Immersive audio technologies like Dolby Atmos and Ambisonics are revolutionizing surround sound. These formats go beyond traditional channel-based systems, offering more precise sound placement and a fuller, more enveloping audio experience.

Object-based audio and spherical sound fields allow for greater flexibility in positioning sounds. This opens up new creative possibilities for sound designers and enhances the listening experience across various platforms, from cinemas to headphones.

Spatial Audio Formats

Dolby Atmos and Object-based Audio

• Dolby Atmos is a surround sound technology developed by Dolby Laboratories that expands on traditional 5.1 and 7.1 setups by adding height channels and object-based audio
• Object-based audio allows sound designers to place and move individual sound elements in 3D space independently of the speaker layout (gunshot, car engine, dialogue)
• This approach provides greater precision and flexibility in positioning sounds compared to traditional channel-based systems
• Dolby Atmos can be used in cinemas, home theaters, and on mobile devices with headphones

Ambisonics and Higher Order Ambisonics (HOA)

• Ambisonics is a full-sphere surround sound technique that aims to capture and reproduce a complete soundfield
• It uses a spherical harmonic representation of the soundfield, allowing for rotation and manipulation of the soundfield during playback
• Traditional first-order Ambisonics (FOA) uses four channels: W (omnidirectional), X (front-back), Y (left-right), and Z (up-down)
• Higher Order Ambisonics (HOA) expands on FOA by using more channels to capture and reproduce the soundfield with greater spatial resolution and accuracy (second-order, third-order)
• HOA requires more microphones during recording and more speakers for playback compared to FOA

Ambisonics Components

B-format and Higher Order Ambisonics (HOA)

• B-format is the standard format for storing and transmitting Ambisonic audio signals
• It consists of four channels: W, X, Y, and Z, which represent the omnidirectional and three-dimensional components of the soundfield
• Higher Order Ambisonics (HOA) extends B-format by adding more channels to capture and reproduce the soundfield with greater spatial resolution
• HOA channels are often denoted by their order and degree, such as second-order (9 channels) or third-order (16 channels)
• As the Ambisonic order increases, the number of channels required grows exponentially, leading to more complex recording and playback setups

VBAP and Binaural Rendering

• VBAP (Vector Base Amplitude Panning) is a method for positioning virtual sound sources in a 3D space using Ambisonic audio
• It works by adjusting the gains of the Ambisonic channels to create the illusion of a sound coming from a specific direction
• Binaural rendering is the process of converting Ambisonic audio to a two-channel format suitable for headphone listening
• This is achieved by convolving the Ambisonic signals with head-related transfer functions (HRTFs), which simulate how sound reaches the left and right ears from different directions
• Binaural rendering allows for immersive 3D audio experiences over headphones without the need for a multi-speaker setup

Immersive Audio Features

Height Channels and Object-based Audio

• Height channels are additional speakers placed above the listener's head to create a sense of vertical sound dimension
• They are used in immersive audio formats like Dolby Atmos and DTS:X to enhance the realism and envelopment of the soundfield
• Object-based audio allows sound designers to place and move individual sound elements in 3D space independently of the speaker layout
• This approach provides greater control over the positioning and movement of sounds compared to traditional channel-based systems (Dolby Atmos, DTS:X)
• Object-based audio metadata is used to describe the position, size, and movement of each sound object in the 3D space

Binaural Rendering and Head-tracking

• Binaural rendering is the process of converting spatial audio formats like Ambisonics to a two-channel format suitable for headphone listening
• It simulates how sound reaches the left and right ears from different directions using head-related transfer functions (HRTFs)
• Head-tracking is a feature that enhances the binaural rendering experience by adjusting the sound based on the listener's head movements
• It uses sensors (accelerometers, gyroscopes) to track the orientation and position of the listener's head in real-time
• The audio is then dynamically adjusted to maintain the correct spatial relationship between the virtual sound sources and the listener's head, creating a more realistic and immersive experience (VR, AR, gaming)