Binaural Rendering with IMU Anchoring for Stable Spatial Audio
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Solution Overview
Problem
Existing binaural rendering technologies face challenges in accurately replicating the acoustic characteristics of a user's listening environment, particularly due to lengthy and sensitive direct measurement of binaural room impulse responses (BRIRs), and head orientation tracking issues such as IMU drift.
Innovation Solution
Utilizing impulse response (IR) measurements to synthesize binaural room impulse responses, anchoring IMU to a playback device for stable head orientation tracking, and integrating time-of-flight measurements to enhance binaural rendering by simulating audio from a fixed reference point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of binaural room impulse responses (BRIRs) is used to replicate acoustic characteristics, then measurement precision is improved, but measurement time increases significantly and the process becomes highly sensitive to environmental factors
Solution Approach 1:
The patent uses impulse response (IR) measurements as a simplified copy or proxy for the more complex and time-consuming direct BRIR measurements. By measuring the acoustic characteristics of the room using standard IR techniques rather than full binaural measurements, the system captures the essential acoustic properties (reverberation, reflections) needed for binaural rendering without requiring the lengthy and sensitive direct BRIR measurement process. This copying approach maintains measurement precision for the essential acoustic characteristics while dramatically reducing measurement time and sensitivity to environmental factors.
2Ease of operation
If IMU (inertial measurement unit) is used for head orientation tracking, then tracking capability is provided, but drift occurs over time reducing reliability
Solution Approach 1:
The patent implements a feedback mechanism where the system periodically re-anchors the IMU to the playback device's known position in space. By continuously comparing the IMU-derived head orientation with the geometric relationship between the playback device and the user's ears (based on time-of-flight measurements), the system can detect and correct drift accumulation. This feedback loop restores reliability by using the stable geometric reference to correct the drifting IMU measurements over time, maintaining accurate head tracking without requiring continuous perfect IMU performance.
Solution Approach 2:
The system performs preliminary anchoring of the IMU to the playback device during initial setup and at periodic intervals. By pre-establishing the geometric relationship and using this as a reference point before drift becomes problematic, the system proactively prevents reliability degradation. This preliminary action creates a stable baseline that the ongoing IMU measurements can reference, reducing the impact of drift before it significantly affects tracking accuracy.
3Reliability
If binaural rendering is adapted to room acoustic characteristics, then immersive effect is improved, but system complexity increases due to multiple measurement and synthesis processes
Solution Approach 1:
The patent introduces an intermediary process that bridges simple IR measurements and complex binaural rendering. Rather than directly implementing full binaural room measurement and reproduction, the system uses IR measurements as an intermediary step to extract room acoustic characteristics (such as impulse response, reverberation parameters), then applies these characteristics to binaural impulse responses through synthesis. This intermediary approach maintains immersive effect consistency by capturing essential room properties while avoiding the complexity of complete binaural measurement and reproduction systems.
4Measurement precision
If time-of-flight measurements are integrated for anchoring, then head orientation accuracy is improved, but device synchronization complexity increases
Solution Approach 1:
The patent makes the time-of-flight measurement capability serve multiple functions within the system. The same time-of-flight measurements that provide head orientation accuracy are also used for spatial audio rendering, distance estimation, and anchoring the coordinate systems between devices. By making this measurement universal across multiple functions, the patent avoids adding separate dedicated systems for each function, thereby reducing overall synchronization complexity while maintaining high measurement precision for head orientation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances binaural rendering by accurately replicating the acoustic characteristics of the listening environment and maintaining immersive effects over time, regardless of user head position, improving multi-modal congruence in audio-visual experiences.
Implementation Method 1
one or more time-of-flight measurements of at least one signal propagating from the non-wearable playback device to the wearable playback device
Implementation Method 2
during binaural rendering of the audio via the binaural renderer, update binaural rendering filters with the determined head tracking data
Data Source
AI summary
Example technologies described herein relate to spatial audio on wearable playback devices, such as headphone and earbuds. Such technologies may include forms of binaural rendering of audio, which is played back on the wearable playback devices. These technologies may create or enhance an immersive listening experience which, to the listener, does not sound like you are listening on a wearable device, but are instead listening to a well-tuned, well-place, three-dimensional audio system of loudspeakers in a particular listening environment, such as the listener's actual living room.