Enclosed space active noise control in process industry

Active noise control (ANC) is a method used to reduce acoustic noise by introducing an opposing acoustic wave, known as anti-noise, to counteract the primary target noise. ANC systems find various applications, from mitigating sound in processing industries to cancelling noise in headphones. A conventional ANC system comprises three main parts: (i) the reference microphone, (ii) digital signal processing (DSP) with a load-speaker as an anti-noise generator part, and (iii) the error microphone. However, conventional ANC systems suffer from two technical shortcomings, leading to instability and limiting their noise cancellation capabilities: (i) anti-noise reflection from the speaker (Anti-noise source) to the reference microphone, and (ii) the delay associated with DSP, resulting in a mismatch between noise detection and anti-noise generation. Both shortcomings result in non-compliance between noise and anti-noise, leading to instability. The primary aim of this project is to resolve these technical shortcomings. Specifically, it is proposed to resolve the noise reflection issue by replacing the noise detection reference microphone with an array of non-acoustical sensors, while compensating for DSP delay using a library of prediction algorithms based on multi-variable linear regression, neural network, and deep learning (based on machine learning algorithms). This approach would allow predicting noise before generation by analyzing ambient conditions and operational characteristics of the source (e.g., fan). Achieving the project’s goals requires a deep understanding of the science underpinning the proposed solutions and thorough evaluation of their effectiveness. Therefore, the project focuses on gaining fundamental insights into the proposed solutions and laying the foundations for testing their effectiveness under realistic conditions. This should make a significant and original contribution to both the field of knowledge and its application. The chosen research configuration involves a cylindrical shell fitted with one fan, representing typical noise sources in various industries. Cylindrical shells are common structures used in pipes, ducts (ventilation systems), aircraft fuselages, rockets, submarine pressure hulls, electric motors, and generators. The proposed program of study comprises two complementary and overlapping components: (i) theoretical/modelling studies, and (ii) experimental studies. Significant progress has been made on the experimental component of the project, including the design, construction, and commissioning of the experimental setup, establishment of methods and techniques, and successful completion of the preliminary experimental campaign. The outcome of the projects is coming in following: 1. Identification of Technical Shortcomings: The project identified two key technical shortcomings in conventional ANC systems: anti-noise reflection and DSP delay, which limit their noise cancellation capabilities and lead to instability. 2. Innovative Solutions Proposed: To address these shortcomings, the project proposes innovative solutions such as replacing the reference microphone with non-acoustical sensors and compensating for DSP delay using prediction algorithms based on multi-variable linear regression, neural networks, and deep learning. 3. Improved Noise Prediction and Attenuation: By implementing the proposed solutions, the project aims to achieve improved noise prediction and attenuation, leading to enhanced performance and stability in ANC systems. 4. Fundamental Insights Gained: The project focuses on gaining fundamental insights into the underlying science of the proposed solutions, laying the groundwork for testing their effectiveness under realistic conditions. 5. Practical Application in Various Industries: The research configuration, involving a cylindrical shell fitted with a fan as a representative noise source, ensures the practical relevance of the project's findings in various industries where cylindrical structures are common. 6. Progress in Theoretical and Experimental Studies: Significant progress has been made in both theoretical and experimental aspects of the project, including the design, construction, and commissioning of the experimental setup, as well as the successful completion of a preliminary experimental campaign.