Feedback Delay Network Binaural Virtualization
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Solution Overview
Problem
Conventional headphone virtualization systems fail to effectively simulate all reflection paths, leading to limited success in achieving natural sounding externalization and often introduce excess timbral distortion due to the lack of flexibility in controlling spatial acoustic attributes like reverb decay time and interaural coherence.
Innovation Solution
The implementation of a method and system that use a feedback delay network (FDN) in a filterbank domain to apply frequency-dependent late reverberation, allowing for systematic control of macro attributes and independent adjustment of parameters for each frequency band, along with mechanisms to maintain proper level and timing relationships between direct and late responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional headphone virtualization systems apply HRTF to simulate direct path sound, then spatial cues such as interaural time difference and interaural level difference are provided, but sufficient cues regarding source distance beyond one meter are not provided and good externalization or perceived distance is not achieved
Solution Approach 1:
The patent segments the BRIR into two distinct portions: direct response (including HRTF) and late reverberation. By separating these components and processing them through different paths (direct path processing subsystem and late reverberation processing subsystem), the system can independently optimize each portion's contribution to spatial perception, thereby achieving accurate near-field cues while extending distance perception capability through controlled reverberation
Solution Approach 2:
The patent introduces late reverberation as an intermediary element that mediates between the direct sound path and the listener's perception of distant sources. The reverberation portion, processed through the FDN, provides additional spatial cues that bridge the gap in distance perception beyond one meter, allowing the system to convey both near and far source information effectively
2Adaptability or versatility
If conventional systems apply BRIR to each channel to simulate reverberant environments, then distance and room size information are conveyed, but excess timbral distortion is introduced due to lack of flexibility in controlling spatial acoustic attributes
Solution Approach 1:
The patent implements dynamic control of spatial acoustic attributes through the FDN structure, which allows real-time adjustment of reverberation decay time, interaural coherence, and other macro attributes. This dynamic capability enables the system to adapt to different acoustic environments and source distances while maintaining natural timbre by optimizing the reverberation characteristics for each specific scenario
Solution Approach 2:
The patent changes key parameters of the reverberation processing, including decay time, interaural coherence, and direct-to-late ratio, to achieve natural sounding externalization without timbral distortion. By independently controlling these parameters through the FDN and filterbank domain processing, the system can precisely match the acoustic characteristics of different environments while preserving the original signal's timbre
3Reliability
If conventional virtualizers apply BRIR convolution to each channel, then complete acoustic pathway simulation is attempted, but computational complexity and inability to independently control direct and reverberation portions are resulting issues
Solution Approach 1:
The patent divides the BRIR application into two separate processing paths: one for direct response and early reflections, and another for late reverberation. This segmentation allows each subsystem to be optimized independently, reducing overall computational complexity while maintaining acoustic simulation accuracy through specialized processing for each portion
Solution Approach 2:
The patent extracts the late reverberation portion from the complete BRIR and processes it separately through the FDN-based late reverberation processing subsystem. This extraction enables independent control of reverberation characteristics and reduces the computational burden on the direct path processing, thereby simplifying the overall system while preserving acoustic fidelity
4Ease of operation
If conventional systems use fixed BRIR application, then simple processing is used, but flexibility in controlling frequency-dependent acoustic attributes like reverb decay time and interaural coherence is lost
Solution Approach 1:
The patent implements dynamic, frequency-dependent control of acoustic attributes through the filterbank domain FDN structure. Each frequency band can have independently controlled decay time and interaural coherence parameters, allowing precise matching of acoustic characteristics across the frequency spectrum while maintaining ease of operation through systematic parameter adjustment
Solution Approach 2:
The patent applies different acoustic attributes to different frequency bands, allowing local optimization of acoustic characteristics. By processing each frequency band independently through the filterbank and applying frequency-dependent reverberation parameters, the system achieves high acoustic attribute accuracy while maintaining operational flexibility through band-specific control
Data Source
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AI summary
In some embodiments, virtualization methods for generating a binaural signal in response to channels of a multi-channel audio signal, which apply a binaural room impulse response (BRIR) to each channel including by using at least one feedback delay network (FDN) to apply a common late reverberation to a downmix of the channels. In some embodiments, input signal channels are processed in a first processing path to apply to each channel a direct response and early reflection portion of a single-channel BRIR for the channel, and the downmix of the channels is processed in a second processing path including at least one FDN which applies the common late reverberation. Typically, the common late reverberation emulates collective macro attributes of late reverberation portions of at least some of the single-channel BRIRs. Other aspects are headphone virtualizers configured to perform any embodiment of the method.