Multi-Channel Equalizer Tuning for Standing Wave Correction
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Solution Overview
Problem
Conventional audio systems with automatic sound field correction struggle to accurately correct peaks in narrow bands caused by standing waves without distorting frequency characteristics or disrupting phase relationships among channels.
Innovation Solution
An audio system featuring two cascaded characteristic-variable equalizers, a sound field characteristics detecting part, and a characteristics adjusting part that selectively generates test signals and adjusts equalizing characteristics to correct low-frequency peaks and then entire audible frequency bands, maintaining phase coherence among channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a BPF or GEQ with low selectivity factor (Q-factor) is used in the measuring or correcting step, then phase differences among channels are minimized, but frequency resolution is not high enough to accurately correct peaks in narrow bands such as standing waves
Solution Approach 1:
The equalization process is divided into two independent stages: first, a BPF with high Q-factor is used to detect and correct peaks in narrow bands (standing waves); second, a GEQ with low Q-factor is used for overall sound field correction. This segmentation allows each stage to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent applies preliminary action by first correcting the peaks in narrow bands using high Q-factor BPF before performing the overall sound field correction with GEQ. This preliminary correction of standing wave peaks prevents distortion during the subsequent full-band equalization process.
2Measurement precision
If a parametric equalizer with high selectivity factor (Q-factor) is used, then peaks in narrow bands can be followed and corrected appropriately, but phase relationship among channels becomes disarranged making ideal sound field reproduction difficult
Solution Approach 1:
The equalization process is divided into two independent stages: first, a BPF with high Q-factor is used to detect and correct peaks in narrow bands (standing waves); second, a GEQ with low Q-factor is used for overall sound field correction. This segmentation allows each stage to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent applies preliminary action by first correcting the peaks in narrow bands using high Q-factor BPF before performing the overall sound field correction with GEQ. This preliminary correction of standing wave peaks prevents distortion during the subsequent full-band equalization process.
3Manufacturing precision
If equalizing characteristics are adjusted for each channel independently, then frequency and phase characteristics can be optimized for each channel, but it becomes extremely difficult for users to manually adjust to achieve optimum sound space
Solution Approach 1:
The system performs self-service by automatically measuring sound pressure levels in the sound field and independently adjusting equalizing characteristics for each channel without requiring manual user intervention. The measurement and adjustment processes are automated, eliminating the need for users to manually optimize channel characteristics.
Data Source
AI summary
Disclosed is an audio system including a group of loudspeakers that form a sound field by delivering into a single space sound signals passed through respective ones of a plurality of sound signal channels. This audio system is comprised of two characteristic-variable equalizers that are cascaded to each other to constitute a part of the sound signal channels; a sound field characteristics detecting part for supplying test signals through the sound signal channels and detecting sound pressure in the sound field and thereby obtaining a sound pressure signal; and a characteristics adjusting part for adjusting, based on the sound pressure signal, equalizing characteristics of the characteristic-variable equalizers individually and with respect to each of the sound signal channels. The sound field characteristics detecting part selectively generates test signals of different bands. The characteristics adjusting part adjusts equalizing characteristics of either one of the two characteristic-variable equalizers according to the band of the test signal.