Digital Noise Reduction System Using Stored Filter Coefficients
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Solution Overview
Problem
Conventional active noise reduction systems are limited by fixed analog filter circuits, which are not adaptable to varying noise environments and result in increased hardware complexity and cost, making them impractical for portable devices. Additionally, adaptive processing methods face challenges with system stability, processing scale, and cost-effectiveness.
Innovation Solution
A digital noise reduction system that retains multiple parameters for various noise environments, allowing for the generation of appropriate noise reducing audio signals using a digital processing section, thereby simplifying the hardware configuration and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple analog filter circuits are provided to adapt to different noise environments, then noise reduction adaptability is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the filter characteristic parameters digitally by selecting from multiple sets of filter coefficients stored in memory, rather than providing multiple physical analog filter circuits. The digital filter circuit uses different coefficient sets to adapt to various noise environments (airport, train station, factory, etc.), achieving adaptability without increasing hardware complexity.
Solution Approach 2:
The patent stores multiple sets of filter coefficients in memory as digital data representations of different filter characteristics. Instead of duplicating physical analog filter circuits for each noise environment, the system copies the filter characteristic parameters into memory and selects them as needed, significantly reducing hardware requirements while maintaining adaptability.
2Adaptability or versatility
If adaptive processing is used to update the filter automatically, then noise reduction adaptability is improved, but system stability and processing complexity worsen
Solution Approach 1:
The patent implements automatic noise environment detection and corresponding filter selection through the noise environment detection section and filter selection section. The system automatically detects the current noise environment and selects the appropriate filter coefficients without requiring manual intervention or complex adaptive algorithms, maintaining system stability while achieving automatic adaptation.
3Adaptability or versatility
If multiple analog filter circuits are provided, then noise reduction adaptability is improved, but manufacturing cost increases
Solution Approach 1:
The patent stores multiple sets of filter coefficients in memory as digital data, replacing the need to manufacture and assemble multiple physical analog filter circuits. This digital copying approach significantly reduces manufacturing costs while maintaining the capability to adapt to various noise environments through software/firmware updates rather than hardware changes.
Solution Approach 2:
The patent replaces the mechanical/analog approach of providing multiple physical filter circuits with a digital system that stores and selects filter coefficients electronically. This substitution of digital for analog/mechanical implementation reduces manufacturing complexity and cost while maintaining or improving adaptability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables effective noise reduction across different environments without the need for multiple analog filter circuits, maintaining a compact hardware configuration and reducing costs, while ensuring practicality for portable devices.
Implementation Method 1
External noise is collected by a microphone as acoustic-to-electric converting means
Implementation Method 2
The generated noise reducing audio signal is acoustically reproduced by a speaker as electric-to-acoustic converting means
Implementation Method 3
The generated noise reducing audio signal is acoustically reproduced by a speaker as electric-to-acoustic converting means, whereby the noise reducing audio signal and the noise are acoustically synthesized. Thus the noise is reduced
Data Source
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AI summary
A noise reducing device includes: an acoustic-to-electric conversion section for collecting noise and outputting an analog noise signal; an analog-to-digital conversion section for converting the analog noise signal into a digital noise signal; and a digital processing section for generating a digital noise reducing signal on a basis of the digital noise signal and a desired parameter. The device further includes: a retaining section for retaining a plurality of parameters corresponding to a plurality of kinds of noise characteristics; a setting section for setting one of the plurality of parameters as the desired parameter of the digital processing section; a digital-to-analog conversion section for converting the digital noise reducing signal into an analog noise reducing signal; and an electric-to-acoustic conversion section for outputting noise reducing sound on a basis of the analog noise reducing signal.