Phase Control Signal Generation for Multi-Band Audio Time Alignment
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Solution Overview
Problem
Existing phase control signal generation devices for time alignment in vehicle interiors face increased processing load and frequency characteristic dips due to the need for multiple delay circuits and multipliers, especially as the number of frequency bands increases.
Innovation Solution
A phase control signal generation device that generates a phase control signal for each frequency band by adjusting propagation delay times, using a setting change mechanism, difference obtaining, updating, and smoothing processes, with optional weighting coefficients and filter coefficients tailored to each band to reduce processing load and dips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an FIR filter with a steep cutoff frequency is used to suppress dips, then frequency characteristic linearity is improved, but the processing load increases due to multiple delay circuits and multipliers
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a bank of bandpass filters, allowing independent phase control for each band. This segmentation enables targeted dip suppression without requiring a complex high-order FIR filter across the entire frequency spectrum, thereby reducing the overall processing load while maintaining frequency characteristic linearity.
Solution Approach 2:
Different phase control strategies are applied to different frequency bands based on their specific characteristics. By analyzing the phase characteristics of each band separately and applying appropriate phase adjustments only where needed, the system achieves effective dip suppression with minimal processing requirements rather than uniformly complex processing across all frequencies.
2Measurement precision
If the number of frequency bands is increased to improve time alignment precision, then the accuracy of delay time adjustment is improved, but the processing load further increases due to more delay circuits and multipliers
Solution Approach 1:
The frequency spectrum is divided into multiple bands using bandpass filters, enabling independent phase control for each band. This segmentation allows precise delay time adjustment tailored to each frequency band's characteristics without requiring a single complex high-order filter, thereby achieving high precision with reduced processing load.
Solution Approach 2:
The system dynamically adjusts phase shift parameters for each frequency band based on measured phase characteristics and dip locations. By changing phase parameters adaptively rather than using fixed complex filtering, the system achieves precise time alignment across frequency bands with computationally efficient operations.
3Stability of the object's composition
If a high order FIR filter is used to achieve linear phase characteristic, then phase constancy across frequency bands is improved, but the number of delay circuits and multipliers increases
Solution Approach 1:
Instead of using a single high-order FIR filter to achieve phase constancy across the entire frequency spectrum, the system segments the frequency range into multiple bands and applies separate phase control to each band. This approach achieves effective phase constancy within each band using simpler, lower-order processing, thereby reducing the total number of delay circuits and multipliers required.
Solution Approach 2:
Phase constancy is achieved locally within each frequency band rather than uniformly across all frequencies. By applying phase correction tailored to each band's specific characteristics, the system maintains stable phase relationships where needed while avoiding the excessive complexity of a global high-order filter.
Data Source
AI summary
A phase control signal generation device generating a phase control signal for each of frequency bands for an audio signal converted into a frequency domain, the phase control signal generation device comprising: a setting change means that is able to change setting of a propagation delay time for each of predetermined frequency bands; a difference obtaining means that obtains a difference between propagation delay times before and after setting change; an updating means that updates a phase control amount of the frequency band for which the propagation delay time is changed, based on the obtained difference; and a phase control signal generating means that generates a phase control signal of each frequency band by performing a smoothing process for the phase control amount in a frequency domain using the updated phase control amount.