Audio Equipment Testing via Phase and Frequency Modulation
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Solution Overview
Problem
Conventional methods for testing audio equipment, such as harmonic and intermodulation distortion tests, fail to accurately measure performance discrepancies in sonic signatures and frequency stability across different devices, particularly in non-mechanical systems like amplifiers and processors.
Innovation Solution
A new testing method that measures induced phase and frequency modulation at the output of audio devices when multiple frequencies are input, allowing for the detection of phase and frequency variations caused by dynamic biasing signals, which is not possible with standard Wow and Flutter tests designed for mechanical systems.
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 performance can be evaluated, but discrepancies in sonic signatures and frequency stability remain undetected
Solution Approach 1:
The patent changes the measurement parameters from conventional amplitude-based distortion tests to phase and frequency modulation-based measurements. By applying multiple frequency signals and measuring the induced phase and frequency modulation at the output, the system detects subtle performance characteristics that conventional tests miss, thereby improving measurement precision without losing sonic signature information
Solution Approach 2:
The patent introduces phase and frequency modulation measurements as intermediary parameters to bridge the gap between conventional distortion tests and actual sonic performance. These intermediary measurements reveal dynamic biasing effects and frequency stability issues that directly correlate with sonic signatures, allowing accurate evaluation without losing critical performance information
2Measurement precision
If standard Wow and Flutter tests are applied to mechanical recording systems, then speed stability can be measured, but they cannot detect phase and frequency variations in non-mechanical electronic systems
Solution Approach 1:
The patent creates a universal measurement method that works for both mechanical recording systems and non-mechanical electronic systems. By measuring induced phase and frequency modulation responses to multiple input frequencies, the system adapts to different system types - detecting speed stability in mechanical systems and phase/frequency variations in electronic systems like amplifiers and processors, thereby achieving multi-functionality
3Measurement precision
If single frequency tests are used for harmonic distortion measurement, then distortion at nominal bias point can be measured, but dynamic biasing effects and frequency modulation distortions remain undetected
Solution Approach 1:
The patent applies periodic action by using multiple frequency signals as test inputs. By introducing signals at different frequencies and measuring the induced phase and frequency modulation, the system dynamically probes the system under test across different operating conditions, revealing dynamic biasing effects and frequency modulation distortions that single-frequency static tests cannot detect
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 with a smaller amplitude higher frequency signal to test a dynamic change in frequency response, gain, and or phase. This dynamic test can reveal frequency modulation effects. Another embodiment may include the use of a multiple frequency signal to dynamically induce a time varying phase or frequency distortion for the device that has differential phase distortion. The device's output is then measured with an FM detector or spectrum analysis system to measure a shift in one of the frequencies used in the test signal or to measure frequency modulation effects of any signals, including distortion products, from the device. Yet another embodiment of the invention may include biasing a device with a voltage to span the output voltage range of the device while measuring harmonic or intermodulation distortion or phase or frequency response at the various operating points.