Mechanical System Noise Research Articles

Noise intensity of a Markov chain.

Stochastic transitions between discrete microscopic states play an important role in many physical and biological systems. Often these transitions lead to fluctuations on a macroscopic scale. A classic example from neuroscience is the stochastic opening and closing of ion channels and the resulting fluctuations in membrane current. When the microscopic transitions are fast, the macroscopic fluctuations are nearly uncorrelated and can be fully characterized by their mean and noise intensity. We show how, for an arbitrary Markov chain, the noise intensity can be determined from an algebraic equation, based on the transition rate matrix; these results are in agreement with earlier results from the theory of zero-frequency noise in quantum mechanical and classical systems. We demonstrate the validity of the theory using an analytically tractable two-state Markovian dichotomous noise, an eight-state model for a calcium channel subunit (De Young-Keizer model), and Markov models of the voltage-gated sodium and potassium channels as they appear in a stochastic version of the Hodgkin-Huxley model.

Architectural acoustics short course presentation material

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects called “Architectural Acoustics,” An architect can earn one continuing education unit (CEU) by attending this short course, if presented by a qualified member of TCAA. The course covers topics in sound isolation, mechanical system noise control, finish treatments, and implementation of quality acoustical spaces. This paper will cover the course material in order to prepare and qualify potential presenters. In order to qualify as an authorized presenter for this AIA/CES short course, attendance at this special session and membership in TCAA are required.

1D convolutional neural network-based adaptive algorithm structure with system fault diagnosis and signal feature extraction for noise and vibration enhancement in mechanical systems

A variety of adaptive algorithms are utilized to control the vibration and noise for mechanical systems in the industrial field, since their characteristics usually changes due to unwanted disturbance and malfunctioning. A reference signal plays an important role in signal tracking through adaptive algorithms, and well-characterized information about the tracked signal should be employed. However, it is typically difficult to determine the signal feature because operating systems generate complex signals. Moreover, when the system state changes due to malfunctions or disturbances, signal feature can also be changed, affecting the performance of adaptive algorithms. This study proposes a novel strategy based on a 1D convolutional neural network (1D CNN) for improving the signal tracking performance. 1D CNN has the ability to deal with consecutive data that is directly measured by an accelerometer attached to mechanical systems, as well as to extract the signal feature through convolutional layers. The development of proposed algorithm can be explained with following three parts: 1) Data measurement opportunities are limited, particularly because fault data is more difficult to measure than normal state data. Therefore, when performing learning, there is a problem of a lack of training data. Thus, a data generator is proposed that is based on a generative adversarial network (GAN) and a variational auto encoder (VAE). 2) In order to extract the frequency and phase and consider the system state to automatically define the reference signal and increase tracking robustness, the methodology of signal feature extraction and diagnosis is proposed based on a 1D CNN. In order to validate the tracking performance, a neural network-based signal tracking algorithm is applied to the developed structure. Furthermore, bearing and linear motion (LM) guide data from experiments is employed to confirm the versatility of the developed algorithm. Through above process, it is demonstrated that based on defined reference signal through the extracted feature, the signal tracking performance can be enhanced.

Mechanical noise control case studies

A few case studies of mechanical system noise are presented. These address before/after background sound levels associated with room and/or mechanical system modifications, comparison of predicted mechanical system noise to measured values, our approach to noise control recommendations, and lessons learned. Interesting cases include a college theater renovation, office noise control involving implementation of a fan array and a VFD, and a challenging hunt for the source of an exterior pharmaceutical campus noise source generating complaints in a nearby neighborhood.

Architectural acoustics short course presentation material

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects called “Architectural Acoustics.” An architect can earn one continuing education unit (CEU) by attending this short course, if presented by a qualified member of TCAA. The course covers topics in sound isolation, mechanical system noise control, finish treatments, and implementation of quality acoustical spaces. This paper will cover the course material to prepare and qualify potential presenters. In order to qualify as an authorized presenter for this AIA/CES short course, attendance at this special session and membership in TCAA are required.

The Seattle Space Needle renovation: Acoustical design considerations and challenges at 600 ft above ground level

Built for the 1962 Seattle World’s Fair as a symbol of humanity’s Space Age aspirations, the Seattle Space Needle is one of the most recognizable landmarks in North America. In September 2017, construction commenced for “The Century Project,” a renovation project designed to reveal the tower’s internal structure while expanding and improving its views. This presentation will discuss the acoustical design criteria for the two levels of all-glass, circular observation levels, as well as design approaches for reverberant sound control, sound isolation for key areas, and mechanical system noise control for a proposed fine dining restaurant at the “Loupe” level. The presentation will also include post-construction measurements and several photos during construction and at project completion.

