We all know that getting the audio right makes the pictures better. Anyone who has seen a movie created for Object Audio like Dolby Atmos will know that there is something special about it. To figure out what that is, let's rewind a little and see why we might need it.
Remember the good old days of mono audio on TV? Mono audio gives a single channel of sound played back through one or more speakers. That's fine for many genres, but to increase the feeling of being in the scene, stereo audio was introduced, so that left and right channels are transmitted, giving our ears the ability to hear sound moving on either side of us like we do in real life while we watch the images.
With the advent of cheaper electronics, we moved to a surround sound system where we added more speakers to give the impression that sounds could come from in front and behind as, as well as either side of us. Typically, today these surround sound systems use 5.1 channels. This means that we have 5 full bandwidth channels:
- Left Front
- Right Front
- Left Rear
- Right Rear
And one low bandwidth channel (this it the ".1")
- Low Frequency Effects (LFE)
This system essentially takes a sound mix from the program creator that is mastered on 5.1 speakers and then maps it on to the 5.1 speakers in your home or in the theater.
Audio processing technology is now very cheap your cellphone can do more audio processing than dedicated hardware from the 1990s. We have much bigger screens today, and with the rollout of UHD, it is likely that we will be sitting even closer to them. To increase the sense of "being there," adding a vertical element to the sound can make a dramatic difference.
It is impractical to move from a situation where we have six fixed speakers to one where we have hundreds of speakers that position the sound exactly, especially when most of the time there will be little or no sound coming from an individual speaker. Imagine instead a "bed" of audio that is the traditional stereo, or 5.1, mix that you add effects or objects to with an audio stream and some control metadata.