Dual listener positions for mixed reality

Abstract

To provide a method for presenting an audio signal in a mixed reality environment.SOLUTION: The method includes identifying a position of a first ear of a listener in a mixed reality environment, identifying a position of a second ear of the listener in the mixed reality environment, identifying a first virtual sound source in the mixed reality environment, identifying a first object in the mixed reality environment, determining a first audio signal in the mixed reality environment, determining a second audio signal in the mixed reality environment, determining a third audio signal based on the second audio signal and the first object, presenting the first audio signal to the first ear of the user via a first speaker, and presenting the third audio signal to the second ear of the user via a second speaker.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] (Field) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 631,422, filed February 15, 2018, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to systems and methods for presenting audio signals, and more particularly to systems and methods for presenting stereo audio signals to a user of a mixed reality system. [Background technology]

[0003] (background) Virtual environments are ubiquitous in computing environments, finding use in video games (where a virtual environment may represent a game world), maps (where a virtual environment may represent a terrain to be navigated), simulations (where a virtual environment may simulate a real environment), digital storytelling (where virtual characters may interact with one another within a virtual environment), and many other applications. Modern computer users are generally comfortable perceiving and interacting with virtual environments. However, a user's experience with a virtual environment may be limited by the technology for presenting the virtual environment. For example, traditional displays (e.g., 2D display screens) and audio systems (e.g., fixed speakers) may be unable to realize a virtual environment in a way that creates a compelling, realistic, and immersive experience.

[0004] Virtual reality (“VR”), augmented reality (“AR”), mixed reality (“MR”), and related technologies (collectively, “XR”) share the ability to present to a user of an XR system sensory information corresponding to a virtual environment represented by data in a computer system. This disclosure considers uniqueness among VR, AR, and MR systems (although some systems may be categorized as VR in one aspect (e.g., visual aspect) and simultaneously categorized as AR or MR in another aspect (e.g., audio aspect)). As used herein, a VR system presents a virtual environment that replaces the user's real environment in at least one aspect. For example, a VR system may present a user with a view of the virtual environment while simultaneously obscuring that view of the real environment, such as with an optically blocking head-mounted display. Similarly, a VR system may present a user with audio corresponding to the virtual environment while simultaneously blocking (attenuating) the audio from the real environment.

[0005] VR systems may suffer from various drawbacks resulting from replacing a user's real environment with a virtual environment. One drawback is motion sickness, which can occur when a user's field of view within the virtual environment no longer corresponds to the state of their inner ear, which detects their balance and orientation in the real (but not the virtual) environment. Similarly, a user may experience disorientation within a VR environment if their body and limbs (the view upon which the user relies to feel "grounded" in the real environment) are not directly visible. Another drawback is the computational burden (e.g., memory, processing power) imposed on a VR system that must present a fully 3D virtual environment, especially in real-time applications that seek to immerse a user in the virtual environment. Similarly, such an environment may need to reach a very high level of realism to be considered immersive, as users tend to be sensitive to even slight imperfections in the virtual environment, any of which can destroy the user's sense of immersion in the virtual environment. Furthermore, another disadvantage of VR systems is that such applications of the systems cannot take advantage of the wide range of sensory data in the real environment, such as the various sights and sounds experienced in the real world. A related disadvantage is that VR systems may struggle to create shared environments in which multiple users can interact, because users who share physical space in the real environment may not be able to see or interact with each other directly in the virtual environment.

[0006] As used herein, an AR system presents a virtual environment that overlaps or overlays the real environment in at least one aspect. For example, an AR system may present a user with a view of the virtual environment overlaid on the user's view of the real environment, such as using a see-through head-mounted display that presents a displayed image while allowing light to pass through the display into the user's eyes. Similarly, an AR system may present a user with audio corresponding to the virtual environment while simultaneously mixing in audio from the real environment. Similarly, as used herein, an MR system, like an AR system, may present a virtual environment that overlaps or overlays the real environment in at least one aspect, and may additionally allow the virtual environment in the MR system to interact with the real environment in at least one aspect. For example, a virtual character in the virtual environment may flip a light switch in the real environment, causing a corresponding light bulb in the real environment to turn on or off. As another example, the virtual character may react to audio signals in the real environment (such as with facial expressions). By maintaining the presentation of the real environment, AR and MR systems may avoid some of the aforementioned disadvantages of VR systems. For example, motion sickness in a user is reduced because visual cues from the real environment (including the user's own body) can remain visible and such systems do not need to present the user with a fully realized 3D environment to be immersive. Furthermore, AR and MR systems can create new applications that utilize real-world sensory input (e.g., views and sounds of scenery, objects, and other users) to augment that input.

[0007] XR systems may provide users with various ways to interact with the virtual environment. For example, XR systems may include various sensors (e.g., cameras, microphones, etc.) to detect the user's position and orientation, facial expressions, speech, and other characteristics and present this information as input to the virtual environment. Some XR systems may incorporate sensor-equipped input devices, such as a virtual "mallet," and may be configured to detect the position, orientation, or other characteristics of the input device.

[0008] XR systems can provide a uniquely high level of immersion and realism by combining virtual visual and audio cues with real sights and sounds. For example, it may be desirable to present audio cues to a user of an XR system to mimic aspects of their own sensory experience, particularly subtle aspects. The present invention is directed to presenting a stereo audio signal originating from a single sound source to a user within a mixed reality environment so that the user can identify the location and orientation of the sound source within the mixed reality environment based on the difference in signals received by the user's left and right ears. By using audio cues to identify the location and orientation of a sound source within the mixed reality environment, the user may experience a high level of perception of virtual sounds originating from that location and orientation. Additionally, a user's immersion within a mixed reality environment can be enhanced by presenting not only stereo audio corresponding to a direct audio signal, but also a fully immersive soundscape generated using a 3D propagation model. Summary of the Invention [Means for solving the problem]

[0009] Embodiments of the present disclosure describe systems and methods for presenting audio signals in a mixed reality environment. In one embodiment, the method includes identifying a first ear position of a listener within the mixed reality environment; identifying a second ear position of the listener within the mixed reality environment; identifying a first virtual sound source within the mixed reality environment; identifying a first object within the mixed reality environment; determining a first audio signal within the mixed reality environment, the first audio signal originating at the first virtual sound source and intersecting with the first ear position of the listener; determining a second audio signal within the mixed reality environment, the second audio signal originating at the first virtual sound source, intersecting with the first object and intersecting with the second ear position of the listener; determining a third audio signal based on the second audio signal and the first object; presenting the first audio signal to the first ear of the user via a first speaker; and presenting the third audio signal to the second ear of the user via a second speaker. The present specification also provides, for example, the following items: (Item 1) 1. A method for presenting an audio signal in a mixed reality environment, the method comprising: identifying a position of a first ear of a listener within the mixed reality environment; identifying a position of a second ear of a listener within the mixed reality environment; identifying a first virtual sound source within the mixed reality environment; identifying a first object within the mixed reality environment; determining a first audio signal within the mixed reality environment, the first audio signal originating at the first virtual sound source and intersecting a first ear position of the listener; determining a second audio signal within the mixed reality environment, the second audio signal originating at the first virtual sound source, intersecting the first object, and intersecting a second ear position of the listener; determining a third audio signal based on the second audio signal and the first object; presenting the first audio signal to a first ear of a user via a first speaker; presenting the third audio signal to a second ear of the user via a second speaker; A method comprising: (Item 2) Item 1. The method of item 1, wherein determining the third audio signal from the second audio signal includes applying a low-pass filter to the second audio signal, the low-pass filter having parameters based on the first object. (Item 3) Item 1. The method of item 1, wherein determining the third audio signal from the second audio signal includes applying an attenuation to the second audio signal, the strength of the attenuation being based on the first object. (Item 4) Item 10. The method of item 1, wherein identifying the first object includes identifying a real object. (Item 5) Item 5. The method of item 4, wherein identifying the real object includes using a sensor to determine the position of the real object relative to the user in the mixed reality environment. (Item 6) Item 6. The method of item 5, wherein the sensor comprises a depth camera. (Item 7) Item 5. The method of item 4, further comprising generating helper data corresponding to the real object. (Item 8) Item 5. The method of item 4, further comprising generating a virtual object corresponding to the real object. (Item 9) Item 10. The method of item 1, further comprising identifying a second virtual object, wherein the first audio signal intersects with the second virtual object, and wherein a fourth audio signal is determined based on the second virtual object. (Item 10) 1. A system comprising: A wearable head device, a display for displaying a mixed reality environment to a user, said display comprising a transparent eyepiece through which the real environment is visible; a first speaker configured to present an audio signal to a first ear of the user; a second speaker configured to present an audio signal to a second ear of the user; a wearable head device comprising: one or more processors, identifying a position of a first ear of a listener within the mixed reality environment; identifying a position of a second ear of a listener within the mixed reality environment; identifying a first virtual sound source within the mixed reality environment; identifying a first object within the mixed reality environment; determining a first audio signal within the mixed reality environment, the first audio signal originating at the first virtual sound source and intersecting a first ear position of the listener; determining a second audio signal within the mixed reality environment, the second audio signal originating at the first virtual sound source, intersecting the first object, and intersecting a second ear position of the listener; determining a third audio signal based on the second audio signal and the first object; presenting the first audio signal to the first ear via a first speaker; presenting the third audio signal to the second ear via a second speaker; one or more processors configured to implement A system comprising: (Item 11) Item 11. The system of item 10, wherein determining the third audio signal from the second audio signal includes applying a low-pass filter to the second audio signal, the low-pass filter having parameters based on the first object. (Item 12) Item 11. The system of item 10, wherein determining the third audio signal from the second audio signal includes applying an attenuation to the second audio signal, the strength of the attenuation being based on the first object. (Item 13) Item 11. The system of item 10, wherein identifying the first object includes identifying a real object. (Item 14) Item 14. The system of item 13, wherein the wearable head device further comprises a sensor, and identifying the real object includes using the sensor to determine the position of the real object relative to the user within the mixed reality environment. (Item 15) Item 15. The system of item 14, wherein the sensor comprises a depth camera. (Item 16) Item 14. The system of item 13, wherein the one or more processors are further configured to generate helper data corresponding to the real object. (Item 17) Item 14. The system of item 13, wherein the one or more processors are further configured to perform generating a virtual object corresponding to the real object. (Item 18) Item 11. The system of item 10, wherein the one or more processors are further configured to identify a second virtual object, wherein the first audio signal intersects with the second virtual object, and wherein a fourth audio signal is determined based on the second virtual object. [Brief explanation of the drawings]

[0010] [Figure 1A]1A-1C illustrate an example mixed reality environment. [Figure 1B] 1A-1C illustrate an example mixed reality environment. [Figure 1C] 1A-1C illustrate an example mixed reality environment.

[0011] [Figure 2A] 2A-2D illustrate components of an example mixed reality system that can be used to interact with a mixed reality environment. [Figure 2B] 2A-2D illustrate components of an example mixed reality system that can be used to interact with a mixed reality environment. [Figure 2C] 2A-2D illustrate components of an example mixed reality system that can be used to interact with a mixed reality environment. [Figure 2D] 2A-2D illustrate components of an example mixed reality system that can be used to interact with a mixed reality environment.

