Noise Control Design Research Articles

Fuzzy active noise modeling and control

The design of active noise control (ANC) has been developed in the last two decades based on linear identification and control tools. However, acoustic processes present nonlinearities coming both from the characteristics of the actuator and from the nature of the process. Recent research has emphasized the importance of nonlinear model-based controllers, which increase the performance of several types of systems. From the different nonlinear techniques, fuzzy modeling is one of the most utilized. Direct and inverse multivariable fuzzy models can be identified directly from data using fuzzy clustering. Inverse models can then be applied directly as controllers, which can be included in an active noise control scheme. This paper proposes the use of fuzzy techniques in ANC. The performance of the proposed control schemes is compared to classical finite impulse response ANC in an experimental setup. The proposed fuzzy control scheme outperforms classical active noise controllers.

Balanced noise control design: A case study for co-generation power plant

Power generation plant generally requires noise mitigation treatment to achieve the specified noise regulations. In this paper, a case study of the noise control design for a cogeneration power plant was presented. Major noise sources included two GE gas combustion turbines, two generators, two heat recovery steam generators (HRSGs), one steam turbine and generator, one 12-cell cooling tower, and other accessory equipment. The acoustic modeling software Cadna/A was used to predict the noise contributions from sources. During the acoustic modeling, alternative noise mitigation measures underwent two specific investigations before they were chosen as a noise solution recommendation. The first was to determine the technical feasibility of attenuating the source equipment. The second was to perform a cost benefit analysis, necessary to find the most cost-effective solution. For example, several acoustic wall and roof assemblies were entered into the acoustic model and the acoustic performance of the ventilation system was varied until we were able to arrive at the most economical acoustic solution. This is the premise on which so called balanced design is based.

Animations and auralizations for noise control education

For students just starting out in acoustics, some basic concepts can be terribly difficult to understand. Ideas like plane, spherical, travelling, standing, and evanescent waves are easily described mathematically but can be difficult to understand physically. The use of animation to show the particle motion, velocity, and/or pressure fields associated with these wave motions helps to solidify the understanding of the basic physics. In noise control, students often have problems conceiving the effects of reverberation on acoustic signals and the perceived noise reduction from various acoustic treatments. These acoustic effects can be simulated through the use of auralization. Animations and auralizations developed using MATLAB, CATT Acoustics, and Cooledit for a senior level architectural engineering undergraduate classes in building noise control and acoustical room design will be presented.

FUZZY ACTIVE NOISE MODELING AND CONTROL OF ENCLOSURES

The design of active noise control has been developed in the last two decades based on linear identification and control tools. However, acoustic processes present nonlinearities coming both from the characteristics of the actuator and from the nature of the process. Recent research has emphasized the importance of nonlinear model-based controllers, which increase the performance of several types of systems. Direct and inverse multivariable fuzzy models can be identified directly from data using fuzzy clustering. Inverse models can then be applied directly as controllers, which can be included in an active noise control scheme. This paper proposes the use of fuzzy techniques in active noise control. The performance of the proposed control schemes is compared to classical FIR active noise control in an experimental setup. Model-based fuzzy controllers clearly outperform classical active noise controllers.

A method for measuring oblique incidence absorption coefficient of absorptive panels by stretched pulse technique

This paper proposes a pulse method for estimating the acoustical performance of absorptive panels to reduce noise reflections when applied to road structures such as parallel walls and ceilings of double deck viaducts. The acoustical performance is specified on the basis of oblique incidence absorption coefficient. It is determined from the ratio of the reflected sound energy from the surface of a test panel to that reflected from a rigid floor. Considering its high power, flat spectrum and stability, an optimum Aoshima's time-stretched pulse (OATSP) is applied as a short duration test signal. The measurements were made on glass fiber with thickness of 50 and 100 mm. The absorption coefficients at oblique angles from 0 to 45° show good agreement with theoretical values based on the empirical model of Delany and Bazley. Ceramics and other materials with non-flat surfaces were also tested. For application, the averaged oblique incidence absorption coefficient, which is averaged over incident angles and weighted on the representative spectrum of A-weighted road traffic noise, is proposed as a single number index for the evaluation of noise control design at highways.

Techniques to numerical simulation of sound field for acoustic design of noise control.

Techniques to numerical simulation of sound field for acoustic design of noise control.

