Reverberation is the result of a sound source being instantiated within an acoustic environment. It usually consists of multiple primary reflections that are the result of the first interaction of the sound waves with the acoustic space, followed by more spaced out and rapidly diminishing echoes. A reverb response can be short and loud, similar to a slap-back echo produced by a highly reflective environment such as a tiled bathroom, or long and slowly fading, such as that produced inside a large cathedral. The human brain is very sensitive to this information, extracting size information very rapidly. That is why budget reverb devices sound budget, and why a good electronic reverb simulation device can cost many thousands of dollars.