Ms. Sound Effect, much like Mr. Fate and Lady Luck, is considered to be a mechanic of the world. As a Mechanic of the World, there is some speculation that they are not quite Titanic enough to be a Titan, but still are agents of change and action. There is some speculation that they are clock-work entities, though which Titan has the responsibility of winding them up is not known.
In the Real World, a sound effect is not sentient, and merely a vibration in the air which is recognized as communicating some basic information.