Performance analysis and design of FxLMS algorithm in broadband ANC system with online secondary-path modeling

The filtered-x LMS (FxLMS) algorithm has been widely used in active noise control (ANC) systems, where the secondary path is usually estimated online by injecting auxiliary noises. In such an ANC system, the ANC controller and the secondary-path estimator are coupled with each other, which make it difficult to analyze the performance of the entire system. Therefore, a comprehensive performance analysis of broadband ANC systems is not available currently to our best knowledge. In this paper, the convergence behavior of the FxLMS algorithm in broadband ANC systems with online secondary-path modeling is studied. Difference equations which describe the mean and mean square convergence behaviors of the adaptive algorithms are derived. Using these difference equations, the stability of the system is analyzed. Finally, the coupled equations at the steady state are solved to obtain the steady-state excess mean square errors (EMSEs) for the ANC controller and the secondary-path estimator. Computer simulations are conducted to verify the agreement between the simulated and theoretically predicted results. Moreover, using the proposed theoretical analysis, a systematic and simple design procedure for ANC systems is proposed. The usefulness of the theoretical results and design procedure is demonstrated by means of a design example. © 2012 IEEE.published_or_final_versio

Review of active noise control techniques with emphasis on sound quality enhancement

The traditional active noise control design aims to attenuate the energy of residual noise, which is indiscriminative in the frequency domain. However, it is necessary to retain residual noise with a specified spectrum to satisfy the requirements of human perception in some applications. In this paper, the evolution of active noise control and sound quality are briefly discussed. This paper emphasizes on the advancement of active noise control method in the past decades in terms of enhancing the sound quality

