Perceived Loudness Control Using Auditory Filter-Based Gain Adjustment
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Solution Overview
Problem
Existing volume control systems in devices like televisions and audio systems fail to efficiently maintain consistent loudness levels during transitions, such as channel changes or commercial breaks, often resulting in unnatural artifacts like pumping and breathing fluctuations due to their brute force methods not accounting for human perception of volume changes.
Innovation Solution
A system that processes audio signals using approximation filters modeling the human hearing system, selectively analyzing dominant channels, and applying gain adjustments to maintain consistent loudness levels, while reducing computational resources through techniques like decimation and smoothing gain coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional automatic gain control is used to maintain consistent loudness levels, then volume changes can be controlled, but unnatural artifacts like pumping and breathing fluctuations occur
Solution Approach 1:
The patent changes the parameter basis from simple amplitude detection to perceived loudness measurement using approximation filters that model human auditory response. This allows the system to adjust gain based on how humans actually perceive volume changes rather than raw signal amplitude, eliminating unnatural artifacts while maintaining loudness consistency.
Solution Approach 2:
The system continuously measures perceived loudness and adjusts gain accordingly through a feedback loop. By using approximation filters to model human hearing and continuously adapting the gain based on measured loudness levels, the system maintains consistent perceived volume without the pumping and breathing effects of traditional AGC.
2Measurement precision
If complex loudness analysis with multiple filters is used to model human hearing, then accurate perceived loudness can be achieved, but computational resources increase
Solution Approach 1:
The patent uses approximation filters that are computationally inexpensive compared to full auditory model implementations. These simplified filters provide sufficient accuracy for perceived loudness measurement while consuming minimal computational resources, making the system suitable for devices with lower-capability processors.
Solution Approach 2:
The system changes the complexity parameter of the filter bank, using approximation filters with reduced order or simplified characteristics that still capture the essential features of human auditory filtering. This reduces computational load while maintaining adequate measurement precision for loudness control.
Data Source
AI summary
A method of adjusting a loudness of an audio signal may include receiving an electronic audio signal and using one or more processors to process at least one channel of the audio signal to determine a loudness of a portion of the audio signal. This processing may include processing the channel with a plurality of approximation filters that can approximate a plurality of auditory filters that further approximate a human hearing system. In addition, the method may include computing at least one gain based at least in part on the determined loudness to cause a loudness of the audio signal to remain substantially constant for a period of time. Moreover, the method may include applying the gain to the electronic audio signal.