Audio Signal Processing for Virtual Bass Enhancement
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Solution Overview
Problem
Existing audio signal processing devices face challenges in generating missing harmonics of low-frequency components, particularly in applications with poor low-frequency response due to constructive and physical limitations, leading to inconsistent virtual bass enhancement and harmonic instabilities.
Innovation Solution
An apparatus comprising an audio processing device that analyzes and modifies audio signals by changing sample points' positions based on a specific audio signal modification rule, generating harmonics of low-frequency components invariant to the input signal level, thereby eliminating the need for automatic gain control stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-linear distortion processing is used to generate harmonics, then bass enhancement is achieved, but harmonic instabilities occur and automatic gain control stages are required
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a filter bank, with each band processed independently to generate harmonics. This segmentation allows targeted harmonic generation for different frequency ranges while maintaining overall signal stability and avoiding the need for complex global gain control.
Solution Approach 2:
The patent transforms the audio signal from time-domain to frequency-domain representation, enabling harmonic generation through frequency parameter manipulation rather than time-domain non-linear distortion. This parameter transformation eliminates harmonic instabilities while maintaining bass enhancement effectiveness.
2Stability of the object's composition
If automatic gain control stages are applied to mitigate harmonic instabilities, then signal stability improves, but processing complexity and difficulty increase
Solution Approach 1:
The patent extracts and processes only the specific frequency components that require harmonic generation, rather than applying complex gain control to the entire signal. By isolating target frequency bands and applying simplified harmonic generation locally, the method achieves harmonic stability without introducing complex AGC stages.
3Reliability
If non-linear characteristic weighting is applied sample by sample, then harmonics are generated, but the enhancement magnitude becomes highly dependent on audio signal level
Solution Approach 1:
The patent transitions from time-domain sample-by-sample processing to frequency-domain processing, adding a frequency dimension to the harmonic generation process. This dimensional transformation enables level-independent harmonic generation by operating on frequency components rather than time-domain amplitude values.
Solution Approach 2:
By changing from time-domain amplitude modulation to frequency-domain harmonic synthesis, the patent achieves bass enhancement that is independent of the original signal level. The frequency-domain approach allows consistent harmonic generation regardless of input signal amplitude variations.
Data Source
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AI summary
Apparatus for processing an audio signal comprising a number of samples, particularly so as to generate missing harmonics of low-frequency components in the audio signal, the apparatus comprising at least one audio processing device configured to: - process an audio signal in a time-dependent representation of the audio signal, particularly in a half-wave representation of the audio signal; - determine an interval between a first zero-crossing and a further zero-crossing of the audio signal; - determine a first set of sample points in the interval, the first set of sample points comprising a number of sample points at first positions in the interval; - determine a second set of sample points in the interval, the second set of sample points comprising a number of sample points at second positions in the interval; - modify the audio signal in the interval, on basis of an audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points; - apply the modified audio signal interval to the respective interval of the original audio signal so as to generate a modified audio signal.