Teoría Austriaca del ciclo económico

S A

(a) Monaural.

A1

A2

S

(b) Binaural.

S A

(c) Monophonic.

A₁

A₂ S

(d) Stereophonic.

A₁

A₂ S

(e) Pseudo-stereophonic.

A1

A2

S

(f) Biphonic.

Figure 3.3: Classification of the various forms of sound repro-duction. See the text for more information. After Snow [1953];

Streicher and Everest [2006].

were reached since the first sound recording/playing device, the phonograph, was invented by Thomas Edison in 1877. As Theile [1990] states, the purpose of cin-ema sound is not about achieving the optimum naturalness of the soundscape but rather about producing spatial effects to a large audience in an economic way.

3.2.1 From silent movies to talkies

Ironically, the phonograph marks the beginning of the history of sound for moving pictures before the actual invention of the moving picture. Indeed, an article in Scientific American [1877] envisioned the combination of Edison’s phonograph with the projection of stereoscopic images from the beginning:

It is already possible by ingenious optical contrivances to throw stereoscopic photographs of people on screens in full view of an audience. Add the talking phonograph to counterfeit their voices, and it would be difficult to carry the illusion of real presence much further. (Scientific American [1877])

However, the audience would have to wait until 1891 to see moving pictures.

Edison, again, designed an apparatus for one spectator (the Kinetoscope), and later in 1895, the Lumi`ere brothers invented a device capable of capturing, processing, and projecting moving images for a larger audience (the Cin´ematographe).

The first movies projected in theaters were sometimes accompanied by live sound performed by an orchestra or a pianist [Altman, 1995]. Until around 1910, the movie experience became closer and closer to live theater performance as pro-fessional actors spoke lines in sync with the images, carefully hidden behind the screen. In parallel, inventors around the world experimented with the synchro-nization between a disc containing a soundtrack and the movie projection. Since these audio systems aimed primarily at reproducing the human voice, thereby re-placing the live actor, the first loudspeakers moved from a position next to the projector (behind the audience) to a position near the screen.

Producers, however, favored music accompaniment from the early 1910s until the time in the mid-1920s, when Bell Labs developed the Vitaphone. This system used electrical amplification to bring the sound to the audience (Figure 3.4). The first feature film with synchronized sound was “Don Juan” in 1926. The sound-track contained music and sound effects. One year later, “The Jazz Singer”, the first feature film with synchronized dialogs, was released, again using Vitaphone sound.

3.2. A BRIEF HISTORY OF SOUND REPRODUCTION IN MOVIE THEATERS

Figure 3.4: A Vitaphone system diagram, circa 1927. © 2000 The American WideScreen Museum.

3.2.2 From monophonic to stereophonic sound

The electrical amplification of sound signals pushed research forward towards stereophonic reproduction. At the same time, the speakers moved behind the screen for a better association between the sound and the image. However, stereo sound did not reach theaters directly, mainly because the 1929 crisis and World War II prevented studios and theater owners to invest at that time.

3.2.3 The development of multiphonic sound

The development of multiphony started with Disney’s “Fantasia”, in 1940. A particular sound system, Fantasound, was conceived for the reproduction of this movie. Two projectors were needed to play the movie, one for the image and a back-up mono soundtrack, and one for the three-channel stereo soundtrack, combined to a synchronization track, all optically encoded. The three channels drove a stereo system behind the screen. In addition, a combination of the left and right signals drove loudspeakers surrounding the room. The movie was presented as a roadshow in 1940 and 1941. However, due to the complexity of the hardware and the political turmoil of the time, the movie was re-released in mono, which was easier to distribute, and Fantasound was not used for any other movie.

Although the use of Fantasound was short-lived, engineers kept the idea of a three-channel stereo system behind the screen. After World War II, improvements in sound reproduction happened around the audience, where dedicated channels were used to reproduce ambience and sound effects. In 1952, the new Cinerama system combined three projectors illuminating a huge curved screen and multi-channel sound. A five-multi-channel stereo system was used behind the screen and the sixth channel drove loudspeakers in the room. Shortly after, Fox’s CinemaScope used four tracks (on 35 mm film) or six tracks (on 70 mm film), again with one channel controlling the loudspeakers in the room, and the others controlling a front stereo system.

