Audio Decoder Head Shadowing Phase Shift Filters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing audio reproduction systems, particularly earphones, fail to accurately simulate the spatial psychoacoustic cues of sound when reproducing stereo signals, often resulting in a less-than-optimal listening experience due to distortion or loss of ambience and sound stage proportions.
Innovation Solution
An audio decoder that applies head shadowing and phase shift filters to both direct and cross-feed signal paths to simulate the spatial effects of loudspeakers placed at different angles, introducing a phase difference representative of the listener's ear positions, thereby enhancing the perceived sound field without introducing comb filtering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-delay is inserted in the cross-feed signal paths to properly simulate sound stage proportions, then the spatial impression is improved, but comb filtering effect occurs in correlated signals
Solution Approach 1:
The patent changes the temporal parameters of the cross-feed signal by introducing frequency-dependent time delays. Different frequency components receive different delay amounts, which prevents the coherent addition that causes comb filtering while still maintaining proper spatial proportions. This parameter transformation resolves the contradiction between accurate spatial simulation and avoidance of harmful interference patterns.
2Object-generated harmful factors
If only frequency dependent head shadowing is simulated without time-delay, then the comb filtering effect is avoided, but the sound stage loses ambience and becomes too narrow
Solution Approach 1:
The patent applies frequency-dependent time delays to different spectral components of the cross-feed signal. This parameter modification allows the system to maintain broad sound stage ambience by preserving temporal coherence across frequencies while avoiding the specific conditions that generate comb filtering effects in correlated signals.
3Ease of operation
If earphones are used for stereo reproduction, then portability and personal listening is improved, but spatial psychoacoustic cues become distorted or missing
Solution Approach 1:
The patent introduces an intermediary signal processing stage between the stereo input and the earphone output. This intermediary system applies head shadowing filters and frequency-dependent time delays to generate artificial spatial cues that compensate for the natural absence of interaural differences in earphone listening. This mediator restores the spatial psychoacoustic information that would otherwise be lost.
Solution Approach 2:
The patent transforms the temporal and spectral parameters of the audio signal to create artificial spatial cues. By applying frequency-dependent time delays and head shadowing filtering, the system modifies the signal parameters to simulate the natural acoustic differences between ears, thereby restoring spatial perception in the earphone reproduction mode.
Data Source
AI summary
The proposed technology provides an audio decoder (100) configured to receive input signals representative of at least two audio input channels. The audio decoder is configured to provide direct signal paths and cross-feed signal paths (10) for the input signals. The audio decoder is configured to apply head shadowing filters (20) in the direct signal paths and cross-feed signal paths for simulating head shadowing of loudspeakers placed at different angles to an intended listener. The audio decoder is also configured to apply phase shift filters (30) in the direct signal paths and cross-feed signal paths for introducing a phase difference between the direct signal paths and the cross-feed signal paths representing a phase difference occurring between the ears of the intended listener. The audio decoder is further configured to sum (40) the direct and cross-feed signal paths to provide output signals.