Audio Distortion Measurement Using Dynamic Multi-Tone Signals
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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 frequency tones, 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 biasing and phase modulation 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 equipment performance can be evaluated, but time-varying and dynamic distortion effects cannot be accurately measured
Solution Approach 1:
The patent applies dynamics by transitioning from static single-tone testing to dynamic multi-tone testing with time-varying signals. The test signal includes multiple frequency components that vary over time, allowing the measurement system to capture dynamic distortion effects that occur during actual audio operation, thereby resolving the contradiction between measurement precision and adaptability to dynamic conditions
Solution Approach 2:
The patent changes the parameters of the test signal from fixed frequency and amplitude to time-varying frequency and amplitude modulated signals. By using signals with varying frequency, amplitude, and phase characteristics, the system can measure distortion under different operating conditions, achieving both precise measurement and dynamic adaptability
2Ease of manufacture
If single frequency tone testing is used, then simple distortion measurement is achieved, but phase modulation and frequency modulation effects are not detected
Solution Approach 1:
The patent segments the test signal into multiple frequency components rather than using a single tone. By applying multiple frequency tones simultaneously and analyzing their individual and interaction effects, the system preserves phase and frequency modulation information while maintaining a relatively simple testing approach
Solution Approach 2:
The patent adds temporal and spectral dimensions to the testing by using time-varying multi-frequency signals. This dimensional expansion allows detection of phase and frequency modulation effects that are invisible in conventional single-frequency testing, without significantly complicating the overall testing methodology
3Stability of the object's composition
If fixed bias point testing is used, then consistent measurement conditions are maintained, but dynamic distortion variations across different operating points are missed
Solution Approach 1:
The patent employs periodic time-varying test signals that cycle through different amplitude and frequency conditions. This periodic action allows the system to probe multiple bias points systematically while maintaining controlled measurement conditions, capturing dynamic distortion variations across the operating range
Solution Approach 2:
The patent creates a universal test signal that functions across multiple operating conditions simultaneously. The multi-component time-varying signal can excite the system at different bias points and distortion regimes in a single measurement sequence, achieving both consistency and dynamic accuracy
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.