Shelving Filter Active Noise Reduction Circuit
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Solution Overview
Problem
Existing active noise reduction systems in mobile devices face challenges due to limited space and energy constraints, which hinder the development of high-performance analog filters that can effectively reduce noise while maintaining the quality of useful signals like music or speech.
Innovation Solution
The implementation of a noise reduction system that includes a shelving filter with a 2nd order passive structure and a linear amplifier, along with a passive filter network, which reduces noise without significantly increasing power consumption or size, and maintains the quality of useful signals by using shelving filters and optional equalizing filters to compensate for frequency imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital circuitry is used for the ANC filter, then the noise reduction performance is improved, but the space consumption and energy consumption increase
Solution Approach 1:
The patent replaces digital circuitry with an analog shelving filter circuit that uses passive components (resistors, capacitors, inductors) and a simple amplifier to achieve noise reduction filtering. This substitution eliminates the need for complex digital signal processing hardware, thereby reducing both space consumption and energy consumption while maintaining effective noise reduction performance across different frequency ranges.
2Reliability
If multiple parametric filters are used to realise the ANC control law transfer function, then the noise reduction performance is improved, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple filtering functions (low-pass, high-pass, band-pass, and shelving filters) into a single integrated analog shelving filter circuit. This unified circuit uses one amplifier and a network of passive components to simultaneously perform what would otherwise require multiple separate parametric filters, thereby reducing device complexity and cost while maintaining the ability to realise the ANC control law transfer function.
3Use of energy by moving object
If analog circuitry is used for the ANC filter, then the space consumption and energy consumption are reduced, but the filtering performance and adaptability are limited
Solution Approach 1:
The patent designs the analog shelving filter circuit with carefully selected parameter values for its passive components (resistors, capacitors, inductors) to achieve desired frequency response characteristics. By optimizing these component parameters, the circuit can effectively model the secondary path transfer function and provide adequate filtering performance across the audio frequency range, matching the performance of more complex digital or parametric filter systems.
Data Source
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AI summary
A noise reducing sound reproduction system is disclosed that comprises a loudspeaker that is connected to a loudspeaker input path and that radiates noise reducing sound; a microphone that is connected to a microphone output path and that picks up the noise or a residual thereof; and an active noise reduction filter that is connected between the microphone output path and the loudspeaker input path; the active noise reduction filter being a or compromising at least one shelving filter.