The reckless future, the mystery of what has not yet happened: this, too, he learned, can be preserved in memory. --Paul Auster, The Invention of Solitude.

Porthole design affects both picture and sound. First, good design practice makes the size of the porthole and viewport the very minimum necessary. Large port apertures act as acoustic reflectors bouncing sound back towards the screen, and can also result in a large amount of ambient light leakage from the booth worklights ... Care should be taken over the quality of glass used, and optimum projection requires coating to further avoid internal reflections. -- Technical guidelines for Dolby Stereo Theatres