Microphone Post Linearization Using Tracking Signal Envelope
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microphones suffer from distortion in their output due to non-linearity in acoustic transducers and processing circuits, particularly at higher sound pressure levels, which affects sound quality.
Innovation Solution
A system and method that uses a known input tracking signal to identify and compensate for distortion in the microphone assembly's output by separating the audio signal component and tracking signal component, estimating the tracking signal envelope, and applying compensation to reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If acoustic transducers and processing circuits operate at higher sound pressure levels, then the microphone can capture louder sounds, but distortion increases due to non-linearity
Solution Approach 1:
The system applies preliminary action by injecting a tracking signal before the actual audio processing occurs. This tracking signal passes through the entire signal chain (acoustic transducer, processing circuit, ADC) to pre-characterize the non-linear behavior. The measured distortion from the tracking signal is then stored and used to create compensation filters that are applied to subsequent audio signals, thereby pre-correcting for the non-linearities that would otherwise occur at higher sound pressure levels.
Solution Approach 2:
The system implements feedback by measuring the actual output response to the known tracking signal and using this information to generate compensation filters. The process continuously monitors the non-linear behavior through the tracking signal path and adjusts the compensation filters accordingly. This closed-loop approach ensures that the compensation adapts to the actual non-linear characteristics of the hardware, maintaining signal accuracy even at varying sound pressure levels.
2Manufacturing precision
If distortion compensation is applied to improve sound quality, then harmonic and intermodulation components are reduced, but system complexity increases
Solution Approach 1:
The system introduces an intermediary element - the tracking signal - that serves as a mediator between the non-linear hardware and the compensation process. This tracking signal acts as a probe that characterizes the non-linear behavior without interfering with the actual audio content. The compensation filters generated from tracking signal analysis serve as intermediaries that pre-process audio signals to pre-correct distortions, thereby simplifying the overall processing required during actual audio capture while maintaining high signal accuracy.
Solution Approach 2:
The system creates a copy of the non-linear behavior characteristics by analyzing the tracking signal response. Instead of directly processing and correcting the main audio signal in real-time (which would be computationally intensive), the system copies the non-linear characteristics from the tracking signal measurement and stores them as compensation filters. This copying approach allows the complex non-linear behavior to be captured once and reused for multiple audio signals, significantly reducing real-time processing complexity while maintaining accurate distortion compensation.
Data Source
AI summary
A microphone assembly includes an acoustic transducer and an audio signal electrical circuit configured to receive an output signal from the acoustic transducer. The output signal includes an audio signal component and a tracking signal component. The audio signal component is representative of an acoustic signal detected by the acoustic transducer and the tracking signal component is based on an input tracking signal applied to the acoustic transducer. The audio signal electrical circuit includes an analog to digital converter configured to convert the output signal into a digital signal, an extraction circuit configured to separate the tracking signal component and the audio signal component from the digital signal, an envelope estimation circuit configured to estimate a tracking signal envelope from the tracking signal component, and a signal correction circuit configured to reduce distortion in the audio signal component using the tracking signal envelope.