Blumlein Binaural Sound(1931–1935)

Binaural Sound was a two-track optical stereo format for 35mm film, among the first formats to host an image and two audio tracks on a single filmstrip. It was invented in 1931 by Alan Blumlein – a young audio engineer, who also invented the moving-coil microphone (Blumlein & Holman, 1932), among other recording technologies – and developed under his supervision at EMI’s Hayes factory in London, England, between 1933 and 1935. The project culminated with the production of several short films, designed to demonstrate the system’s acoustic and dramatic potential for narrative motion pictures. However, the films suffered from a number of acoustical problems, most notably the prominence of background noise. And due to limited resources at EMI, which primarily specialized in music recording and playback technology, these problems were never fully addressed, and the format was not developed further for commercial use.

Blumlein reportedly conceived of the format in 1931 after taking his wife to the cinema (Alexander, 1999: p. 60). Like most talking pictures at the time, the film they watched featured a mono soundtrack, where all the dialogue emanated from a single speaker positioned behind the center of the screen, regardless of the actor’s location in the frame. Blumlein found this auditory experience unsatisfying, which led him to envision a stereo theater system where sounds would be perceived to travel between the left and right sides of the screen, in concert with the actors’ movements. That December, he submitted a patent application for such a technology. It outlined new microphone techniques for separating sounds into two signals, new methods for encoding these signals onto optical tracks, and new processes for reproducing these signals through two loudspeakers (Blumlein, 1933). He later named this system “Binaural Sound”.

Once his British patent was approved in 1933, Blumlein enlisted a colleague at EMI, Cecil Oswald Browne, to create a prototype for his new stereo system. The two then assembled a team of engineers from EMI’s sound, film, and television divisions – including Herbert Holman, Ivan Turnbull, Maurice Harker and Henry Clark – to help build the necessary recording and mixing equipment (Alexander, 1999: pp. 81–2). They completed their working prototype in 1935, at which point Blumlein oversaw the production of several test films that would showcase the new format’s capabilities. The films, which were produced at EMI’s research and development factory, included short actualities of trains arriving at the nearby Hayes Station (and passing from frame-right to frame-left), as well as staged demonstrations filmed on the factory’s auditorium stage, where EMI engineers (including Blumlein) addressed the camera while moving across the frame. The final film, produced twice, was a comedic playlet called Move the Orchestra, set in a restaurant, where the conspicuous playing of an offscreen orchestra makes it difficult for customers to place their orders with the waiter. Screenings were held for film industry insiders as well as dignitaries, including the Prince of Wales (soon to become the short-reigning monarch, Edward VIII) (Burns, 200: p. 140).

EMI nevertheless chose to shelve the project shortly after these demonstrations. Studio heads and theater owners had only recently converted to talking pictures, and few had the appetite to invest in yet another costly overhaul of their facilities. Indeed, every attempt to introduce multi-track sound to motion pictures during the 1930s faced similar resistance (Dienstfrey, 2024). Other, rival attempts included the two-track premiere of Hell’s Angels (1930), the limited run of A Midsummer Night’s Dream (1935), in a three-speaker format later branded Vitasound, and Joseph Maxfield’s two-track optical stereo system developed at Electronic Research Products, Inc (ERPI). As with Binaural Sound, studios and theaters had virtually no interest, at the time, in adopting any of these stereophonic formats. Instead, they were focused on improving the quality of their existing mono systems.

EMI also had limited resources. Binaural Sound showed potential, but it was acoustically flawed. The use of narrow optical audio tracks substantially increased the volume of background hiss. Additionally, Humphries’ Laboratories – where the films were processed – had yet to adopt a system that enabled the optical tracks and images to be printed simultaneously. Instead, they employed a two-stage chemical process that resulted in the two audio tracks losing much of their definition and contrast, weakening each film’s directional effects and leading to even more background noise (Alexander, 1999: pp. 85, 91). Blumlein’s team would later incorporate a “squeeze track” process that removed much of this noise (Burns, 2000: p. 510). Yet, even with these improvements in clarity, EMI’s head of research, Isaac Schoenberg, felt that it would be more prudent to invest, instead, in the company’s emerging television technologies (Alexander, 1999: p. 91).

Blumlein subsequently turned his attention to the development of improved aviation technologies. He died on June 7, 1942, while testing a new radar system on a Handley Page Halifax bomber, which crashed near the England–Wales border, with the loss of all those onboard (Burns, 2000: p. 455). Cecil Browne, who helped develop Blumlein’s Binaural Sound system at EMI, also died in the crash.