Active Noise Control and Sound Quality of Propeller-driven Aircraft

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 이수갑.터보프롭 중형항공기 내부 소음은 톤 성분이 강한 저주파 성분으로 구성된 것으로 알려져 있는데, 점진적으로 높아지는 수요와 중요성에도 불구하고 여전히 높은 소음도로 인해 승객의 만족감이 높지 못한 것으로 알려져 있다. 또한 연구 방법에 대해 한 가지 연구 방법론 (수치해석적 연구 또는 실험적 연구)에 한정된 연구만이 진행되고 있어, 항공기 내부 소음을 개선하기 위한 근본적인 연구 또는 해결책이 부재하고 있는 상황이다. 따라서 본 연구에서는 차세대 운송 수단으로 주목받고 있는 터보프롭 중형항공기의 객실 내부의 음질을 개선하기 위한 기초 연구를 진행하며, 이를 위해 수치해석적 연구 방법과 실험적 연구 방법을 연계한 다학제간 연구를 진행한다. 전반부(2~3장)에서는 객실 내부 소음에 대한 공력 소음의 주도적 영향성을 확인하고자수치해석적 연구를 진행한다. 이를 위해 먼저 2장에서는 공력 및 소음해석기법에 대한 신뢰성 검증을 진행한다. 검증을 위해 NASA에서 개발한 터보프롭용 프로펠러 SR-3를 사용하며, 공력 해석 기법 검증을 수행한 후 소음 해석 기법 검증을 진행한다. 공력 해석 기법 검증을 위해 등와선도 후류 모델과 곡선와류요소를 적용한 자유 후류 와류 격자 기법을 사용하며, 최종적으로 계산된 공력 성능과 (이전 연구에서) 실험적으로 측정된 공력 계수값들 간의 비교를 통해 공력 해석 기법 검증을 수행한다. 소음 해석 기법 검증을 위해서는 음향상사법을 사용한다. 소음도를 산출하기 위해서 공력 성능 계산 결과를 활용하며, 최종적으로 산출된 소음도 값과 (이전 연구에서) 실험적으로 측정된 소음데이터 간의 비교를 통해 소음 해석 기법 검증을 수행한다. 다음으로 3장에서는 객실 내부의 소음 예측을 통한 공력 소음의 내부 소음에 대한 영향성을 확인하기 위해 2장에서 검증한 해석기법은 물론 동체 내부 소음 예측 모델을 사용한다. 이를 통해 BPF 성분이 포함된 주파수 영역에 대해 1/3 옥타브 밴드 스펙트럼 데이터를 계산하며, 최종적으로 실제 운항 시 측정된 소음데이터와의 비교 및 분석을 수행한다. 후반부(4~6장)에서는 객실 내부 소음에 대해 능동소음제어기법을 적용함으로써 얻을 수 있는 불쾌감 저감 효과를 확인하기 위한 실험적 연구를 진행한다. 먼저 4장에서는 객실 내부 소음에 대한 인지적 특성을 심리음향학적 인자의 인지 한계점을 측정함으로써 확인한다. 실험 결과를 통해 객실 내부 소음의 주파수 대역에 대한 민감도를 분석하며, 능동소음제어기법을 적용할 때 고려할 수 있는 여러 경우에 대한 분석을 진행한다. 다음으로 5장에서는 능동소음제어기법을 적용하여 실질적으로 얻을 수 있는 소음 저감 효과를 확인한다. 이를 위해 소프트웨어는 물론이고 하드웨어를 직접 디자인하는 과정을 수행하며, 적절한 위치에 제어장치를 배치하기 위해 실험 공간에 대한 모드 분석을 수행한다. 최종적으로, 시스템의 복잡도에 따른 능동소음제어효과를 확인하며, 4장에서 도출된 실험 결과와 연계하여 결과 분석을 진행한다. 마지막으로 6장에서는 능동소음제어기법을 적용함으로써 얻을 수 있는 불쾌감 저감 효과를 심리음향학적 인자와 불쾌감 간의 상관관계를 분석함으로써 확인한다. 청감 실험을 진행할 때, 실험자가 의도하지 않은 요소들에 의한 영향성을 최대한 배제하고 피험자 개개인의 특성을 실험 결과에 반영하기 위해 master scale을 사용하며, 심리음향학적 인자와 불쾌감 간의 상관관계를 정량화하기 위해 회귀 분석을 진행한다. 최종적으로 능동소음제어기법의 적용 효과를 심리음향학적 관점에서 분석하며, 6장까지 진행된 연구 결과를 통해 능동소음제어기법의 적용 방식과 향후 발전 방향에 대해 살펴본다.1. 서론 1 1.1 연구의 필요성 1 1.2 연구 목적 및 내용 8 2. 터보프롭 항공기 프로펠러의 공력 및 소음 해석 기법 검증 11 2.1 공력 검증 11 2.1.1 해석 및 검증 절차 11 2.1.2 결과 분석 17 2.2 소음 검증 21 2.2.1 결과 분석 21 3. 항공기 내부 소음에 대한 공력 소음의 영향성 분석 25 3.1 해석 절차 26 3.1.1 공력 특성 해석 26 3.1.2 소음 특성 해석 28 3.2 해석 결과 분석 35 4. 항공기 내부 소음에 대한 심리음향학적 인자의 인지 한계 평가 37 4.1 청감 실험 37 4.1.1 자극음 구성 37 4.1.2 실험 환경 45 4.1.3 실험 절차 47 4.2 실험 결과 분석 53 4.2.1 Loudness 인지 한계 분석 53 4.2.2 Sharpness 인지 한계 분석 59 4.2.3 분석 결과에 관한 논의 61 5. 능동소음제어기법 적용을 통한 내부소음 저감 효과 분석 63 5.1 능동소음제어 실험 63 5.1.1 능동소음제어기법 63 5.1.2 알고리즘 분석 68 5.1.3 시스템 내 소프트웨어 구성 방법 84 5.1.4 실험 환경 86 5.1.5 실험 절차 96 5.2 실험 결과 분석 100 6. 청감실험을 통한 불쾌감 저감 효과 분석 104 6.1 청감 실험 104 6.1.1 자극음 구성 104 6.1.2 실험 환경 107 6.1.3 실험 절차 107 6.2 실험 결과 분석 109 6.2.1 PNE를 통한 Loudness 및 Sharpness 영향 분석 109 6.2.2 중형항공기 내부 소음에 대한 불쾌감 개선 효과 분석 114 6.2.3 능동소음제어 적용 및 향후 연구 방향에 대한 고찰 115 7. 결론 119 7.1 연구 요약 119 7.1.1 공력 및 소음 해석 119 7.1.2 능동소음제어 적용 및 효과 분석 120 7.2 연구 의의 및 한계점 122 7.2.1 연구 의의 122 7.2.2 연구의 한계점 및 후속 연구를 위한 제언 123 참고문헌 125 부록 135 Abstract 149Docto

