5.2 Ambisonics and spatial audio formats
6 min read•august 19, 2024
is a cutting-edge audio technique that creates a full-sphere soundfield, offering a more immersive experience than traditional formats. It captures and reproduces sound from all directions, including height, allowing for flexible playback on various systems.
Ambisonics uses spherical harmonics to decompose the soundfield, representing it with coefficients that describe sound pressure and direction. Different formats like A-format, B-format, and Higher Order Ambisonics (HOA) offer various ways to store and transmit these immersive audio signals.
Ambisonics overview
- Ambisonics is a full-sphere surround sound technique that aims to recreate a complete soundfield at a given point in space
- Provides a more immersive and realistic spatial audio experience compared to traditional audio formats
- Allows for flexible playback on various speaker configurations or headphones
History of ambisonics
Top images from around the web for History of ambisonics
Friday Interview #3: Jörn Nettingsmeier | Libre Music Production View original
Is this image relevant?
LAC 2012 - The why and how of with-height surround production in Ambisonics : linuxaudio.org ... View original
Is this image relevant?
How Immersive Sound Brings Mixed Reality to Life – Microsoft Design – Medium View original
Is this image relevant?
Friday Interview #3: Jörn Nettingsmeier | Libre Music Production View original
Is this image relevant?
LAC 2012 - The why and how of with-height surround production in Ambisonics : linuxaudio.org ... View original
Is this image relevant?
1 of 3
Top images from around the web for History of ambisonics
Friday Interview #3: Jörn Nettingsmeier | Libre Music Production View original
Is this image relevant?
LAC 2012 - The why and how of with-height surround production in Ambisonics : linuxaudio.org ... View original
Is this image relevant?
How Immersive Sound Brings Mixed Reality to Life – Microsoft Design – Medium View original
Is this image relevant?
Friday Interview #3: Jörn Nettingsmeier | Libre Music Production View original
Is this image relevant?
LAC 2012 - The why and how of with-height surround production in Ambisonics : linuxaudio.org ... View original
Is this image relevant?
1 of 3
- Developed in the 1970s by Michael Gerzon and Peter Fellgett
- Initially aimed to improve upon quadraphonic sound systems
- Gained popularity in recent years due to advancements in virtual reality and 360° audio
Ambisonics vs stereo
- Stereo audio uses two channels (left and right) to create a limited spatial image
- Ambisonics captures and reproduces sound from all directions, including height information
- Ambisonic recordings can be rotated and tilted during playback, unlike stereo
Ambisonics vs surround sound
- Surround sound systems (5.1, 7.1) use discrete channels for specific speaker positions
- Ambisonics encodes the full soundfield, allowing for flexible speaker placement and scalability
- Ambisonics can be decoded to various speaker configurations or binaurally rendered for headphones
Ambisonic theory
- Based on the decomposition of a soundfield into spherical harmonics
- Represents the soundfield using a set of coefficients that describe the sound pressure and direction
- Higher-order ambisonics capture more spatial detail and allow for a larger sweet spot
Sound field decomposition
- Soundfield is decomposed into a series of spherical harmonics
- Spherical harmonics are a set of orthogonal basis functions on the surface of a sphere
- Each harmonic represents a specific spatial pattern of sound pressure
Spherical harmonics
- Denoted by the order (n) and degree (m)
- Zero-order (W) represents the omnidirectional component
- First-order (X, Y, Z) captures directional information
- Higher-order harmonics capture more detailed spatial information
Ambisonic order
- Determines the spatial resolution and the number of channels required
- First-order ambisonics (FOA) uses four channels (W, X, Y, Z)
- Higher-order ambisonics (HOA) use more channels for increased spatial resolution
- Second-order ambisonics use nine channels
- Third-order ambisonics use 16 channels
Periphonic vs pantophonic
- Periphonic ambisonics capture and reproduce sound in full-sphere (including height)
- Pantophonic ambisonics only capture and reproduce sound in the horizontal plane
- Periphonic ambisonics require more channels and a 3D speaker setup for accurate reproduction
Ambisonic formats
- Different representations of the ambisonic signal
- Describe how the ambisonic components are stored and transmitted
- Choice of format depends on the application and workflow
A-format
- Raw output from a soundfield microphone or tetrahedral microphone array