Analysis of the Dynamic Stiffness, Hysteresis Resonances and Complex Responses for Nonlinear Spring Systems in Power-Form Order

Power-form nonlinear contact force models are widely adopted in relatively moving parts of macro (e.g., rolling bearings considering Hertzian contact restoring force between rolling elements and bearing raceways) or micro (e.g., the micro cantilever probe system of atomic force microscopy) scale mechanical systems, and contact resonance could cause serious problems of wear, contact fatigue, vibration, and noise, which has attracted widespread attention. In the present paper, the softening/hardening stiffness characteristics of continuous and one-sided contact power-form nonlinear spring models are addressed, respectively, by the analysis of the monotone features of resonant frequency-response skeleton lines. Herein, the period-n solution branch and its stability characteristics are obtained by the harmonic balance and alternating frequency/time domain (HB–AFT) method and Floquet theory. Compared with previous studies, this paper will furtherly clarify the influences of externally normal load, the power form exponent term, and excitation amplitude on the softening/hardening stiffness characteristics of general power-form spring systems. In addition, for a power-form system with a one-sided contact, the phenomena of primary and super/sub-harmonic hysteretic resonances inducing period-doubling, folding bifurcation, the coexistence of multiple solutions are demonstrated. Besides, it gives the evolution mechanism of two types of intermittency chaos in a one-sided contact system. The overall results may have certain basic theoretical significance and engineering values for the control of vibration and noise in contact mechanical systems.

Reduction of Noise and Vibration in Mechanical Systems by the Dynamic Vibration Absorber using Magneto-Rheological Elastomer

Reduction of Noise and Vibration in Mechanical Systems by the Dynamic Vibration Absorber using Magneto-Rheological Elastomer

ASSESSING SOUND-MUFFLING CHARACTERISTICS OF FLY-ASH NANO-PARTICLE REINFORCED EPOXY RESIN COMPOSITES

Effective reduction and control of noise have continued to attract attention globally due to the adverse effects noise poses to human health, effective knowledge dissemination and desirable environmental tranquility. The use of natural and synthetic reinforced composites in noise pollution control is an emerging area of research. In this study, coal fly-ash in nanoparticles varied at 5 – 25 wt. % was employed as reinforcement in the fabrication of epoxy resin composites. The composites were characterised both for noise reduction capability and mechanical properties necessary for a damage-free handling during installation. Results showed that at 5 – 15 wt. % fly-ash nanoparticles addition, the composites demonstrated the following mechanical properties in terms of flexural strength, 43.7 MPa; impact energy, 4.8 J and hardness, 25.4 HV. Samples of the composites at 15 wt. % exhibited the highest noise reduction coefficient (NRC) of 0.8072. Contributions to these levels of performances appeared to have stemmed from the nature (connected or isolated) and dispersion of pores induced in the material during mixing and subsequent curing. The composites are adjudged suitable for deployment as noise muffling material in facilities that are usually subjected to low mechanical system noise sources.

Development of the Broad Band Frequency-tunable Dynamic Absorber Using Magneto-rheological Elastomer for the Noise and Vibration Reduction in Mechanical Systems

Development of the Broad Band Frequency-tunable Dynamic Absorber Using Magneto-rheological Elastomer for the Noise and Vibration Reduction in Mechanical Systems

Repetitive Control Process for Periodic Disturbance Cancellation Using Data Classification With a Fuzzy Regression Approach

The utilization of a repetitive controller to cancel periodic disturbance or noise in mechanical systems has become increasingly important for industrial applications. In this study, a repetitive control process was developed using a data classification method, with a fuzzy regression approach and basis function, to reduce tracking errors in feedback controllers. First, a system model using the basis function is illustrated to compute the matched basis functions and their associated coefficients. A real case example of improving the focus of an electron beam subjected to periodic fluctuations has been described for verification and error analysis. Next, model algorithms containing pure and fuzzy regression are introduced into a repetitive feedback control system to reduce tracking errors caused by a periodic disturbance. System output data are categorized using fuzzy inference rules as similar data forming a single group are typically more reliable than the entire output data. The fuzzy theorem approach adopts a Gaussian membership function for system output variables owing to uncertainties that arise from modeling errors, environmental noise, etc. It is determined that the repetitive control process based on data classification with a fuzzy regression approach is more effective than using a pure regression approach. Increasing the number of data classifications initially improves accuracy; however, this decreases when the number of data classifications continues to increase. The optimal root-mean-square output tracking error convergence value was determined as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14.09</sup> when the system output data was classified into four categories, demonstrating the satisfactory reduction of a periodic disturbance. Similar results were obtained using the pure regression algorithm, where the lowest averaged verification error was 2.71% for the linear basis function model, with data classified into four categories, and this corresponded to an average prediction error of 3.86%.

Three music facility makeovers in Arizona

Considerable prior experience at higher education music campuses in Flagstaff, Chandler and Mesa, Arizona led to our engagement in substantial repurposing and renovation of their rehearsal, recording, practice, and performance facilities. Specific challenges due to existing mechanical system noise, poor sound isolation, and overall room-acoustics issues are discussed as well as their solutions and measured data upon completion.Considerable prior experience at higher education music campuses in Flagstaff, Chandler and Mesa, Arizona led to our engagement in substantial repurposing and renovation of their rehearsal, recording, practice, and performance facilities. Specific challenges due to existing mechanical system noise, poor sound isolation, and overall room-acoustics issues are discussed as well as their solutions and measured data upon completion.

