Frequency-Band HRTF Phase Adjustment for Diffuse Sound Fields
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Solution Overview
Problem
Existing audio processing technologies face challenges in effectively reducing Interaural Time Differences (ITD) and Interaural Coherence at high frequencies when modeling or simulating a diffuse sound field using Head-Related Transfer Functions (HRTFs), leading to undesirable perceptual effects.
Innovation Solution
A method and system that apply a phase adjustment to each HRTF for reducing ITD above a threshold frequency and add a direction-dependent Interaural Phase Difference (IPD) to each HRTF to maintain perceptually similar coherence, thereby improving the simulation of diffuse sound fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase adjustment is applied to reduce ITD above threshold frequency, then ITD reduction is achieved, but Interaural Coherence may be affected
Solution Approach 1:
The patent applies different processing strategies to different frequency regions: below threshold frequency, original HRTFs are used to preserve ITD cues, while above threshold frequency, phase adjustment is applied to reduce ITD. This local differentiation resolves the contradiction by optimizing each frequency band according to its specific requirements.
Solution Approach 2:
The patent modifies the phase parameter of HRTFs above threshold frequency to reduce ITD, while carefully controlling the modification to maintain acceptable Interaural Coherence. By changing specific parameters (phase) in a controlled manner, both ITD reduction and coherence preservation are achieved.
2Reliability
If direction-dependent IPD is added to reduce Interaural Coherence, then diffuse sound field modeling is improved, but HRTF complexity increases
Solution Approach 1:
The patent pre-calculates and stores direction-dependent IPD values for different frequency bands and directions. During actual diffuse sound field modeling, these pre-computed IPD values are directly applied rather than calculated in real-time, significantly reducing processing complexity while maintaining modeling accuracy.
3Measurement precision
If HRTFs are processed to reduce ITD and adjust coherence, then perceptual transparency is improved, but processing time increases
Solution Approach 1:
The patent divides the frequency spectrum into multiple bands (below and above threshold frequency) and applies different processing strategies to each band. This segmentation allows efficient processing by applying complex operations only where necessary (above threshold) while preserving original characteristics where simple (below threshold), reducing overall processing time.
Data Source
AI summary
There is provided a method and corresponding system for processing a set including Head-Related Transfer Functions, HRTFs, for at least two different directions of sound incidence to enable improved generation, modeling or simulation of ear signals corresponding to a diffuse sound field. For each direction of sound incidence to the head, a left-ear HRTF represents the transfer function from a sound source to the left ear, and a right-ear HRTF represents the corresponding transfer function to the right ear. The method comprises applying (S1) a phase adjustment to each HRTF, for each ear and direction, for reducing Interaural Time Differences, ITD, above a threshold frequency or in a frequency band above the threshold frequency; and adding (S2) a direction-dependent Interaural Phase Difference, IPD, to each HRTF, for each ear and direction, for reducing Interaural Coherence when modelling or simulating a diffuse sound field.