- Consists of four unprocessed capsule signals (LFU, RFD, LBD, RBU)
- Requires encoding to B-format for further processing and playback
B-format
- Most common ambisonic format for first-order ambisonics
- Consists of four channels (W, X, Y, Z)
- W: omnidirectional component
- X: front-back directional component
- Y: left-right directional component
- Z: up-down directional component
- Can be easily manipulated and decoded for various playback systems
Higher order ambisonics (HOA)
- Extension of B-format to higher orders
- Captures more detailed spatial information
- Requires more channels and processing power
- Enables a larger sweet spot and more accurate spatial reproduction
Ambisonic recording
- Capturing a soundfield using specialized microphone arrays
- Aims to preserve the spatial characteristics of the recorded environment
- Requires encoding of the raw microphone signals into an ambisonic format
Soundfield microphones
- Integrated microphone arrays designed for ambisonic recording
- Typically consist of four closely-spaced capsules arranged in a tetrahedron
- Examples: Core Sound TetraMic, Sennheiser AMBEO VR Mic
Tetrahedral microphone arrays
- Custom-built microphone arrays using four matched capsules
- Capsules are arranged in a tetrahedral configuration
- Allows for flexibility in capsule selection and spacing
Ambisonic encoding
- Process of converting raw microphone signals into an ambisonic format
- Involves applying a matrix transformation to the capsule signals
- Encoding coefficients depend on the microphone array geometry and normalization scheme
Ambisonic processing
- Manipulating and transforming ambisonic signals
- Allows for creative control and adaptation to different playback scenarios
- Includes decoding, rendering, and mixing techniques
Ambisonic decoding
- Process of converting ambisonic signals to speaker feeds
- Involves applying a decoding matrix based on the speaker layout
- Different decoding schemes available (e.g., projection, pseudo-inverse, mode-matching)
Binaural rendering of ambisonics
- Creating a binaural stereo output from ambisonic signals
- Allows for immersive headphone playback
- Utilizes head-related transfer functions (HRTFs) to simulate spatial cues
- Requires head-tracking for accurate localization
Ambisonic manipulation
- Rotating, tilting, and zooming ambisonic soundfields
- Achieved by applying rotation matrices to the ambisonic coefficients
- Enables dynamic spatial transformations and interactive audio experiences
Ambisonic mixing
- Combining multiple ambisonic signals and mono/stereo sources
- Involves encoding non-ambisonic sources into the ambisonic domain
- Requires careful consideration of source positions and spatial coherence
Ambisonic playback
- Reproducing ambisonic audio on various playback systems
- Ranges from dedicated ambisonic speaker arrays to headphone playback
- Aims to recreate the original soundfield and provide an immersive listening experience
Ambisonic speaker layouts
- Regular speaker arrangements for optimal ambisonic playback
- Examples: cube, octahedron, icosahedron
- Higher-order ambisonics require more speakers for accurate reproduction
Virtual loudspeakers
- Technique for playing ambisonics on non-regular speaker layouts
- Involves virtualizing a regular ambisonic speaker layout using VBAP or DBAP
- Allows for flexible playback on existing surround sound systems
Headphone playback of ambisonics
- Reproducing ambisonics on headphones using binaural rendering
- Requires head-tracking for accurate localization
- Provides an immersive experience without the need for a physical speaker setup
Spatial audio formats
- Different approaches to representing and storing spatial audio information
- Includes channel-based, object-based, and scene-based formats
- Choice of format depends on the application, content, and playback system
Channel-based formats
- Traditional approach using discrete audio channels for each speaker
- Examples: stereo, 5.1, 7.1, 22.2
- Limited flexibility and adaptability to different playback systems
Object-based formats
- Represents audio as individual sound objects with metadata
- Metadata includes position, size, and other properties
- Allows for dynamic rendering and personalization of the audio scene
- Examples: Dolby Atmos, DTS:X, MPEG-H 3D Audio
Scene-based formats
- Represents the entire soundfield using a set of basis functions
- Ambisonics is an example of a scene-based format
- Provides a compact and flexible representation of spatial audio
- Enables rendering to various playback systems and speaker layouts
Ambisonics applications
- Ambisonics finds use in various fields related to immersive audio and virtual reality
- Provides a compelling and realistic spatial audio experience
- Enhances the sense of presence and immersion in virtual environments