[0012] [Figure 3A] FIG. 3A illustrates an example mixed reality handheld controller that can be used to provide input to a mixed reality environment.

[0013] [Figure 3B] FIG. 3B illustrates an example auxiliary unit that may be included in an example mixed reality system.

[0014] [Figure 4] FIG. 4 illustrates an example functional block diagram for an example mixed reality system.

[0015] [Figure 5A] 5A-5B illustrate an example mixed reality environment including a user, a virtual sound source, and an audio signal originating from the virtual sound source. [Figure 5B]5A-5B illustrate an example mixed reality environment including a user, a virtual sound source, and an audio signal originating from the virtual sound source.

[0016] [Figure 6] FIG. 6 illustrates an example flowchart of a process for presenting a stereo audio signal to a user of a mixed reality environment.

[0017] [Figure 7] FIG. 7 illustrates an example functional block diagram of an example augmented reality processing system. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following description of the embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown, by way of illustration, specific embodiments which may be practiced. It is to be understood that other embodiments may be used and structural changes may be made without departing from the scope of the disclosed embodiments.

[0019] Mixed Reality Environment

[0020] Like all people, users of mixed reality systems exist in a real environment, i.e., three-dimensional portions of the "real world" and all of its content are perceptible to the user. For example, users perceive the real environment using normal human senses, i.e., sight, sound, touch, taste, and smell, and interact with the real environment by moving their body within the real environment. Locations within the real environment can be described as coordinates within a coordinate space. For example, coordinates can include latitude, longitude, and altitude relative to sea level, distance in three orthogonal dimensions from a reference point, or other suitable values. Similarly, a vector can describe a quantity, having a direction and magnitude within the coordinate space.

[0021] A computing device may maintain a representation of a virtual environment, for example, in a memory associated with the device. As used herein, a virtual environment is a computed representation of a three-dimensional space. The virtual environment may include representations of any objects, actions, signals, parameters, coordinates, vectors, or other properties associated with that space. In some examples, the circuitry (e.g., a processor) of the computing device may maintain and update the state of the virtual environment. That is, the processor may determine the state of the virtual environment at a second time t1 based on data associated with the virtual environment and / or input provided by a user at a first time t0. For example, if an object in the virtual environment is located at a first coordinate and has certain programmed physical parameters (e.g., mass, coefficient of friction) at time t0, and input received from the user indicates that a force should be applied to the object in a certain directional vector, the processor may apply the laws of kinematics and use basic mechanics to determine the location of the object at time t1. The processor may determine the state of the virtual environment at time t1 using any suitable information known about the virtual environment and / or any suitable input. In maintaining and updating the state of the virtual environment, the processor may execute any suitable software, including software related to creating and deleting virtual objects within the virtual environment, software (e.g., scripts) for defining the behavior of virtual objects or characters within the virtual environment, software for defining the behavior of signals (e.g., audio signals) within the virtual environment, software for creating and updating parameters associated with the virtual environment, software for generating audio signals within the virtual environment, software for handling input and output, software for implementing network operations, software for applying asset data (e.g., animation data for moving a virtual object over time), or many other possibilities.

[0022] An output device, such as a display or speakers, can present any or all aspects of the virtual environment to the user. For example, the virtual environment may include virtual objects (which may include representations of inanimate objects, people, animals, lights, etc.) that can be presented to the user. A processor can determine a view of the virtual environment (e.g., corresponding to a "camera," with its origin coordinates, viewing axis, and frustum) and render on the display a viewable scene of the virtual environment corresponding to that view. Any suitable rendering technique may be used for this purpose. In some examples, the viewable scene may include only some virtual objects in the virtual environment and exclude certain other virtual objects. Similarly, the virtual environment may include audio aspects that can be presented to the user as one or more audio signals. For example, a virtual object in the virtual environment may generate a sound originating from the object's location coordinates (e.g., a virtual character may speak or produce a sound effect), or the virtual environment may be associated with a musical cue or ambient sound that may or may not be associated with a particular location. The processor can determine audio signals corresponding to the "listener" coordinates, e.g., audio signals corresponding to the synthesis of sounds in the virtual environment and mixed and processed to simulate the audio signals that would be heard by a listener at the listener coordinates, and present the audio signals to the user via one or more speakers.

[0023] Because the virtual environment exists only as a computational construct, the user cannot directly perceive the virtual environment using their normal senses. Instead, the user can only indirectly perceive the virtual environment, as presented to the user, for example, by a display, speakers, tactile output device, etc. Similarly, the user cannot directly touch, manipulate, or otherwise interact with the virtual environment, but can provide input data via input devices or sensors to a processor, which can use the device or sensor data to update the virtual environment. For example, a camera sensor can provide optical data indicating that the user is attempting to move an object in the virtual environment, and the processor can use that data to cause the object to respond appropriately within the virtual environment.

[0024] A mixed reality system can present a user with a mixed reality environment (“MRE”) that combines aspects of a real environment and a virtual environment, for example, using a see-through display and / or one or more speakers (which may, for example, be incorporated into a wearable head device). In some embodiments, the one or more speakers may be external to the wearable head device. As used herein, an MRE is a simultaneous representation of a real environment and a corresponding virtual environment. In some examples, the corresponding real and virtual environments share a single coordinate space. In some examples, the real coordinate space and the corresponding virtual coordinate space are related to each other by a transformation matrix (or other suitable representation). Thus, a single coordinate (in some examples, together with the transformation matrix) may define a first location in the real environment and a second corresponding location in the virtual environment, and vice versa.

[0025] In an MRE, a virtual object (e.g., in a virtual environment associated with the MRE) may correspond to a real object (e.g., in a real environment associated with the MRE). For example, if the real environment of the MRE includes a real lamppost (real object) at certain location coordinates, the virtual environment of the MRE may include a virtual lamppost (virtual object) at the corresponding location coordinates. As used herein, a real object in combination with its corresponding virtual object together constitutes a “mixed reality object.” It is not necessary for a virtual object to perfectly match or match the corresponding real object. In some embodiments, a virtual object can be a simplified version of the corresponding real object. For example, if the real environment includes a real lamppost, the corresponding virtual object may include a cylinder of approximately the same height and radius as the real lamppost (reflecting that a lamppost may be approximately cylindrical in shape). Simplifying virtual objects in this way can enable computational efficiency and simplify calculations to be performed on such virtual objects. Furthermore, in some embodiments of an MRE, not all real objects in the real environment may be associated with a corresponding virtual object. Similarly, in some embodiments of an MRE, not all virtual objects in the virtual environment may be associated with corresponding real objects, i.e., some virtual objects may exist solely within the virtual environment of the MRE without any real-world counterpart.

[0026] In some embodiments, virtual objects may have characteristics (sometimes significantly different, and distinct from those of their corresponding real objects). For example, a real environment in an MRE may include a green, two-pronged cactus, i.e., a thorny, inanimate object, while the corresponding virtual object in the MRE may have the characteristics of a green, two-armed virtual character with human facial features and a surly attitude. In this embodiment, the virtual object resembles its corresponding real object in some characteristics (color, number of arms) but differs from the real object in other characteristics (facial features, personality). In this manner, virtual objects have the potential to represent real objects in a creative, abstract, exaggerated, or fictional manner, or to impart behavior (e.g., human personality) to otherwise inanimate real objects. In some embodiments, a virtual object may be a purely fictional creation with no real-world counterpart (e.g., a virtual monster in a virtual environment, perhaps in a location corresponding to a void in the real environment).

[0027] Compared to VR systems, which present a virtual environment to a user while obscuring the real environment, mixed reality systems that present an MRE offer the advantage that the real environment remains perceptible while the virtual environment is presented. Thus, a user of a mixed reality system can experience and interact with the corresponding virtual environment using visual and audio cues associated with the real environment. As an example, a user of a VR system may struggle to perceive or interact with virtual objects displayed in the virtual environment because, as noted above, the user cannot directly perceive or interact with the virtual environment. However, a user of an MR system may find it intuitive and natural to interact with virtual objects by seeing, hearing, and touching the corresponding real objects in their own real environment. This level of interaction may enhance the user's sense of immersion, connection, and engagement with the virtual environment. Similarly, by simultaneously presenting a real environment and a virtual environment, a mixed reality system may reduce negative psychological sensations (e.g., cognitive dissonance) and negative physical sensations (e.g., motion sickness) associated with VR systems. Mixed reality systems also offer many possibilities for applications that can augment or modify our experience of the real world.

[0028] 1A illustrates an exemplary real environment 100 in which a user 110 uses a mixed reality system 112. The mixed reality system 112 may include a display (e.g., a see-through display) and one or more speakers, as well as one or more sensors (e.g., cameras), for example, as described below. The illustrated real environment 100 includes a rectangular room 104A in which the user 110 is standing and real objects 122A (lamp), 124A (table), 126A (sofa), and 128A (painting). The room 104A further includes a location coordinate 106, which may be considered the origin of the real environment 100. As shown in FIG. 1A, an environment / world coordinate system 108 (comprising an x-axis 108X, a y-axis 108Y, and a z-axis 108Z) with its origin at point 106 (world coordinates) may define a coordinate space for the real environment 100. In some embodiments, origin 106 of environment / world coordinate system 108 may correspond to where mixed reality system 112 is powered on. In some embodiments, origin 106 of environment / world coordinate system 108 may be reset during operation. In some examples, user 110 may be considered a real object in real environment 100. Similarly, body parts (e.g., hands, feet) of user 110 may be considered real objects in real environment 100. In some examples, user / listener / head coordinate system 114 (comprising x-axis 114X, y-axis 114Y, and z-axis 114Z), with its origin at point 115 (e.g., user / listener / head coordinate), may define a coordinate space for user / listener / head on which mixed reality system 112 is located. Origin 115 of user / listener / head coordinate system 114 may be defined with respect to one or more components of mixed reality system 112. For example, the origin 115 of the user / listener / head coordinate system 114 may be defined relative to the display of the mixed reality system 112, such as during an initial calibration of the mixed reality system 112. A matrix (which may include a translation matrix and a quaternion matrix or other rotation matrix) or other suitable representation can characterize the transformation between the user / listener / head coordinate system 114 space and the environment / world coordinate system 108 space.In some embodiments, left ear coordinates 116 and right ear coordinates 117 may be defined relative to the origin 115 of the user / listener / head coordinate system 114. A matrix (which may include a translation matrix and a quaternion matrix or other rotation matrix) or other suitable representation can characterize the transformation between the left ear coordinates 116 and right ear coordinates 117 and the user / listener / head coordinate system 114 space. The user / listener / head coordinate system 114 can simplify the representation of locations relative to the user's head or wearable head device, for example, relative to the environment / world coordinate system 108. Using simultaneous localization and mapping (SLAM), visual odometry, or other techniques, the transformation between the user coordinate system 114 and the environment coordinate system 108 can be determined and updated in real time.