Distributed and Collaborative Processing of Audio Signals: Algorithms, Tools and Applications

Tesis por compendio[ES] Esta tesis se enmarca en el campo de las Tecnologías de la Información y las Comunicaciones (TIC), especialmente en el área del procesado digital de la señal. En la actualidad, y debido al auge del Internet de los cosas (IoT), existe un creciente interés por las redes de sensores inalámbricos (WSN), es decir, redes compuestas de diferentes tipos de dispositivos específicamente distribuidos en una determinada zona para realizar diferentes tareas de procesado de señal. Estos dispositivos o nodos suelen estar equipados con transductores electroacústicos así como con potentes y eficientes procesadores con capacidad de comunicación. En el caso particular de las redes de sensores acústicos (ASN), los nodos se dedican a resolver diferentes tareas de procesado de señales acústicas. El desarrollo de potentes sistemas de procesado centralizado han permitido aumentar el número de canales de audio, ampliar el área de control o implementar algoritmos más complejos. En la mayoría de los casos, una topología de ASN distribuida puede ser deseable debido a varios factores tales como el número limitado de canales utilizados por los dispositivos de adquisición y reproducción de audio, la conveniencia de un sistema escalable o las altas exigencias computacionales de los sistemas centralizados. Todos estos aspectos pueden llevar a la utilización de nuevas técnicas de procesado distribuido de señales con el fin de aplicarlas en ASNs. Para ello, una de las principales aportaciones de esta tesis es el desarrollo de algoritmos de filtrado adaptativo para sistemas de audio multicanal en redes distribuidas. Es importante tener en cuenta que, para aplicaciones de control del campo sonoro (SFC), como el control activo de ruido (ANC) o la ecualización activa de ruido (ANE), los nodos acústicos deben estar equipados con actuadores con el fin de controlar y modificar el campo sonoro. Sin embargo, la mayoría de las propuestas de redes distribuidas adaptativas utilizadas para resolver problemas de control del campo sonoro no tienen en cuenta que los nodos pueden interferir o modificar el comportamiento del resto. Por lo tanto, otra contribución destacable de esta tesis se centra en el análisis de cómo el sistema acústico afecta el comportamiento de los nodos dentro de una ASN. En los casos en que el entorno acústico afecta negativamente a la estabilidad del sistema, se han propuesto varias estrategias distribuidas para resolver el problema de interferencia acústica con el objetivo de estabilizar los sistemas de ANC. En el diseño de los algoritmos distribuidos también se han tenido en cuenta aspectos de implementación práctica. Además, con el objetivo de crear perfiles de ecualización diferentes en zonas de escucha independientes en presencia de ruidos multitonales, se han presentado varios algoritmos distribuidos de ANE en banda estrecha y banda ancha sobre una ASN con una comunicación colaborativa y compuesta por nodos acústicos. Se presentan además resultados experimentales para validar el uso de los algoritmos distribuidos propuestos en el trabajo para aplicaciones prácticas. Para ello, se ha diseñado un software de simulación acústica que permite analizar el rendimiento de los algoritmos desarrollados en la tesis. Finalmente, se ha realizado una implementación práctica que permite ejecutar aplicaciones multicanal de SFC. Para ello, se ha desarrollado un prototipo en tiempo real que controla las aplicaciones de ANC y ANE utilizando nodos acústicos colaborativos. El prototipo consiste en dos sistemas de control de audio personalizado (PAC) compuestos por un asiento de coche y un nodo acústico, el cual está equipado con dos altavoces, dos micrófonos y un procesador con capacidad de comunicación entre los dos nodos. De esta manera, es posible crear dos zonas independientes de control de ruido que mejoran el confort acústico del usuario sin necesidad de utilizar auriculares.[CA] Aquesta tesi s'emmarca en el camp de les Tecnologies de la Informació i les Comunicacions (TIC), especialment en l'àrea del processament digital del senyal. En l'actualitat, i a causa de l'auge de la Internet dels coses (IoT), existeix un creixent interés per les xarxes de sensors sense fils (WSN), és a dir, xarxes compostes de diferents tipus de dispositius específicament distribuïts en una determinada zona per a fer diferents tasques de processament de senyal. Aquests dispositius o nodes solen estar equipats amb transductors electroacústics així com amb potents i eficients processadors amb capacitat de comunicació. En el cas particular de les xarxes de sensors acústics (ASN), els nodes es dediquen a resoldre diferents tasques de processament de senyals acústics. El desenvolupament de potents sistemes de processament centralitzat han permés augmentar el nombre de canals d'àudio, ampliar l'àrea de control o implementar algorismes més complexos. En la majoria dels casos, una topologia de ASN distribuïda pot ser desitjable a causa de diversos factors tals com el nombre limitat de canals utilitzats pels dispositius d'adquisició i reproducció d'àudio, la conveniència d'un sistema escalable o les altes exigències computacionals dels sistemes centralitzats. Tots aquests aspectes poden portar a la utilització de noves tècniques de processament distribuït de senyals amb la finalitat d'aplicar-les en ASNs. Per a això, una de les principals aportacions d'aquesta tesi és el desenvolupament d'algorismes de filtrat adaptatiu per a sistemes d'àudio multicanal en xarxes distribuïdes. És important tindre en compte que, per a aplicacions de control del camp sonor (SFC), com el control actiu de soroll (ANC) o l'equalització activa de soroll (ANE), els nodes acústics han d'estar equipats amb actuadors amb la finalitat de controlar i modificar el camp sonor. No obstant això, la majoria de les propostes de xarxes distribuïdes adaptatives utilitzades per