Audio Distortion Testing for Dynamic Phase and Frequency Modulation
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Solution Overview
Problem
Conventional methods for testing audio equipment, such as analog to digital converters and amplifiers, fail to accurately measure time-varying harmonic and intermodulation distortion, particularly in non-mechanical systems, as they rely on fixed bias points and single-tone tests, which do not account for dynamic biasing and phase modulation effects.
Innovation Solution
The use of filter banks and arbitrary low-frequency signals with stairstep or multiple-step signals to measure Nth order harmonic and intermodulation distortion, allowing for dynamic distortion analysis by coupling multiple frequencies to the device under test and employing phase or frequency modulation detectors to assess induced phase and frequency modulation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional harmonic and intermodulation distortion tests are used, then basic distortion performance can be evaluated, but time-varying and dynamic distortion effects cannot be measured
Solution Approach 1:
The patent applies dynamics by transitioning from static single-tone tests to dynamic multi-tone signals with time-varying characteristics. The test signal includes multiple frequencies that vary over time, enabling measurement of distortion products that change with signal dynamics, thus resolving the contradiction between measurement precision and dynamic analysis capability
Solution Approach 2:
The patent uses periodic multi-tone test signals with specific frequency relationships to generate measurable distortion products. By employing periodic action with multiple frequencies simultaneously, the system can detect time-varying harmonic and intermodulation distortion that conventional single-tone periodic tests cannot capture
2Device complexity
If single-tone tests at fixed bias points are used, then simple distortion measurements can be obtained, but phase modulation and frequency modulation effects are missed
Solution Approach 1:
The patent segments the test signal into multiple frequency components rather than using a single tone. This segmentation allows separate analysis of phase and frequency modulation effects on each component while maintaining overall signal integrity, thus capturing information that would be lost in simple single-tone tests
Solution Approach 2:
The patent adds temporal and spectral dimensions to the test signal by using multiple frequencies that vary over time. This dimensional expansion enables detection of phase and frequency modulation effects that exist in the time-varying domain, converting a one-dimensional static measurement into a multi-dimensional dynamic analysis
3Productivity
If conventional distortion measurements are performed, then basic performance metrics can be obtained, but discrepancies in sonic signature between equipment with comparable distortion performance remain unexplained
Solution Approach 1:
The patent creates a universal test method that simultaneously measures multiple distortion parameters including harmonic distortion, intermodulation distortion, phase modulation, and frequency modulation effects. This multi-functional approach explains sonic signature differences between equipment by capturing comprehensive performance characteristics that conventional single-parameter tests cannot distinguish
Data Source
AI summary
A system is provided to analyze cross-modulation distortion in audio devices, which may include testing with audio frequencies. One or more distortion signals from the audio device may be measured for an amplitude, phase, and or frequency modulation effect. In another embodiment a musical signal may be used as a test signal. Providing additional test signals to the audio device can induce a time varying cross-modulation distortion signal from an output of the audio device. Also utilizing at least one additional filter, filter bank, demodulator and or frequency converter and or frequency multiplier provides extra examination of distortion. Also frequency and or phase response can be measured with the presence of a de-sensing signal and or another signal that induce near slew rate limiting or near overload condition of the device under test.