Reverb is a dense collection of echoes. Sabine’s equation ( RT_60 = 0.161 \fracVA ) (where (V) is volume and (A) is total absorption) dictates that for maximum reverb, absorption (A) must approach zero. In digital systems, this is trivial to simulate, but psychoacoustically, once echo density exceeds the fusion time (~50–80 ms), the ear stops hearing individual reflections and perceives a "wash."
While a short pre-delay sounds natural, an extremely long pre-delay ( 400ms or more ) can create surreal, trippy effects where the reverb appears long after the sound that triggered it. Creative Applications maximum reverb sound effect