Multiband DRC Audio Level Circuit for Crossover Gain Control
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Solution Overview
Problem
Existing level adjusting circuits in audio systems suffer from poor sound quality due to excessive gain compression across frequency bands, leading to inaudible voices and deteriorated sound quality, particularly at crossover frequencies, and excessive gain fluctuations causing disharmony in hearing sense.
Innovation Solution
A level adjusting circuit with multiple filters and dynamic range compression (DRC) circuits, along with band pass filters and gain correcting units, is implemented to adjust gains based on signal levels across bands, preventing excessive signal levels at crossover frequencies and reducing gain fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single DRC circuit is used for the entire audio signal, then the circuit complexity is low, but the sound quality deteriorates due to excessive gain compression across all frequency bands
Solution Approach 1:
The audio signal is divided into multiple frequency bands using band-pass filters, with each band processed by a separate DRC circuit. This segmentation allows independent gain control for each frequency band, preventing excessive compression of non-excessive bands while effectively controlling excessive levels in specific bands, thereby maintaining sound quality.
Solution Approach 2:
Each DRC circuit is configured with different threshold levels and compression ratios tailored to its specific frequency band characteristics. This local quality approach ensures that gain compression is applied appropriately to each band based on its own signal characteristics, rather than applying uniform compression across all frequencies.
2Manufacturing precision
If multiple DRC circuits are used for each frequency band, then the sound quality is improved by allowing band-specific DRC processing, but the device complexity increases
Solution Approach 1:
The outputs of multiple band-specific DRC circuits are merged through an adder to reconstruct the full audio signal. This combining approach allows sophisticated band-specific processing while maintaining a relatively simple overall structure, avoiding the need for complex multi-stage processing or additional correction circuits.
3Device complexity
If DRC processing is applied to all bands uniformly, then the circuit structure is simple, but gain fluctuations cause disharmony in hearing sense
Solution Approach 1:
By segmenting the audio signal into multiple frequency bands and applying DRC processing independently to each band, the system can control gain fluctuations specifically in bands where they occur, rather than applying uniform compression that affects all bands. This maintains natural sound characteristics and prevents disharmony in the hearing sense.
Data Source
AI summary
Level adjusting circuit for adjusting level of input audio signal, includes: N filters, N being integer of two or more; N dynamic range compression (DRC) circuits corresponding to N filters; adder; (N−1) band pass filters corresponding to crossover frequencies of N filters; and (N−1) gain correcting units corresponding to (N−1) band pass filters. Each filter receives and passes input audio signal through its respective set band. ith (1≦i≦N) DRC circuit amplifies signal from ith filter and adjust its gain to prevent level of its output signal from exceeding threshold level. Adder adds each of output signals of DRC circuits. jth (1≦j≦N−1) band pass filter passes band including crossover frequencies of jth and (j+1)th filters from output signal of adder. jth gain correcting unit adjusts at least one of gains of jth and (j+1)th DRC circuits based on level of output signal of jth band pass filter.