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The Significance of Sound in Cinema

June 9, 2020


In the mid-1920s, the Warner brothers — the very ones the studio is named after — were in desperate need of a hit. Their numbers were down and they were getting destroyed by their competition (namely MGM, 20th Century Fox, Paramount, and RKO). They needed something new. So, they turned to sound. A buggy gimmick up until that point in time, Warner Bros. hoped to take silent cinema into a whole new era. This era became known as Talkies, and its impact continues still to this day nearly a century later.

They achieved this by synchronizing the film with a phonograph turntable so that the audio could be played back. Technicians would synchronize and mix multiple sound sources to the picture in a repeatable manner, often with archaic technology like motorized spindles and chains. From there, sound engineers continued to revolutionize the process by synching to more and more advanced audio playback machines until audio began to be printed straight onto the reel of the film itself (similar to how a vinyl record works). These reels — or "mag units" — were magnetized like audio cassette tapes, to equip them with a gorgeous sound.

Digital Sound for Film

Just as actual film reels eventually began to fade from the multiplex in favor of digital film files, the need for sound to be synced right onto the magnetic film strip started to grow old. Once considered analog, sound was now on the road to a major digital switch. Instead of manipulating analog audio using analog signal processing (ASP) with analog electrical circuits to create sophisticated audio mixes, filmmakers and sound technicians alike were embracing the bright, shiny, and new world of digital.

Initially, digital audio used sound wave samples to create a digital version of them using an analog to digital converter (A/D or ADC), which was then stored and manipulated in digital circuits. When the time came for the audio to be played back, a digital to analog converter (D/A or DAC) converted it back to analog audio. However, as time went on, equipment became more advanced, memory and storage got cheaper, and pure digital audio was adopted.

Digital Cinema

Long after audio went digital, film finally followed suit. Referred to as D-cinema, digital cinema emerged as the new standard in the 21st century. Thanks to filmmaking pioneers like George Lucas and James Cameron, big-budget films embraced digital cinema and digital audio in what became known as a DCP: a digital cinema package. It was a long road to that point, initially envisioned in sketches on the back of a napkin by a group of engineers a couple of decades prior, but digital cinema wasn't going anywhere anytime soon.

At the same time as the development of the DCP, a group of engineers from SMPTE were working on what they called an IMF: an interoperable master format. This was like a DCP with some added benefits. In the simplest terms, it was a collection of images, audio, and text files that played in sync with each other just like a DCP. However, an IMF can play many more types of files than a DCP can.

Of course, digital cinema would be nowhere without DSP: digital signal processing. DSP is the processing power of computers combined with dedicated signal processing chips to perform audio processing, and it's carried out using mathematical manipulation of both simple and complex digital signals. This results in high-quality audio that can stand the test of time far better than any tape, CD, or vinyl. For this reason, DSP has led to an unprecedented boom in more advanced sound production across film, television, and music alike.

Immersive Sound

The greatest benefit of DSP in a film is the ability to immerse the audience in the movie like never before. The sound is truly immersive, blasting out of speakers above and all around the viewer and effectively enveloping them in a multi-dimensional auditory experience. A long way off from the phonograph turntables of the past, DSPs allowed cinema to enter a brand new age of immersive sound that is unlike anything the medium has ever seen before. Films are no longer seen — they're experienced.

Until recently, delivering immersive audio required proprietary bitstreams to each system, but SMPTE has now standardized the immersive audio bitstream (IAB) with ST 2098-2. Companion standards have also been created that specify how to wrap it in MXF and carry it in a DCP or an IMF. The rollout of IAB is beginning this year and is sure to be an absolute game-changer in the interoperable delivery of immersive audio.


In addition to being integral to the way we enjoy films today, Digital audio and DSP have become a key component of TVs, phones, video gaming systems, home theaters, soundbars, and even car speakers. The sheer power and scope of digital audio and DSPs would be unfathomable to the pioneers at the forefront of the movement decades ago and incomprehensible to the sound engineers of early 20th-century cinema. Of course, none of it would be possible without the invention of compression.

When dealing with the massive sizes of audio files, it's essential to utilize codecs. A portmanteau of compression-decompression, codecs are needed to decode audio signals and broadcast them through the output. There are two kinds of compression that codecs deal with: lossless and lossy. With lossless compression things are removed during encoding, thus creating metadata that describes exactly what was removed. This is favored by Dolby and DTS Master Audio as well as streaming services. Lossy compression decides what bits and pieces of the audio file can be permanently removed during encoding to shrink the size of the file. This is favored by MP3s and DTS Surround, among other file types.

The Importance of a Great Sound System

Having great, immersive sound experience in a movie theater is just as important as a good screen and a clear projection, but you don't often hear people saying this. It's part of what makes the moviegoing experience far superior to watching movies at home on TV or on a laptop or phone. The built-in speakers on a TV or laptop won't bring you the same surround sound experience of a multiplex, and it's impossible — at least right now — to get that immersive sound experience out of the standard factory speakers on a phone, laptop or TV. High-end sound systems at the movie theater are essential for reproducing real detail (not just loud volumes). These are the details our brains understand, the ones that embed themselves into our consciousness, the ones that make the story seem all the more realistic. If you want to genuinely comprehend the true significance of sound in cinema, listen closely the next time you go to the theater.



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