Audio Source Loudness Normalization Without Playback Artifacts
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Solution Overview
Problem
Existing volume control methods for audio sources, such as radio stations, often result in audible artifacts like sudden volume changes and reduced dynamic range, which are not suitable for high-quality audio systems, and manual adjustment can be distracting and unsafe, especially in vehicles.
Innovation Solution
An apparatus and method featuring a loudness analyzer that determines and stores loudness values for each audio source over a period, allowing for adaptive volume control to normalize audio signals to a consistent level, maintaining dynamic range and avoiding abrupt changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If adaptive volume control is implemented to automatically adjust volume based on signal, then volume normalization is improved, but audio quality deteriorates due to artifacts such as pumps and reduced dynamics
Solution Approach 1:
The system performs preliminary loudness analysis and stores reference loudness values for different radio stations before playback. When a station is selected, the pre-stored reference value is immediately retrieved and used for volume normalization, avoiding real-time adaptive adjustments that cause audio artifacts.
Solution Approach 2:
The volume control system is segmented into two independent parts: a loudness analysis phase that stores reference values for each station, and a playback phase that retrieves and applies these values. This segmentation prevents continuous adaptive adjustments during playback, maintaining audio quality while achieving volume normalization.
2Manufacturing precision
If manual volume adjustment is implemented to compensate for loudness differences, then audio quality is maintained, but driver safety deteriorates due to distraction
Solution Approach 1:
The system performs self-service by automatically analyzing loudness characteristics of each radio station and storing reference values. During playback, the system automatically retrieves and applies the appropriate volume normalization based on the selected station, completely eliminating the need for manual driver intervention while maintaining high audio quality.
3Adaptability or versatility
If real-time loudness analysis is performed to adjust volume, then adaptive normalization is improved, but audio artifacts increase due to fast volume adjustments
Solution Approach 1:
Loudness analysis and reference value storage are performed in advance during system initialization or when stations are first tuned. This preliminary action eliminates the need for real-time loudness analysis during playback, preventing fast volume adjustments and associated audio artifacts while maintaining adaptive normalization capabilities.
Solution Approach 2:
The system performs loudness analysis periodically or on-demand rather than continuously during playback. Reference loudness values are updated only when necessary (e.g., when tuning to a new station), avoiding continuous real-time adjustments that generate audio artifacts while maintaining adaptability.
Data Source
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AI summary
An apparatus for volume control for at least two audio sources comprises a loudness analyser and a volume control. The loudness analyser is designed to analyse an audio signal from the first and second of the two audio sources over a period, to take this as a basis for ascertaining a first and a second loudness value, respectively, and to store said loudness value with an association with the first and second audio sources. The volume control is designed to adjust the audio signal from the currently selected first and/or second of the two audio sources in accordance with the corresponding first and/or second loudness value.