Binaural Sound Reproduction via Virtual Loudspeaker Wave Fields
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Solution Overview
Problem
Existing transaural sound reproduction systems using loudspeakers face challenges in crosstalk cancellation, particularly due to listener movements and environmental acoustics, which affect the accuracy of binaural sound localization and increase the complexity of filter design and calculation.
Innovation Solution
The method involves synthesizing a wave field from remote virtual loudspeakers positioned outside the listening area, using a plurality of real loudspeakers to create a synthesized wave field with substantially planar wave fronts, which reduces the impact of listener movements and environmental acoustics, allowing for simplified adaptation to listener orientation and position through transaural filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transaural filtering is used to cancel crosstalk between ears, then binaural sound localization accuracy is improved, but the system becomes highly sensitive to listener movements and environmental acoustics
Solution Approach 1:
The patent introduces an intermediary processing stage between the audio signal and the transaural filtering. A head-related transfer function (HRTF) estimation module estimates the acoustic path from loudspeakers to ears, and this estimated HRTF is used to pre-process the audio signal before transaural filtering. This intermediary step creates a more robust system that adapts to listener position and orientation, reducing sensitivity to movements while maintaining localization accuracy.
Solution Approach 2:
The patent dynamically adjusts filtering parameters based on estimated listener position and orientation. The HRTF estimation module continuously monitors acoustic path parameters, and these parameter changes are fed back to modify the transaural filter characteristics in real-time, allowing the system to maintain optimal performance despite listener movements.
2Measurement precision
If transaural filters are designed to cancel crosstalk, then sound transmission to dedicated ears is improved, but filter design complexity and calculation requirements increase
Solution Approach 1:
The patent performs preliminary HRTF estimation and audio signal processing before the actual transaural filtering stage. By pre-estimating the acoustic characteristics and pre-processing the signal with these estimates, the system simplifies the subsequent transaural filter design and reduces real-time calculation complexity while maintaining crosstalk cancellation accuracy.
3Measurement precision
If loudspeakers are positioned close to the listening area, then sound reproduction quality is improved, but the system becomes more sensitive to environmental acoustics and listener position
Solution Approach 1:
The patent implements a feedback mechanism where the HRTF estimation module continuously monitors the acoustic environment and listener position. This feedback information is used to dynamically adjust the audio signal processing and transaural filtering parameters, compensating for environmental acoustics and maintaining sound reproduction quality despite changes in listener position or room characteristics.
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 approach significantly reduces the sensitivity of sound reproduction to listener movements and environmental acoustics, simplifying filter calculations and improving crosstalk cancellation efficiency by maintaining consistent acoustical path modifications due to listener orientation and position.
Implementation Method 1
the signal emitted by a given loudspeaker is perceived differently at both ears. This is due to the ears' physical separation (propagation delay) and the shadowing of the head that modifies the spectral content
Implementation Method 2
the shadowing of the head that modifies the spectral content of the contralateral ear compared to the ipsilateral ear
Data Source
AI summary
The invention relates to a method and device for reproducing sound from a first input audio signal (1) using a plurality of first loudspeakers (4) and producing a target binaural impression to a listener (6) within a listening area (55). In order to decrease the sensibility of the reproduction of sound to the environment acoustics and to simplify the adaptation of the reproduced sound to the listener's head orientation and position, it is proposed to first define a plurality of second virtual loudspeakers (49) positioned outside of the listening area (55), then to estimate a transfer function (17) between each second virtual loudspeaker (49) and the listener's ears (7a and 7b), to compute from the estimated transfer functions (17) transaural filters (2) that modify the said first input audio signal (1) to synthesize second audio input signals (30) and to synthesize input signals (3) from second audio input signals (30) for creating a synthesized wave field (34) by the said first loudspeakers (4) that appears, within the listening area (55), to be emitted by the plurality of second virtual loudspeakers (49) as a plurality of wave fronts (50) in order to reproduce the target binaural impression at the ears of the listener (7a and 7b).