Speech recognition protocols were part of a holographic program that recognized what an individual was saying to the hologram and allowed it to respond.
In 2374, while working on a replacement for USS Voyager's Emergency Medical Hologram with Harry Kim, Tom Paris became annoyed as the replacement doctor continued to incessantly recite passages from Gray's Anatomy, telling it to be quiet. Kim explained that the replacement couldn't comply because it didn't have speech recognition protocols yet, and Paris told Kim to give him some. (VOY: "Message in a Bottle")