Equalization Control Curves to Prevent Frequency Response Ringing
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Solution Overview
Problem
Existing signal equalization methods face challenges in smoothly scaling equalization across the frequency spectrum without introducing artifacts such as time-domain ringing, which occurs when sudden steps in frequency response are difficult to implement with reasonable length filters.
Innovation Solution
The method employs a control curve that smoothly scales equalization by using Bezier, linear, or spline interpolation to create a contoured equalization curve, allowing for user-controlled or automated reduction of equalization in specific frequency regions, avoiding sudden steps and thus minimizing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equalization is applied over the entire frequency spectrum, then comprehensive frequency correction is achieved, but artifacts such as time-domain ringing occur due to sudden stops in equalization at given frequencies
Solution Approach 1:
The patent applies curvature by replacing sudden linear transitions in equalization with smooth curved transitions using Bezier and spline interpolation. The control curve with control points creates a continuous, differentiable function that gradually reduces equalization magnitude across frequency bands, eliminating the sharp discontinuities that cause time-domain ringing artifacts while maintaining comprehensive frequency correction.
2Manufacturing precision
If sudden steps in magnitude or slope of frequency response are implemented, then equalization can be precisely controlled at specific frequencies, but artifacts such as time-domain ringing are introduced
Solution Approach 1:
The patent introduces dynamics by transforming the static, step-based equalization control into a dynamic, continuous control system. The equalization magnitude and slope vary continuously across frequency according to the control curve defined by control points, allowing precise control at specific frequencies while maintaining smooth transitions that prevent audible artifacts.
Solution Approach 2:
The patent changes the parameter representation from discrete step functions to continuous polynomial functions (Bezier and spline). By representing equalization magnitude as a continuous function of frequency with adjustable control points, the system achieves both precise frequency-specific control and smooth transitions, eliminating the harmful artifacts associated with sudden parameter changes.
3Adaptability or versatility
If equalization is reduced in certain frequency regions, then contoured equalization is achieved, but sudden transitions create implementation difficulties with reasonable length filters
Solution Approach 1:
The patent applies segmentation by dividing the frequency spectrum into multiple controllable regions defined by control points. Each control point represents a specific frequency region where equalization magnitude can be independently adjusted, allowing flexible frequency region control while the continuous interpolation between points simplifies filter implementation compared to traditional approaches requiring sharp transitions.
Data Source
AI summary
A method for equalization contouring provides a reduction of equalization in certain frequency regions either by user control or by automated selection of frequency, without introducing artifacts. A control curve smoothly scales the magnitude of the equalization in the areas where less equalization is desired to obtain a contoured equalization. The control curve varies by frequency and may be defined specifically for every sampled frequency value of the equalization, may be a continuous function of frequency, or may be a function of control points at a select number of frequency points. The control curve may also have automatic inputs, e.g. a machine-detected cutoff frequency of a speaker may be used to determine a control point in the control curve. As another example, the reverberation time (e.g. RT60) may be used to determine a control point in the control curve. The result is a contoured equalization curve without sudden steps.