The radiation efficiency grouping of free-space acoustic radiation modes

The use of a modal representation for the exterior acoustic field of a structure has received increasing attention in recent years. This modal approach generally seeks a set of orthogonal functions, representing independent surface velocity distributions, termed acoustic radiation modes, which diagonalize a radiation operator in the exterior domain of the structure. These orthogonal acoustic radiation modes may be found, among other methods, through an eigenvalue analysis of a radiation operator and possess a corresponding set of eigenvalues that are proportional to the radiation efficiencies of the acoustic radiation modes. In free space, the acoustic radiation modes of a sphere display a grouping characteristic in their radiation efficiencies, where each acoustic radiation mode’s radiation efficiency within a group has the same frequency dependency. This is a consequence of the fact that the acoustic radiation modes of a sphere are the spherical harmonics. Further, the acoustic radiation modes of an arbitrary three-dimensional structure exhibit the same frequency grouping as those for the sphere. The basis for the arbitrary structure’s grouping follows from the sphere’s grouping. The observation that the acoustic radiation modes of an arbitrary body are dominated by spherical harmonics provides insight on the behavior of such modes. These results have significance for various applications of acoustic radiation modes, including active noise control design, radiation modeling, etc.

Noise control for a vacuum excavator: A mutually beneficial solution

The Central Artery/Tunnel (CA/T) Project in Boston (the Big Dig) makes use of several vacuum excavator trucks (vac-trucks) in order to reduce accidental utility disruptions. Unfortunately, these vac-trucks generate very loud low-frequency noise due to their vacuum blowers which can cause nearby buildings to vibrate and has led to significant numbers of complaints from distressed abutters. In reaction, the CA/T Project undertook an intensive study to determine what mechanisms were producing the offensive low-frequency noise, and to devise mitigation measures to effectively control the low-frequency noise so as to allow the vac-trucks to continue working without causing noise complaints. Working cooperatively with the manufacturer (Guzzler) as well as with the contractor (Walton Systems), new and improved (Universal) silencers were retro-fitted to a test vac-truck and the improvements in low-frequency insertion loss were measured and documented. The new silencers effectively reduced the 40–125-Hz third-octave band range noise by 10–15 dB, thus approaching the noise control design goals selected to avoid causing nearby buildings to vibrate. This is a prime example of how cooperative efforts between vehicle manufacturers, construction contractors, and project officials can lead to mutually beneficial results.

Feedforward active noise controller design in ducts without independent noise source measurements

Feedforward control architectures have been widely used in active noise control systems to achieve broad-band noise reductions. The basic principle of the control algorithm requires that the feedforward signal, usually the noise source, be independent from the actuator's output. Failure to meet this requirement implies that the overall system contains an acoustic feedback loop and stability and robustness issues become important. The paper investigates this problem in a one-dimensional sound field (e.g., ducts) using a unidirectional sound wave as the feedforward signal. Controller design based on a distributed parameter model is studied. Several experiments are conducted to illustrate the design procedure as well as verify the effectiveness of broad-band noise reductions.

Modified FIR filter with phase compensation technique to feedforward active noise controller design

In this paper, a finite-impulse response (FIR) filter with phase compensation is proposed to design the digital controller for active noise cancellation in ducts. This method can overcome the influence of delay effects, which arise from the analog devices, and then help to improve the ability of noise reduction. Moreover, all the control algorithms are implemented in a fixed-point-type digital signal processor that produces an antinoise signal to cancel noise in the authors' experiments. Experiments are demonstrated in a polyvinyl chloride material circular duct. It is proved that, by using the FIR filter with phase compensation, the reduction of broadband noise is about 20 dB, and about 50 dB of narrowband noise. The system also provides the ability to cancel the noise with two harmonic components, like automobile noise.

OPTIMIZATION OF RESILIENT WHEELS FOR ROLLING NOISE CONTROL

Resilient wheels are currently used on light rail systems such as tramways to prevent squealing noise and to reduce impact noise. On the other hand, they are rarely found on main lines (passenger rolling stock and freight rolling stock). Although manufacturers often claim that resilient wheels are favourable for rolling noise control, no extensive theoretical investigation confirming this statement has been published to date. In this paper, it is shown how resilient wheels can be effectively optimised in order to reduce rolling noise emission, compared to a conventional monobloc wheel. A preliminary analysis of the physical phenomena accounting for rolling noise generation emphasizes the key design parameters affecting both wheel and radiation. These parameters are the radial dynamic stiffness and damping loss factor of the rubber layer. The tread mass is also relevant. The influence of these design parameters is then qualified by a parametric study performed with the TWINS software. An optimum radial dynamic stiffness of the resilient layer is found which depends on operating conditions. Reductions in overall rolling noise up to 3 dB(A) are calculated for the configurations investigated. However, poor selection of the design parameters can lead to a noise increase compared to a standard monobloc wheel. It is also shown that a proper design for rolling noise control will not affect wheel efficiency with regard to squeal noise.

