Audio Equipment Distortion Measurement via Multi-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 distortion and frequency modulation, particularly in non-mechanical systems, leading to discrepancies in sonic performance and inability to detect Wow and Flutter effects.
Innovation Solution
A new testing method involving the measurement of induced phase and frequency modulation by coupling two or more frequencies to the input of the device under test, using a modifier circuit to isolate and remove lower frequency signals, allowing for the measurement of phase and frequency variations at the output, which is not possible with standard Wow and Flutter tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional harmonic and intermodulation distortion tests are used to measure audio equipment performance, then basic distortion evaluation is achieved, but the tests fail to detect phase and frequency modulation distortions including Wow and Flutter effects
Solution Approach 1:
The patent applies dynamics by transitioning from static single-frequency testing to dynamic multi-frequency testing. The system uses multiple tones at different frequencies that are modulated over time to reveal phase and frequency modulation distortions. This dynamic approach allows the detection of Wow and Flutter effects that static tests cannot capture, thereby improving both measurement precision and adaptability across different distortion types.
Solution Approach 2:
The patent introduces a new dimension to audio equipment testing by measuring phase and frequency modulation in addition to traditional amplitude-based distortion measurements. By adding phase angle and frequency deviation as measurement dimensions, the system can detect distortions that manifest in the time domain rather than just the frequency domain, enabling detection of Wow and Flutter effects while maintaining compatibility with conventional distortion evaluation.
2Adaptability or versatility
If standard Wow and Flutter tests using a single tone are applied, then mechanical speed stability can be assessed, but the tests cannot measure induced phase and frequency modulation in non-mechanical electronic systems
Solution Approach 1:
The patent achieves universality by designing a testing method that can evaluate both mechanical systems (like tape recorders with Wow and Flutter) and non-mechanical electronic systems (like digital audio processors). The multi-frequency modulation approach works for both types of systems: mechanical systems produce physical speed variations detectable by the method, while electronic systems produce digital phase and frequency modulation that the same method can measure, thus providing a unified testing framework across different system types.
Solution Approach 2:
The patent applies parameter changes by using multiple frequencies with different amplitude relationships that can be modulated to reveal various distortion characteristics. By varying the frequency parameters and amplitude ratios of the test tones, the system can adapt its measurement sensitivity to detect both mechanical speed instabilities and electronic phase/frequency modulation, achieving accurate measurements across different system types without requiring separate test methodologies.
3Measurement precision
If two or more frequencies are coupled to the input to measure induced modulation, then comprehensive distortion evaluation is achieved, but the complexity of the testing apparatus and signal processing increases
Solution Approach 1:
The patent applies segmentation by dividing the complex multi-frequency signal into individual frequency components for separate analysis. Each tone in the multi-tone test signal is processed independently through the device under test, and their interactions (intermodulation products, phase modulation, frequency modulation) are measured and analyzed separately. This segmentation simplifies the measurement process by allowing the use of standard spectral analysis techniques to isolate and quantify different types of distortion without being overwhelmed by the complexity of the full signal.
Data Source
AI summary
A testing method or apparatus utilizes multiple frequencies applied to a device under test for measuring newly discovered frequency modulation effects. An embodiment may include a lower frequency signal combined with two (or more) higher frequency signals to test a dynamic change in frequency response, gain, and or phase of the lower frequency signal from an audio device. This dynamic test can reveal frequency modulation effects via the two higher frequency signals emulate a modulated signal that provides a phase or frequency modulation frequency related to the difference of the two higher frequency signals. Another embodiment may include the use of a higher frequency signal and pulsed waveform to dynamically induce a time varying phase or frequency distortion of the pulsed waveform or components of the pulsed waveform from the device that has differential phase distortion. In another embodiment, the device's output is then measured with an FM detector and or phase detector to measure a phase and or frequency shift in one or more signals of the frequencies related to the pulsed waveform, such as a signal of the fundamental frequency and or one or more harmonic related to the pulsed waveform the device.