VR and 360° video
- Ambisonics is well-suited for spatial audio in virtual reality applications
- Allows for head-tracked audio that responds to user movements
- Provides a seamless and in 360° videos
Immersive installations
- Ambisonics enables the creation of immersive audio installations
- Surrounds the listener with a full-sphere soundfield
- Ideal for soundscapes, interactive art, and experiential exhibits
Game audio
- Ambisonics can enhance the spatial audio in video games
- Provides a more realistic and immersive sound environment
- Allows for dynamic audio that adapts to the player's actions and position
Music production
- Ambisonics offers new creative possibilities for music production
- Enables the creation of immersive and spatially-rich musical experiences
- Allows for spatial composition, mixing, and live performances in 3D space
Key Terms to Review (18)
3D Audio Rendering: 3D audio rendering refers to the process of creating sound that simulates a three-dimensional space, allowing listeners to perceive sounds as coming from specific directions and distances. This technique enhances immersive experiences in virtual and augmented reality by providing a realistic auditory environment that matches visual elements, making users feel as if they are truly present in the space. 3D audio rendering is essential for creating believable interactions within virtual worlds and helps in establishing an emotional connection with the experience.
Ambisonics: Ambisonics is a spatial audio technique that captures and reproduces sound in three-dimensional space, allowing for an immersive audio experience. This method encodes sound using spherical harmonics, enabling accurate localization of sound sources regardless of the listener's position. It connects with various aspects of audio technology, including sound design in virtual environments and enhancing the perception of spatial audio formats.
Audio-reactive visuals: Audio-reactive visuals are dynamic visual elements that respond in real-time to audio input, creating a synchronized experience between sound and imagery. This interaction enhances the immersive quality of environments, particularly in virtual reality and multimedia art installations, allowing audiences to engage more deeply with the experience. By utilizing various data from the audio, such as frequency, amplitude, and rhythm, these visuals can be transformed, animated, or generated in accordance with the sound.
Auditory Scene Analysis: Auditory scene analysis is the process by which the auditory system organizes sound information into meaningful perceptions, allowing us to distinguish between different sound sources in our environment. This process is crucial for understanding complex auditory environments, as it enables listeners to separate overlapping sounds and identify their origins. By doing so, it plays a significant role in how we perceive spatial audio and sound within immersive virtual environments.
Binaural Audio: Binaural audio is a recording technique that captures sound using two microphones, creating a three-dimensional auditory experience for listeners. This technique mimics human hearing, allowing sounds to be perceived from specific locations in space, which is crucial for creating immersive experiences in virtual reality and enhancing the realism of sound in various applications. Binaural audio enhances the listener's ability to identify the direction and distance of sounds, making it essential for spatial audio formats and integrating with audio middleware to create rich auditory environments.
David McKeown: David McKeown is a prominent figure in the field of spatial audio and immersive sound design, known for his work in advancing techniques related to ambisonics and immersive sound formats. He has contributed significantly to the development of tools and methodologies that enhance the user experience in virtual environments through spatial audio technologies. His research emphasizes the importance of accurately representing sound sources in three-dimensional space, which is crucial for creating realistic auditory experiences in virtual and augmented realities.
Immersive audio experience: An immersive audio experience is a sound environment that envelops the listener, creating a sense of presence and engagement in a virtual or augmented reality setting. This type of audio goes beyond traditional stereo sound, utilizing advanced techniques like Ambisonics and spatial audio formats to replicate real-world acoustics, allowing users to perceive sounds from various directions and distances. By enhancing the realism of sound in these environments, it plays a crucial role in how individuals interact with and perceive virtual spaces.
