Adaptive Audio Filter Bandwidth for Stable S/N and Natural Audibility
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Solution Overview
Problem
Miniaturization of microphones in digital cameras leads to reduced sensitivity and S/N ratio, causing user discomfort due to unpredictable changes in the passband characteristic of audio processing filters.
Innovation Solution
A sound processing apparatus with a band-limiting filter whose bandwidth is controlled by a controller to adjust based on the input sound signal level, expanding bandwidth faster when increasing and narrowing slower when decreasing, to maintain a stable S/N ratio and reduce audibility discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the passing band characteristic of the filter is changed according to input signal level, then the S/N ratio is improved, but the user feels discomfort in audibility
Solution Approach 1:
The patent applies dynamics by making the filter's passing band characteristic changeable according to input signal level. The controller dynamically adjusts the filter characteristics based on detected signal levels, allowing the system to adapt between different operating conditions (low signal vs. high signal) to maintain both good S/N ratio and natural audibility.
Solution Approach 2:
The patent changes physical parameters of the filter system by adjusting the passing band characteristic and gain according to input signal level. The controller modifies filter parameters (passing band width, center frequency) and gain settings based on detected signal levels, enabling optimal performance across different signal conditions while maintaining audibility comfort.
2Volume of moving object
If the microphone is miniaturized, then the digital camera is miniaturized, but the sensitivity and S/N ratio of the microphone deteriorate
Solution Approach 1:
The patent replaces mechanical improvement (larger microphone) with electronic/digital signal processing solutions. Instead of increasing microphone size to improve sensitivity, the system uses electronic filtering and gain control to enhance signal quality, allowing miniaturization to proceed without sacrificing audio performance.
Solution Approach 2:
The patent changes the electrical parameters of the signal processing system by adjusting filter characteristics and gain based on input signal level. This electronic parameter adjustment compensates for the reduced sensitivity of miniaturized microphones, maintaining audio quality while enabling camera miniaturization.
Data Source
AI summary
A sound processing apparatus includes a sound input unit configured to input a sound signal, a signal processor having a band-limiting filter for limiting a passing band of the sound signal, and being configured to apply a predetermined signal processing on a sound signal output from the band-limiting filter, and a controller configured to control a band width of the passing band of the band-limiting filter. The controller changes the band width of the passing band according to a level of the sound signal, and makes a speed at the time of expanding the band width faster than a speed at the time of narrowing the band width.