HRTF Interpolation via Coupled Phase Mixing
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Solution Overview
Problem
Conventional methods for interpolating head-related transfer functions (HRTFs) often introduce significant comb filtering distortion, which results in undesirable artifacts in audio signals, making it challenging to accurately simulate sound sources at arbitrary angles without notches in the frequency response.
Innovation Solution
The method involves generating a set of coupled HRTFs with altered phase responses above a coupling frequency, allowing for linear mixing without comb filtering distortion, and using an HRTF basis set to determine interpolated HRTFs that match the inter-aural phase response of normal HRTFs below the coupling frequency while reducing inter-aural group delay at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional interpolation methods are used on HRTFs, then sound sources can be simulated at arbitrary angles, but significant comb filtering distortion is introduced
Solution Approach 1:
The HRTF interpolation process is segmented into two distinct stages: (1) generating coupled HRTFs by modifying phase responses of original HRTFs above a coupling frequency, and (2) performing linear mixing on the coupled HRTFs to generate interpolated HRTFs. This segmentation allows each stage to address specific requirements - the first stage prepares the data structure to avoid comb filtering, while the second stage enables smooth interpolation across arbitrary angles.
Solution Approach 2:
The phase response modification is performed as a preliminary action before interpolation. By altering the phase responses above the coupling frequency to create coupled HRTFs with consistent phase relationships, the patent prevents comb filtering distortion from occurring during the subsequent linear mixing operation, rather than attempting to correct it afterward.
2Productivity
If linear mixing is performed on conventional HRTFs, then interpolated HRTFs can be generated efficiently, but comb filtering distortion occurs in the frequency response
Solution Approach 1:
The patent changes the phase response parameter of HRTFs above a specific coupling frequency to create coupled HRTFs. This parameter modification ensures that when linear mixing is performed, the phase relationships between different HRTFs remain consistent, preventing the constructive and destructive interference that causes comb filtering distortion while maintaining the efficiency of linear mixing for generating interpolated HRTFs.
3Device complexity
If HRTFs are interpolated without phase coupling, then simplicity is maintained, but inter-aural phase response accuracy is compromised
Solution Approach 1:
The patent extracts and modifies only the phase response component of HRTFs above the coupling frequency, leaving the magnitude response unchanged. This selective extraction and modification approach maintains the simplicity of the overall process while specifically addressing the inter-aural phase response accuracy requirement, as phase coupling is applied only where it is most critical for maintaining accuracy during interpolation.
Data Source
AI summary
A method for performing linear mixing on coupled Head-related transfer functions (HRTFs) to determine an interpolated HRTF for any specified arrival direction in a range (e.g., a range spanning at least 60 degrees in a plane, or a full range of 360 degrees in a plane), where the coupled HRTFs have been predetermined to have properties such that linear mixing can be performed thereon (to generate interpolated HRTFs) without introducing significant comb filtering distortion. In some embodiments, the method includes steps of: in response to a signal indicative of a specified arrival direction, performing linear mixing on data indicative of coupled HRTFs of a coupled HRTF set to determine an HRTF for the specified arrival direction; and performing HRTF filtering on an audio input signal using the HRTF for the specified arrival direction.