Much of the earliest work on Audio Engineering using electronics -- as opposed to purely acoustical systems -- was for the telephone system and for sound for motion pictures. The history of motion picture sound engineering will be found in the Journal of the Society of Motion Picture and Television Engineers, SMPTE. Many historic articles about ground-breaking audio work in the Bell System were published in the Bell System Technical Journal. Topics of articles published in one or both of these journals include the development of microphones, loudspeakers, amplifiers, room acoustics, stereophony, high-fidelity transmission systems and recording and reproduction on mechanical disks, optical film, and magnetic film.
Before the advent of television -- from its founding in 1916 to 1950 -- SMPTE was known as the Society of Motion Picture Engineers, SMPE.
We have scanned and posted here, with permission from SMPTE, a detailed history as given by EW Kellogg in "History of Sound Motion Pictures", Journal of the SMPTE, Vol 64 (1955), in three installments: June, pp 291...302 (1.8 MB); July, pp 356...374 (4.0 MB); August, pp 422...437 (2.4 MB). Forty-four pages total, with 406 (!) references.
The history of motion picture sound recording, in all of its aspects, will be found in two books that may be found at used book dealers:
Frayne, John G & Wolfe, Halley, "Elements of Sound Recording", John Wiley and Sons, 1949.
Some interesting links on motion picture sound include:
An animated sound film from 1929, " Finding His Voice", that explains motion picture sound.
A 1943 film from Encyclopedia of Britannica, " Sound Recording and Reproduction (Sound on Film)"
The "American Widescreen Museum", that has historical materials including reprints of historical engineering papers.