Audio Volume Leveling With Adaptive Gain and Artifact Control
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Solution Overview
Problem
Dynamic range compression and limiters in audio processing can cause 'breathing' and 'pumping' artifacts, leading to inconsistent listening experiences due to large level changes in audio signals across different songs or content providers.
Innovation Solution
The implementation of automatic volume leveling (AVL) systems that use noise and silence detection, adaptive gain determination, and smoothing algorithms to optimize signal processing based on audio type, minimizing distortion and artifacts while maintaining consistent loudness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dynamic range compression and limiters are used to compress signal level, then consistent listening experience is improved, but breathing and pumping artifacts are introduced
Solution Approach 1:
The patent introduces an intermediary mechanism (noise gate and expander) between the compressor and the audio signal. The noise gate detects silent periods and prevents the compressor from acting on them, while the expander restores the dynamic range after compression, thereby eliminating breathing and pumping artifacts while maintaining level consistency
Solution Approach 2:
The system performs preliminary detection of noise and silence conditions before applying compression. By anticipating when compression should be applied or avoided, the system prevents artifacts from occurring in the first place, rather than trying to correct them afterward
2Stability of the object's composition
If low level signals are increased to compress dynamic range, then signal level consistency is improved, but noise floor rises causing breathing artifacts
Solution Approach 1:
The noise gate acts as an intermediary that detects when the signal is at the noise floor level and prevents the expander from increasing it further. This mediation allows the system to maintain consistent levels for legitimate low signals while ignoring noise floor fluctuations
Solution Approach 2:
The system uses feedback from noise detection to control the expander's behavior. When noise is detected, the feedback mechanism adjusts the expander to avoid boosting the noise floor, thereby maintaining signal consistency without introducing breathing artifacts
Data Source
AI summary
Devices and techniques are generally described for automatic volume leveling of an audio signal. An audio signal may be received and a first portion of the audio signal may be stored in a buffer. A root mean square (RMS) estimate of a level of the first portion of the audio signal may be determined based at least in part on a second portion of the audio signal previous to the first portion. A modified audio signal may be generated by multiplying the first portion of the audio signal in the buffer by a variable gain. The variable gain may be based at least in part on the RMS estimate. The modified audio signal may be sent to a loudspeaker.