Comb Filter Gain Control for Preemptive Howling Suppression
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Solution Overview
Problem
Conventional howling prevention devices only start attenuation after howling occurs, leading to discomforting sounds when howling increases abruptly.
Innovation Solution
A howling suppression device with a comb filter configuration where passbands and stopbands are alternately arranged on a frequency axis, and a gain control unit that temporally varies the output gain of each filter, allowing for pre-emptive suppression of howling without detecting the center frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional howling prevention devices detect center frequency and start attenuation only after howling occurs, then the device complexity is reduced and ease of operation is improved, but the response time is delayed causing discomforting sounds when howling increases abruptly
Solution Approach 1:
The patent applies preliminary action by performing attenuation in advance across all frequency bands using multiple comb filters with alternating passbands and stopbands. Instead of waiting to detect howling and then responding, the system proactively suppresses potential howling frequencies before they can cause abrupt increases, thereby reducing response time without requiring complex howling detection mechanisms.
Solution Approach 2:
The patent segments the frequency spectrum into multiple bands using several comb filters, each with alternating passbands and stopbands. This segmentation allows different frequency regions to be suppressed by different filters, enabling comprehensive coverage of potential howling frequencies while maintaining a relatively simple overall structure through the coordinated operation of these segmented filters.
2Object-affected harmful factors
If attenuation is applied only after howling detection, then the manufacturing precision and measurement precision requirements are reduced, but the harmful factors increase due to abrupt noise amplification
Solution Approach 1:
The patent changes the parameter of filter configuration by using multiple comb filters with alternating passband and stopband patterns. This parameter change ensures that regardless of the specific howling frequency, at least one filter will have its stopband covering that frequency, thereby reducing harmful discomforting sounds without requiring high precision in detecting or precisely targeting specific frequencies.
Solution Approach 2:
By applying attenuation across all frequency bands in advance through the comb filter configuration, the system performs preliminary suppression before howling can become problematic. This eliminates the need for precise howling frequency detection and reduces the harmful effects of abrupt noise amplification.
3Reliability
If multiple filters with alternating passbands and stopbands are used, then the coverage of frequency bands for attenuation is improved, but the device complexity and computational load increase
Solution Approach 1:
The patent merges multiple comb filters into a single howling suppression device, where each filter has alternating passbands and stopbands that complement the others. This combining of filters ensures comprehensive frequency coverage - when one filter's stopband covers a particular frequency, another filter's passband allows it through, and vice versa - thereby improving howling suppression reliability while keeping the overall device integrated and manageable.
Data Source
AI summary
A howling suppression device is provided, including: a plurality of filters in which a passband and a stopband are arranged alternately on a frequency axis; and a gain control unit which temporally varies an output gain of each of the plurality of filters and sums signals thus varied to output, wherein each of the plurality of filters has a passband in at least part of a stopband of another filter.