Adaptive Noise Reduction Filter for Acoustic Path Compensation
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Solution Overview
Problem
Active noise control (ANC) systems face challenges due to the complexity of implementing a constantly updated control filter and the need to periodically update acoustic characteristics affected by environmental changes such as temperature and humidity.
Innovation Solution
A noise reduction system that includes a microphone, a loudspeaker, and processing circuitry functioning as a mode switching unit, a control signal generator, a path characteristic measuring unit, and a control filter generating unit. This system uses a noise feature signal and path characteristic measurements to generate a control filter, allowing for effective noise reduction even with changing acoustic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed control filter is used to simplify system implementation, then ease of operation is improved, but noise reduction effectiveness deteriorates for frequencies above 100 Hz
Solution Approach 1:
The control filter is designed with frequency-dependent characteristics that adapt to different frequency ranges. The filter dynamically adjusts its response based on the discrete frequency components of the noise, allowing effective noise reduction across a broader frequency spectrum while maintaining system simplicity through a fixed filter structure.
Solution Approach 2:
The invention changes the parameters of the control filter to optimize performance for discrete frequency noise. By carefully selecting filter parameters such as cutoff frequencies and gain values, the system achieves effective noise reduction for frequencies above 100 Hz without requiring constant updates or complex adaptive algorithms.
2Area of stationary object
If the distance between loudspeaker and microphone is increased to improve spatial coverage, then area of stationary object is improved, but time delay increases causing upper limit of controllable frequency to lower
Solution Approach 1:
The system performs preliminary measurement of the acoustic path characteristics between the loudspeaker and microphone. By characterizing the path in advance and incorporating this information into the control filter design, the system compensates for the time delay introduced by larger distances, thereby maintaining effective noise reduction at higher frequencies.
3Reliability
If acoustic characteristics are periodically updated to maintain noise control effectiveness, then noise reduction effectiveness is improved, but device complexity increases
Solution Approach 1:
The noise control system is segmented into distinct functional components: a fixed control filter for real-time noise reduction and a separate path characteristic measurement unit for periodic updates. This segmentation allows the main noise control function to operate with simple, fixed parameters while periodic updates are performed using a dedicated measurement subsystem, thereby maintaining effectiveness without significantly increasing overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves efficient noise reduction for discrete frequency components, including frequencies above 100 Hz, and maintains effectiveness even when the distance between the microphone and loudspeaker is large, thus overcoming limitations of conventional fixed control filters.
Implementation Method 1
a microphone 120, a loudspeaker 130, and processing circuitry 111. The microphone 120 is configured to convert a sound wave into an electric signal.
Implementation Method 2
The loudspeaker 130 is configured to convert an electric signal into a sound wave.
Implementation Method 3
a control filter 213 that generates a control signal that causes the loudspeaker 130 to output a control sound for reducing noise, based on a detection signal obtained by detecting a sound in a space including noise and a control sound with the microphone 120
Data Source
AI summary
According to one embodiment, a noise reduction system includes a microphone, a loudspeaker, and processing circuitry. The processing circuitry switches an operating mode between a control mode and a path characteristic measurement mode, includes a control filter that generates a control signal that causes the loudspeaker to output a control sound for reducing noise, based on a detection signal obtained by detecting a first sound including the noise with the microphone, measures a path characteristic including an acoustic characteristic between the loudspeaker and the microphone, and generates the control filter by using a measurement result of the path characteristic and a noise feature signal including a feature of the noise.