Multi-Band Audio Gain Control for Harmonic Tone Preservation
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Solution Overview
Problem
Conventional audio signal processing methods that separate audio signals into multiple frequency bands often result in undesirable changes to the timbre and tone of musical instruments due to independent gain adjustments across bands, failing to provide fine-grained control over the audio spectrum.
Innovation Solution
A method and apparatus that process audio signals by separating them into multiple frequency bands with corresponding primary band frequencies, determining initial gain adjustment factors, selecting final gain adjustment factors from sets that include harmonic relationships, and applying these adjustments to minimize tone quality alterations, using a digital or analog signal processor to produce a final processed audio signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If independent gain adjustment factors are applied to each audio frequency band, then fine-grained control of the audio spectrum is achieved, but undesirable changes in timbre and tone quality occur
Solution Approach 1:
The patent merges the gain adjustment control for harmonically related frequency bands by selecting a single gain adjustment factor that applies to multiple bands containing harmonic relationships. This combining approach maintains fine-grained spectral control while preserving the natural amplitude relationships between fundamental frequencies and their harmonics, thereby avoiding undesirable timbre changes.
Solution Approach 2:
The patent applies local quality by selectively applying independent gain adjustment only where necessary (when no harmonic relationships exist between bands) while maintaining coupled gain adjustment in regions where harmonic relationships are present. This allows fine-grained control in non-harmonic regions while preserving tonal quality in harmonic regions.
2Object-affected harmful factors
If a small number of frequency bands are used, then tonal quality is preserved, but fine-grained control of the audio spectrum is lost
Solution Approach 1:
The patent segments the audio spectrum into multiple frequency bands while implementing intelligent grouping based on harmonic relationships. Bands containing harmonic relationships are grouped together and controlled by a single gain factor, while non-harmonic bands maintain independent control. This segmentation strategy enables fine-grained control without compromising tonal quality.
Solution Approach 2:
The patent implements dynamic gain adjustment factor selection that adapts based on the harmonic relationships detected between frequency bands. The system dynamically determines whether to apply independent or coupled gain adjustment for each band pair, enabling fine-grained control where appropriate while preserving tonal relationships where needed.
3Productivity
If gain adjustment factors are made dynamic and signal-dependent, then audio processing effectiveness is improved, but complexity of the processing system increases
Solution Approach 1:
The patent changes the parameter of gain adjustment from completely independent per-band control to harmonically-coupled control. By modifying the control parameter structure to account for harmonic relationships between bands, the system achieves more effective audio processing (preserving timbre while allowing spectral shaping) without requiring complex dynamic signal-dependent processing in each band.
Data Source
AI summary
A method and apparatus for processing an audio signal in multiple audio frequency bands while minimizing undesirable changes in tonal qualities of the audio signal by determining an initial gain adjustment factor for each audio frequency band resulting from the application of an audio processing technique. A final gain adjustment factor for each band is selected from a corresponding set of weighted or unweighted initial gain adjustment factors. The set of initial gain adjustment factors from which the final gain adjustment factor for a specified audio frequency band is obtained is derived from other audio frequency bands that have the frequency of the specified band as a harmonic frequency. Changes in audio signal level within one audio frequency band thereby affect the signal level of harmonic frequencies to decrease relative changes in volume between a fundamental frequency and its harmonics.