Interactive Sound Design: Interactive sound design refers to the creation and implementation of sound elements that respond to user actions or environmental changes within a digital medium. This type of sound design enhances the immersive experience by allowing users to engage with audio elements that adapt dynamically, creating a more responsive and engaging atmosphere. It is particularly important in fields like gaming and virtual reality, where sound can significantly impact user experience and immersion.
Julius Smith: Julius Smith is a prominent figure in the field of spatial audio and ambisonics, recognized for his contributions to audio engineering and immersive sound experiences. He is known for developing important tools and algorithms that have enhanced the understanding and implementation of spatial audio formats, particularly in the context of creating immersive environments for virtual reality and multimedia applications. His work has been instrumental in shaping how we perceive and interact with sound in three-dimensional space.
Listening tests: Listening tests are evaluations designed to assess an individual's ability to perceive and analyze audio content, specifically in the context of spatial audio formats and ambisonics. These tests can involve various tasks such as identifying sound locations, recognizing sound sources, or discerning differences in audio quality. They are crucial for understanding how listeners interact with complex audio environments and can help in evaluating the effectiveness of spatial audio systems.
Max/MSP: Max/MSP is a visual programming language primarily used for music and multimedia, allowing users to create interactive software by connecting graphical elements. It integrates audio, video, and sensor input, making it a powerful tool for artists and developers who want to create immersive experiences. Max/MSP's flexibility enables artists to experiment with sound spatialization techniques and biofeedback applications in their works.
Psychoacoustics: Psychoacoustics is the study of how humans perceive sound, examining the psychological and physiological effects of sound waves on our senses. This field explores not just the physical properties of sound, but also how we interpret those sounds in our environment, which is essential for creating realistic audio experiences in various formats. Understanding psychoacoustics is crucial for designing immersive audio environments, such as those found in virtual reality, where sound localization and spatial audio enhance user experience.
Reaper: In the context of ambisonics and spatial audio formats, a reaper is a digital audio workstation (DAW) that supports advanced audio recording, editing, and mixing capabilities. It allows artists and sound designers to manipulate audio tracks in a way that can incorporate spatial sound formats, creating immersive experiences that engage listeners from multiple dimensions and angles.
Sound localization: Sound localization is the ability to identify the origin of a sound in three-dimensional space, allowing listeners to perceive where a sound is coming from. This skill is crucial for creating immersive audio experiences, as it helps to replicate real-world auditory environments in virtual settings and enhances the overall realism of the experience.
Soundscape: A soundscape refers to the acoustic environment as perceived by individuals, encompassing all sounds in a particular location or setting. It includes natural sounds, human-made noises, and the interactions between them, shaping our auditory experience and influencing our perception of space. Soundscapes play a crucial role in virtual environments, where the representation and manipulation of sound can enhance immersion and emotional response.
Spatialization: Spatialization refers to the technique of positioning sound within a three-dimensional space, creating an immersive audio experience that mimics how we perceive sound in real life. This concept is crucial for enhancing realism and engagement in virtual environments by allowing users to hear sounds from specific directions and distances, replicating natural auditory cues and creating a sense of presence.
Subjective Assessment: Subjective assessment refers to a method of evaluation that is influenced by personal opinions, interpretations, feelings, and biases. In the context of immersive and virtual reality experiences, this type of assessment becomes crucial as it captures individual perceptions of sound and spatial audio. Understanding subjective assessment helps in evaluating the effectiveness of ambisonics and spatial audio formats, as different listeners may have varying reactions to audio presentations based on their unique experiences and preferences.
Surround Sound Mixing: Surround sound mixing is the process of creating a multi-channel audio experience that envelops the listener in sound from all directions, rather than just from a single source. This technique enhances the auditory experience by placing sounds in a three-dimensional space, making it feel more immersive and engaging. It is crucial in various formats such as films, video games, and virtual reality, where spatial audio can significantly enhance the narrative and emotional impact of the content.