Equalizer Center Frequency Setting for Asymmetric Audio Correction
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Solution Overview
Problem
Conventional equalizers require a large number of bands to correct asymmetric frequency characteristics of audio signals, leading to over-correction at certain frequencies and under-correction at others.
Innovation Solution
A control device that calculates a center frequency between frequencies with a gain difference of 1/√2 times the maximum gain difference, closest to the peak frequency, to determine equalizer parameters, reducing the number of bands needed for correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional equalizer parameter setting methods are used (setting center frequency to peak frequency), then the equalizer can correct frequency characteristics, but a large number of bands are required when frequency characteristics are asymmetric
Solution Approach 1:
The patent applies asymmetry by calculating the center frequency based on the geometric mean of the lower and upper frequencies (fc = sqrt(f1 × f2)) rather than using the peak frequency directly. This asymmetric calculation method accounts for the asymmetric nature of frequency characteristics, allowing accurate correction with fewer bands. The center frequency is positioned to balance the correction effect across asymmetric frequency deviations.
2Ease of operation
If the center frequency is set to the peak frequency, then the equalizer parameters are easy to determine, but correction is too much at certain frequencies or not enough at others for asymmetric characteristics
Solution Approach 1:
The patent implements self-service by having the system automatically calculate the center frequency and equalizer parameters based on the measured frequency characteristics of the audio signal. The control device performs FFT analysis, identifies peak frequency, calculates lower and upper frequencies where gain difference equals 1/√2 times maximum gain difference, and determines the optimal center frequency without manual intervention, achieving both automation and precision.
3Manufacturing precision
If multiple bands are used to correct asymmetric frequency characteristics, then correction precision improves, but the device complexity and processing load increase
Solution Approach 1:
The patent changes the parameter calculation method by using the geometric mean of frequencies (fc = sqrt(f1 × f2)) and setting the gain based on the maximum gain difference. This parameter transformation allows a single band to achieve correction效果 that would otherwise require multiple bands, reducing device complexity while maintaining precision.
Data Source
AI summary
A control device includes: a difference calculator that calculates a maximum gain difference between frequency characteristics of an audio signal and desired frequency characteristics in a predetermined frequency band; a center frequency calculator that calculates a center frequency between a first frequency at which the gain difference is 1/√2 times the maximum gain difference and which is closest to a peak frequency corresponding to the maximum gain difference among one or more frequencies lower than the peak frequency and a second frequency at which the gain difference is 1/√2 times the maximum gain difference and which is closest to the peak frequency among one or more frequencies higher than the peak frequency; a determiner that determines parameters of an equalizer based on the maximum gain difference and the center frequency; and an outputter that outputs the parameters to the equalizer.