Cinema Sound and the Loudness Issue: its Origins and Implications

Abstract

For over five decades after the introduction of ‘talking movies’, the soundtracks of films were recorded in various types of analogue forms, such as variable-area optical film, variable-density optical film and magnetically-coated film. From the1920s to the early 1970s, the background noise (hiss) inherent in the recording processes limited the level to which the sound could be amplified before the noise became unpleasant and annoying. The cinemas, themselves, were often made from converted theatres, whose acoustics were designed more for reinforcing the voices of live actors, rather than for sound reproduction via loudspeakers. However, these limitations were usually taken into account by the film directors and sound mixers, who kept the soundtracks relatively simple. Actors also tended to deliver their dialogue with a semi-theatrical projection, and in most cases spoke clearly. Accompanying music and effects were usually interspersed with the dialogue, so each occurred in its own time.
Ever conscious of the need for the cinema audiences to follow the plots, soundtracks were almost universally mixed in theatres which were of reasonably similar size to the cinemas, and with similar amplifiers and loudspeakers. In this way, the mixers could hear during the post-production process a sound which was a reasonable representation of how the public would hear it in the less-than-optimal conditions of most cinemas. Various forms of standardised, high-frequency equalisation were also introduced, to aid in establishing a good balance between the capabilities of the loudspeaker systems, the noise from the recording media, and the intelligibility of the sounds. Nevertheless, other than for limited release formats in premier cinemas with expensive sound reproduction equipment, the general level of sound in the average cinemas was little more than ‘adequate’. Responding to this problem, in the early 1970s, Dolby Laboratories introduced their A-type noise reduction to cinema soundtracks, along with Dolby Stereo. The latter was a ‘4-2-4’ phase-matrixed system, allowing four channels of sound reproduction which could wrap around the audience, although without the accompanying noise-reduction system the noise level would have been unacceptable. In the 1980s Dolby improved the situation still further with the introduction of Dolby SR noise-reduction, but the system was still limited to the four, matrixed channels because there was no more room on a 35 mm film to add more tracks. The answer to delivering more channels in a compact form seemed to lie in the use of digital soundtracks.

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ORCID for Keith Holland: orcid.org/0000-0001-7439-2375

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