3. Technical Terms


Degrees of Freedom (DOF)


3DOF

Typically refers to a single sensor (accelerometer or gyroscope) 3 axis output values

Synonyms :

6DOF

Typically refers to the usage of two sensors (accelerometer and/or gyroscope and/or magnometer) 6 axis output values

Synonyms :

9DOF

Typically refers to the usage of three sensors (accelerometer, gyroscope and magnometer) 9 axis output values

Synonyms :

10DOF (and greater)

Typically refers to the usage and combination of sensors for 10 or more axis data output values

Synonyms :

Inputs & Outputs


Source

Typically referring to a sound source or a single mono or stereo input sound/track

Synonyms : Input

Listener

Typically referring to the listening object representing your first person perspective ears or the virtual microphone object or location for stereo capture and playback

Synonyms : Decode, Monitor, Monitoring, Listening, Stereo Playback, Binauralized

Encode

Having audio content input into a spatial or multichannel soundfield.

Synonyms : Pan, Panning, Input to Spatial Soundfield

Decode

Having spatial or multichannel soundfield content output for an intended two ear or two channel playback.

Synonyms : Monitor, Monitoring, Listening, Stereo Playback, Binauralized, Listener

Describing Rotations


Azimuth

Refers to the horizontal angle or direction or rotation. Typically when discussing spatial audio a common example of usage of azimuth would be the azimuth of a sound source panned around you as the listener.

Synonyms : Yaw

Elevation

Refers to the angular distance of the source above or below the horizon.

Synonyms : Height, Pitch

Heading

A direction or bearing, combining the above terms of Azimuth and Elevation.

Synonyms :

Euler

Description of rotations comprised of 3 angles. Commonly using:

  • Yaw
  • Pitch
  • Roll / Tilt

but sometimes referred to as X, Y, Z in some 3D systems (be mindful of the order in which X, Y, Z can refer to Yaw, Pitch, Roll)

Read more on this here.

Synonyms :

Quaternion

Mathematical notation for representing spatial orientations and rotations of elements in three dimensional space. Useful for avoiding common issues when describing 3D rotations in Euler such as Gimbal Lock

Synonyms : Quat

Degrees

Used to describe rotation angles in which a full rotation is 360 degree units.

Synonyms :

Radians

Used to describe rotation angles in which a full rotation is or 6.28318530718.

Synonyms :

Spatial Audio: Common Issues


Gimbal Lock

Gimbal lock is a loss of a degree of freedom when two axes rotate in parralel, the output rotation becomes one less degree of freedom.

To explain this more simply; two or more axes line up in a way so that the applied Euler rotation cannot distiguish which of the two axes are rotating because they yield the same results.

Example: If you add 90 pitch upward in degrees to an object, rotating yaw or roll would yield the same result.

Synonyms :

Latency

Describes when something has a latent or delayed reaction. Typically in spatial audio world we can describe headtracking or 3D rotations as being latent when you can percieve a time delay from your real world motion to the interacted virtual motion. This can be a very destructive issue for any hardware that has motion based sensors in them when applied to audio for spatial audio perception.

When discussing latency in the audio world in general it can refer to the actual audio signal itself having a perceived delay.

Synonyms :

Additional Technologies


IMU

Stands for Inertial Motion Unit, a series of sensors usually within a silicon chip that can typically include any number of the following sensor types:

  • Accelerometer
  • Gyroscope
  • Magnometer

Each of these sensor outputs can have typically 3 data outputs so the IMU typically includes a process called Sensor Fusion to combine the datasets of all sensors into one dataset for orientation and/or position.

Synonyms :

Sensor Fusion

Sensor Fusion is a a mathematics for combining multiple datasets relating to motion or force into one dataset for predicting orientation, heading and/or position. The output data can be collected into different types such as Radians or Degrees or Quaternion.

Synonyms :

Technical Descriptions


Realtime

Refers to a process or effect that can be applied in realtime, usually during playback but in general any process that can be computed faster than actual time.

Synonyms :

Runtime

Refers to all processes that happen during the playback of the sound content.

Spatial audio processes that are limited to runtime processes have to compensate for what processing power is available on that device, this limitation means that these processes have to be able to run faster than realtime and can sometimes be limited in quality.

Synonyms :

Render

Refers to a process of pre-determining all intended processes and effects to an output file usually to be faithfully replayed or reused without change.

Spatial audio content that has been pre-rendered or rendered has the added benefit of using more time expensive and higher quality processing effects that might not normally be too expensive to be processed in realtime, especially from device to device.

Synonyms : Pre-rendered