Parallel Transfer Function Measurement for Active Noise Reduction
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Solution Overview
Problem
Conventional active noise reduction devices face inefficiencies in measuring transfer functions due to the time-consuming process of serially outputting sounds from multiple loudspeakers, which prolongs the measurement process and introduces errors.
Innovation Solution
A method where multiple loudspeakers simultaneously output sounds with different frequencies, allowing for parallel measurement of transfer functions, and adjusting measurement time to minimize error components, thereby reducing the total measurement time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple loudspeakers output sounds serially one by one, then the measurement process is simple to implement, but the total measurement time becomes excessively long
Solution Approach 1:
The patent combines multiple transfer function measurements into a single simultaneous measurement process. Multiple loudspeakers output sounds with different frequencies at the same time, and the microphone captures all sounds together. The processing unit then separates and calculates each transfer function from the composite signal, achieving parallel measurement that dramatically reduces total measurement time.
Solution Approach 2:
The patent employs periodic sine wave signals with different frequencies from each loudspeaker. By using periodic signals with known frequency characteristics, the system can identify and separate each loudspeaker's contribution in the composite signal through frequency analysis, enabling accurate simultaneous measurement of multiple transfer functions.
2Loss of time
If multiple loudspeakers output sounds simultaneously with different frequencies, then the total measurement time is shortened, but error components may increase due to signal interference
Solution Approach 1:
The patent uses periodic sine wave signals with distinct frequencies from each loudspeaker. This periodicity allows the processing unit to easily identify and separate each signal component through frequency analysis, preventing measurement errors despite simultaneous output. The known frequency characteristics serve as unique identifiers for each loudspeaker's contribution.
Solution Approach 2:
The patent assigns different frequency characteristics to each loudspeaker's output signal. This local differentiation in frequency domain allows the system to distinguish and measure each transfer function independently within the composite signal, maintaining measurement precision even though all sounds are output simultaneously.
3Measurement precision
If the measurement time is extended to reduce errors, then measurement precision improves, but productivity decreases due to longer measurement duration
Solution Approach 1:
The patent merges multiple sequential measurements into a single simultaneous measurement process. By capturing all transfer function data in one measurement cycle rather than sequentially, the system achieves both high precision (through proper signal separation) and high productivity (through time efficiency), resolving the trade-off between measurement time and accuracy.
Solution Approach 2:
The use of periodic signals with distinct frequencies enables accurate measurement within a short time frame. The periodic nature allows rapid frequency analysis and signal separation, achieving precise transfer function measurement without requiring extended measurement durations, thus maintaining both precision and productivity.
Data Source
AI summary
A transfer function measuring method includes: outputting a first signal to each of a plurality of loudspeakers to cause the plurality of loudspeakers to simultaneously output sounds with mutually different frequencies; acquiring second signals output from a microphone as a result of acquiring the sounds with the mutually different frequencies; and calculating a transfer function of each of the sounds with the mutually different frequencies based on the first signal and the second signals.