Non-linear Digital Loudspeaker Model for Echo Cancellation

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Solution Overview

Problem

Existing feedback cancellation systems in electroacoustic communication apparatuses, such as smartphones and cars, struggle to accurately model non-linear behavior of loudspeakers, leading to inaccurate feedback cancellation and undesirable sonic artifacts like echoes.

Innovation Solution

Incorporating a non-linear digital loudspeaker model that uses voice coil current and voltage parameters, represented by non-linear functions, coupled with an adaptive digital filter to accurately model the external feedback path and improve echo cancellation performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a linear adaptive digital filter is used to model the external feedback path, then the system structure remains simple, but the feedback cancellation accuracy deteriorates due to inability to model non-linear loudspeaker behavior

Engineering Contradiction:

Improvefeedback cancellation accuracyVSAvoidcancellation system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The feedback cancellation system is divided into two independent segments: a non-linear digital loudspeaker model that handles non-linear behavior, and a linear adaptive digital filter that handles linear feedback path modeling. This segmentation allows each component to specialize in its strength, improving overall accuracy without requiring the entire system to be non-linear.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges the non-linear digital loudspeaker model with the linear adaptive digital filter in a series configuration. The non-linear model processes the audio signal first to account for loudspeaker non-linearities, then the linear filter models the external feedback path. This combination achieves both non-linear and linear modeling capabilities simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If individual loudspeaker characterization is performed during manufacturing, then the feedback cancellation precision improves, but the manufacturing time and complexity increase

Engineering Contradiction:

Improvefeedback cancellation precisionVSAvoidmanufacturing calibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Instead of performing time-consuming individual loudspeaker characterization, the system uses a non-linear digital model with parameters that can be adjusted based on general loudspeaker behavior patterns. The model incorporates non-linear functions with adjustable parameters that capture typical loudspeaker non-linearities without requiring individual calibration, thus reducing manufacturing time while maintaining precision.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If non-linear functions with multiple parameters are used to model loudspeaker behavior, then the feedback cancellation accuracy improves, but the computational resource requirement increases

Engineering Contradiction:

Improvefeedback cancellation accuracyVSAvoidcomputational resource consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The non-linear digital loudspeaker model applies non-linear functions selectively to specific parameters (such as force factor, compliance, damping) rather than treating all parameters uniformly. This localized application of non-linearity where needed most improves accuracy for critical feedback cancellation while reducing overall computational burden compared to applying non-linear processing to all signal paths.

Inventive Principle:

Principle #3Local quality

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

This approach significantly enhances feedback cancellation performance by accurately modeling non-linear loudspeaker behavior, reducing echoes and instability, while minimizing computational resource expenditure and allowing for calibration without individual loudspeaker characterization.

Implementation Method 1

generation and emission of an outgoing sound signal to an external environment through an electrodynamic loudspeaker

Methodology Applied

Scientific EffectElectrodynamic transduction: Electromagnetic Induction

Implementation Method 2

signal reception path comprising a microphone for generation of a microphone input signal corresponding to sound received from the external environment

Methodology Applied

Scientific EffectMicrophone transduction:

Data Source

PatentUS9531433B2Echo cancellation methodology and assembly for electroacoustic communication apparatuses

Publication Date: 2016.12.27 ANALOG DEVICES INT UNLTD CO

AI summary

A feedback cancellation assembly for an electroacoustic communication apparatus may include a signal transmission path for generation and emission of an outgoing sound signal to an external environment through an electrodynamic loudspeaker and a signal reception path comprising a microphone for generation of a microphone input signal corresponding to sound received from the external environment. The signal reception path may generate a digital microphone signal. The outgoing sound signal may be acoustically coupled to the microphone. An electronic feedback cancellation path may be coupled between a tapping node and a summing node to produce a feedback cancellation signal to the summing node.