Architectural Acoustics, Its Past and Its Possibilities
Authors: Sabine P. E. 
Published: September 2005

As a science, Architectural Acoustics originated in 1895 in the first scientific work ever done on the phenomenon of reverberation in rooms by Wallace C. Sabine at Harvard. The first twenty years of its history is covered by his single-handed attack on the problem of the quantitative aspects of reverberation and absorption of sound. The second stage covering the period from 1915 to about 1925 marks a rapid increase both in interest on the part of scientists in the subject, and an expanding use of the practical applications of the new science. During this period numerous laboratories were built with reverberation chambers for the measurement of sound absorption coefficients and the transmission of sound through walls, floors, and ceilings. In this period the organ pipe as a source, the threshold of hearing as a fixed level of intensity, and the stop-watch as a timing device comprised the instrumental equipment for measurements with Sabine's technique.

With the development of new and powerful sources of sound in the dynamic type of loudspeaker, improved microphones with constant characteristics, vacuum-tube amplifiers and audiofrequency oscillators came a revolution in experimental technique. The advent of the radio and the talking motion picture created a new field for the application of knowledge for the control of acoustic conditions in broadcasting studios and sound-motion picture stages, and to meet the more exacting requirements of motion picture theaters, with their greatly increased seating capacities and amplified and directed sound.

The architectural trends during this period have been toward larger auditoriums and simplified decorative treatment of the interiors. This adds to the difficulties of the acoustical problem, and also makes its solution an essential part of the architect's program in auditorium design. The earlier practice of designing to taste and leaving acoustics to be taken care of by absorbent treatment is gradually giving way to the more enlightened policy of including acoustic demands in the geometrical design of audience rooms.

Architectural acoustics has become the basis of a large and rapidly growing industry, in the manufacture and installation of acoustical absorbents. Competition in this field has been in the direction of the production of materials with ever higher absorption coefficients, often at the expense of other desirable properties of interior surface materials. With this has been a growing tendency toward what in the author's opinion are over-damped rooms. The frequency-absorption characteristics of many commercial materials with their relatively low absorption for low frequency sounds leave much to be desired. Absorbents with controllable frequency characteristics which do not depend upon the porosity or the inelastic compressibility of materials constitute a possibility for the future in this field.

Another possibility lies in the development of cheap practical means of reducing sound transmission in moderate-priced homes, apartments, hotels and hospitals. The increasing use of electrically operated household devices together with the light and closely fabricated construction employed in cheap housing, often makes a dream cottage a nightmare of irritating noise.

On the theoretical side lies the possibility that the approximations of reverberation theory may be ultimately replaced by some more precise and general solution of the problem of “What is the behavior of vibrational energy in a three-dimensional medium bounded by imperfectly reflecting walls.” The solution of this problem may conceivably have an important bearing on the wider problem of the relation between quantum physics and the field equations of relativity.