Digital Audio Filter Phase Tuning to Reduce Pre-Ringing
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Solution Overview
Problem
Modern digital audio filters become complex in attempting to compensate for room acoustics, leading to pre-ringing in audio outputs, which can be disturbing for listeners.
Innovation Solution
A method to configure digital audio filters by determining and modifying poles outside the unit circle, incorporating phase modification components based on frequency-dependent phase responses to reduce pre-ringing effectively while maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex signal processing is used to compensate for room acoustics, then compensation effectiveness is improved, but pre-ringing is introduced which disturbs the listener
Solution Approach 1:
The patent segments the transfer function into multiple components (minimum phase component and non-minimum phase component) based on pole locations relative to the unit circle. By separating poles inside and outside the unit circle, the compensation function is divided into parts that cause pre-ringing and parts that do not, allowing selective handling of each component to reduce pre-ringing while maintaining compensation effectiveness.
Solution Approach 2:
The patent modifies parameters of the transfer function by adjusting pole positions and adding phase modification components. Specifically, poles outside the unit circle are moved or compensated through phase modification to reduce pre-ringing effects while preserving the magnitude response and compensation characteristics of the original transfer function.
2Object-affected harmful factors
If poles outside the unit circle are modified to reduce pre-ringing, then pre-ringing is reduced, but sound quality may be affected
Solution Approach 1:
The patent applies local quality modification by introducing subset-specific phase modification components that affect only specific frequency ranges associated with poles outside the unit circle. This localized approach reduces pre-ringing in problematic frequency regions while leaving other frequency regions unchanged, thereby preserving overall sound quality.
Solution Approach 2:
The patent converts the harmful effect of poles outside the unit circle (which cause pre-ringing) into a benefit by using their phase information to create phase modification components. These components are designed to cancel or reduce the pre-ringing effects while maintaining the useful compensation characteristics, thus transforming a harmful element into a tool for improvement.
Data Source
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AI summary
A method for configuring a digital audio filter (8)includes: determining the poles of an initial transfer function of the digital audio filter in the z-domain, with the initial transfer function comprising a target function component and a compensation function component; selecting at least one subset of the poles (40, 42, 44, 46) of the transfer function that are outside the unit circle; for each of the at least one subset of the poles (40, 42, 44, 46) of the transfer function that are outside the unit circle: determining a subset-specific partial transfer function, determining a subset-specific, frequency-dependent phase response of the subset-specific partial transfer function, and determining a subset-specific phase modification component, with the subset-specific phase modification component being dependent on the subset-specific, frequency-dependent phase response of the subset-specific partial transfer function; and providing a modified transfer function, comprising the target function component, the compensation function component, and at least one subset-specific phase modification component.