[0029] 1B illustrates an exemplary virtual environment 130 corresponding to real environment 100. The illustrated virtual environment 130 includes a virtual rectangular room 104B corresponding to real rectangular room 104A, a virtual object 122B corresponding to real object 122A, a virtual object 124B corresponding to real object 124A, and a virtual object 126B corresponding to real object 126A. Metadata associated with virtual objects 122B, 124B, and 126B may include information derived from the corresponding real objects 122A, 124A, and 126A. Virtual environment 130 additionally includes a virtual monster 132, which does not correspond to any real object in real environment 100. Real object 128A in real environment 100 does not correspond to any virtual object in virtual environment 130. A persistent coordinate system 133 (comprising an x-axis 133X, a y-axis 133Y, and a z-axis 133Z) with its origin at point 134 (persistent coordinate) may define a coordinate space for the virtual content. The origin 134 of the persistent coordinate system 133 may be defined relative to / with respect to one or more real objects, such as real object 126A. A matrix (which may include a translation matrix and a quaternion matrix or other rotation matrix) or other suitable representation can characterize the transformation between the persistent coordinate system 133 space and the environment / world coordinate system 108 space. In some embodiments, virtual objects 122B, 124B, 126B, and 132 may each have its own persistent coordinate point relative to the origin 134 of the persistent coordinate system 133. In some embodiments, there may be multiple persistent coordinate systems, and virtual objects 122B, 124B, 126B, and 132 may each have their own persistent coordinate points relative to one or more persistent coordinate systems.

[0030] 1A and 1B, environment / world coordinate system 108 defines a shared coordinate space for both real environment 100 and virtual environment 130. In the illustrated embodiment, the coordinate space has its origin at point 106. Furthermore, the coordinate space is defined by the same three orthogonal axes (108X, 108Y, 108Z). Thus, a first location in real environment 100 and a second corresponding location in virtual environment 130 can be described with respect to the same coordinate space. This simplifies identifying and displaying corresponding locations in the real and virtual environments because the same coordinates can be used to identify both locations. However, in some embodiments, the corresponding real and virtual environments need not use a shared coordinate space. For example, in some embodiments (not shown), a matrix (which may include a translation matrix and a quaternion matrix or other rotation matrix) or other suitable representation can characterize the transformation between the real environment coordinate space and the virtual environment coordinate space.

[0031] 1C illustrates an exemplary MRE 150 that simultaneously presents aspects of real environment 100 and virtual environment 130 to user 110 via mixed reality system 112. In the example shown, MRE 150 simultaneously presents to user 110 real objects 122A, 124A, 126A, and 128A from real environment 100 (e.g., through a transparent portion of the display of mixed reality system 112) and virtual objects 122B, 124B, 126B, and 132 from virtual environment 130 (e.g., through an active display portion of the display of mixed reality system 112). As described above, origin 106 serves as the origin for a coordinate space corresponding to MRE 150, and coordinate system 108 defines the x-, y-, and z-axes for the coordinate space.

[0032] In the illustrated example, the mixed reality objects comprise corresponding pairs of real and virtual objects (i.e., 122A / 122B, 124A / 124B, 126A / 126B) that occupy corresponding locations in coordinate space 108. In some examples, both real and virtual objects may be visible to user 110 simultaneously. This may be desirable in instances where, for example, a virtual object presents information designed to augment the view of the corresponding real object (such as in a museum application where a virtual object presents a missing portion of an ancient, damaged statue). In some examples, the virtual objects (122B, 124B, and / or 126B) may be displayed so as to occlude the corresponding real objects (122A, 124A, and / or 126A) (e.g., via active pixelated occlusion using a pixelated occlusion shutter). This may be desirable, for example, in instances where a virtual object acts as a visual replacement for a corresponding real object (such as in interactive storytelling applications where inanimate real objects become "living" characters).

[0033] In some examples, real objects (e.g., 122A, 124A, 126A) may be associated with virtual content or helper data that does not necessarily constitute a virtual object. The virtual content or helper data can facilitate processing or handling of the virtual object within a mixed reality environment. For example, such virtual content may include a two-dimensional representation of the corresponding real object, a custom asset type associated with the corresponding real object, or statistical data associated with the corresponding real object. This information can enable or facilitate calculations involving the real object without incurring unnecessary computational overhead.

[0034] In some embodiments, the presentation described above may also incorporate audio aspects. For example, in MRE 150, virtual monster 132 may be associated with one or more audio signals, such as footstep effects, that are generated as the monster walks around MRE 150. As described further below, a processor in mixed reality system 112 may calculate an audio signal corresponding to a mixed and processed combination of all such sounds within MRE 150 and present the audio signal to user 110 via one or more speakers included within mixed reality system 112 and / or one or more external speakers.

[0035] Exemplary Mixed Reality System

[0036] An exemplary mixed reality system 112 can include a wearable head device (e.g., a wearable augmented reality or mixed reality head device) that includes a display (which may include left and right see-through displays, which may be eyepiece displays, and associated components for coupling light from the displays to the user's eyes), left and right speakers (e.g., positioned adjacent the user's left and right ears, respectively), an inertial measurement unit (IMU) (e.g., mounted on temple arms of the head device), a quadrature coil electromagnetic receiver (e.g., mounted on the left temple component), left and right cameras (e.g., depth (time-of-flight) cameras) oriented away from the user, and left and right eye cameras oriented toward the user (e.g., to detect the user's eye movements). However, the mixed reality system 112 can incorporate any suitable display technology and any suitable sensors (e.g., optical, infrared, acoustic, LIDAR, EOG, GPS, magnetic). Additionally, mixed reality system 112 may incorporate networking features (e.g., Wi-Fi capabilities) to communicate with other devices and systems, including other mixed reality systems. Mixed reality system 112 may further include a battery (which may be mounted in an auxiliary unit, such as a belt pack designed to be worn around the user's waist), a processor, and memory. The wearable head device of mixed reality system 112 may include a tracking component, such as an IMU or other suitable sensor, configured to output a set of coordinates of the wearable head device relative to the user's environment. In some examples, the tracking component may provide input to a processor and implement simultaneous localization and mapping (SLAM) and / or visual odometry algorithms. In some examples, mixed reality system 112 may also include a handheld controller 300 and / or an auxiliary unit 320, which may be a wearable belt pack, as described further below.

[0037] 2A-2D illustrate components of an exemplary mixed reality system 200 (which may correspond to mixed reality system 112) that may be used to present an MRE (which may correspond to MRE 150) or other virtual environment to a user. FIG. 2A illustrates a perspective view of a wearable head device 2102 included within the exemplary mixed reality system 200. FIG. 2B illustrates a top view of the wearable head device 2102 worn on a user's head 2202. FIG. 2C illustrates a front view of the wearable head device 2102. FIG. 2D illustrates an edge view of an exemplary eyepiece 2110 of the wearable head device 2102. As shown in FIGS. 2A-2C, the exemplary wearable head device 2102 includes an exemplary left eyepiece (e.g., a left transparent waveguide set eyepiece) 2108 and an exemplary right eyepiece (e.g., a right transparent waveguide set eyepiece) 2110. Each eyepiece 2108 and 2110 can include a transmissive element through which the real environment is visible and a display element for presenting a display (e.g., via image-modulated light) that is overlaid on the real environment. In some embodiments, such display elements can include surface diffractive optical elements for controlling the flow of the image-modulated light. For example, the left eyepiece 2108 can include a left internal coupling grating set 2112, a left orthogonal pupil-extension (OPE) grating set 2120, and a left exit (output) pupil-extension (EPE) grating set 2122. Similarly, the right eyepiece 2110 can include a right internal coupling grating set 2118, a right OPE grating set 2114, and a right EPE grating set 2116. The image-modulated light can be transferred to the user's eye via the internal coupling gratings 2112 and 2118, the OPEs 2114 and 2120, and the EPEs 2116 and 2122. Each internal coupling grating set 2112, 2118 can be configured to deflect light toward its corresponding OPE grating set 2120, 2114. Each OPE grating set 2120, 2114 can be designed to progressively deflect light downward toward its associated EPE 2122, 2116, thereby extending the exit pupil formed horizontally.Each EPE 2122, 2116 can be configured to progressively redirect at least a portion of the light received from its corresponding OPE grating set 2120, 2114 outward toward a user eyebox location (not shown), defined behind the eyepieces 2108, 2110, such that the exit pupil formed in the eyebox extends vertically. Alternatively, instead of the internal coupling grating sets 2112 and 2118, the OPE grating sets 2114 and 2120, and the EPE grating sets 2116 and 2122, the eyepieces 2108 and 2110 can include gratings and / or other arrangements of refractive and reflective features to control the coupling of image-modulated light into the user's eye.

[0038] In some examples, the wearable head device 2102 can include a left temple arm 2130 and a right temple arm 2132, where the left temple arm 2130 includes a left speaker 2134 and the right temple arm 2132 includes a right speaker 2136. A quadrature coil electromagnetic receiver 2138 can be located in the left temple piece or another suitable location within the wearable head device 2102. An inertial measurement unit (IMU) 2140 can be located in the right temple arm 2132 or another suitable location within the wearable head device 2102. The wearable head device 2102 can also include a left depth (e.g., time-of-flight) camera 2142 and a right depth camera 2144. The depth cameras 2142, 2144 can preferably be oriented in different directions so that both cover a wider field of view.

[0039] 2A-2D , a left source of image-wise modulated light 2124 can be optically coupled into the left eyepiece 2108 through a left internal coupling grating set 2112, and a right source of image-wise modulated light 2126 can be optically coupled into the right eyepiece 2110 through a right internal coupling grating set 2118. The source of image-wise modulated light 2124, 2126 can include, for example, a fiber optic scanner, a projector including an electronic light modulator such as a digital light processing (DLP) chip or a liquid crystal on silicon (LCoS) modulator, or an emissive display such as a micro light emitting diode (μLED) or micro organic light emitting diode (μOLED) panel that is coupled into the internal coupling grating sets 2112, 2118 using one or more lenses per side. The input coupling grating sets 2112, 2118 can deflect light from the source of image-wise modulated light 2124, 2126 to an angle above the critical angle for total internal reflection (TIR) ​​for the eyepieces 2108, 2110. The OPE grating sets 2114, 2120 progressively deflect the propagating light downward by TIR towards the EPE grating sets 2116, 2122. The EPE grating sets 2116, 2122 progressively couple the light towards the user's face, including the pupils of the user's eyes.

[0040] In some embodiments, as shown in FIG. 2D , the left eyepiece 2108 and the right eyepiece 2110 each include multiple waveguides 2402. For example, each eyepiece 2108, 2110 can include multiple individual waveguides, each dedicated to a separate color channel (e.g., red, blue, and green). In some embodiments, each eyepiece 2108, 2110 can include multiple sets of such waveguides, each configured to impart a different wavefront curvature to the emitted light. The wavefront curvature may be convex with respect to the user's eye, for example, to present a virtual object positioned at a distance in front of the user (e.g., a distance corresponding to the inverse of the wavefront curvature). In some embodiments, the EPE grating sets 2116, 2122 can include curved grating grooves to impart a convex wavefront curvature by modifying the Poynting vector of light exiting across each EPE.

