Audio Distortion Testing With Dynamic Bias and Phase Modulation Analysis
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Solution Overview
Problem
Conventional harmonic and intermodulation distortion tests used in audio equipment evaluation are inadequate as they do not account for time-varying distortions and discrepancies in sonic signatures between equipment with comparable distortion performance.
Innovation Solution
The use of a filter bank and an arbitrary low-frequency signal to measure time-varying harmonic and intermodulation distortion, allowing for dynamic biasing and measurement of distortion as a function of time and offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional harmonic and intermodulation distortion tests are used, then basic distortion performance can be measured, but time-varying distortions and dynamic performance cannot be detected
Solution Approach 1:
The patent applies dynamics by transitioning from static distortion measurements at fixed bias points to dynamic measurements that track distortion as a function of time and varying offset voltages. The test method continuously monitors distortion parameters while the bias point changes, enabling detection of time-varying distortions that static tests miss.
Solution Approach 2:
The patent changes the measurement parameters by introducing time-varying offset voltages and measuring distortion at multiple bias points rather than a single fixed point. This parameter variation allows the test to capture dynamic distortion behavior and differentiate between equipment with similar static distortion characteristics but different dynamic performance.
2Ease of operation
If conventional distortion tests with zero offset signal are used, then simple measurements can be performed, but discrepancies in sonic signatures between equipment cannot be explained
Solution Approach 1:
The patent performs preliminary actions by systematically varying the offset voltage and measuring distortion at multiple predetermined bias points before making a final assessment. This preliminary exploration of the distortion characteristics across different operating conditions provides comprehensive information that explains sonic signature differences.
3Productivity
If static distortion measurements at fixed bias points are used, then quick evaluations can be made, but dynamic distortion behavior cannot be assessed
Solution Approach 1:
The patent maintains continuity of useful action by continuously measuring distortion while the bias point varies over time, rather than taking discrete static measurements. This continuous measurement approach captures the dynamic behavior of distortion without significantly increasing test time, as the bias variation and measurement occur in an integrated continuous process.
Data Source
AI summary
A system is provided to analyze distortion in an electronic or electromechanical device, which may include testing with one or more modulated signals and/or with one or more demodulators. In one embodiment a change in pitch (or frequency) is measured at an output of the device. One or more signals from a demodulator output may be measured for an amplitude, noise, phase, aliasing, spurious signal, and/or frequency modulation effect. In another embodiment a musical signal may be used as a test signal. Also frequency and/or phase response can be measured with the presence of a de-sensing signal and or near overload condition of the device under test. Another system is provided to analyze modulation index differences between input and output signals for a test signal including modulation. Another system includes providing a nested or layered modulated signal and/or a nested or layered demodulation apparatus or method.