A versatile form of surround sound technology, more commonly referred to as 'immersive sound´, developed and marketed by Dolby Labs and introduced in 2012 with the Disney/Pixar film, Brave. While mostly employed for film and television content, it is increasingly being used in music productions, identified as 'Dolby Atmos Music'. DTS:X is a broadly similar rival technology.
The most obvious improvement compared to conventional 5.1 and 7.1 surround sound formats is that Dolby Atmos adds height channels — speakers in the ceiling — which greatly enhances the sensation of being enveloped with sound, hence the 'immersive' moniker. However, the underlying technology is also considerably more advanced as it combines conventional (static) channels of surround sound with 'object-based' audio content which can be directed to any speaker (or to move between speakers) by metadata encoded with the audio. It is this feature which provides the content creators with enormous flexibility over where individual sounds are placed and moved within the mix, in addition to a conventional 'bed' of surround sound.
Moreover, Dolby Atmos decoders are designed to map the source audio content dynamically to the connected sound system accommodating virtually any number and layout of loudspeakers, or even just to stereo earphones, maintaining the best possible impressive of the intended immersive sound stage (using binaural encoding in the case of stereo earphones).