[0041] In some examples, stereoscopically adjusted left and right eye images can be presented to the user through light modulators 2124, 2126 and eyepieces 2108, 2110 for each image to create the perception that the displayed content is three-dimensional. The perceived realism of the presentation of three-dimensional virtual objects can be enhanced by selecting the waveguides (and thus the corresponding wavefront curvatures) so that the virtual objects are displayed at distances that approximate the distances indicated by the stereoscopic left and right images. This technique can also reduce motion sickness experienced by some users, which can be caused by differences between the depth perception cues provided by the stereoscopic left and right eye images and the automatic accommodation (e.g., object distance-dependent focus) of the human eye.

[0042] FIG. 2D illustrates an edge view from above of the right eyepiece 2110 of the exemplary wearable head device 2102. As shown in FIG. 2D , the plurality of waveguides 2402 can include a first subset of three waveguides 2404 and a second subset of three waveguides 2406. The two subsets of waveguides 2404, 2406 can be distinguished by different EPE gratings featuring different grating line curvatures to impart different wavefront curvatures to the exiting light. Within each of the subsets of waveguides 2404, 2406, each waveguide can be used to couple a different spectral channel (e.g., one of the red, green, and blue spectral channels) to the user's right eye 2206. (Although not shown in FIG. 2D , the structure of the left eyepiece 2108 is similar to that of the right eyepiece 2110.)

[0043] 3A illustrates example handheld controller components 300 of mixed reality system 200. In some examples, handheld controller 300 includes a grip portion 346 and one or more buttons 350 disposed along a top surface 348. In some examples, button 350 may be configured for use as an optical tracking target to track six degrees of freedom (6DOF) movement of handheld controller 300, for example, in conjunction with a camera or other optical sensor (which may be mounted in a head unit (e.g., wearable head device 2102) of mixed reality system 200). In some examples, handheld controller 300 includes a tracking component (e.g., an IMU or other suitable sensor) for detecting a position or orientation, such as a position or orientation relative to wearable head device 2102. In some examples, such a tracking component may be positioned in a handle of handheld controller 300 and / or may be mechanically coupled to the handheld controller. The handheld controller 300 can be configured to provide one or more output signals corresponding to one or more of a button press state, or the position, orientation, and / or movement (e.g., via an IMU) of the handheld controller 300. Such output signals may be used as inputs to a processor of the mixed reality system 200. Such inputs may correspond to the position, orientation, and / or movement of the handheld controller (or, for that matter, the position, orientation, and / or movement of a user's hand holding the controller). Such inputs may also correspond to a user pressing a button 350.

[0044] 3B illustrates an example auxiliary unit 320 of the mixed reality system 200. The auxiliary unit 320 can include a battery for providing energy to operate the system 200 and can include a processor for executing programs to operate the system 200. As shown, the example auxiliary unit 320 includes a clip 2128 for attaching the auxiliary unit 320 to a user's belt, etc. It will also be apparent that other form factors are suitable for the auxiliary unit 320, including form factors that do not involve mounting the unit on a user's belt. In some embodiments, the auxiliary unit 320 is coupled to the wearable head device 2102 through a multi-tube cable, which may include, for example, electrical wires and optical fibers. A wireless connection between the auxiliary unit 320 and the wearable head device 2102 can also be used.

[0045] In some examples, mixed reality system 200 can include one or more microphones to detect sound and provide a corresponding signal to the mixed reality system. In some examples, the microphones may be attached to or integrated with wearable head device 2102 and configured to detect the user's voice. In some examples, microphones may be attached to or integrated with handheld controller 300 and / or auxiliary unit 320. Such microphones may be configured to detect environmental sounds, ambient noise, the user's or a third party's voice, or other sounds.

[0046] 4 shows an example functional block diagram that may correspond to an example mixed reality system, such as mixed reality system 200 described above (which may correspond to mixed reality system 112 with respect to FIG. 1). As shown in FIG. 4, example handheld controller 400B (which may correspond to handheld controller 300 (“totem”)) includes a totem / wearable head device six degrees of freedom (6DOF) totem subsystem 404A, and example wearable head device 400A (which may correspond to wearable head device 2102) includes a totem / wearable head device 6DOF subsystem 404B. In an example, 6DOF totem subsystem 404A and 6DOF subsystem 404B cooperate to determine six coordinates of handheld controller 400B relative to wearable head device 400A (e.g., offsets in three translational directions and rotations along three axes). The six degrees of freedom may be expressed relative to the coordinate system of wearable head device 400A. The three translational offsets may be represented as X, Y, and Z offsets within such a coordinate system, a translation matrix, or some other representation. The rotational degrees of freedom may be represented as a sequence of yaw, pitch, and roll rotations, a rotation matrix, a quaternion, or some other representation. In some examples, the wearable head device 400A, one or more depth cameras 444 (and / or one or more non-depth cameras) included within the wearable head device 400A, and / or one or more optical targets (e.g., buttons 350 of handheld controller 400B as described above or dedicated optical targets included within handheld controller 400B) can be used for 6DOF tracking. In some examples, the handheld controller 400B can include cameras as described above, and the wearable head device 400A can include optical targets for optical tracking in conjunction with the cameras. In some embodiments, the wearable head device 400A and the handheld controller 400B each include a set of three orthogonally oriented solenoids, which are used to wirelessly transmit and receive three distinguishable signals.By measuring the relative magnitudes of the three distinguishable signals received in each of the coils used to receive, the 6DOF of the wearable head device 400A relative to the handheld controller 400B can be determined. Additionally, the 6DOF totem subsystem 404A can include an inertial measurement unit (IMU), which is useful for providing improved accuracy and / or more timely information regarding high speed movements of the handheld controller 400B.

[0047] In some examples, it may be necessary to transform coordinates from a local coordinate space (e.g., a coordinate space that is fixed relative to the wearable head device 400A) to an inertial coordinate space (e.g., a coordinate space that is fixed relative to the real environment), e.g., to compensate for movement of the wearable head device 400A relative to coordinate system 108. For example, such a transformation may be necessary so that the display of the wearable head device 400A presents virtual objects in an expected position and orientation relative to the real environment (e.g., a virtual person sitting in a real chair facing forward, regardless of the position and orientation of the wearable head device), rather than in a fixed position and orientation on the display (e.g., the same position in the bottom right corner of the display), preserving the illusion that the virtual objects exist in the real environment (and do not appear unnaturally positioned in the real environment, e.g., as the wearable head device 400A shifts and rotates). In some examples, a compensatory transformation between coordinate spaces can be determined by processing images from depth camera 444 using SLAM and / or visual odometry procedures to determine the transformation of wearable head device 400A relative to coordinate system 108. In the example shown in FIG. 4 , depth camera 444 is coupled to SLAM / visual odometry block 406 and can provide images to block 406. The SLAM / visual odometry block 406 implementation can include a processor configured to process the images and then determine the position and orientation of the user's head, which can be used to identify a transformation between the head coordinate space and another coordinate space (e.g., an inertial coordinate space). Similarly, in some examples, an additional source of information about the user's head pose and location is obtained from IMU 409. Information from IMU 409 can be integrated with information from SLAM / visual odometry block 406 to provide improved accuracy and / or more timely information for rapid adjustments of the user's head pose and position.

[0048] In some examples, depth camera 444 can provide 3D images to hand gesture tracker 411, which can be implemented within a processor of wearable head device 400A. Hand gesture tracker 411 can identify the user's hand gestures, for example, by matching the 3D images received from depth camera 444 to stored patterns representing hand gestures. Other suitable techniques for identifying the user's hand gestures will also be apparent.

[0049] In some embodiments, one or more processors 416 may be configured to receive data from the 6DOF wearable head device subsystem 404B, the IMU 409, the SLAM / visual odometry block 406, the depth camera 444, and / or the hand gesture tracker 411 of the wearable head device. The processor 416 may also send and receive control signals to and from the 6DOF totem system 404A. The processor 416 may be wirelessly coupled to the 6DOF totem system 404A, such as in embodiments in which the handheld controller 400B is untethered. The processor 416 may further communicate with additional components, such as an audiovisual content memory 418, a graphical processing unit (GPU) 420, and / or a digital signal processor (DSP) audio spatializer 422. The DSP audio spatializer 422 may be coupled to a head-related transfer function (HRTF) memory 425. The GPU 420 may include a left channel output coupled to a left source of imagewise modulated light 424 and a right channel output coupled to a right source of imagewise modulated light 426. The GPU 420 may output stereoscopic image data to the sources of imagewise modulated light 424, 426, for example, as described above with respect to FIGS. 2A-2D . The DSP audio spatializer 422 may output audio to the left speaker 412 and / or the right speaker 414. The DSP audio spatializer 422 may receive an input from the processor 419 indicating a direction vector from the user to a virtual sound source (which may be moved by the user, e.g., via the handheld controller 320). Based on the direction vector, the DSP audio spatializer 422 may determine a corresponding HRTF (e.g., by accessing an HRTF or by interpolating multiple HRTFs). The DSP audio spatializer 422 may then apply the determined HRTF to an audio signal, such as an audio signal corresponding to a virtual sound generated by a virtual object.This can improve the believability and realism of virtual sounds by incorporating the user's relative position and orientation to the virtual sounds in the mixed reality environment, i.e., by presenting virtual sounds that match the user's expectations of what they would hear if the virtual sounds were real sounds in a real environment.

[0050] 4 , one or more of the processor 416, GPU 420, DSP audio spatializer 422, HRTF memory 425, and audio / visual content memory 418 may be included in auxiliary unit 400C (which may correspond to auxiliary unit 320 described above). Auxiliary unit 400C may include battery 427 to power its components and / or provide power to wearable head device 400A or handheld controller 400B. Including such components in an auxiliary unit, which may be mounted on the user's waist, can limit the size and weight of wearable head device 400A, which in turn can reduce fatigue in the user's head and neck.

[0051] While Figure 4 presents elements corresponding to various components of an exemplary mixed reality system, various other suitable arrangements of these components will be apparent to those skilled in the art. For example, elements shown in Figure 4 as associated with auxiliary unit 400C may instead be associated with wearable head device 400A or handheld controller 400B. Furthermore, some mixed reality systems may dispense with handheld controller 400B or auxiliary unit 400C entirely. Such variations and modifications should be understood as being within the scope of the disclosed embodiments.

[0052] Virtual Sound Source

[0053] As described above, an MRE (as experienced via a mixed reality system, e.g., mixed reality system 200 described above) can present audio signals to a user that may correspond to “listener” coordinates, such that the audio signals represent what the user may hear at those listener coordinates. Some audio signals may correspond to the position and / or orientation of a sound source within the MRE. That is, signals may be presented as they appear to originate from the position of the sound source within the MRE and propagate in the direction of the orientation of the sound source within the MRE. In some cases, such audio signals may be considered virtual in that they correspond to virtual content within the virtual environment and not necessarily to real sounds in the real environment. Sounds associated with virtual content may be synthesized or generated by processing stored sound samples. Virtual audio signals can be presented to a user as real audio signals detectable by the human ear, for example, as generated via speakers 2134 and 2136 of wearable head device 2102 in FIGS. 2A-2D .