Internal model-based LQG/H/sub ∞/ design of robust active noise controllers for an acoustic duct system

In this paper, a method of linear quadratic Gaussian (LQG) control with an H/sub /spl infin// performance bound is modified for a robust active noise control design of an acoustic duct system. This H/sub /spl infin//-constraint LQG (LQG/H/sub /spl infin//) method is incorporated with an internal model principle to design robust internal model-based active noise controllers to attenuate a narrow-band disturbance noise in a duct. Computer simulation results show an enhanced robust control performance of this internal model-based LQG/H/sub /spl infin// design with respect to the variation of the disturbance noise frequency and demonstrate a global control performance along the duct. Experimental results further demonstrate its global performance robustness capability and support the feasibility of the proposed internal model-based LQG/H/sub /spl infin// design method.

Observer-Based Time-Delay Control of a Four-Cylinder Electrohydraulic Servosystem. Controller Design.

Synchronizing control of a four-cylinder electrohydraulic servosystem is considered in this paper. For simplification of design, the system is separated into four subsystems, which track the same output signal of a reference model. The interaction forces among the four cylinders are considered as disturbance forces and the time delay control scheme is used here to estimate the disturbance force and and unknown system dynamics. For reducing the sensor noise controller design, the observed state variables are used in place of the numerical differentiated ones. The feasibility of the proposed control strategies is verified via experimental studies in this paper and the stability of this closed-loop system is proved in Part II.

Criteria for designing multiple-sprung masses for wideband noise control

In a companion paper the characterization of a multiple-sprung masses design for wideband noise control is presented. The characterization is largely conducted in terms of the point impedance of a set of sprung masses. The sprung masses in the set are collectively acting at a point. In that companion paper the dependencies of the joint impedance on the number of sprung masses, the modal overlap factors, the total mass, and the resonance frequency distribution are of particular interest. In the present paper this characterization of a set of sprung masses is utilized to define a number of design criteria that determine the potential viability of the set as a noise control device. In the final analysis, the device must be assessed in an in situ setting. In that setting the device is tested in terms of the overall gain. The determination of the overall gain requires, in addition to the joint impedance of the device, the impedance of the hosting master structure at the point of attachment. (The device is meant to control the noise in the master structure.) It is argued that although the overall gain is the final judge, the potential viability of a device may be a useful critique of the intended performance of the device. In this vein, a viability and a criterion of promise are defined to assist with the design processes of this noise control device. In assessing the viability and in satisfying the criterion of promise, the desired characteristics in a set of sprung masses can be judicially selected.

Robust internal model‐based LQG design for active noise control of a one‐dimensional acoustic duct system

A control design method is proposed to design controllers to achieve global sound pressure attenuation for noise of narrow-band frequencies in a one-dimensional acoustic duct system. This method combines a linear-quadratic-gaussian (LQG) theory with an internal model principle to design internal model-based active noise controllers so that noise of a specific (target) frequency in a duct can be reduced. The designed controller is, nevertheless, hyper sensitive to the perturbation of the target noise frequency. A reduced parameter sensitivity technique is further incorporated to improve robustness such that noise of narrow-band frequencies can be attenuated. Computer simulation shows the effectiveness of robustness improvement for the proposed design method. In addition, global sound pressure attenuation along the duct is achieved. Experimental results also demonstrate frequency robustness improvement and global sound pressure attenuation despite the fact that the dynamic effects of the actuator are not considered in the control design. Both simulation and experimental results support the feasibility of the proposed design method. Copyright © 1999 John Wiley & Sons, Ltd.

Robust internal model-based LQG design for active noise control of a one-dimensional acoustic duct system

A control design method is proposed to design controllers to achieve global sound pressure attenuation for noise of narrow-band frequencies in a one-dimensional acoustic duct system. This method combines a linear-quadratic-gaussian (LQG) theory with an internal model principle to design internal model-based active noise controllers so that noise of a specific (target) frequency in a duct can be reduced. The designed controller is, nevertheless, hyper sensitive to the perturbation of the target noise frequency. A reduced parameter sensitivity technique is further incorporated to improve robustness such that noise of narrow-band frequencies can be attenuated. Computer simulation shows the effectiveness of robustness improvement for the proposed design method. In addition, global sound pressure attenuation along the duct is achieved. Experimental results also demonstrate frequency robustness improvement and global sound pressure attenuation despite the fact that the dynamic effects of the actuator are not considered in the control design. Both simulation and experimental results support the feasibility of the proposed design method. Copyright © 1999 John Wiley & Sons, Ltd.

