Near-field audio rendering

A system comprising:

• a wearable head device;
• one or more speakers;
• and
• one or more processors configured to perform a method comprising:
• identifying a source location corresponding to an audio signal;
• determining an acoustic axis corresponding to the audio signal;
• determining a reference point;
• for each of a respective left and right ear of a user of the wearable head device:
• determining an angle between the acoustic axis and the respective ear;
• determining, of a virtual speaker array, a virtual speaker position substantially collinear with the source location and a position of the respective ear, wherein the virtual speaker array comprises a plurality of virtual speaker positions, each virtual speaker position of the plurality of virtual speaker positions located on the surface of a sphere concentric with the reference point, the sphere having a first radius;
• determining a head-related transfer function (HRTF) corresponding to the virtual speaker position and to the respective ear;
• determining a source radiation filter based on the determined angle;
• processing the audio signal to generate an output audio signal for the respective ear, wherein processing the audio signal comprises applying the HRTF and the source radiation filter to the audio signal;
• attenuating the audio signal based on a distance between the source location and the respective ear wherein the distance is clamped at a minimum value;
• and
• presenting the output audio signal to the respective ear of the user via the one or more speakers,
• wherein determining the reference point comprises:
• determining a position of the wearable head device based on a sensor of the wearable head device, and
• applying a transformation to the determined position of the wearable head device based on a spatial relationship between the wearable head device and the user's head.

A non-transitory computer-readable medium storing instructions, which when executed by one or more processors cause the one or more processors to perform a method of presenting an audio signal to a user of a wearable head device, the method comprising:

• identifying a source location corresponding to the audio signal;
• determining an acoustic axis corresponding to the audio signal;
• determining a reference point;
• for each of a respective left and right ear of the user:
• determining an angle between the acoustic axis and the respective ear;
• determining, of a virtual speaker array, a virtual speaker position substantially collinear with the source location and a position of the respective ear, wherein the virtual speaker array comprises a plurality of virtual speaker positions, each virtual speaker position of the plurality of virtual speaker positions located on the surface of a sphere concentric with the reference point, the sphere having a first radius;
• determining a head-related transfer function (HRTF) corresponding to the virtual speaker position and to the respective ear;
• determining a source radiation filter based on the determined angle;
• processing the audio signal to generate an output audio signal for the respective ear, wherein processing the audio signal comprises applying the HRTF and the source radiation filter to the audio signal;
• attenuating the audio signal based on a distance between the source location and the respective ear wherein the distance is clamped at a minimum value;
• and
• presenting the output audio signal to the respective ear of the user via one or more speakers associated with the wearable head device,
• wherein determining the reference point comprises:
• determining a position of the wearable head device based on a sensor of the wearable head device, and
• applying a transformation to the determined position of the wearable head device based on a spatial relationship between the wearable head device and the user's head.