[0054] A sound source may correspond to a real object and / or a virtual object. For example, a virtual object (e.g., virtual monster 132 in FIG. 1C ) can emit an audio signal within the MRE, which is represented as a virtual audio signal within the MRE and presented to the user as a real audio signal. For example, virtual monster 132 in FIG. 1C can emit virtual sounds or sound effects corresponding to the monster's utterances (e.g., dialogue). Similarly, a real object (e.g., real object 122A in FIG. 1C ) can also emit virtual sounds within the MRE, which are represented as a virtual audio signal within the MRE and presented to the user as a real audio signal. For example, real lamp 122A can emit virtual sounds corresponding to the sound effect of a lamp being turned on or off, even though the lamp is not turned on or off in the real environment. (The lamp brightness can be generated virtually using the eyepieces 2108, 2110 and image-modulated light sources 2124, 2126.) The virtual sound may correspond to the position and orientation of a sound source (whether real or virtual). For example, if the virtual sound is presented to the user as a real audio signal (e.g., via speakers 2134 and 2136), the user may perceive the virtual sound as emanating from the position of the sound source and traveling in the direction of the sound source's orientation. (The sound source may be referred to herein as a "virtual sound source," even though the sound source itself may correspond to a real object as described above.)

[0055] In some virtual or mixed reality environments, when a user is presented with an audio signal as described above, it is an intuitive and natural ability to identify audio sources in a real environment, but it can be difficult to quickly and accurately identify the source of an audio signal in a virtual environment. It is desirable to improve a user's ability to perceive the location or orientation of sound sources within an MRE so that the user's experience in a virtual or mixed reality environment more closely resembles the user's experience in the real world.

[0056] Similarly, some virtual or mixed reality environments suffer from the perception that the environment does not feel real or authentic. One reason for this perception is that audio and visual cues do not always match one another in the virtual environment. For example, if a user is positioned behind a large brick wall in an MRE, the user may expect sounds coming from behind the brick wall to be quieter and more muffled than sounds coming from directly next to the user. This expectation is based on one's own auditory experience in the real world, where sounds can become quiet and muffled when obstructed by a large, dense object. When a user is presented with an audio signal that purports to originate from behind the brick wall but is not muffled and is presented at full volume, the illusion that the user is behind the brick wall or that sounds are originating from behind it is damaged. The entire virtual experience may feel fake and inauthentic, in part because it does not match one's expectations based on real-world interactions. Furthermore, in some cases, the "uncanny valley" problem arises, where even slight differences between the virtual and real experiences can create a sense of discomfort. It is desirable to improve the user's experience by presenting audio signals within the MRE that appear to interact realistically, even in subtle ways, with objects in the user's environment. The more consistent such audio signals are with one's expectations based on real-world experience, the more immersive and engaging the user's MRE experience will be.

[0057] One way the human brain detects the location and orientation of a sound source is by interpreting the difference between sounds received by the left and right ears. For example, if an audio signal in a real environment reaches a user's left ear before reaching the right ear (which the human auditory system may determine, for example, by identifying a time delay or phase shift between the left and right ear signals), the brain may recognize that the source of the audio signal is to the user's left. Similarly, if the audio signal appears louder to the left ear than to the right ear because the effective power of the audio signal generally decreases with distance and may be obstructed by the user's own head, the brain may recognize that the source is to the user's left. Similarly, our brains recognize that differences in frequency characteristics between left and right ear signals may indicate the location of the source or the direction in which the audio signal is traveling.

[0058] The above-described techniques, implemented subconsciously by the human brain, work by processing stereo audio signals, specifically analyzing differences (e.g., in amplitude, phase, and frequency response) between separate audio signals generated by a single sound source and received at the left and right ears, if applicable. As humans, we inevitably rely on these stereo auditory techniques to quickly and accurately identify where sounds in our real environments originate and the direction they are traveling. We also rely on such stereo techniques to better understand the world around us, for example, whether a sound source is on the other side of a nearby wall, and, if applicable, the thickness of that wall and the material from which it is made.

[0059] It may be desirable for an MRE to convincingly place virtual sound sources within the MRE in a way that the user can quickly locate, utilizing the same natural stereo techniques that our brains use in the real world. Similarly, it may be desirable to use these same techniques to enhance the sense that such virtual sound sources coexist with real and virtual content within the MRE, for example, by presenting stereo audio signals corresponding to those sound sources that behave like stereo audio signals in the real world. By presenting users of the MRE with audio experiences that evoke the audio experiences of our daily lives, the MRE can enhance the user's sense of immersion and connection when engaging with the MRE.

[0060] 5A and 5B depict perspective and top views, respectively, of an exemplary mixed reality environment 500 (which may correspond to mixed reality environment 150 of FIG. 1C ). In MRE 500, user 501 has a left ear 502 and a right ear 504. In the example shown, user 501 is wearing wearable head device 510 (which may correspond to wearable head device 2102) that includes left speaker 512 and right speaker 514 (which may correspond to speakers 2134 and 2136, respectively). Left speaker 512 is configured to present an audio signal to left ear 502, and right speaker 514 is configured to present an audio signal to right ear 504.

[0061] The example MRE 500 includes a virtual sound source 520, which may have a position and orientation within a coordinate system of the MRE 500. In some examples, the virtual sound source 520 may be a virtual object (e.g., virtual object 122A in FIG. 1C) or may be associated with a real object (e.g., real object 122B in FIG. 1C). Thus, the virtual sound source 520 may have any or all of the characteristics described above with respect to virtual objects.

[0062] In some embodiments, virtual sound source 520 may be associated with one or more physical parameters, such as size, shape, mass, or material. In some embodiments, the orientation of virtual sound source 520 may correspond to one or more such physical parameters. For example, in an embodiment in which virtual sound source 520 corresponds to a speaker with a speaker cone, the orientation of virtual sound source 520 may correspond to the axis of the speaker cone. In embodiments in which virtual sound source 520 is associated with a real object, the physical parameters associated with virtual sound source 520 may be derived from one or more physical parameters of the real object. For example, if the real object is a speaker with a 12-inch speaker cone, virtual sound source 520 may have physical parameters corresponding to the 12-inch speaker cone (e.g., virtual object 122B may derive physical parameters or dimensions from corresponding real object 122A of MRE 150).

[0063] In some embodiments, the virtual sound source 520 may be associated with one or more virtual parameters, which may affect the audio signal or other signals or properties associated with the virtual sound source. The virtual parameters may include spatial properties (e.g., position, orientation, shape, dimensions) within the coordinate space of the MRE, visual properties (e.g., color, transparency, reflectivity), physical properties (e.g., density, elasticity, tensile strength, temperature, smoothness, wettability, resonance, conductivity), or other suitable properties of an object. The mixed reality system can determine such parameters and thus generate virtual objects having those parameters. These virtual objects can be rendered to the user (e.g., by the wearable head device 510) according to these parameters.

[0064] In one embodiment of MRE 500, virtual audio signal 530 is emitted by virtual sound source 520 at the location of the virtual sound source and propagates outward from the virtual sound source. In some instances, an anisotropic directional pattern (e.g., exhibiting frequency-dependent anisotropy) can be associated with the virtual sound source, and the virtual audio signal to be emitted in a certain direction (e.g., toward user 501) can be determined based on the directional pattern. The virtual audio signal is not directly perceptible by a user of the MRE, but can be converted into a real audio signal by one or more speakers (e.g., speaker 512 or 514), which generates a real audio signal that can be heard by the user. For example, the virtual audio signal may be a computed representation of digital audio data that can be converted to an analog signal via a digital-to-audio converter, e.g., by a processor and / or memory associated with the MRE, and then amplified and used to drive speakers to generate a sound perceptible by a listener. Such calculated representations may comprise, for example, coordinates within the MRE where the virtual audio signal originates, a vector within the MRE along which the virtual audio signal propagates, a directionality, a time where the virtual audio signal originates, a velocity along which the virtual audio signal propagates, or other suitable characteristics.

[0065] The MRE may also include a representation of one or more listener coordinates, each corresponding to a location (“listener”) in the coordinate system where the virtual audio signal may be perceived. In some embodiments, the MRE may also include a representation of one or more listener vectors, representing the orientation of the listener (e.g., for use in determining audio signals that may be affected by the direction the listener is facing). Within the MRE, the listener coordinates may correspond to the actual locations of the user's ears, which may be determined using SLAM, visual odometry, and / or with an IMU (e.g., IMU 409, described above with respect to FIG. 4). In some embodiments, the MRE may include left and right listener coordinates, corresponding to the locations of the user's left and right ears, respectively, within the MRE's coordinate system. By determining the vector of the virtual audio signal from the virtual sound source to the listener coordinates, a real audio signal can be determined that corresponds to how a human listener with ears at those coordinates would perceive the virtual audio signal.

[0066] In some examples, the virtual audio signal comprises bass sound data (e.g., a computer file representing an audio waveform) and one or more parameters that can be applied to the bass sound data. Such parameters may correspond to bass sound attenuation (e.g., volume reduction), bass sound filtering (e.g., a low-pass filter), bass sound time delay (e.g., phase shift), reverberation parameters for applying artificial reverberation and echo effects, voltage-controlled oscillator (VCO) parameters for applying time-based modulation effects, pitch modulation of the bass sound (e.g., to simulate the Doppler effect), or other suitable parameters. In some examples, these parameters may be a function of the relationship of the virtual audio source to the listener coordinate. For example, the parameters may define the attenuation of the real audio signal as a decreasing function of the distance from the listener coordinate to the location of the virtual audio source. That is, as the distance from the listener to the virtual audio source increases, the gain of the audio signal decreases. As another example, the parameters may define a low-pass filter applied to the virtual audio signal as a function of the distance from the listener coordinate (and / or the angle of the listener vector) to the propagation vector of the virtual audio signal. For example, a listener farther away from the virtual audio signal may perceive less frequency power in the signal than a listener closer to the signal. As a further example, the parameters may define a time delay (e.g., a phase shift) to be applied based on the distance between the listener coordinates and the origin of the virtual audio signal. In some embodiments, the processing of the virtual audio signal can be calculated using the DSP audio spatializer 422 of FIG. 4, which can utilize HRTFs to present the audio signal based on the position and orientation of the user's head.

