You will be given a definition of a task first, then some input of the task.
In this task, you are given a paragraph, event and an entity. The event is part of the given paragraph and it changes the state of the entity. Your task is to classify the state of the entity into three classes: 1) not exist, 2) unknown location and 3) known location. "not exist" means the entity doesn't exist in that state anymore. "unknown location" means the entity exists in that state but location is unknown. "known location" means the entity exists and location is known. 

 "process paragraph : : Something happens to produce a sound. The sound travels in waves. The sound waves hit an object. The object absorbs some of the sound waves. Some of the sound waves bounce off of the object. The reflected sound waves can be heard, though they have slightly different properties than the original sound. The sound continues to bounce off of things and produce echoes until it is totally absorbed or dissipated. ", "event : The sound travels in waves.", "entity : sound ; sound waves" 
Output:
 unknown location 