Ultrasonic Audio Error Correction via Hilbert Transform
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Solution Overview
Problem
Ultrasonic audio systems face challenges in reducing distortion, particularly intermodulation and harmonic distortion, which affect the fidelity of audio reproduction due to nonlinear interactions in air, leading to unwanted frequency creation.
Innovation Solution
The implementation of error correction systems that calculate and apply error functions, such as Hilbert transforms, to pre-condition audio signals before modulation, allowing for the cancellation of distortion products by phase shifting and amplitude adjustments, thereby improving audio fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic audio signals are transmitted through air, then audio reproduction is achieved, but distortion is introduced due to nonlinear interactions
Solution Approach 1:
The system performs preliminary action by calculating error functions that predict distortion before the ultrasonic signal is transmitted. These error functions are used to pre-condition the audio signal in advance, so that when the signal passes through the nonlinear air medium, the pre-applied corrections cancel out the expected distortion, resulting in faithful audio reproduction.
Solution Approach 2:
The system applies preliminary anti-action by generating error functions that represent the expected distortion and combining them with the original audio signal in a way that creates a pre-corrected signal. This pre-corrected signal, when transmitted through air, produces distortion that is already compensated for, effectively canceling the harmful distortion effects before they degrade the audio quality.
2Reliability
If error correction is applied to reduce distortion, then audio fidelity is improved, but system complexity increases
Solution Approach 1:
The system replaces complex physical acoustic correction mechanisms with computational error function calculations. Instead of using additional physical components or complex mechanical systems to correct distortion, the invention uses mathematical operations (Hilbert transforms, phase shifting, amplitude adjustments) to calculate and apply corrections digitally, significantly reducing physical system complexity while maintaining correction effectiveness.
Solution Approach 2:
The system changes parameters of the audio signal in the mathematical domain rather than requiring complex physical system modifications. By transforming the audio signal through error function calculations that adjust phase and amplitude parameters, the system achieves distortion correction through computational parameter changes rather than complex hardware modifications.
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 reduces distortion, enhancing the quality of audio reproduction by separating and correcting intermodulation and harmonic distortion individually, leading to improved sound fidelity and reduced unwanted tones.
Implementation Method 1
This process occurs because of the known physical principle that when two sound waves with different frequencies are radiated simultaneously in the same medium, a modulated waveform including the sum and difference of the two frequencies is produced by the non-linear (parametric) interaction of the two sound waves.
Implementation Method 2
Self-demodulation, or down-conversion, occurs along the air column resulting in the production of an audible acoustic signal.
Implementation Method 3
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.
Data Source
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AI summary
Systems and methods for removing or reducing distortion in an ultrasonic audio system can include receiving a first audio signal, wherein the first audio signal represents audio content to be reproduced using the ultrasonic audio system; calculating a first error function for the ultrasonic audio system, the first error function comprising an estimate of distortion introduced by reproduction of the audio content by the ultrasonic audio system; transforming the first audio signal into a first pre-conditioned audio signal by combining the first error function with the first audio signal; and modulating the transformed audio signal onto an ultrasonic carrier.