Cinema Electro-Acoustic Quality Redux

摘要

Multiple, closely similar, stadium-seating cinemas equipped with a variety of state-of-the-art sound systems from various manufacturers were thoroughly characterized for sound quality. All the auditoriums were acoustically similar and met all contemporary standards. Findings including acoustical issues remaining after the standard reverberation time, background noise level, and isolation, have been addressed. New or extended findings were made, particularly related to the effects of auditorium features such as stadium seating, regularly spaced rows of seats, the low wall(s) that separate the lead-in ramp area from the stairs up to seating, and backwall absorption. Traditional problems such as screen loss and reflections between the screen and horns were investigated, as well as sound system design elements. The principal findings involve a new method of mapping the coverage of the sound system, with individual response curves for both the long-term steady-state and the first arrival sound, mapped on a grid of typically ten points in the auditorium. Thus problems arising from directional effects in the loudspeaker output or screen modification of the output in coverage, and room acoustics, are well documented. Also included are subwoofer placement effects, the differences between compression drivers equipped with titanium and those with beryllium diaphragms, and others.