Audio Equipment Dynamic Distortion Evaluation
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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-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 to measure Nth order harmonic and intermodulation distortion dynamically, combined with multiple tones and a stairstep signal, allows for the detection of time-varying distortion and phase modulation effects by coupling these signals to the device under test and analyzing the output with phase or frequency modulation detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-tone tests at fixed 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 transforms static single-tone tests into dynamic multi-tone tests with time-varying bias points. The testing system dynamically adjusts bias points and applies multiple tones simultaneously to capture time-varying distortion characteristics, converting a static measurement approach into a dynamic one that reflects real operating conditions.
Solution Approach 2:
The patent segments the distortion measurement into multiple frequency components using filter banks. By separating the output signal into individual frequency bands, the system can precisely measure harmonic distortion and intermodulation distortion products at different frequencies, enabling accurate characterization of time-varying distortion behavior.
2Measurement precision
If conventional harmonic distortion tests at zero offset signal are used, then the testing procedure is straightforward, but the measurement cannot detect differential phase and frequency modulation effects
Solution Approach 1:
The patent extends the measurement from purely amplitude-based harmonic distortion to include phase and frequency modulation dimensions. By introducing time-varying bias points and analyzing phase relationships across multiple frequencies, the system captures differential phase and frequency modulation effects that conventional amplitude-only measurements miss.
Solution Approach 2:
The patent changes the testing parameters from fixed bias points to time-varying bias points, and from single-frequency to multi-frequency excitation. This parameter transformation enables the detection of phase and frequency modulation effects by observing how distortion products vary with changing bias conditions.
3Measurement precision
If conventional intermodulation distortion tests with two tones are used, then the test setup is simple, but the measurement cannot evaluate dynamic distortion under time-varying bias conditions
Solution Approach 1:
The patent employs periodic modulation of bias points combined with multi-tone excitation signals. By applying periodic variations to the bias conditions while maintaining tonal excitation, the system creates a structured test signal that reveals dynamic distortion characteristics through the periodic modulation of distortion product amplitudes and phases.
Solution Approach 2:
The patent creates a universal testing framework that simultaneously measures harmonic distortion, intermodulation distortion, differential phase modulation, and frequency modulation effects. The multi-tone excitation with time-varying bias points serves multiple measurement functions in a single test configuration, eliminating the need for separate specialized tests.
4Measurement precision
If traditional testing methods are used for electronic amplifiers, then the testing is quick and simple, but previously unnoticed issues like Wow and Flutter effects remain undetected
Solution Approach 1:
The patent applies preliminary multi-tone excitation with time-varying bias points before conventional single-tone testing. This preliminary measurement reveals subtle effects like Wow and Flutter by exposing the amplifier to dynamic operating conditions that trigger these artifacts, allowing early detection before final evaluation.
Solution Approach 2:
The patent introduces an intermediary measurement stage that uses filter banks and phase-sensitive detection to isolate subtle distortion effects. This intermediary analysis layer processes the multi-tone output signals to extract phase and frequency modulation information, acting as a mediator between the amplifier output and final evaluation metrics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a more comprehensive evaluation of audio equipment performance by detecting distortion and phase modulation variations as a function of time and bias points, revealing previously unnoticed issues like Wow and Flutter in electronic amplifiers, which traditional tests miss.
Implementation Method 1
A filter banks or filter banks are utilized to measure time varying or dynamic harmonic distortion or intermodulation distortion
Implementation Method 2
measuring the phase and or frequency modulation effects on any signal frequency from the output of the device
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. Another system is provided to analyze modulation index differences between input and output signals for a test signal including modulation.