Loudspeaker Distortion Prediction With Adaptive Audio Processing
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Solution Overview
Problem
Audio systems, particularly those in vehicles and mobile devices, suffer from distortion due to non-linearities in loudspeakers and amplifiers, which existing methods struggle to accurately predict and mitigate, especially for large diaphragm displacements.
Innovation Solution
An audio system that estimates and controls distortion by using a combination of linear and non-linear loudspeaker response models, with a controller adjusting operating parameters like gain and compression ratio based on predicted distortion levels, and applying perceptual weighting to irrelevant frequency components, allowing for simpler models and reduced sensitivity to model accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-distortion is applied using a nonlinear loudspeaker model, then distortion is reduced for moderate diaphragm displacements, but the model fails to predict behavior for large displacements
Solution Approach 1:
The patent implements a feedback mechanism where the actual diaphragm displacement is measured and used to adjust the input signal in real-time. This closed-loop approach compensates for the inaccuracies of nonlinear models at large displacements by continuously adapting to the actual system behavior, thereby maintaining reliable distortion reduction across the full operating range.
Solution Approach 2:
The system dynamically changes operating parameters based on the measured diaphragm displacement. When large displacements are detected, the system adjusts the pre-distortion parameters or applies additional compensation techniques, allowing the system to maintain accuracy across different operating conditions rather than relying on a fixed nonlinear model.
2Object-affected harmful factors
If maximum voltage limiting is applied to control distortion, then distortion is limited for single sine waves, but the system cannot accurately predict distortion in the general case due to nonlinear superposition
Solution Approach 1:
By measuring actual diaphragm displacement and using this information to adjust the input signal, the system overcomes the limitations of open-loop voltage limiting. The feedback mechanism enables accurate distortion control for complex signals by continuously adapting to the actual nonlinear behavior, rather than relying on predictions based on single-frequency measurements.
3Manufacturing precision
If accurate nonlinear loudspeaker modeling is used, then pre-distortion can effectively linearize the response, but the system becomes highly sensitive to model accuracy requirements
Solution Approach 1:
The feedback mechanism reduces sensitivity to model accuracy by continuously measuring actual diaphragm displacement and adjusting the input signal accordingly. This closed-loop approach compensates for model inaccuracies, allowing the system to achieve effective linearization without requiring extremely precise nonlinear models, thereby reducing overall system complexity.
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 effectively limits distortion in audio output, improving perceived audio quality with reduced reliance on precise loudspeaker modeling, and adapts to varying distortion levels and frequency sensitivity, enhancing performance across different audio systems.
Implementation Method 1
A loudspeaker may be any transducer that converts electrical energy into acoustical energy
Data Source
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AI summary
An audio system is described including an audio processor, an amplifier and a speaker and a distortion estimator. The distortion estimator calculates at least one of an expected response of the amplifier to an audio signal and an expected response of the loudspeaker to an audio signal. The distortion estimator is operable to generate a distortion prediction signal determined by a difference between an expected non-linear response of at least one of the loudspeaker and the amplifier and an expected linear response of at least one of the loudspeaker and the amplifier. A controller coupled to the audio processor and a control input of the audio processor may vary the operating parameters of the audio processor depending on the estimated distortion.