Audio Distortion Limiting via Paired Bandpass and Equalizing Filters
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Solution Overview
Problem
Audio output devices, such as loudspeakers, often experience distortion due to signal level and frequency-dependent issues, which existing technologies fail to address effectively, leading to suboptimal sound quality and increased processor demand.
Innovation Solution
A system utilizing a paired combination of bandpass and attenuating equalizing filters to identify and limit specific frequencies causing distortion, employing a bank of these pairs in series to adjust signal levels and reduce distortion, while maintaining processing in the time domain to avoid latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a frequency-dependent signal limiter using bandpass and attenuating equalizing filters is implemented to reduce distortion, then sound quality is improved, but device complexity increases
Solution Approach 1:
The audio signal is divided into multiple frequency bands using bandpass filters, each targeting specific frequency ranges known to cause distortion. This segmentation allows independent processing of problematic frequencies while preserving other frequency components, reducing overall distortion without requiring a complete system redesign
Solution Approach 2:
Different filtering operations are applied to different frequency bands based on their specific distortion characteristics. The attenuating equalizing filters are configured with different parameters for each frequency band, providing localized correction where needed rather than uniform processing across the entire audio spectrum
2Manufacturing precision
If multiple filter pairs are used in series to limit selected frequencies, then distortion is reduced, but processing time increases
Solution Approach 1:
The system pre-identifies frequency bands known to cause distortion in the audio output device and pre-configures the bandpass and attenuating equalizing filters for these specific frequencies. This preliminary configuration allows the filters to be applied in series without requiring real-time analysis, reducing processing time while maintaining effective distortion limitation
3Manufacturing precision
If signal levels are limited to avoid distortion, then sound quality is improved, but loss of information increases
Solution Approach 1:
The attenuating equalizing filters are applied selectively to specific frequency bands where distortion occurs, rather than uniformly attenuating the entire audio signal. This localized approach limits distortion in problematic frequencies while preserving the full dynamic range and information content of other frequency components
Solution Approach 2:
The filtering operation dynamically adjusts the attenuation parameters based on the measured signal level in each frequency band. When the signal exceeds the threshold level, the filters apply attenuation proportional to the excess amount, allowing the system to maintain high signal levels when safe and reduce levels only when necessary to avoid distortion
Data Source
AI summary
A frequency-dependent signal limiter using a paired combination of a bandpass filter (or “selection filter”) and an attenuating equalizing filter (or “cutting filter”) limit the amount of distortion generated by an audio output device in an acoustic rendering system. A bank of one or more of these pairs in series can be used to limit selected frequencies identified as primary causes of distortion in the audio output device to specified levels that avoid distortion.