Subband Audio Signal Weighting for Loudness Without Timbre Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for modifying audio signals to match perceived loudness are computationally intensive and do not efficiently compensate for the varying sensitivity of human hearing across different frequencies, leading to unwanted changes in timbre during loudness control.
Innovation Solution
An apparatus and method using a lookup table to determine spectral weighting factors based on excitation parameters of audio signal subbands, allowing for multiplicative scaling to modify the signal, thereby reducing computational complexity and maintaining optimal loudness perception without altering timbre.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to modify audio signals to match perceived loudness, then loudness perception is improved, but computational complexity increases significantly
Solution Approach 1:
The patent pre-calculates and stores spectral weighting factors in lookup tables before runtime. These tables contain pre-computed values based on excitation parameters and frequency bands, allowing the system to retrieve ready-made weighting factors during audio processing instead of performing complex calculations in real-time, thus reducing computational complexity while maintaining loudness perception accuracy
Solution Approach 2:
The patent creates simplified representations of the complex auditory model by copying essential characteristics into lookup tables. Instead of implementing the full complex computational model during audio signal processing, the system uses pre-computed tables that capture the essential spectral weighting relationships, achieving comparable results with significantly reduced computation
2Measurement precision
If spectral weighting is applied to compensate for frequency sensitivity, then loudness perception is improved, but timbre changes occur
Solution Approach 1:
The patent applies different spectral weighting factors to different frequency bands based on excitation parameters. By tailoring the weighting to specific frequency regions and their local characteristics rather than applying uniform processing, the system compensates for frequency sensitivity variations while preserving the natural timbre characteristics of each frequency band
Solution Approach 2:
The patent dynamically adjusts spectral weighting factors based on the excitation parameter of each subband. The weighting applied to each frequency band varies according to its instantaneous excitation level, allowing the system to adaptively compensate for frequency sensitivity while maintaining timbre consistency across different signal conditions
3Measurement precision
If complex loudness calculation methods are used, then measurement accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs complex loudness calculation operations in advance and stores the results in lookup tables. During actual audio processing, the system simply retrieves pre-computed spectral weighting factors from these tables based on excitation parameters, eliminating the need for repeated complex calculations and significantly reducing processing time while maintaining measurement accuracy
Solution Approach 2:
The patent creates simplified copy representations of complex loudness calculations in the form of lookup tables. These tables contain pre-computed spectral weighting factors that replicate the essential results of complex loudness models, allowing fast retrieval and application during audio processing without performing the full complex calculations in real-time
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An apparatus for modifying an input audio signal comprises an excitation determiner, a storage device and a signal modifier. The excitation determiner determines a value of an excitation parameter of a subband of a plurality of subbands of the input audio signal based on an energy content of the subband. Further, the storage device stores a lookup table containing a plurality of spectral weighting factors. A spectral weighting factor of the plurality of spectral weighting factors is associated to a predefined value of the excitation parameter and a subband of the plurality of subbands. The storage device provides a spectral weighting factor corresponding to the determined value of the excitation parameter and corresponding to the subband, the value of the excitation parameter is determined for. Further, the signal modifier modifies a content of the subband of the audio signal, the value of the excitation parameter is determined for, based on the provided spectral weighting factor to provide a modified subband.