine, moving walls and ceilings (e.g. doors, lifts, rising stairs, crushers) may be either normal or "blazing": blazing sectors rise or fall much more rapidly than normal sectors.

When the player closes a blazing door by walking up to it and pressing "action" (the space bar in vanilla Doom), the expected sound effect (DSBDCLS) is heard. When a blazing door is allowed to close by itself, however, the same sound effect is played twice.