In 1922, a book was published called Collected Papers on Acoustics which covered all the work of the late Wallace Clement Sabine, known now as the father of architectural acoustics. The work spanned several decades and synthesised all the work of his acoustic predecessors such as Helmholtz and Rayleigh, within the scope of architectural design. The entire series of work is beautifully underpinned by a single problem - fixing the acoustics of the Fogg Lecture Hall in the newly constructed Fogg Art Museum. Sabine was tasked by Harvard University to acoustically correct the lecture hall after it had been abandoned and deemed impractical for use. In doing so, he describes the inadequacy of previous acoustic testing – inconsistencies in what was being listened to, or who was doing the listening, as well as a lack of description of the spaces themselves. Sabine’s experiments in measuring acoustic qualities involved years of moving materials, furnishings, and cushions with known absorption coefficients between different lecture halls and measuring the reverberation of the room with organ pipes of known frequencies, and a chronograph. Measurements would be made as consistently as possible, noting down the specific locations sound sources and positions of recordings of recordings. The tests would be detailed as to test the impact of moving only one or two cushions and measuring the acoustic response at several locations.

Through these experiments, Sabine derived his most significant contribution to architectural acoustics, reverberation time. Prior to this, reverberation was a qualitative measure of the way sound faded over time. Through his testing with absorption materials and lecture halls, Sabine redefined it as the amount of time it took for a sound produced by his organ pipe (approximately 60 decibels (dB), a logarithmic unit to measure sound level) to inaudible (0 dB) and was a function of the total volume of the room and total absorption. For concert halls, he suggested a reverberation time of approximately 2-2.25 seconds, while for lecture halls and rooms of speech, approximately 1 second. Sabine went on to use this equation in the design of the Boston Symphony Hall (as it is now known) in 1900. Though it is generally discussed as the first concert hall designed by quantitative methods, Sabine, in fact, utilised methods similar to The Golden Hall and refined them via his methods. He referred to both the Leipzig Gewandhaus and Old Boston Music Hall’s proportions, and by manipulating the overall ratios of both dimensions and absorbing materials, developed the design for the Boston Symphony Hall which is firmly placed among the best concert halls ever built.

Sabine’s work has since been developed further over the course of the 20th century. In 1964, Schroeder, defined a new method involving an integral with respect to time to find a smooth decay curve of reverberation time, increasing the accuracy. The quantitative measures now used to measure the quality of acoustics have also expanded to include strength, clarity, and early decay time, all of which can be derived from the decay curve. Additionally, the importance of lateral energy was highlighted, and measures are now included and taken through binaural (two-eared) microphones. All of this form the international standards (ISO3382) for acoustic performance measurements we use today.