Rotating Head-Related Transfer Function for Spatial Audio
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Solution Overview
Problem
Ambisonics technology requires a large number of speakers for effective spatial sound reproduction, making it impractical for home use and difficult to provide desired audio effects to an entire audience in spaces like movie theaters, due to its narrow 'sweet spot' and high operational and memory usage.
Innovation Solution
Combining ambisonics with binaural reproduction technology using a signal processing device that rotates the head-related transfer function in the spherical harmonic domain and synthesizes it with sound signals to generate headphone drive signals, reducing the number of speakers and memory usage while maintaining spatial audio fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ambisonics is used with a large number of speakers to increase spatial resolution, then sound reproduction quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses virtual speakers generated through spherical harmonic decomposition and head-related transfer function convolution to replicate the acoustic field of physical speaker arrays. This allows high spatial resolution without requiring actual physical speakers in those positions, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical speaker array system with a signal processing system that uses digital signal processing, spherical harmonic transforms, and headphone delivery. This substitution eliminates the need for complex physical speaker installations while achieving comparable or superior spatial resolution through computational methods.
2Measurement precision
If ambisonics is used to reproduce sound space, then spatial audio effects are improved, but the sweet spot becomes narrower
Solution Approach 1:
The patent segments the sound field into spherical harmonic components and processes them independently through head-related transfer functions. This segmentation allows for precise control of spatial audio effects while enabling wide-area reproduction through headphone delivery, eliminating the narrow sweet spot limitation of traditional ambisonics.
Solution Approach 2:
The patent transitions from three-dimensional speaker array geometry to a one-dimensional headphone delivery system with multi-dimensional audio processing. By using spherical harmonic decomposition and head-related transfer functions, the system achieves spatial audio effects in a different dimensional space, allowing wide-area coverage without requiring physical speakers in multiple dimensions.
3Measurement precision
If binaural reproduction with head-related transfer function is used, then spatial audio effects are improved, but operational complexity and memory usage increase
Solution Approach 1:
The patent pre-calculates and stores head-related transfer functions for various directions and spherical harmonic orders. By performing this computationally intensive task in advance and storing the results in memory, the system reduces real-time operational complexity while maintaining high spatial audio effects quality during actual audio reproduction.
Solution Approach 2:
The patent changes the parameter space from time-domain convolution to frequency-domain spherical harmonic multiplication. This parameter transformation reduces computational complexity by replacing complex time-domain operations with simpler frequency-domain operations, while maintaining the same spatial audio effects through the mathematical equivalence of the transformations.
Data Source
AI summary
The present technology relates to signal processing device and method that make it possible to reproduce sound more effectively. A signal processing device includes a rotation operation unit that rotates a head-related transfer function in a spherical harmonic domain by an operation on the basis of a rotation matrix corresponding to rotation of a head of a listener, the operation in which an order of the rotation matrix is limited, and a synthesis unit that synthesizes the head-related transfer function after rotation obtained by the operation and a sound signal of the spherical harmonic domain to generate a headphone drive signal. The present technology is applicable to an audio processor.