Computer says no!
If the room with the sentry is connected to the room the player is standing in, the player will hear the sentry regardless of whether or not the room is being rendered.
If the room with the sentry is cut off from the room the player is standing in, so there is no passageway between them at all and the only way to get there would be teleportation or noclip, the sounds from the sentry will not be heard.
If you wanted the sentries to be silent, you could spawn them only when they are needed using a point_template. Or have them in separate part of the map and parent them to a moving brush entity, or use teleport logic, to bring them in when the players are present.