Sudden Sound Noise Reduction Using Reference Signal Subtraction
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Solution Overview
Problem
Conventional noise reduction methods for voice communication in mobile devices struggle to effectively remove persistent and periodic sudden sounds without interfering with voice signals, often resulting in a 'strangeness' or degradation of voice quality.
Innovation Solution
A noise reduction apparatus comprising multiple microphones, a sudden sound detecting unit, and an adder that stores and uses reference signals to remove sudden sounds from voice signals, ensuring clear voice transmission by aligning phases and using correlation values to isolate and eliminate the noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an adaptive filter is constantly operated to reduce persistent and periodic sudden sound, then the sudden sound can be reduced, but the circuit size increases due to increased number of taps
Solution Approach 1:
The patent extracts only the necessary components for sudden sound reduction by using a simple subtractor circuit instead of a full adaptive filter. The system separates the sudden sound detection and subtraction function from the general noise reduction function, implementing only the essential operation needed to remove periodic sudden sounds while maintaining voice quality.
Solution Approach 2:
The patent employs a simple subtractor circuit with minimal taps instead of a complex adaptive filter requiring many taps. This disposable-like approach uses a lightweight, simple structure that can be quickly applied and removed without the burden of maintaining a complex adaptive filter system, achieving sudden sound reduction with minimal circuit resources.
2Object-affected harmful factors
If signal blocking and interpolation is used to reduce sudden sound, then the sudden sound can be reduced in pure noise sections, but voice quality deteriorates when sudden sound is superimposed on voice
Solution Approach 1:
The patent dynamically adjusts the noise reduction operation based on the detected sudden sound characteristics. The system continuously monitors the input signal and applies subtraction only when periodic sudden sound is detected, adapting the processing in real-time to preserve voice quality while removing noise. This dynamic approach prevents the static blocking method from degrading voice in voice-containing sections.
Solution Approach 2:
The patent changes the processing parameters based on the signal characteristics. Instead of uniformly blocking and interpolating all sudden sound sections, the system varies the subtraction amount and timing parameters according to the detected sudden sound properties, preserving voice components while removing noise. This parameter adaptation prevents voice quality deterioration.
3Object-affected harmful factors
If frequency-based sudden sound reduction is applied (removing frequency components >= 4 kHz), then high frequency sudden sound can be reduced, but voice components are also removed and voice quality deteriorates
Solution Approach 1:
The patent segments the noise reduction function from general high-frequency filtering. Instead of removing all frequency components above 4 kHz, the system specifically targets and segments only the periodic sudden sound components for removal. This segmentation allows preservation of voice frequency components while eliminating noise, preventing voice quality deterioration.
Solution Approach 2:
The patent replaces the mechanical frequency-based filtering approach with a signal-based subtraction method. Instead of mechanically removing all high-frequency components, the system uses correlation detection to identify and subtract only the periodic sudden sound waveform, preserving voice components that would otherwise be removed by frequency-based filtering.
Data Source
AI summary
Provided is a noise reduction apparatus, a noise reduction method, and a program for generating voice that is easy to hear while reducing sudden sound. The noise reduction apparatus includes a first microphone configured to collect mainly voice and output the voice as a first signal, a second microphone configured to collect mainly sound other than the voice and output the sound as a second signal, a sudden sound detecting unit configured to detect sudden sound in the first signal and the second signal, a sudden sound information storage unit configured to store the sudden sound as one or a plurality of reference signals, and an adder configured to remove the sudden sound from the first signal based on the reference signal stored in the sudden sound information storage unit.