A senior engineering design elective with industry and community-sponsored noise control projects

One of the transitions that engineering students must make as they enter the work force is the progression from theoretical concepts, or book learning to applied or real world applications. At the University of Hartford, engineering design courses serve as culminating experiences devised to bridge this passage. One such course, Noise Control Design, challenges the student to apply the past three years’ conceptual base to a problem solving opportunity replete with actual scenarios encountered in industry or the community. Each year local firms and organizations approach the laboratory for assistance with a variety of sound or vibration problems. After an initial training period, students make use of the laboratory’s dual channel FFT and real time analyzers, anechoic chamber, sound intensity and modal analysis software, acoustic modeling software, vibration tables and transducers, portable sound level meters and digital tape recorders. Using a consultant-client model, students work collaboratively in teams of two defining the problem, developing a method of approach, making appropriate measurements, devising alternate solutions, and ultimately delivering a written and oral presentation at the end of the semester. The paper discusses specific projects and some experiences students had with their first industrial assignment.

Architectural Acoustics: Principles and Practice

Preface. About the Authors. Acknowledgments. Chapter 1 Introduction to Architectural Acoustics and Basic Principles (WILLIAM J. CAVANAUGH). 1.1 Introduction. 1.2 Basic Concepts. 1.3 Design Criteria. 1.4 Selected Standards in Building Acoustics. Further Reading. CASE STUDY: Fogg Art Museum Lecture Hall, Harvard University (1895 1973) 33. Chapter 2 Acoustical Materials and Methods (REIN PIRN AND JEFFREY L. FULLERTON). 2.1 Introduction. 2.2 Sound Attenuation. 2.3 Sound Absorption 44. 2.4 Common Building Materials. 2.5 Acoustical Materials. 2.6 Special Devices. 2.7 Performance Tables. References. Further Reading. Selected Web Resources. CASE STUDY: Duke University Chapel: A Lesson on Acoustical Materials. CASE STUDY: Boston Waterfront Development Under a Flight Path: Sound-Isolating Facade. Constructions to Reduce Intrusive Noise. CASE STUDY: Berklee College of Music: Sound-Isolating Constructions Between Percussion Studios. Chapter 3 Building Noise Control Applications (GREGORY C. TOCCI). 3.1 Introduction. 3.2 Acoustical Analysis. 3.3 Standards Organizations for the Building Industry. 3.4 Overview of Building Noise Control Design. 3.5 Heating, Ventilating, and Air-Conditioning System Noise Control. References. Further Reading. CASE STUDY: Mechanics Hall, Worcester, Massachusetts: Cooling Tower Sound Isolation. CASE STUDY: Field Impact Insulation Class Rating Measurements of Condominium Floor/Ceiling Construction. CASE STUDY: Noise Insulation Class Rating Measurements of a Hotel Guestroom Door. CASE STUDY: 500 Atlantic Avenue Hotel/Condominium Building Vibration Isolation. Chapter 4 Acoustical Design: Places for Listening (L. GERALD MARSHALL). 4.1 Introduction. 4.2 Sound Outdoors and Transition to Indoor Acoustics. 4.3 Concert Halls and Recital Halls. 4.4 Opera Houses, Theaters, General-Purpose Auditoriums, and Worship Spaces. 4.5 Other Places for Speech and Music Activities. References. Further Reading. CASE STUDY: Holy Cross Church, Dewitt, New York. CASE STUDY: Mitchell Hall at the University of Delaware, Newark, Delaware Historic Renovation. CASE STUDY: The New Hitchcock Presbyterian Church, Scarsdale, New York. CASE STUDY: Katherine M. Elfers Concert Hall at the Esther Eastman Music Center, Hotchkiss School, Lakeville, Connecticut. CASE STUDY: Ozawa Hall, Tanglewood Music Center, Lenox, Massachusetts. CASE STUDY: Hollywood Bowl Stage Redesign, Los Angeles, California. Chapter 5 Sound Systems (MATTHEW J. MOORE). 5.1 Introduction. 5.2 Loudspeaker Systems. 5.3 Equipment. 5.4 Examples of Sound Reinforcement and Reproduction Systems. 5.5 Special Sound System Installations. Further Reading. CASE STUDY: Hanover Theatre, Worcester, Massachusetts. CASE STUDY: Agganis Arena and Boston University Fitness and Recreation Center, Boston, Massachusetts. CASE STUDY: Ave Maria University Oratory, Ave Maria, Florida. CASE STUDY: University of Connecticut Student Union, Storrs, Connecticut. CASE STUDY: Rhode Island Senate Chamber, Providence, Rhode Island. CASE STUDY: Rhodes Arts Center, Northfield Mount Hermon School, Gill, Massachusetts. CASE STUDY: Tufts University Granoff Music Center, Medford, Massachusetts. CASE STUDY: Jay Pritzker Music Pavilion, Chicago, Illinois. Chapter 6 Recent Innovations in Acoustical Design and Research (GARY W. SIEBEIN AND BERTRAM Y. KINZEY, JR.). 6.1 Introduction. 6.2 Understanding and Measuring Room Acoustic Qualities. 6.3 Acoustical Modeling and Aural Simulation. 6.4 Other Directions in Architectural Acoustics Research. 6.5 Conclusions. References. Further Reading. CASE STUDY: Recent Halls for the Performing Arts and Acoustical Model Studies. CASE STUDY: Segerstrom Hall, Orange County Performing Arts Center, Orange County, California. CASE STUDY: McDermott Concert Hall, Morton H. Meyerson Symphony Center, Dallas, Texas. CASE STUDY: Evangeline Atwood Concert Hall, Alaska Center for the Performing Arts, Anchorage, Alaska. CASE STUDY: Bass Performance Hall, Fort Worth, Texas. CASE STUDY: The Esplanade Concert Hall, Theaters on the Bay, Singapore. CASE STUDY: Tokyo Opera City Concert Hall, Takemitsu Memorial, Tokyo, Japan. CASE STUDY: Walt Disney Concert Hall, Los Angeles, California. CASE STUDY: Computer Model Tests. Chapter 7 Sustainable Design and Acoustics (ETHAN SALTER, LEED AP). 7.1 Introduction. 7.2 Organizations Leading the Green Building Movement. 7.3 Acoustical Challenges of Green Design. 7.4 Postoccupancy Evaluations of Green Buildings. 7.5 Examples of Building Types Designed for Green Ratings. 7.6 Conclusion. References. Further Reading. Internet and Web Resources. CASE STUDY: Global Ecology Research Center at Stanford University, Palo Alto, California. CASE STUDY: Dougherty Valley High School, San Ramon, California. CASE STUDY: Charles Salter Associates Tenant Improvement Office, San Francisco, California. Appendixes. Appendix A: Conversion Factors, Abbreviations, and Unit Symbols. Appendix B: Acoustical Societies Throughout the World. Appendix C: Selection of an Acoustical Consultant. Appendix D: Self-Study Guide for Using this Book. Glossary.