[0067] The virtual audio signal parameters may be affected by virtual or real objects, i.e., sound occluders, through which the virtual audio signal passes on its way to the listener coordinates. (As used herein, virtual or real object includes any suitable representation of a virtual or real object in the MRE.) For example, if the virtual audio signal intersects with (e.g., is blocked by) a virtual wall in the MRE, the MRE may apply attenuation to the virtual audio signal (resulting in a signal that appears quieter to the listener). The MRE may also apply a low-pass filter to the virtual audio signal, resulting in a signal that appears more muffled as high-frequency components are rolled off. These effects are consistent with our expectations when hearing sounds from behind a wall: the nature of walls in real environments is such that sounds from the other side of the wall are quieter and have fewer high-frequency components because the wall blocks sound waves originating on the other side of the wall from the listener. The application of such parameters to the audio signal may be based on the nature of the virtual wall. For example, a virtual wall corresponding to a thicker or denser material may result in a greater degree of attenuation or low-pass filtering than a virtual wall corresponding to a thinner or less dense material. In some cases, a virtual object may apply a phase shift or additive effect to the virtual audio signal. The effect that a virtual object has on a virtual audio signal can be determined by physical modeling of the virtual object; for example, if the virtual object corresponds to a particular material (e.g., brick, aluminum, water), the effect can be applied based on the known transmission characteristics of the audio signal in the presence of that material in the real world.

[0068] In some embodiments, virtual objects that the virtual audio signal intersects may correspond to real objects (e.g., real objects 122A, 124A, and 126A correspond to virtual objects 122B, 124B, and 126B in FIG. 1C). In some embodiments, such virtual objects may not correspond to real objects (e.g., virtual monster 132 in FIG. 1C). If the virtual objects correspond to real objects, the virtual objects may adopt parameters (e.g., dimensions, materials) that correspond to the properties of those real objects.

[0069] In some embodiments, the virtual audio signal may intersect with a real object that does not have a corresponding virtual object. For example, the properties of the real object (e.g., position, orientation, dimensions, material) can be determined by a sensor (such as attached to the wearable head device 510), and the properties can be used to process the virtual audio signal as described above with respect to the virtual object occluder.

[0070] Stereo Effect

[0071] As described above, by determining the vector of a virtual audio signal from a virtual sound source in a listener coordinate, a real audio signal can be determined that corresponds to how a human listener with ears at that listener coordinate would perceive the virtual audio signal. In some embodiments, left and right stereo listener coordinates (corresponding to the left and right ears) can be used instead of simply a single listener coordinate, allowing the effects of real objects on the audio signal, such as attenuation or filtering based on the interaction of the audio signal with the real object, to be determined separately for each ear. This can enhance the realism of a virtual environment by mimicking a real-world stereo audio experience, and receiving different audio signals at each ear can help us understand the sounds around us. Such effects of the left and right ears experiencing differently affected audio signals can be particularly noticeable when real objects may be in close proximity to the user. For example, if the user 501 is sneaking a meowing virtual cat around the corner of a real object, the sound of the cat's meow can be determined and presented differently for each ear. That is, sounds for an ear positioned behind the real object may reflect that a real object between the cat and the ear may attenuate and filter the cat's sounds as they are heard by that ear, while sounds for another ear positioned beyond the real object may reflect that the real object does not perform such attenuation or filtering. Such sounds can be presented via the user's ears 512, 514 of the wearable head device 510.

[0072] The desired stereo auditory effect as described above can be simulated by determining two such vectors, one for each ear, and identifying a unique virtual audio signal for each ear. Each of these two unique virtual audio signals can then be converted into a real audio signal and presented to a separate ear via the speaker associated with that ear. The user's brain will process those real audio signals in the same way that it would process a normal stereo audio signal in the real world, as described above.

[0073] This is illustrated by example MRE 500 in Figures 5A and 5B. MRE 500 includes a wall 540 between a virtual sound source 520 and a user 501. In some embodiments, wall 540 may be a real object not different from real object 126A of Figure 1C. In some embodiments, wall 540 may be a virtual object, such as virtual object 122B of Figure 1C. Furthermore, in some such embodiments, the virtual object may correspond to a real object, such as real object 122A of Figure 1C.

[0074] In embodiments where wall 540 is a real object, wall 540 may be detected, for example, using a depth camera or other sensor in wearable head device 510. This can identify one or more characteristics of the real object, such as its position, orientation, visual properties, or material properties. These characteristics can be associated with wall 540 and included in updating and maintaining MRE 500, as described above. These characteristics can then be used to process virtual audio signals according to how those virtual audio signals would be affected by wall 540, as described below. In some embodiments, virtual content, such as helper data, may be associated with real objects to facilitate processing of virtual audio signals affected by the real objects. For example, the helper data may include a geometric primitive similar to the real object, two-dimensional image data associated with the real object, or a custom asset type that identifies one or more properties associated with the real object.

[0075] In some embodiments where wall 540 is a virtual object, the virtual object may be calculated to correspond to a real object, which may be detected as described above. For example, as described above with respect to FIG. 1C , real object 122A may be detected by wearable head device 510, and virtual object 122B may be generated to correspond to one or more properties of real object 122A. Additionally, one or more properties may be associated with the virtual object that are not derived from its corresponding real object. An advantage of identifying a virtual object associated with a corresponding real object is that the virtual object can be used to simplify calculations associated with wall 540. For example, the virtual object may be geometrically simpler than the corresponding real object. However, in some embodiments where wall 540 is a virtual object, a corresponding real object may not exist, and wall 540 may be determined by software (e.g., a software script that specifies the presence of wall 540 at a particular position and orientation). The properties associated with wall 540 can be included in maintaining and updating MRE 500 as described above. These characteristics can then be used to process the virtual audio signals according to how they would be affected by the wall 540, as explained below.

[0076] Wall 540, whether real or virtual, may be considered a sound occluder, as described above. As seen in the top view shown in FIG. 5B , two vectors 532 and 534 may represent separate paths of virtual audio signal 530 from virtual sound source 520 within MRE 500 to the user's left ear 502 and right ear 504. Vectors 532 and 534 may correspond to unique left and right audio signals to be presented to the left and right ears, respectively. As shown in the example, vector 534 (corresponding to right ear 504) intersects with wall 540, while vector 532 (corresponding to left ear 502) does not. Thus, wall 540 may impart different characteristics to the right audio signal than the left audio signal. For example, the right audio signal may have attenuation and low-pass filtering applied to accommodate wall 540, while the left audio signal does not. In some embodiments, the left audio signal may be phase-shifted or time-shifted relative to the right audio signal to accommodate the greater distance from the right ear 504 to the virtual sound source 520 (which would result in the audio signal from that source arriving slightly later at the left ear 502 than at the right ear 504). The user's auditory system, just as in the real world, can interpret this phase or time shift to help identify that the virtual sound source 520 is to one side (e.g., the right side) of the user within the MRE 500.

[0077] The relative importance of these stereo differences may depend on the differences in the frequency spectra of the signals. For example, phase shifts may be more useful for locating high-frequency signals than for locating low-frequency audio signals (i.e., signals with wavelengths approximately the width of a listener's head). For such low-frequency signals, the time of arrival difference between the left and right ears may be useful for locating the source of these signals.

[0078] 5A-5B, an object (whether real or virtual), such as a wall 540, need not be between the user 501 and the virtual sound source 520. In such an embodiment, such as when the wall 540 is behind the user, the wall may impart different characteristics to the left and right audio signals via reflections of the virtual audio signal 530 toward the left and right ears 502 and 504 against the wall 540.

[0079] An advantage of MRE 500 over some environments, such as video games presented by traditional display monitors and room speakers, is that the actual location of the user's ears within MRE 500 can be determined. As described above with respect to FIG. 4, wearable head device 510 can be configured to identify the location of user 501 through the use of sensors and measurement hardware, such as SLAM, visual odometry techniques, and / or an IMU. In some examples, wearable head device 510 may be configured to detect the individual locations of the user's ears directly (e.g., via sensors associated with ears 502 and 504, speakers 512 and 514, or temple arms (such as temple arms 2130 and 2132 shown in FIGS. 2A-2D )). In some examples, the wearable head device 510 may be configured to detect the position of the user's head and, based on that position, approximate individual locations of the user's ears (e.g., by estimating or detecting the width of the user's head and identifying ear locations located along the circumference of the head and separated by the head width). By identifying the user's ear locations, audio signals can be presented to the ears corresponding to those specific locations. Compared to techniques that determine audio signals based on audio receiver coordinates (e.g., the origin coordinates of a virtual camera in a virtual 3D environment), which may or may not correspond to the user's actual ears, determining ear locations and presenting audio signals based on those locations can improve the user's immersion and connection within the MRE.

[0080] By being presented with unique and separately determined left and right audio signals via speakers 512 and 514, which correspond to the left and right listener positions (e.g., the locations of the user's ears 502 and 504 within MRE 500), respectively, user 501 is able to identify the position and / or orientation of virtual sound source 520. This is because the user's auditory system naturally attributes differences (e.g., in gain, frequency, and phase) between the left and right audio signals, along with the presence of sound occluders such as wall 540, to the position and orientation of virtual sound source 520. These stereo audio cues therefore improve user 501's perception of virtual sound source 520 and wall 540 within MRE 500. This, in turn, can enhance user 501's sense of engagement with MRE 500. For example, if virtual sound source 520 corresponds to an important object in MRE 500, such as a virtual character speaking to user 501, user 501 can use the stereo audio signal to quickly identify the location of that object. This, in turn, can reduce the cognitive burden placed on user 501 to identify the location of the object and can also reduce the computational burden placed on MRE 501. For example, a processor and / or memory (e.g., processor 416 and / or memory 418 of FIG. 4) may no longer need to present high-fidelity visual cues to user 501 to identify the location of an object (e.g., via high-resolution assets such as 3D models and textures and lighting effects) because audio cues have done much of that work.

[0081] Asymmetric occlusion effects as described above may be particularly noticeable in situations where a real or virtual object, such as wall 540, is physically close to the user's face, or where a real or virtual object occludes one ear but not the other (such as when the center of the user's face is aligned with the edge of wall 540, as seen in FIG. 5B). These situations may be exploited to advantage. For example, in MRE 500, user 501 may hide behind the edge of wall 540, peek around a corner, and locate a virtual object (e.g., corresponding to virtual sound source 520) based on the stereo audio effect imparted by the wall to that object's sound emissions (e.g., virtual audio signal 530). This can enable, for example, tactical gameplay within a gaming environment based on the MRE 500, architectural design applications where the user 501 checks for proper acoustics in different areas of a virtual room, or educational or creative benefits where the user 501 explores the interaction of various audio sources (e.g., virtual bird calls) with their environment.

[0082] In some embodiments, the left and right audio signals may not each be independently determined, but may be based on other or common audio sources. For example, if a single audio source generates both the left and right audio signals, the left and right audio signals may be considered to be acoustically related to each other via the single audio source, rather than being entirely independent.

[0083] 6 shows an example process 600 for presenting left and right audio signals to a user of an MRE, such as user 501 of MRE 500. Example process 600 may be implemented by a processor (e.g., corresponding to processor 416 of FIG. 4) and / or a DSP module (e.g., corresponding to DSP audio spatializer 422 of FIG. 4) of wearable head device 510.

