Eigen-HRTFu is an audio spatializer for a near field of the listener in Unity engine focused for VR, is capable of spatialization between distance 20 ⩽ d ⩽ 160 cm, azimuth 0° ⩽ θ < 360°, and elevation -40° ⩽ ϕ ⩽ 90° base on an Eigen decomposition of the database created by Qu et al. in [1]. Methods used to create this database is described here [2].

Getting start

This API is tested in Unity 2020.1.6, to get it, just copy the HRTFu folder in the Assets folder.

Currently, this spatializer works for MacOS in 64 bits Intel architecture and Windows.

If you are using Plugins in your project, mind that Eigen-HRTFu has its own Plugins directory. You will need to move the Plugin of HRTFu in your own Plugins directory, or move your Plugins in the HRTFu Plugin directory.

To work with this spatializer, we recommend to set up this Audio setting in Unity (Edit > Project Settings > Audio):

• Default speaker mode as Stereo

Usage

To spatialize an Audio Source with this spatializer you need to:

• Attach the HRTFu script to an object that has an Audio Source property in Unity.
• Disable any spatialization option in the Audio Source options (i.e., Spatial Bend and Spatialize options).

Here is a description of the properties you can edit for this spatializer:

Properties

Propiertie	Description
Scale	Is a scale of the distance from the listener object to the audio source, according to the units used to define the geometry of objects. By default is .01
Pinna	This spatializer have 2 pinnae simulators included, you can select Large or Small pinnae simulator. By default is Small.
Listener	This property specifies the listener in the scene, by default is the Audio Listener in the scene.
Gain	Gain in dB. Modification of the gain may change the subjective perception of distance. We strongly recommend do not modify this parameter. Use it at your own discretion. Default value 0 dB

External resources

• The compressed database along with an offline spatializer implemented in Matlab is available in the following repository:

https://github.com/arevaloarboled/HRTF-Eigen-decomposition

• Spatializer in a form of VST plugin implemented in Matlab is also available in the following repository:

https://www.mathworks.com/matlabcentral/fileexchange/92453-eigenhrtf

References

[1] T. Qu, Z. Xiao, M. Gong, Y. Huang, X. Li, and X. Wu, “Distance-Dependent Head-Related Transfer Functions Measured With High Spa-tial Resolution Using a Spark Gap,”IEEE Trans. on Audio, Speech &Language Processing, vol. 17, no. 6, pp. 1124–1132, 2009.
[2] Arevalo, Camilo & Villegas, Julián. (2020). Compressing Head-Related Transfer Function databases by Eigen decomposition. 1-6. 10.1109/MMSP48831.2020.9287134.