Parametric Audio Pre-Distortion for Harmonic Distortion Reduction
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Solution Overview
Problem
Parametric audio reproduction systems suffer from significant distortion due to non-linearities in the medium and transducers, leading to unwanted harmonics and artifacts, which are difficult to mitigate effectively.
Innovation Solution
A preprocessing method is introduced that involves approximating the system response using an infinite series expression of the non-linear system transfer function, deriving its inverse to condition the input signal, thereby reducing distortion by linearizing the output with respect to the input, even in non-linear systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parametric audio reproduction systems use non-linear medium and transducers to generate ultrasound signals, then audio reproduction capability is achieved, but significant distortion and unwanted harmonics are generated
Solution Approach 1:
The patent applies preliminary action by pre-distorting the input signal before it enters the non-linear parametric system. The preprocessing module modifies the input signal in advance to compensate for the expected non-linear distortion, so that when the signal passes through the non-linear medium and transducers, the final output is corrected and has reduced distortion levels comparable to conventional linear acoustic systems.
2Object-generated harmful factors
If conventional linear acoustic systems are used, then low distortion is achieved, but parametric array capabilities such as directional sound projection are not available
Solution Approach 1:
The patent converts the harmful non-linear distortion characteristics of parametric systems into a benefit by using pre-distortion preprocessing. The known non-linear transfer function of the parametric system is inverted and applied to the input signal, transforming the inevitable distortion into a controlled correction mechanism. This allows the system to maintain its directional sound projection capabilities while achieving distortion levels comparable to linear systems.
3Object-generated harmful factors
If input signal is pre-distorted using inverse transfer function, then distortion is reduced in output, but system complexity increases due to preprocessing requirements
Solution Approach 1:
The patent applies parameter changes by modifying the input signal parameters (amplitude, frequency, phase) through pre-distortion preprocessing. The system changes the parameters of the input signal in advance according to the inverse transfer function, so that when the signal passes through the non-linear parametric system, the parameter transformations cancel out the distortion effects, resulting in a corrected output signal with reduced harmonic content.
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 dramatically reduces distortion levels in parametric arrays to be comparable to conventional acoustic reproduction systems, improving sound quality by pre-distorting the input signal before it enters the non-linear system, effectively mitigating inherent distortions.
Implementation Method 1
Parametric audio reproduction systems produce sound through the heterodyning of two acoustic signals in a non-linear process that occurs in a medium such as air
Implementation Method 2
The non-linearity of the medium results in acoustic signals produced by the medium that are the sum and difference of the acoustic signals
Implementation Method 3
deriving its inverse to condition the input signal, thereby reducing distortion by linearizing the output with respect to the input
Implementation Method 4
approximating the system response using an infinite series expression of the non-linear system transfer function
Data Source
AI summary
A system and methods for distortion reduction in a non-linear audio system are disclosed. A method includes the operation of defining a non-linear system transfer function which relates a system electronic input signal with a system acoustic output over a range in which the system acoustic output is in a transition between non-saturated and saturated conditions in a medium in which the system acoustic output of the non-linear audio system is broadcast. A preprocessing transfer function is created that is the inverse of the non-linear system transfer function. The preprocessing transfer function is applied to the system electronic input signal to reduce the level of harmonic distortion at the system acoustic output.