Noise Reduction System Using Dynamic Kalman Filter

Solution Overview

Problem

Existing communication systems for public safety and professional communications face challenges in effectively reducing background noise, which can lead to cognitive strain and inhibit radio communication, especially in noisy environments, due to their high sensitivity to microphone calibration and environmental changes.

Innovation Solution

A communication terminal with a noise reduction system that uses a Kalman filter and Khobotov-Marcotte algorithm to dynamically identify an optimal correction filter by processing signals from multiple microphones, reducing noise through a sequence of autocorrelation and cross-correlation estimates, and applying a noise filter to achieve improved noise suppression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If beamforming technology and spectral subtraction technique are used to reduce background noise, then noise suppression effectiveness is improved, but device complexity and manufacturing cost increase due to high sensitivity to microphone calibration

Engineering Contradiction:

Improvenoise suppression effectivenessVSAvoidmicrophone calibration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system performs self-calibration by automatically adapting the transfer function between microphones based on environmental noise characteristics. The calibration process is embedded in the normal operation of the device, eliminating the need for separate factory calibration procedures. The system continuously learns and adjusts to optimize noise suppression without external intervention.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The transfer function between microphones is made dynamic rather than static. The system continuously adapts the transfer function based on changing environmental conditions and noise characteristics. This dynamic adaptation allows the system to maintain effectiveness without requiring precise fixed calibration, reducing manufacturing complexity.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If factory calibration and dynamic equalization algorithms are implemented to improve noise reduction accuracy, then measurement precision is improved, but ease of manufacture deteriorates due to additional calibration steps

Engineering Contradiction:

Improvemicrophone response accuracyVSAvoidmanufacturing process simplicity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The system performs preliminary adaptation during the initial operation phase, automatically characterizing the microphone responses and environmental conditions. This preliminary action embeds the calibration process within the first usage period, eliminating the need for separate factory calibration steps while achieving the same precision benefits.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system performs self-calibration by automatically adapting the transfer function between microphones based on environmental noise characteristics. The calibration process is embedded in the normal operation of the device, eliminating the need for separate factory calibration procedures.

Inventive Principle:

Principle #25Self-service

3Reliability

If multiple microphones with complex calibration are used to achieve satisfactory noise suppression, then noise reduction effectiveness is improved, but productivity and ease of deployment deteriorate

Engineering Contradiction:

Improvenoise reduction effectivenessVSAvoiddeployment simplicity

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system performs self-calibration by automatically adapting the transfer function between microphones based on environmental noise characteristics. The calibration process is embedded in the normal operation of the device, eliminating the need for separate factory calibration procedures and enabling immediate deployment.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11610598B2Voice enhancement in presence of noise

Publication Date: 2023.03.21 L3HARRIS GLOBAL COMMUNICATIONS INC

AI summary

Communication terminal includes a first microphone system, a second microphone system, and a noise reduction processing unit (NRPU). The NRPU receives a primary signal from the first microphone system and a secondary signal from the second microphone system. The NRPU dynamically identify an optimal transfer function of a correction filter which can be applied to the secondary signal provided by the second microphone system to obtain a correction signal. The correction signal is subtracted from the primary signal to obtain a remainder signal which approximates a signal of interest contained within the primary signal.