a resoldre problemes de control del camp sonor no tenen en compte que els nodes poden modificar el comportament de la resta. Per tant, una altra contribució destacable d'aquesta tesi se centra en l'anàlisi de com el sistema acústic afecta el comportament dels nodes dins d'una ASN. En els casos en què l'entorn acústic afecta negativament a l'estabilitat del sistema, s'han proposat diverses estratègies distribuïdes per a resoldre el problema d'interferència acústica amb l'objectiu d'estabilitzar els sistemes de ANC. En el disseny dels algorismes distribuïts també s'han tingut en compte aspectes d'implementació pràctica. A més, amb l'objectiu de crear perfils d'equalització diferents en zones d'escolta independents en presència de sorolls multitonales, s'han presentat diversos algorismes distribuïts de ANE en banda estreta i banda ampla sobre una ASN amb una comunicació col·laborativa i composta per nodes acústics. Es presenten a més resultats experimentals per a validar l'ús dels algorismes distribuïts proposats en el treball per a aplicacions pràctiques. Per a això, s'ha dissenyat un programari de simulació acústica que permet analitzar el rendiment dels algorismes desenvolupats en la tesi. Finalment, s'ha realitzat una implementació pràctica que permet executar aplicacions multicanal de SFC. Per a això, s'ha desenvolupat un prototip en temps real que controla les aplicacions de ANC i ANE utilitzant nodes acústics col·laboratius. El prototip consisteix en dos sistemes de control d'àudio personalitzat (PAC) compostos per un seient de cotxe i un node acústic, el qual està equipat amb dos altaveus, dos micròfons i un processador amb capacitat de comunicació entre els dos nodes. D'aquesta manera, és possible crear dues zones independents de control de soroll que milloren el confort acústic de l'usuari sense necessitat d'utilitzar auriculars.[EN] This thesis fits into the field of Information and Communications Technology (ICT), especially in the area of digital signal processing. Nowadays and due to the rise of the Internet of Things (IoT), there is a growing interest in wireless sensor networks (WSN), that is, networks composed of different types of devices specifically distributed in some area to perform different signal processsing tasks. These devices, also referred to as nodes, are usually equipped with electroacoustic transducers as well as powerful and efficient processors with communication capability. In the particular case of acoustic sensor networks (ASN), nodes are dedicated to solving different acoustic signal processing tasks. These audio signal processing applications have been undergone a major development in recent years due in part to the advances made in computer hardware and software. The development of powerful centralized processing systems has allowed the number of audio channels to be increased, the control area to be extended or more complex algorithmms to be implemented. In most cases, a distributed ASN topology can be desirable due to several factors such as the limited number of channels used by the sound acquisition and reproduction devices, the convenience of a scalable system or the high computational demands of a centralized fashion. All these aspects may lead to the use of novel distributed signal processing techniques with the aim to be applied over ASNs. To this end, one of the main contributions of this dissertation is the development of adaptive filtering algorithms for multichannel sound systems over distributed networks. Note that, for sound field control (SFC) applications, such as active noise control (ANC) or active noise equalization (ANE), acoustic nodes must be not only equipped with sensors but also with actuators in order to control and modify the sound field. However, most of the adaptive distributed networks approaches used to solve soundfield control problems do not take into account that the nodes may interfere or modify the behaviour of the rest. Therefore, other important contribution of this thesis is focused on analyzing how the acoustic system affects the behavior of the nodes within an ASN. In cases where the acoustic environment adversely affects the system stability, several distributed strategies have been proposed for solving the acoustic interference problem with the aim to stabilize ANC control systems. These strategies are based on both collaborative and non-collaborative approaches. Implementation aspects such as hardware constraints, sensor locations, convergenge rate or computational and communication burden, have been also considered on the design of the distributed algorithms. Moreover and with the aim to create independent-zone equalization profiles in the presence of multi-tonal noises, distributed narrowband and broadband ANE algorithms over an ASN with a collaborative learning and composed of acoustic nodes have been presented. Experimental results are presented to validate the use of the distributed algorithms proposed in the work for practical applications. For this purpose, an acoustic simulation software has been specifically designed to analyze the performance of the developed algorithms. Finally, the performance of the proposed distributed algorithms for multichannel SFC applications has been evaluated by means of a real practical implementation. To this end, a real-time prototype that controls both ANC and ANE applications by using collaborative acoustic nodes has been developed. The prototype consists of two personal audio control (PAC) systems composed of a car seat and an acoustic node, which is equipped with two loudspeakers, two microphones and a processor with communications capability. In this way, it is possible to create two independent noise control zones improving the acoustic comfort of the user without the use of headphones.Antoñanzas Manuel, C. (2019). Distributed and Collaborative Processing of Audio Signals: Algorithms, Tools and Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/130209TESISCompendi

