Noise Estimation System With Dynamic Time Constants

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Solution Overview

Problem

Audio processing systems face challenges in accurately estimating noise levels due to slow adaptation to sudden environmental changes, leading to inaccurate noise suppression in varying noise conditions.

Innovation Solution

The system adjusts noise level estimation using different time constants based on signal changes, accelerating adjustments when the signal exceeds the noise level and decelerating when it falls, ensuring quicker noise floor reduction and more precise noise suppression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a slow time constant is applied for noise level estimation, then the estimate is more stable and less prone to false increases, but it is less accurate when adapting to sudden changes in noise environment

Engineering Contradiction:

Improvestability of noise level estimateVSAvoidadaptation speed to noise changes

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies different time constants dynamically based on the current noise environment. A first (faster) time constant is used when the signal is below the noise threshold to quickly adapt to noise changes, while a second (slower) time constant is used when the signal exceeds the threshold to maintain stability and prevent false detections. This dynamic switching resolves the contradiction between stability and adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the time constant parameter based on the relationship between signal level and noise threshold. By monitoring whether the signal exceeds the threshold by more than a predetermined amount, the system switches between different time constant values, optimizing both response speed and stability for different operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a fast time constant is applied for noise level estimation, then the estimate adapts quickly to sudden noise changes, but it is less accurate when the signal suddenly rises and may cause false noise increases

Engineering Contradiction:

Improveadaptation speed to noise changesVSAvoidaccuracy of noise level estimate

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system dynamically selects the time constant based on signal conditions. When the signal exceeds the noise threshold significantly, a slower time constant is applied to prevent false noise increases. When the signal is below the threshold, a faster time constant enables quick adaptation to actual noise changes. This dynamic approach resolves the contradiction between measurement speed and precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback by continuously monitoring the relationship between signal level and noise threshold. Based on this feedback, the system determines which time constant to apply, ensuring that the estimation process adapts its precision and speed based on real-time conditions, thereby resolving the contradiction between fast adaptation and measurement accuracy.

Inventive Principle:

Principle #23Feedback

3Device complexity

If a single time constant is used for noise level estimation, then the system is simpler to implement, but it cannot accurately handle both sudden noise changes and sudden signal rises

Engineering Contradiction:

Improvesimplicity of estimation systemVSAvoidhandling of varying signal conditions

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

Instead of using a fixed time constant, the patent implements a dynamic switching mechanism that selects between two time constants based on signal conditions. This adds minimal complexity while significantly improving the system's ability to handle both sudden noise changes and signal rises accurately.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention applies different time constant characteristics to different operating conditions (local quality). When the signal is below the noise threshold, a faster time constant is used for quick adaptation. When the signal exceeds the threshold, a slower time constant is used for stable estimation. This localized approach handles varying conditions effectively without excessive complexity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9137611B2Method, system and computer program product for estimating a level of noise

Publication Date: 2015.09.15 TEXAS INSTRUMENTS INC

AI summary

In response to a signal failing to exceed an estimated level of noise by more than a predetermined amount for more than a predetermined continuous duration, the estimated level of noise is adjusted according to a first time constant in response to the signal rising and a second time constant in response to the signal falling, so that the estimated level of noise falls more quickly than it rises. In response to the signal exceeding the estimated level of noise by more than the predetermined amount for more than the predetermined continuous duration, a speed of adjusting the estimated level of noise is accelerated.