AND REVERBERATE (5 letters) The term 'effect sound' can be broken down into two crossword solutions: ECHO (4 letters) AND REVERBERATE (5 letters). ECHO is a sound that is heard again after it is produced, usually due to reflection off of a surface. REVERBERATE is the persistence of sound after its source has stopped, which is caused by multiple reflections of sound waves. Both ECHO AND REVERBERATE are examples of effect sound, which is sound that has been altered or modified in some way.