ANR Signal Path Gain Control for Overload Artifact Reduction
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Solution Overview
Problem
Active noise reduction (ANR) devices face challenges in managing overload conditions, particularly in small form-factor devices like in-ear headphones, where low frequency disturbances can cause audible artifacts and degrade user experience.
Innovation Solution
The method involves automatically adjusting the gain of a variable gain amplifier (VGA) and selecting coefficients for a tunable digital filter in the ANR signal flow path based on characteristics of the input signal, allowing for selective throttling of compensation in specific frequency ranges to mitigate overload conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gain of the variable gain amplifier is increased to improve noise reduction performance, then the noise reduction capability is enhanced, but the device becomes more prone to overload conditions causing audible artifacts
Solution Approach 1:
The patent implements automatic gain control that dynamically adjusts the gain of the variable gain amplifier based on real-time analysis of the input signal characteristics. The system monitors the signal and automatically modifies the gain level to prevent overload conditions while maintaining optimal noise reduction performance, thereby resolving the contradiction between noise reduction capability and overload susceptibility.
Solution Approach 2:
The system changes the gain parameter of the amplifier dynamically based on the characteristics of the input signal. By analyzing signal properties and adjusting the gain parameter accordingly, the system maintains reliable noise reduction while avoiding the harmful effects of overload, thus resolving the technical contradiction.
2Object-affected harmful factors
If the gain is automatically adjusted based on input signal characteristics, then overload conditions are mitigated, but the device complexity increases
Solution Approach 1:
The automatic gain control system operates autonomously by analyzing its own input signal characteristics and self-adjusting the amplifier gain without external intervention. This self-service mechanism mitigates overload conditions while adding minimal complexity, as the system uses its existing signal processing capabilities to perform the gain adjustment.
3Object-affected harmful factors
If selective throttling of compensation is applied in specific frequency ranges, then overload conditions are reduced, but the noise reduction performance in those frequency ranges is impacted
Solution Approach 1:
The system applies different gain levels to different frequency ranges based on the local characteristics of the input signal. By analyzing which frequency ranges are prone to overload and applying selective gain reduction only to those specific ranges, the system mitigates overload conditions while preserving noise reduction performance in frequency ranges that do not require throttling.
Data Source
AI summary
The technology described in this document can be embodied in a method that includes receiving an input signal captured by one or more sensors associated with an active noise reduction (ANR) headphone, and determining one or more characteristics of a first portion of the input signal. Based on the one or more characteristics of the first portion of the input signal, a gain of a variable gain amplifier (VGA) disposed in an ANR signal flow path can be adjusted, and accordingly, a set of coefficients for a tunable digital filter disposed in the ANR signal flow path can be selected. The method further includes processing a second portion of the input signal in the ANR signal flow path using the adjusted gain and selected set of coefficients to generate a second output signal for the electroacoustic transducer of the ANR headphone.