Noise Control Device Adaptive Acoustic Identification
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Solution Overview
Problem
Existing noise control systems face inefficiencies when dealing with changes in acoustic properties within a noise reduction region, as they require a preliminary identification operation that halts noise control and can cause discomfort due to the need for high sound pressure signals, and are prone to feedback issues from microphone and speaker proximity.
Innovation Solution
A noise control apparatus that includes reference sensors, sound emitting sources, error sensors, and adaptive signal processing to continuously identify and adjust to changes in the acoustic environment during noise control, allowing for real-time noise reduction without halting the process and minimizing feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a preliminary identification operation is performed before noise control, then the acoustic property can be identified, but the noise control process must be halted and high sound pressure signals cause discomfort
Solution Approach 1:
The patent performs identification operations preliminarily before noise control begins, capturing acoustic properties in advance. This allows the noise control to proceed continuously without halting, as the pre-identified acoustic properties are used for real-time noise reduction calculations
Solution Approach 2:
The patent uses periodic identification signals with specific frequencies and time intervals to identify acoustic properties without requiring high sound pressure levels that would cause discomfort. The periodic nature allows continuous noise control while periodically updating acoustic property data
2Volume of moving object
If microphones and speakers are placed close together for compact design, then device size is reduced, but feedback occurs between the microphone and speaker
Solution Approach 1:
The patent extracts and separately processes the feedback signal from the microphone input by identifying and removing components that originate from the speaker output. This allows the compact design to be maintained while the harmful feedback is isolated and eliminated through signal processing
Solution Approach 2:
The patent intentionally uses feedback principles by monitoring the microphone signal for speaker-generated components and actively canceling them through adaptive filtering. The system models the feedback path and generates anti-phase signals to neutralize the harmful feedback while maintaining compact hardware placement
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
Enables effective noise control even with environmental changes, reducing the need for preliminary identification operations and minimizing disruptions, while maintaining efficient noise reduction and reducing human perception of noise signals.
Implementation Method 1
ANC cancels noise in a noise reduction region (region that is a target for noise control; this definition applies to the following description) by emitting a noise reduction signal with the same strength but with a phase that is the inverse of that of a noise signal and causing the noise signal and the noise reduction signal to interfere with each other.
Data Source
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AI summary
To provide a noise reduction control apparatus capable of exercising noise reduction control in response to a change of an acoustic property in a noise reduction region. The apparatus includes one or more reference sensors for detecting a noise signal produced by a noise source, one or more sound emitting sources for emitting a noise reduction signal and an identification signal, an error sensor for detecting the noise signal, noise reduction signal, and identification signal, identification means for carrying out an identification operation of identifying an acoustic property in a noise reduction region based on the identification signal detected by the error sensor, and noise reduction signal generating means for generating the noise reduction signal by adaptive signal processing based on the detection by at least one of the reference sensors and the detection by the error sensor. The identification means carries out the identification operation while at least one of the sound emitting sources emits the noise reduction signal.