Audio Signal Spectral Shaping With Complementary Gain Paths
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Solution Overview
Problem
Existing audio signal processing techniques often require multiple adjustments that introduce undesirable artefacts, necessitating improved methods to achieve desirable spectral modifications without introducing new artefacts.
Innovation Solution
An audio signal processing apparatus and method utilizing a first and second gain-adjustable amplifier with complementary gain control signals, combined with parallel filtering elements having different filtering characteristics, to achieve desired spectral modifications with minimal phase shift and delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple adjustments are made to achieve desirable spectral responses, then spectral modification is improved, but undesirable artefacts are introduced
Solution Approach 1:
The audio signal is divided into multiple frequency bands using parallel filter elements with different filtering characteristics (e.g., different Q-factors or center frequencies). Each band is processed independently by separate gain-adjustable amplifiers, allowing precise spectral modification without the interactions that cause artefacts in single-stage processing.
Solution Approach 2:
The feed-forward path applies gain adjustments to enhance specific frequency components, while the feed-back path applies complementary reciprocal gain control to attenuate the same frequencies. This partial action approach allows desirable spectral shaping while the feedback component prevents over-enhancement that would create artefacts.
2Manufacturing precision
If multiple adjustments are made to achieve desirable spectral responses, then spectral modification is improved, but device complexity increases
Solution Approach 1:
Multiple filter elements with different characteristics are connected in parallel, sharing common input and output pathways. This merging approach achieves complex spectral modification functionality while reducing the total component count compared to cascaded configurations, as each parallel branch can be implemented with minimal independent components.
Solution Approach 2:
The gain controller performs multiple functions simultaneously: it generates gain control signals for the feed-forward amplifiers and complementary reciprocal gain control signals for the feed-back amplifiers. This multi-functionality reduces the need for separate control circuits, simplifying the overall device while maintaining precise spectral modification capabilities.
3Manufacturing precision
If feed-forward and feed-back amplification processes are used, then spectral rearrangement is improved, but phase shift and delay increase
Solution Approach 1:
A feed-back signal path is introduced where the output is fed back through gain-adjustable amplifiers with reciprocal gain control to the input. This feedback mechanism allows the system to correct phase shifts and timing delays that occur in the feed-forward path, maintaining spectral rearrangement precision while compensating for time loss through the complementary gain control relationship.
Data Source
AI summary
The processing of audio signals is shown in which a first gain-adjustable amplifier is configured to receive a feed forward signal from an input and a second gain-adjustable amplifier is configured to receive a feedback signal from an output. A gain controller supplies a first gain control signal to the first gain-adjustable amplifier, wherein the gain controller supplies a complementary second gain control signal to the second gain-adjustable amplifier, which may be the reciprocal of the first gain control signal. A first combiner is arranged to combine a first output from the first gain-adjustable amplifier with a second output from the second gain-adjustable amplifier. A plurality of filter elements are configured in parallel, wherein each filter element receives an output from the first combiner. A second combiner combines outputs from the filter elements with the original input signal and the filter elements have mutually different filtering characteristic.