Stereo Expansion Using Binaural Modeling and Equalization
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Solution Overview
Problem
Conventional stereo reproduction systems create a narrow spatial image due to speaker proximity and unmatched speaker-room frequency responses, failing to provide an immersive listening experience as they often drown out vocals and introduce mid-range coloration, while existing methods for stereo expansion are not robust and defeat equalization.
Innovation Solution
A method that removes the effects of actual speaker to listener positioning and introduces an artificial effect using inter-aural delay and head-shadow models to create a widened and centered sound stage, integrating a novel binaural listening model and speaker-room equalization techniques to preserve audio quality and spatial widening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional stereo signal combining approaches (L+α(L−R) and R+α(R−L)) are used to expand the acoustic field, then the spatial image is widened, but vocals are drowned out and midrange coloration is introduced
Solution Approach 1:
The patent segments the audio processing into distinct frequency bands using filter banks, allowing different processing strategies for different frequency ranges. This enables selective expansion in certain bands while preserving vocals and midrange clarity in others, resolving the contradiction between sound field width and audio quality preservation.
Solution Approach 2:
The patent applies different processing characteristics to different spatial locations and frequency bands. By using binaural rendering with HRTFs specific to different elevation angles and incorporating room equalization, the system provides localized quality optimization that widens the sound field without uniformly degrading all frequency regions, thus preserving vocals and midrange.
2Measurement precision
If Head-Related-Transfer-Functions (HRTFs) with specific direction are used for stereo expansion, then spatial localization is improved, but the approach is not robust due to pinna variation among listeners and equalization is defeated
Solution Approach 1:
The patent uses a hybrid approach that combines binaural HRTF rendering for spatial localization with conventional stereo signal processing and room equalization. This multi-functional system maintains robustness across different listeners by not relying solely on individualized HRTFs,而是 incorporating universal spatial processing techniques that work across varying pinna characteristics while still providing accurate localization.
Solution Approach 2:
The patent introduces an intermediary processing stage that bridges HRTF-based spatial rendering and room equalization. By using intermediate representations and coordinated processing between spatial and spectral domains, the system maintains both localization accuracy and equalization effectiveness, avoiding the defeat of equalization that occurs with pure HRTF approaches.
3Manufacturing precision
If speaker-room equalization is applied to correct frequency responses, then audio fidelity is improved, but stereo expansion techniques defeat the equalization benefits
Solution Approach 1:
The patent extends the processing from the traditional two-dimensional stereo domain to a three-dimensional binaural space by incorporating elevation information and head-related transfer functions. This dimensional extension allows simultaneous achievement of room equalization in the spectral domain and stereo expansion in the spatial domain, as they operate in different dimensions and do not interfere with each other.
Solution Approach 2:
The patent applies room equalization as a preliminary processing step before stereo expansion. By pre-correcting the frequency response characteristics and then applying spatial rendering on top of the equalized signal, the system ensures that equalization benefits are preserved while still achieving sound field expansion. The preliminary equalization establishes a clean spectral foundation that subsequent spatial processing builds upon without defeating.
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
This method effectively widens the stereo sound field without defeating equalization, providing an immersive listening experience by determining speaker angles, inter-aural delays, and headshadow responses, and converting filters to maintain audio quality and spatialization.
Implementation Method 1
using the inter-aural delay and the head-shadow models for the virtual speakers at desired angles relative to the listener
Implementation Method 2
using the inter-aural delay and the head-shadow models for the virtual speakers at desired angles relative to the listener
Data Source
AI summary
A method for stereo expansion includes a step to remove the effects of actual relative speaker to listener positioning and head shadow and a step to introduce an artificial effect based on a desired virtual relative speaker to listener positioning using the inter-aural delay and the head-shadow models for the virtual speakers at desired angles relative to the listener thereby creating the impression of a widened and centered sound stage and an immersive listening experience. Known methods drown out vocals and add mid-range coloration thereby defeating equalization. The present method includes the integration of a novel binaural listening model and speaker-room equalization techniques to provide widening while not defeating equalization.