Audio Equipment Dynamic Distortion Measurement
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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 static bias points and single-frequency tests, which do not account for dynamic biasing and phase modulation effects.
Innovation Solution
The use of filter banks and multiple frequency signals to measure dynamic harmonic and intermodulation distortion, allowing for the detection of phase and frequency modulation effects by applying a stairstep signal or multiple step signals in conjunction with a low-frequency signal to the device under test, and coupling the output to phase or frequency detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-frequency tests with static bias points are used, then the testing method is simple and equipment is easy to operate, but the measurement precision of time-varying distortion is insufficient
Solution Approach 1:
The patent applies dynamics by transitioning from static single-frequency tests to dynamic multi-frequency swept sine wave tests. The test signal continuously varies in frequency over time, enabling the measurement of time-varying distortion characteristics that static tests cannot capture. This dynamic approach allows the system to track how distortion changes as the operating point shifts, providing comprehensive performance evaluation of audio equipment under realistic operating conditions.
Solution Approach 2:
The patent employs periodic action through the use of swept sine wave signals that periodically traverse through a range of frequencies. This periodic excitation allows the system to repeatedly measure distortion at different frequency points, enabling the detection of time-varying characteristics and ensuring consistent, reproducible measurements of dynamic distortion behavior in audio equipment.
2Loss of information
If conventional distortion measurement methods are used, then the testing procedure is straightforward, but the ability to detect phase modulation and frequency modulation effects is limited
Solution Approach 1:
The patent applies another dimension by extending measurements from the traditional amplitude domain to include phase and frequency domains. By using phase detectors and frequency counters in conjunction with multi-frequency swept sine wave inputs, the system captures phase modulation and frequency modulation effects that conventional amplitude-only measurements miss. This dimensional expansion provides a more complete characterization of audio equipment performance.
Solution Approach 2:
The patent introduces intermediary devices such as phase detectors and frequency counters that mediate between the audio equipment output and the measurement system. These intermediaries convert phase and frequency variations into measurable electrical signals, enabling the detection of subtle modulation effects that would otherwise be difficult to quantify. The multi-frequency swept sine wave signal acts as an intermediary that probes the system's dynamic response across different operating conditions.
3Adaptability or versatility
If static bias point measurements are used, then the testing method is simple, but it fails to account for dynamic biasing effects in non-mechanical systems
Solution Approach 1:
The patent applies dynamics by implementing a test method that automatically adapts to dynamic biasing conditions through continuous frequency sweeping. The swept sine wave signal dynamically shifts the operating point of the audio equipment, allowing the measurement system to capture distortion characteristics under varying bias conditions without requiring manual intervention or multiple separate tests. This dynamic adaptability makes the system versatile for evaluating both mechanical and non-mechanical audio equipment.
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.