Parametric Binaural Headphone Rendering via Sum and Cross Filters
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Solution Overview
Problem
Existing audio signal enhancement systems for headphones introduce unwanted artifacts like coloration, resonance, and distortion when reproducing surround sound or stereo recordings, leading to an unnatural listening experience.
Innovation Solution
A sound enhancement system (SES) that transforms sound system outputs using derived sum and cross filters from known HRTFs, avoiding unwanted artifacts while maintaining stereo or surround sound enhancements, by normalizing, smoothing, and performing arithmetic transformations on direct and indirect HRTFs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stereo or surround sound recordings are reproduced over headphones using conventional enhancement systems, then the listening experience is enhanced, but unwanted artifacts such as coloration, resonance, reverberation, and distortion of timbre or sound source angle and position are introduced
Solution Approach 1:
The patent introduces sum and cross filters as intermediary elements that mediate between the stereo/surround sound signal and the HRTF processing. These filters preprocess the audio signal to prevent the introduction of unwanted artifacts while maintaining enhanced listening experience. The sum filter combines left and right channel signals, and the cross filter extracts spatial information, together forming an intermediary processing stage that avoids direct application of HRTFs which would cause artifacts.
Solution Approach 2:
The patent transforms the audio signal by changing its parameter representation from standard stereo left/right channels to sum/cross components. This parameter transformation allows the system to process the signal in a domain where spatial information can be extracted and manipulated without introducing the artifacts that occur in the time domain. The sum and cross filters effect this parameter change, enabling artifact-free spatial audio reproduction.
2Manufacturing precision
If direct and indirect HRTFs are applied directly to transform audio signals for headphone reproduction, then spatial sound enhancement is achieved, but artifacts such as coloration and distortion of timbre are introduced
Solution Approach 1:
The patent applies preliminary action by preprocessing the audio signal through sum and cross filters before applying HRTF transformations. The sum filter computes the sum of left and right channel signals, and the cross filter computes the difference, creating a preprocessed signal that is then transformed using HRTFs. This preliminary filtering action prevents the direct application of HRTFs to the original stereo signal, thereby avoiding coloration and timbre distortion while maintaining spatial accuracy.
3Adaptability or versatility
If conventional stereo enhancement systems are used for headphones, then surround sound effects are achieved, but sound source angle and position distortion occur
Solution Approach 1:
The patent segments the stereo audio signal into distinct sum and cross components through separate filtering paths. The sum filter processes the combined left-right signal to capture spatial envelope information, while the cross filter processes the left-right difference to capture directional information. This segmentation allows independent processing of different spatial characteristics, enabling accurate sound source localization while maintaining surround sound effects without position distortion.
Data Source
AI summary
A sound enhancement system (SES) that can enhance reproduction of sound emitted by headphones and other sound systems. The SES improves sound reproduction by simulating a desired sound system without including unwanted artifacts typically associated with simulations of sound systems. The SES facilitates such improvements by transforming sound system outputs through a set of one or more sum and cross filters, where such filters have been derived from a database of known direct and indirect head-related transfer functions (HRTFs).