[0084] In stage 605 of process 600, the individual locations (e.g., listener coordinates and / or vectors) of the first ear (e.g., the user's left ear 502) and the second ear (e.g., the user's right ear 504) are determined. These locations can be determined using sensors in the wearable head device 510, as described above. Such coordinates can be relative to a local user coordinate system of the wearable head device (e.g., the user coordinate system 114 described above with respect to FIG. 1A). In such a user coordinate system, the origin of such a coordinate system may approximately correspond to the center of the user's head, simplifying the representation of the locations of the left and right virtual listeners. Using SLAM, visual odometry, and / or an IMU, the displacement and rotation (e.g., six degrees of freedom) of the user coordinate system 114 relative to the environment coordinate system 108 can be updated in real time.

[0085] In stage 610, a first virtual sound source can be defined, which may correspond to virtual sound source 520. In some examples, the virtual sound source may correspond to a virtual or real object, which may be identified and located via a depth camera or sensor of wearable head device 510. In some examples, the virtual object may correspond to a real object as described above. For example, the virtual object may have one or more characteristics (e.g., position, orientation, material, visual properties, acoustic properties) of the corresponding real object. The location of the virtual sound source can be established within coordinate system 108 (FIGS. 1A-1C).

[0086] In stage 620A, a first virtual audio signal may be identified that propagates along vector 532 and may correspond to virtual audio signal 530 that intersects with a first virtual listener (e.g., a first approximate ear position). For example, in response to determining that a sound signal was generated by a first virtual sound source at a first time t, a vector from the first sound source to the first virtual listener may be calculated. The first virtual audio signal may be associated with base audio data (e.g., a waveform file) and, optionally, one or more parameters for modifying the base audio data as described above. Similarly, in stage 620B, a second virtual audio signal may be identified that propagates along vector 534 and may correspond to virtual audio signal 530 that intersects with a second virtual listener (e.g., a second approximate ear position).

[0087] In stage 630A, real or virtual objects (one of which may correspond, for example, to wall 540) intersected by the first virtual audio signal are identified. For example, a trace may be calculated along a vector from a first sound source in MRE 500 to the first virtual listener, and real or virtual objects intersecting the trace may be identified (in some embodiments, along with parameters of the intersection, such as the position and vector along which the real or virtual object is intersected). In some cases, such real or virtual objects may not exist. Similarly, in stage 630B, real or virtual objects intersected by the second virtual audio signal are identified. Again, in some cases, such real or virtual objects may not exist.

[0088] In some examples, the real objects identified in stage 630A or stage 630B can be identified using a depth camera or other sensor associated with wearable head device 510. In some examples, the virtual objects identified in stage 630A or stage 630B may correspond to real objects and real objects 122A, 124A, and 126A, and corresponding virtual objects 122B, 124B, and 126B, as described with respect to FIG. 1C . In such examples, such real objects can be identified using a depth camera or other sensor associated with wearable head device 510, and virtual objects can be generated to correspond to those real objects as described above.

[0089] At stage 640A, each real or virtual object identified at stage 630A is processed to identify any signal-modifying parameters associated with that real or virtual object at stage 650A. For example, as described above, such signal-modifying parameters may include functions for determining attenuation, filtering, phase shift, time-based effects (e.g., delay, reverberation, modulation), and / or other effects to be applied to the first virtual audio signal. As described above, these parameters may depend on other parameters associated with the real or virtual object, such as the size, shape, or material of the real or virtual object. At stage 660A, the signal-modifying parameters are applied to the first virtual audio signal. For example, if the signal modification parameters specify that the first virtual audio signal should be attenuated by a factor that increases linearly with the distance between the listener coordinates and the audio source, then that factor may be calculated (i.e., by calculating the distance between the first ear and the first virtual sound source in MRE 500) and applied to the first virtual audio signal (i.e., by multiplying the amplitude of the signal by the resulting gain factor) in stage 660A. In some embodiments, the signal modification parameters may be determined or applied using DSP audio spatializer 422 of FIG. 4, which may utilize HRTFs to modify the audio signal based on the position and orientation of the user's head as described above. Once all real or virtual objects identified in stage 630A have been applied in stage 660A, a processed first virtual audio signal (e.g., representing all signal modification parameters of the identified real or virtual objects) is output by stage 640A. Similarly, in stage 640B, each real or virtual object identified in stage 630B is processed to identify signal modification parameters (stage 650B) and apply those signal modification parameters to a second virtual audio signal (stage 660B).Once all real or virtual objects identified in stage 630B have been applied in stage 660B, a processed first virtual audio signal (e.g., representing all signal modification parameters of the identified real or virtual objects) is output by stage 640B.

[0090] In stage 670A, the processed first virtual audio signal output from stage 640A can be used to determine a first audio signal (e.g., a left channel audio signal) that can be presented to a first ear. For example, in stage 670A, the first virtual audio signal can be mixed with another left-channel audio signal (e.g., another virtual audio signal, music, or dialogue). In some embodiments, such as in a simple mixed reality environment without other sounds, stage 670A may perform little or no processing to determine the first audio signal from the processed first virtual audio signal. Stage 670A can incorporate any suitable stereo mixing technique. Similarly, in stage 680A, the processed second virtual audio signal output from stage 640B can be used to determine a second audio signal (e.g., a right channel audio signal) that can be presented to a second ear.

[0091] In stages 680A and 680B, the audio signals output by stages 670A and 670B, respectively, are presented to the first and second ears, respectively. For example, the left and right stereo signals may be amplified and converted to left and right analog signals (e.g., by DSP audio spatializer 422 of FIG. 4) that are presented to left and right speakers 512 and 514, respectively. When left and right speakers 512 and 514 are configured to acoustically couple to left and right ears 502 and 504, respectively, left and right ears 502 and 504 may be presented with their respective left and right stereo signals in sufficient isolation from other stereo signals to produce a stereo effect.

[0092] FIG. 7 shows a functional block diagram of an exemplary augmented reality processing system 700 that can be used to implement one or more of the above-described embodiments. The exemplary system 700 can be implemented within a mixed reality system, such as the above-described mixed reality system 112. FIG. 7 shows aspects of the audio architecture of the system 700. In the illustrated embodiment, a game engine 702 generates virtual 3D content 704 and simulates events involving the virtual 3D content 704 (the events may include interactions between the virtual 3D content 704 and real objects). The virtual 3D content 704 may include, for example, static virtual objects, virtual objects with functionality, such as virtual musical instruments, virtual animals, and virtual people. In the illustrated embodiment, the virtual 3D content 704 includes a localized virtual sound source 706. The localized virtual sound source 706 may include, for example, a sound source corresponding to the song of a virtual bird, a sound emitted by a virtual musical instrument played by a user or a virtual person, or the voice of a virtual person.

[0093] The exemplary augmented reality processing system 700 can integrate virtual 3D content 704 into the real world with a high degree of realism. For example, audio associated with a localized virtual sound source may be located at a distance from the user and in a location that would be partially obstructed by a real object if the audio were a real audio signal. However, in the exemplary system 700, the audio can be output by left and right speakers 412, 414, 2134, 2136 (which may, for example, belong to the wearable head device 400A of the mixed reality system 112). The audio, which travels only a short distance from the speakers 2134, 2136 to the user's ears, is not physically affected by obstacles. However, the system 700 can modify the audio to take into account the effects of obstacles, as described below.

[0094] In the exemplary system 700, a user coordinate determination subsystem 708 may preferably be physically stored within the wearable head device 200, 400A. The user coordinate determination subsystem 708 may maintain information about the position (e.g., X, Y, and Z coordinates) and orientation (e.g., roll, pitch, yaw; quaternions) of the wearable head device relative to the real-world environment. Virtual content is defined within the environmental coordinate system 108 (FIGS. 1A-1C), which is generally fixed relative to the real world. However, in embodiments, the same virtual content is typically output via eyepieces 408, 410 and speakers 412, 414, 2134, 2136, which are fixed to the wearable head device 200, 400A and move relative to the real world as the user's head moves. As the wearable head device 200, 400A is displaced or rotated, the spatialization of the virtual audio may be adjusted, and the visual display of the virtual content should be re-rendered to account for the displacement and / or rotation. The user coordinate determination subsystem 708 may include an inertial measurement unit (IMU) 710, which may include a set of three orthogonal accelerometers (not shown in FIG. 7 ) that provide measurements of acceleration (from which displacement may be determined by integration) and three orthogonal gyroscopes (not shown in FIG. 7 ) that provide measurements of rotation (from which orientation may be determined by integration). To adjust for drift errors in the displacement and orientation obtained from the IMU 710, a simultaneous localization and mapping (SLAM) and / or visual odometry block 406 may be included within the user coordinate determination system 708. As shown in FIG. 4 , a depth camera 444 may be coupled to and provide image input for the SLAM and / or visual odometry block 406.

[0095] A spatially significant real-world occluding object sensor subsystem 712 ("occlusion subsystem") is included within the exemplary augmented reality processing system 700. The occlusion subsystem 712 may include, for example, a depth camera 444, a non-depth camera (not shown in FIG. 7), a sound navigation and ranging (sonar) sensor (not shown in FIG. 7), and / or a light detection and ranging (LIDAR) sensor (not shown in FIG. 7). The occlusion subsystem 712 may have sufficient spatial resolution to distinguish obstacles that affect virtual propagation paths corresponding to left and right listener positions. For example, if a user of the wearable head device 200, 400A is sneaking a real-world angle look at a virtual sound-emitting virtual object (e.g., an enemy in a virtual game where a cornered wall blocks a direct line of sight to the user's left ear but not to the user's right ear), the occlusion subsystem 712 may sense the obstacle with sufficient resolution to determine that only the direct path to the left ear will be occluded. In some embodiments, the occlusion subsystem 712 may have better spatial resolution and may be able to determine the size (or solid angle relative to it) and distance to the occluding real object.

[0096] In the example shown in FIG. 7 , the occlusion subsystem 712 is coupled to a per-channel (i.e., left and right audio channel) intersection and obstacle range calculator (herein, “obstacle calculator”) 714. In an example, the user coordinate determination system 708 and the game engine 702 are also coupled to the obstacle calculator 714. The obstacle calculator 714 may receive information indicating coordinates of virtual audio sources from the game engine 702, user coordinates from the user coordinate determination system 708, and obstacle coordinates (e.g., angular coordinates, optionally including distance) from the occlusion subsystem 712. By applying geometry, the obstacle calculator 714 can determine whether an obstructed or unobstructed line of sight exists from each virtual audio source to each of the left and right listener positions. Although shown as a separate block in FIG. 7 , the obstacle calculator 714 may be integrated with the game engine 702. In some embodiments, occlusions may be initially detected by the occlusion subsystem 712 in a user-centered coordinate system based on information from the user coordinate determination system 708, and the coordinates of the occlusions are transformed to the environment coordinate system 108 for purposes of analyzing obstacle geometry. In some embodiments, the coordinates of virtual sound sources may be transformed to the user-centered coordinate system for purposes of calculating obstacle geometry. In some embodiments where the occlusion subsystem 712 provides spatially resolved information about occluding objects, the obstacle calculator 714 may determine the range of solid angles centered on the line of sight that are occluded by the occluding object. Obstacles with a larger solid angle range may be considered by applying greater attenuation and / or greater attenuation of the range of high-frequency components.