CONTROL OF AIRCRAFT INTERIOR BROADBAND NOISE WITH FOAM-PVDF SMART SKIN

A foam-PVDF smart skin design for aircraft interior noise control is discussed. The smart skin is designed to reduce sound by the action of the passive absorption of an acoustic foam (which is effective at higher frequencies) and the active input of a PVDF element driven by an oscillating electrical input (which is effective at lower frequencies). For performance testing, the foam-PVDF smart skin is mounted in the cockpit of a Cessna Citation III fuselage. The fuselage crown panels are excited with a speaker located on the outside of the cockpit and driven by a band-limited random excitation. A MIMO feedforward Filtered-x LMS controller is implemented to minimize the error sensor signals provided by microphones in the close proximity of the smart skin elements. Three different reference signals are implemented for the feedforward controller and are compared in terms of the interior noise attenuation achieved. The voltage sent to the disturbance speaker provides an optimal reference signal which is not realistic in practice. Therefore, the use of either a structural sensor (accelerometer directly mounted on the fuselage) or an acoustic sensor (microphone located close to the fuselage) is investigated to supply a practical reference signal. The potential of the smart foam-PVDF skin for reducing interior noise is demonstrated.

Modeling of an Acoustic Path and PID Feedback Control Systems Design for Active Noise Control.

Focus is placed on the feedback (FB) active noise control (ANC) in order to reduce costs by simplifying ANC systems, because FB-ANC does not need reference signals. The purpose of this paper is to obtain a low order accurate model of an acoustic plant for FB-ANC and design a simple controller based on this model. The plant in this case is from the input to a single secondary loudspeaker to the output of a single error sensor (microphone). First, as a modeling method, physical modeling is applied. Second, Smith predictor is modified for FB-ANC to eliminate the influence of time delay in an acoustic field, and a PID controller is designed. Finally, effectiveness of the modeling methods and the proposed FB-ANC are demonstrated through numerical experiments using actual data.