Overlapping Multi-Band Limiter for Dead-Zone-Free Peak Control
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Solution Overview
Problem
Multi-band limiters suffer from a 'dead zone' issue where signals are not properly attenuated across frequency bands, leading to incomplete gain reduction and potential sound recording failures due to overpeak volumes, especially when filters are set to cross at −6 dB.
Innovation Solution
Implementing an overlap filter configuration where adjacent frequency bands overlap rather than cross at −6 dB, followed by a trimming process to remove overlapping signal components, ensuring a flat frequency characteristic and preventing dead zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If filters are set to cross at −6 dB to achieve flat frequency characteristic, then frequency response is improved, but dead zones are created where limiter function is not applied
Solution Approach 1:
The frequency spectrum is divided into multiple bands with overlapping frequency ranges. Each band is processed independently by dedicated limiter circuits, ensuring comprehensive coverage. The overlap region is specifically handled by assigning it to a higher frequency band while applying attenuation to prevent double-processing, thus eliminating dead zones while maintaining flat frequency response.
Solution Approach 2:
The patent introduces a spatial dimension to frequency band division by creating overlapping bands rather than adjacent non-overlapping bands. This overlapping structure in the frequency domain allows the limiter function to be applied continuously across all frequencies without gaps, while the attenuation mechanism in the overlap region resolves the conflict between coverage and flatness.
2Ease of manufacture
If independent multi-band limiting is implemented to prevent gain reduction in non-peak bands, then sound quality is improved, but dead zones occur where limiter is not applied
Solution Approach 1:
The audio signal is segmented into multiple frequency bands, each with its own limiter circuit operating independently. This segmentation allows peak detection and gain reduction to be applied selectively to specific frequency bands where peaks occur, preserving sound quality in non-peak bands while ensuring that dead zones are eliminated through overlapping band structure.
Solution Approach 2:
Different limiter operations are applied to different frequency bands based on local signal characteristics. Each band undergoes independent limiting only when needed, allowing the system to maintain high sound quality where peaks are absent while providing reliable peak limitation where needed, with overlapping bands ensuring no dead zones.
3Device complexity
If filter slope is reduced to simplify design, then device complexity is reduced, but dead zones are widened due to signal presence in multiple bands
Solution Approach 1:
The signal processing system is segmented into multiple independent band-limiting paths, each handling a specific frequency range. This segmentation allows the use of simpler filters with reduced slopes in each band while maintaining overall system reliability through the overlapping band structure that prevents dead zones and ensures comprehensive peak detection.
Data Source
AI summary
A multi-band limiter, a sound recording apparatus, and a program are provided having a multi-band limit function with a flat frequency characteristic while removing a dead zone of the multi-band limiter. A multi-band limiter is provided including an overlap filter unit (200) that divides an input sound signal into low-band, middle-band, and high-band components such that the components overlap each other between adjacent bands, limiters (202, 204, 208, 210, 214, 216) that apply a limit process to limit a level in each band, trimming filter units (206, 212, 218) that apply a trimming process to trim an overlapping signal component in each of the limit-processed components, and an adder (220) that combines and outputs the trimming-processed components.