[0097] In some embodiments, the localized virtual sound source 706 may include a mono audio signal or left and right spatialized audio signals. Such left and right spatialized audio signals may be determined by applying left and right head-related transfer functions (HRTFs), which may be selected based on the coordinates of the localized virtual sound source relative to the user. In embodiment 700, the game engine 702 is coupled to a user coordinate determination system 708 and receives the coordinates (e.g., position and orientation) of the user. The game engine 702 itself may determine the coordinates of the virtual sound source (e.g., in response to user input) and, in response to receiving the user coordinates, may determine the coordinates of the sound source relative to the user by way of a geometric shape.

[0098] 7, obstacle calculator 714 is coupled to filter activation and control device 716. In some embodiments, filter activation and control device 716 is coupled to a left control input 718A of left filter bypass switch 718 and a right control input 720A of right filter bypass switch 720. In some embodiments, as with other components of example system 700, bypass switches 718, 720 can be implemented in software. In the illustrated embodiment, left filter bypass switch 718 receives the left channel of spatialized audio from game engine 702, and right filter bypass switch 720 receives the right spatialized audio from game engine 704. In some embodiments where game engine 702 outputs a mono audio signal, both bypass switches 718, 720 can receive the same mono audio signal.

[0099] 7, a first output 718B of the left bypass switch 718 is coupled to a left digital-to-analog converter ("left D / A") 724 through a left obstacle filter 722, and a second output 718C of the left bypass switch 718 is coupled to the left D / A 724 (bypassing the left obstacle filter 722). Similarly, in an embodiment, a first output 720B of the right bypass switch 720 is coupled to a right digital-to-analog converter ("right D / A") 728 through a right obstacle filter 726, and a second output 720C is coupled to the right D / A 728 (bypassing the right obstacle filter 726).

[0100] In the example shown in FIG. 7 , a set of filter configurations 730 can be used (e.g., by the filter activation and control unit 716) to configure the left obstacle filter 722 and / or the right obstacle filter based on the output of the per-channel intersection and obstacle range calculator 722. In some examples, instead of providing bypass switches 718, 720, non-filtering pass-through configurations of the obstacle filters 722, 726 can be used. The obstacle filters 722, 726 can be time-domain or frequency-domain filters. In examples where the filters are time-domain filters, each filter configuration can include a set of tap coefficients. In examples where the filters are frequency-domain filters, each filter configuration can include a set of frequency band weights. In some examples, instead of a set of a predetermined number of filter configurations, the filter activation and control unit 716 can be configured (e.g., programmatically) to define filters with a certain level of attenuation depending on the size of the obstacle. The filter activation and control unit 716 may select or define a filter configuration (e.g., a configuration that provides more attenuation for larger obstacles) and / or may select or define a filter that attenuates higher frequency bands (e.g., to a greater extent for larger obstacles to simulate the effect of real obstacles).

[0101] 7, filter activation and control device 716 is coupled to a control input 722A of left obstacle filter 722 and a control input 726A of right obstacle filter 726. Filter activation and control device 716 can independently configure left obstacle filter 722 and right obstacle filter 726 using a configuration selected from filter configurations 730 based on the output from per-channel intersection and obstacle range calculator 714.

[0102] 7, the left D / A 724 is coupled to an input 732A of a left audio amplifier 732, and the right D / A 728 is coupled to an input 734A of a right audio amplifier 734. In an embodiment, an output 732B of the left audio amplifier 732 is coupled to a left speaker 2134, 412, and an output 734B of the right audio amplifier 734 is coupled to a right speaker 2136, 414.

[0103] It should be noted that the elements of the exemplary functional block diagram shown in Figure 7 can be arranged in any suitable order, not necessarily in the order shown. Additionally, some elements shown in the example in Figure 7 (e.g., bypass switches 718, 720) can be omitted, if desired. The present disclosure is not limited to any particular order or arrangement of functional components shown in the example.

[0104] Some embodiments of the present disclosure provide a method of presenting an audio signal in a mixed reality environment, comprising the steps of: identifying a first ear position of a listener in the mixed reality environment; identifying a second ear position of the listener in the mixed reality environment; identifying a first virtual sound source in the mixed reality environment; identifying a first object in the mixed reality environment; and determining a first audio signal in the mixed reality environment, the first audio signal originating at the first virtual sound source and intersecting the first ear position of the listener;

[0010] In some embodiments, determining a third audio signal from the second audio signal includes applying a low-pass filter to the second audio signal, the low-pass filter having parameters based on the first virtual object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, determining the third audio signal from the second audio signal includes applying an attenuation to the second audio signal, wherein the magnitude of the attenuation is based on the first object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, identifying the first object includes identifying a real object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, identifying the real object includes determining a position of the real object relative to the user in the mixed reality environment using a sensor.Additionally or in the alternative to one or more of the embodiments disclosed above, in some embodiments, the sensor comprises a depth camera. Additionally or in the alternative to one or more of the embodiments disclosed above, in some embodiments, the method further includes generating helper data corresponding to the real object. Additionally or in the alternative to one or more of the embodiments disclosed above, in some embodiments, the method further includes generating a virtual object corresponding to the real object. Additionally or in the alternative to one or more of the embodiments disclosed above, in some embodiments, the method further includes identifying a second virtual object, wherein the first audio signal intersects with the second virtual object and the fourth audio signal is determined based on the second virtual object.

[0105] Some embodiments of the present disclosure provide a system, comprising: a wearable head device, the wearable head device comprising: a display for displaying a mixed reality environment to a user, the display comprising a transparent eyepiece through which a real environment is visible; a first speaker configured to present an audio signal to a first ear of the user; and a second speaker configured to present the audio signal to a second ear of the user; and a method for identifying a position of a first ear of a listener within the mixed reality environment; identifying a position of a second ear of the listener within the mixed reality environment; identifying a first virtual sound source within the mixed reality environment; identifying a first object within the mixed reality environment; and and one or more processors configured to perform the steps of: determining a first audio signal within a mixed reality environment, the first audio signal originating at a first virtual sound source and intersecting a first ear position of a listener; determining a second audio signal within a mixed reality environment, the second audio signal originating at the first virtual sound source and intersecting a first object and intersecting a second ear position of the listener; determining a third audio signal based on the second audio signal and the first object; presenting the first audio signal to the first ear via a first speaker; and presenting the third audio signal to the second ear via a second speaker. In addition to or in the alternative to one or more of the embodiments disclosed above, in some embodiments, determining the third audio signal from the second audio signal includes applying a low-pass filter to the second audio signal, the low-pass filter having parameters based on the first object. In addition to or as an alternative to one or more of the embodiments disclosed above, in some embodiments, determining the third audio signal from the second audio signal includes applying an attenuation to the second audio signal, wherein the magnitude of the attenuation is based on the first object.Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, identifying the first object includes identifying a real object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, the wearable head device further includes a sensor, and identifying the real object includes determining a position of the real object relative to the user in the mixed reality environment using the sensor. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, the sensor includes a depth camera. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, the one or more processors are further configured to perform generating helper data corresponding to the real object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, the one or more processors are further configured to perform generating a virtual object corresponding to the real object. Additionally or alternatively to one or more of the embodiments disclosed above, in some embodiments, the one or more processors are further configured to perform identifying a second virtual object, wherein the first audio signal intersects with the second virtual object and the fourth audio signal is determined based on the second virtual object.

[0106] Although the disclosed embodiments have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will be apparent to those skilled in the art. For example, elements of one or more implementations may be combined, deleted, modified, or supplemented to form further implementations. Such changes and modifications are to be understood as being included within the scope of the disclosed embodiments as defined by the appended claims.

Claims

1. A method for determining an audio signal in a mixed reality environment, the method comprising: determining a first audio signal within the mixed reality environment, the first audio signal being associated with a virtual sound source within the mixed reality environment; determining a second audio signal based on the first audio signal and further based on parameters of objects in the mixed reality environment; Including, the parameters of the object are determined via one or more sensors of a first wearable head device; the parameters of the object are associated with at least one of a filter, a phase shift, a delay, and a modulation; the second audio signal is associated with an interaction of the first audio signal with the object in the mixed reality environment; the second audio signal is determined further based on the interaction; The method, wherein the second audio signal is presented through a speaker of a second wearable head device.

2. The method described in claim 1, wherein the first audio signal corresponds to a signal path that intersects with the object in the mixed reality environment.

3. The position of the listener within the mixed reality environment is identified via the one or more sensors of the first wearable head device; The method of claim 1 , wherein the position of the listener is associated with the second wearable head device.

4. The method of claim 1, wherein the object includes a real object.

5. The method of claim 1, further comprising determining the position of the object within the mixed reality environment via the one or more sensors.

6. The method of claim 1, wherein the object includes a virtual object.

7. The method described in claim 1, wherein the second audio signal is determined further in accordance with a determination that the first audio signal corresponds to a signal path that intersects with the object within the mixed reality environment.

8. The method described in claim 1, wherein the parameter is further associated with attenuation.

9. The method of claim 1, wherein the parameter is further associated with reverberation.

10. The method of claim 1, wherein the one or more sensors include a camera.

11. The method of claim 1, wherein determining the second audio signal includes applying at least one of a filter and attenuation to the first audio signal.

12. The method described in claim 1, wherein the interaction includes an intersection between the first audio signal and the object.

13. The method of claim 1, wherein the first wearable head device includes the second wearable head device.

14. A first wearable head device having one or more sensors; a second wearable head device comprising a speaker; one or more processors configured to perform the method; A system comprising: The method comprises: determining a first audio signal within a mixed reality environment, the first audio signal being associated with a virtual sound source within the mixed reality environment; determining a second audio signal based on the first audio signal and further based on parameters of objects in the mixed reality environment; Including, the parameters of the object are determined via the one or more sensors; the parameters of the object are associated with at least one of a filter, a phase shift, a delay, and a modulation; the second audio signal is associated with an interaction of the first audio signal with the object in the mixed reality environment; the second audio signal is determined further based on the interaction; The system wherein the second audio signal is presented through the speaker.

15. The system described in claim 14, wherein the first audio signal corresponds to a signal path that intersects with the object in the mixed reality environment.

16. The system of claim 14, wherein the object includes a real object.

17. The system of claim 14, wherein the object includes a virtual object.

18. The system described in claim 14, wherein the one or more sensors include a camera.

19. The system described in claim 14, wherein the interaction includes an intersection between the first audio signal and the object.

20. A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform a method: The method comprises: determining a first audio signal within a mixed reality environment, the first audio signal being associated with a virtual sound source within the mixed reality environment; determining a second audio signal based on the first audio signal and further based on parameters of objects in the mixed reality environment; Including, the parameters of the object are determined via one or more sensors of a first wearable head device; the parameters of the object are associated with at least one of a filter, a phase shift, a delay, and a modulation; the second audio signal is associated with an interaction of the first audio signal with the object in the mixed reality environment; the second audio signal is determined further based on the interaction; The second audio signal is presented through a speaker of a second wearable head device.

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