Obsidiplates are new pressure plates made from blocks of obsidian (that only work when players step on them) or mossy cobble (that only works when NPCs step on them). Obsidiplates can be crafted with a block of wool to make silent versions (which doesn't make clicking noises when stepped on). You can craft any of those four variants in the middle of alternating nether quartz and glowstone dust to make shrouded (see-through) versions as well. Smelting a silent or hidden plate will return the Obsidiplate into a regular obsidian pressure plate.
Obsidian Pressure Plate
Mossy Pressure Plate
The mossy pressure plate can be used in the silent, shrouded and shrouded silent pressure plate recipes instead of the obsidian pressure plate.