Automatic Loudness Control Using Psychoacoustic Band Adjustment
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Solution Overview
Problem
Existing automatic loudness control systems are not sufficiently effective in leveling out loudness fluctuations in audio content, often resulting in unpleasant or annoying sound experiences, especially in environments with varying signal levels and background noise.
Innovation Solution
An improved automatic loudness control system that includes a controllable gain/attenuation unit, a psychoacoustic modeling unit, and a noise synthesizer, which evaluates actual and desired loudness levels and applies frequency-dependent gain/attenuation to adjust audio signals based on psychoacoustic models and background noise characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If common automatic loudness control systems are used to level out loudness fluctuations, then loudness variations are reduced, but the audio content quality deteriorates and the system becomes insufficiently effective
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a filter bank, allowing independent gain/attenuation control for each band. This segmentation enables precise loudness control without uniformly degrading the entire audio spectrum, thus maintaining audio quality while stabilizing loudness.
Solution Approach 2:
Different gain/attenuation values are applied to different frequency bands based on their individual characteristics and the perceived loudness in each band. This local quality approach ensures that only necessary adjustments are made in specific frequency ranges, preserving the natural quality of audio content while achieving overall loudness stabilization.
2Duration of action of moving object
If excessive loudness levels are allowed in audio content, then dynamic range is maintained, but the listening experience becomes unpleasant or annoying
Solution Approach 1:
The system continuously monitors the actual loudness of the audio signal and compares it with the desired loudness level. Based on this feedback, the gain/attenuation values are dynamically adjusted to maintain the desired loudness, preventing excessive levels that would cause discomfort while preserving appropriate dynamic range.
Solution Approach 2:
The gain/attenuation values are made dynamic and time-varying, allowing the system to adapt to changing audio content characteristics. This enables the system to maintain comfortable loudness levels throughout the audio playback while preserving the natural dynamics of the original content.
3Device complexity
If simple gain control is used to adjust loudness, then system complexity is reduced, but the ability to account for background noise and psychoacoustic factors is lost
Solution Approach 1:
The system changes multiple parameters including gain/attenuation values for different frequency bands, noise level estimates, and psychoacoustic model parameters. These parameter changes enable the system to adapt to different listening environments and background noise conditions while maintaining a manageable system structure through efficient parameter management.
Solution Approach 2:
A psychoacoustic model serves as an intermediary between the raw audio signal and the gain control mechanism. This intermediary processes the audio signal to extract perceptually relevant features and guides the gain/attenuation adjustments, enabling environmental adaptation without requiring direct complex processing of all audio characteristics.
Data Source
AI summary
An improved automatic loudness control system and method comprise controlling gain/attenuation applied to an input audio signal and providing an output audio signal that is the amplified/attenuated input audio signal; evaluating an actual loudness of the input audio signal from the input audio signal and a desired loudness of the input audio signal from a volume control input; and evaluating the gain/attenuation applied to the input audio signal from the actual loudness and the desired loudness of the input audio signal.