Real-time Forecasting and Control for Oscillating Wave Energy Devices

Ocean wave energy represents a signicant resource of renewable energy and can make an important contribution to the development of a more sustainable solution in support of the contemporary society, which is becoming more and more energy intensive. A perspective is given on the benefits that wave energy can introduce, in terms of variability of the power supply, when combined with oshore wind. Despite its potential, however, the technology for the generation of electricity from ocean waves is not mature yet. In order to raise the economic performance of Wave energy converters (WECs), still far from being competitive, a large scope exists for the improvement of their capacity factor through more intelligent control systems. Most control solutions proposed in the literature, for the enhancement of the power absorption of WECs, are not implemented in practise because they require future knowledge of the wave elevation or wave excitation force. The non-causality of the unconstrained optimal conditions, termed complex-conjugate control, for the maximum wave energy absorption of WECs consisting of oscillating systems, is analysed. A link between fundamental properties of the radiation of the floating body and the prediction horizon required for an effective implementation of complex-conjugate control is identified. An extensive investigation of the problem of wave elevation and wave excitation force forecasting is then presented. The prediction is treated as a purely stochastic problem, where future values of the wave elevation or wave excitation force are estimated from past measurements at the device location only. The correlation of ocean waves, in fact, allows the achievement of accurate predictions for 1 or 2 wave periods into the future, with linear Autoregressive (AR) models. A relationship between predictability of the excitation force and excitation properties of the floating body is also identified. Finally, a controller for an oscillating wave energy device is developed. Based on the assumption that the excitation force is a narrow-banded harmonic process, the controller is effectively tuned through a single parameter of immediate physical meaning, for performance and motion constraint handling. The non-causality is removed by the parametrisation, the only input of the controller being an on-line estimate of the frequency and amplitude of the excitation force. Simulations in (synthetic and real) irregular waves demonstrate that the solution allows the achievement of levels of power capture that are very close to non-causal complex-conjugate control, in the unconstrained case, and Model predictive control (MPC), in the constrained case. In addition, the hierarchical structure of the proposed controller allows the treatment of the issue of robustness to model uncertainties in quite a straightforward and effective way