Task: Question Generation
Input (English): 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. 
Output (English): How do echoes occur?