Near-field audio rendering
Examples of the disclosure describe systems and methods for presenting an audio signal to a user of a wearable head device. According to an example method, a source location corresponding to the audio signal is identified. For each of the respective left and right ear of the user, a virtual speaker position, of a virtual speaker array, is determined, the virtual speaker position collinear with the source location and with a position of the respective ear. For each of the respective left and right ear of the user, a head-related transfer function (HRTF) corresponding to the virtual speaker position and to the respective ear is determined; and the output audio signal is presented to the respective ear of the user via one or more speakers associated with the wearable head device. Processing the audio signal includes applying the HRTF to the audio signal.
1. A method of presenting an audio signal to a user of a wearable head device, the method comprising:
determining a reference point based on a location of the wearable head device; and
for each of a respective left ear and right ear of the user:
determining, for a virtual speaker array associated with a sphere concentric with the reference point, the sphere having a first radius, a virtual speaker position substantially collinear with a source location and a position of the respective ear, wherein the determined virtual speaker position comprises a location substantially on a surface of the sphere and the source location corresponds to the audio signal;
determining a transfer function corresponding to the virtual speaker position;
generating, based on the transfer function and based further on the audio signal, an output audio signal for the respective ear;
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.
2. The method of claim 1 , wherein the source location is separated from the reference point by a distance less than the first radius.
3. The method of claim 1 , wherein the source location is separated from the reference point by a distance greater than the first radius.
4. The method of claim 1 , wherein the source location is separated from the reference point by a distance equal to the first radius.
5. The method of claim 1 , wherein said generating the output audio signal comprises applying an interaural time difference to the audio signal.
6. The method of claim 1 , wherein said determining the transfer function corresponding to the virtual speaker position comprises selecting the transfer function from a plurality of transfer functions, wherein each transfer function of the plurality of transfer functions describes a relationship between a listener and an audio source, the audio source separated from the listener by a distance substantially equal to the first radius.
7. The method of claim 1 , wherein the wearable head device comprises the one or more speakers.
8. The method of claim 1 , further comprising identifying the source location corresponding to the audio signal.
9. A system comprising:
a wearable head device;
one or more speakers; and
one or more processors configured to perform a method comprising:
determining a reference point based on a location of the wearable head device; and
for each of a respective left ear and right ear of the user:
determining, for a virtual speaker array associated with a sphere concentric with the reference point, the sphere having a first radius, a virtual speaker position substantially collinear with a source location and a position of the respective ear, wherein the determined virtual speaker position comprises a location substantially on a surface of the sphere and the source location corresponds to the audio signal;
determining a transfer function corresponding to the virtual speaker position;
generating, based on the transfer function and based further on the audio signal, an output audio signal for the respective ear;
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.
10. The system of claim 9 , wherein the source location is separated from the reference point by a distance less than the first radius.
11. The system of claim 9 , wherein the source location is separated from the reference point by a distance greater than the first radius.
12. The system of claim 9 , wherein the source location is separated from the reference point by a distance equal to the first radius.
13. The system of claim 9 , wherein said generating the output audio signal comprises applying an interaural time difference to the audio signal.
14. The system of claim 9 , wherein said determining the transfer function corresponding to the virtual speaker position comprises selecting the transfer function from a plurality of transfer functions, wherein each transfer function of the plurality of transfer functions describes a relationship between a listener and an audio source, the audio source separated from the listener by a distance substantially equal to the first radius.
15. The system of claim 9 , wherein the wearable head device comprises the one or more speakers.
16. The system of claim 9 , the method further comprising identifying the source location corresponding to the audio signal.
17. 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:
determining a reference point based on a location of the wearable head device; and
for each of a respective left ear and right ear of the user:
determining, for a virtual speaker array associated with a sphere concentric with the reference point, the sphere having a first radius, a virtual speaker position substantially collinear with a source location and a position of the respective ear, wherein the determined virtual speaker position comprises a location substantially on a surface of the sphere and the source location corresponds to the audio signal;
determining a transfer function corresponding to the virtual speaker position;
generating, based on the transfer function and based further on the audio signal, an output audio signal for the respective ear;
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.
18. The non-transitory computer-readable medium of claim 17 , wherein the source location is separated from the reference point by a distance equal to the first radius.
19. The non-transitory computer-readable medium of claim 17 , wherein said generating the output audio signal comprises applying an interaural time difference to the audio signal.
20. The non-transitory computer-readable medium of claim 17 , wherein the wearable head device comprises the one or more speakers.