Magnetic recording of the soundtrack was very expensive, and prevented the generalization of surround sound in movie theaters. This was the case until the first episode of the “Star Wars” saga, which used Dolby Stereo, an optical encoding of four tracks on 35 mm film. This encoding combined a noise reduction technique (called Dolby A) to a 4:2:4 matrixing. This means that four tracks were recorded, encoded into two channels, and decoded back to four channels in the theater.

Hence the name “stereo”, which indicates that the four tracks only occupy the space of two tracks on the film. These four tracks were divided into a three channel stereo system at the front (left, L, center, C, and right, R) of the theater, and a surround channel at the back. A conventional loudspeaker arrangement is illustrated in Figure 3.5.

3.2.4 The digital sound era

The sound of movies went through digitalization long before the image. Dolby launched Dolby Digital with the release of “Batman Returns”, in 1992. But it was rather “Jurassic Park”, one year later, that encouraged theater owners to upgrade to digital sound. Digital sound at that time was still printed on film, just as in Dolby Stereo. Both systems could actually live next to each other, as well as next to their competitors SDDS (Sony Dynamic Digital Sound), and a time code for DTS (Digital Theater System). The latter stored the sound information on an additional CD-ROM. A picture showing these four systems on a film track is shown in Figure 3.6.

Dolby Digital and DTS surround allowed up to six channels. These are com-monly referred to as 5.1. Five channels drive full range loudspeakers, from about 20 Hz to about 20 kHz. The five tracks divide in a three channel stereo system at the front (L, C, and R) of the theater, and two surround channels at the back, at

3.2. A BRIEF HISTORY OF SOUND REPRODUCTION IN MOVIE THEATERS

Seating area Screen

C

L R

Surround

Figure 3.5: Arrangement of loudspeakers for conventional motion picture sound. The surround channel may be divided into several channels, depending on the encoding. AfterStreicher and Everest [2006].

the left (LS) and the right (RS) of the room. The sixth channel, 0.1, is a special channel that drives a subwoofer, with a range of about 20 Hz to 120 Hz, or about one tenth of the normal range in logarithmic units. This channel has a particular use in cinema sound as it conveys the low-frequency effects (LFE). SDDS has the particularity to add two channels at the front, between the three stereo channels already defined.

In 1999, Dolby, working with THX, released its new format called Dolby Digital Surround EX for the movie “Star Wars Episode I: The Phantom Menace.” The new format added a center surround channel, matrixed in the left and right surround channels for backward compatibility with 5.1.

Recently, the channel count has stabilized to 7.1, although, contrary to 5.1, this layout has not been standardized. The two channels in addition to 5.1 can be placed on the sides (Dolby, DTS) or at the front (SDDS). Dolby and DTS have also released lossless audio codecs, respectively called Dolby TrueHD and DTS HD Master Audio.

Along with the new available channels came the challenge of recording for such

Figure 3.6: A photo of a 35 mm film print featuring four au-dio formats – from left to right: SDDS (blue area to the left of the sprocket holes), Dolby Digital (grey area between the sprocket holes labeled with the Dolby Double-D logo in the mid-dle), analog optical sound (the two white lines to the right of the sprocket holes), and the DTS time code (the dashed line to the far right.) License: Creative Commons Attribution-Share Alike 3.0 Unported license.

formats. Different microphone arrangements exist to capture a natural sound field for subsequent 5.1 reproduction. Some arrangements focus on the quality of the spatial image, mainly sought in the frontal direction (INA 3, near-coincident line, Decca-Tree, and OCT, see [Theile, 2000] for a discussion), and some combine a frontal spatial image with an enveloping ambience at the back into one arrange-ment (INA 5, Fukada Tree, and OCT-Surround, see [Theile,2000] for a discussion).

Most of the time, such a microphone rig is used in combination with spot micro-phones placed close to particular sources of interest, resulting in dry signals, and the various signals are mixed to produce the final soundtrack, spread on the whole loudspeaker layout.

3.2.5 A glimpse into the near future

Several formats, available for production today, go beyond 7.1. This increase in channel count is mainly an attempt to increase the area of correct reproduction, or sweet-spot, of the reproduction system [Hamasaki et al., 2004]. More recently, the focus has also been on adding height information [Hamasaki et al.,2006;Van Daele and Van Baelen,2012].

Advertising it as “twice as good as 5.1”, Tomlinson Holman introduced the