Dynamic Range Enhancer Gain Control for ANC Artifact Reduction
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Solution Overview
Problem
Audio output systems with dynamic range enhancement (DRE) in adaptive noise cancellation (ANC) applications often produce audible artifacts like clicks and pops due to changes in the DRE operating point, especially when the noise-canceling component is significant relative to the total amplitude of the input signal.
Innovation Solution
The system includes detection circuits to determine the amplitude of the noise-canceling component and the audio input signal, with a control circuit that adjusts the dynamic range enhancer's characteristics to override its default behavior, preventing audible artifacts by controlling the gain adjustments based on the significance of the noise-canceling component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dynamic range enhancer adjusts gain to reduce baseband noise when output signal amplitude is low, then the noise performance is improved, but audible artifacts like clicks and pops are generated when the noise-canceling component is significant
Solution Approach 1:
The system dynamically adjusts the DRE operating point based on the detected significance of the noise-canceling component. When ANC significance is high, the system maintains a higher gain setting to prevent audible artifacts, while allowing normal dynamic range enhancement when ANC is not significant. This dynamic adaptation resolves the contradiction by making the noise reduction behavior conditional rather than fixed.
Solution Approach 2:
The system uses detection circuits to continuously monitor the input signal and determine the significance of the noise-canceling component. This feedback information is fed to the control circuit, which adjusts the DRE operating point accordingly. The feedback mechanism enables the system to automatically adapt to changing signal conditions and prevent audible artifacts before they occur.
2Adaptability or versatility
If the dynamic range enhancer operates with a wide dynamic range (e.g., 96 dB) to handle large output signals, then the signal amplitude capability is improved, but the system becomes sensitive to transient artifacts when switching between operating modes
Solution Approach 1:
The system performs preliminary detection of the noise-canceling component significance before the DRE operating point needs to be adjusted. By detecting ANC significance in advance, the system can prevent unnecessary gain changes that would otherwise cause transient artifacts. This preliminary action allows the system to maintain wide dynamic range capability while avoiding mode switching artifacts.
3Reliability
If the control circuit adjusts the DRE operating point to optimize noise performance, then the signal-to-noise ratio is improved, but DC offset differences between operating modes generate audible transients
Solution Approach 1:
The system converts the potential harm of DC offset differences into a benefit by using the detected ANC significance information to control when operating mode changes occur. By timing the mode changes to coincide with periods when they will not generate audible transients (when ANC is not significant), the system effectively uses the detection capability to prevent the harmful effects of DC offset switching while maintaining the noise performance benefits.
Data Source
AI summary
A system that reproduces an output signal including dynamic range enhancement (DRE) reduces audible artifacts generated by changes in operating range of the dynamic range enhancement (DRE) when the output signal includes an adaptive noise canceling (ANC) component. A first detection circuit determines an input signal amplitude and a second detection circuit determines a measure of an amplitude of a noise canceling component of the input signal. A control circuit determines whether the amplitude of the noise canceling component is significant with respect to the input signal amplitude and controls characteristics of a dynamic range enhancer to override a default behavior of the dynamic range enhancer if the amplitude of the noise-canceling component is significant with respect to the input signal amplitude. The characteristics may include rise/fall times of a gain control of the dynamic range enhancer and may be controlled in multiple separate frequency bands.