Audio System Frequency Filter for Targeted Sound Reduction
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Solution Overview
Problem
Existing audio systems that output different sound sources to multiple users struggle to effectively reduce sound output to other users, particularly in the frequency range where human ear sensitivity is highest (around 2 to 4 kHz), and fail to widen the region where high-frequency noise can be reduced.
Innovation Solution
The audio system employs multiple sound source devices, speakers, and filters, where each filter adjusts the frequency transfer characteristic to reduce sound output at frequencies where the gain from the speaker to other users is higher than to the intended user, and increases sound at frequencies where the gain to other users is lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If directivity control is used to reduce sound output to other users, then sound reduction effect is improved in high frequency range (5 kHz or more), but sound reduction effect is insufficient in the frequency range where human ear sensitivity is highest (around 2 to 4 kHz)
Solution Approach 1:
The patent applies parameter changes by adjusting the frequency transfer characteristic of the filter dynamically based on the frequency band. Different filter characteristics are applied to different frequency ranges: for frequencies where the gain from speaker to other users is higher than to the intended user, the filter reduces sound; for frequencies where the gain to other users is lower, the filter increases sound. This frequency-dependent parameter adjustment resolves the contradiction by optimizing sound reduction across all frequency ranges including the critical 2-4 kHz range.
2Object-affected harmful factors
If active noise control is used to reduce noise from speakers, then noise reduction is achieved, but the region where high frequency noise can be reduced is limited and sufficient effect is difficult to obtain
Solution Approach 1:
The patent applies local quality by implementing frequency-dependent filter characteristics that are specifically optimized for different frequency ranges. The filter is designed to provide enhanced noise reduction in the critical 2-4 kHz frequency range where human ear sensitivity is highest, while also addressing high frequency noise. This localized optimization of filter characteristics for specific frequency bands expands the effective region for noise reduction and achieves more sufficient overall effect.
3Ease of manufacture
If filter with fixed frequency transfer characteristic is used, then implementation is simple, but sound reduction effect is insufficient across different frequency ranges
Solution Approach 1:
The patent applies dynamics by making the frequency transfer characteristic of the filter variable rather than fixed. The filter characteristic changes dynamically based on the frequency band being processed. The control unit adjusts the filter's frequency transfer characteristic according to the frequency of the audio signal, enabling optimal sound reduction performance across different frequency ranges while maintaining practical implementability through automated control.
Data Source
AI summary
A voice output from an i-th audio source apparatus is adjusted with a frequency transfer function Wii(f) set in an i-th noise reduction filter and is output from an i-th speaker. In the noise reduction filter, a frequency transfer function Wii(f) is set in which the sound is made smaller at frequencies where the gain of the frequency transfer function Cim(f) from the SPKi to a user tends to be relatively larger than the gain of the frequency transfer function Cii(f) from the SPKi to the user, and the sound is increased at frequencies where the gain of Cim(f) tends to be relatively smaller than the gain of Cii(f), where m is an integer excluding i from 1 to n.