Introduction to the special issue on noise and vibration in complex mechanical and electrical systems and its control

Introduction to the special issue on noise and vibration in complex mechanical and electrical systems and its control

Vibration and noise control using shunted piezoelectric transducers: A review

Abstract Among various strategies developed for the attenuation of noise and vibration in mechanical structures, piezoelectric shunt damping, which consists in connecting piezoelectric transducers integrated in a structure to electric or electronic circuits, is a promising alternative for use in small- and mid-scale structural components. Despite the fact that the shunt damping technology has been investigated for quite a long time, it is recognized that its application to real-world structures still requires developments aiming at improving its effectiveness and range of application under unavoidable practical constraints. As a result, research on improved solutions related to piezoelectric shunt damping is still very active. Due to the very nature of the piezoelectric shunt damping, it becomes clear that further improvements must consider both mechanical and electrical/electronic aspects. Based on the current state-of-the-art, this paper provides a systematic literature review of different piezoelectric shunt damping strategies developed for the attenuation of vibration and noise in mechanical systems, including an assessment of the basic principles underlying the electromechanical behavior, as well as design procedures and numerical modeling of piezoelectric shunt damping devices applied to elastic vibrating systems. Emphasis is placed on the various types of shunt circuits, including the traditional passive resonant circuits, multimode resonant circuits, adaptive tuning circuits, switching circuits, and negative capacitance. The strategies for location and shape of the piezoelectric transducers is also discussed. A variety of applications recently reported in the scientific literature and in patents are presented. An assessment is made about more significant recent achievements and technological issues to be faced in further developments.

Optimization of noisiness of mechanical system by using a pneumatic tuner during a failure of piston machine

Abstract The stage of construction and operation of the machines requires monitoring of the steps causing negative effects on humans and environment in the form of noise during their use. Current technologies allow for appropriate optimization of mechanical systems as part of these machines. One possible optimization of the mechanical systems is considered to be the use of pneumatic tuners. The aim of this article is to demonstrate the effect of the pneumatic tuner on noisiness of mechanical system even in case of failure of mechanical drive part. Performed experimental measurement presents the change of noise in mechanical system by changing a pressure of gaseous medium in pneumatic tuner's compression space. The solution is an issue of appropriate mechanical tuning system when there is a change of dynamic parameters of the system and thus to change the entire mechanical system noise. Subsequent obtained results set out suggestions for the use of pneumatic tuners in mechanical systems in order to achieve the lowest possible noise during their operation mode.

A CWT-based methodology for piston slap experimental characterization

Noise and vibration control in mechanical systems has become ever more significant for automotive industry where the comfort of the passenger compartment represents a challenging issue for car manufacturers. The reduction of piston slap noise is pivotal for a good design of IC engines. In this scenario, a methodology has been developed for the vibro-acoustic assessment of IC diesel engines by means of design changes in piston to cylinder bore clearance. Vibration signals have been analysed by means of advanced signal processing techniques taking advantage of cyclostationarity theory. The procedure departs from the analysis of the Continuous Wavelet Transform (CWT) in order to identify a representative frequency band of piston slap phenomenon. Such a frequency band has been exploited as the input data in the further signal processing analysis that involves the envelope analysis of the second order cyclostationary component of the signal. The second order harmonic component has been used as the benchmark parameter of piston slap noise. An experimental procedure of vibrational benchmarking is proposed and verified at different operational conditions in real IC engines actually equipped on cars. This study clearly underlines the crucial role of the transducer positioning when differences among real piston-to-cylinder clearances are considered. In particular, the proposed methodology is effective for the sensors placed on the outer cylinder wall in all the tested conditions.

TCAA short course presentation material

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects, called “Architectural Acoustics.” An architect can earn one continuing education unit (CEU) by attending this short course, if it is presented by a qualified member of TCAA. The course covers topics in sound isolation, mechanical system noise control, and finish treatments. This paper will cover the course material in order to prepare and qualify potential presenters. In order to qualify as an authorized presenter for this AIA/CES short course, attendance at this workshop and membership in TCAA are required.

What do teachers think about noise in the classroom?

Surveys were sent to 396 Orlando-area elementary school teachers to gauge their subjective evaluation of noise in their classroom, and their general attitudes toward classroom noise. The 87 responses were correlated with the types of mechanical systems in their respective schools: (1) fan and compressor in room, (2) fan in room and remote compressor, or (3) remote fan and remote compressor. Results were also compared to the results of a previous study of the same 73 schools that linked school mechanical system type with student achievement. While teachers were more likely to be annoyed by noise in the schools with the noisiest types of mechanical systems, they were still less likely to be annoyed than the research might suggest—and when teachers did express annoyance, it was more likely to be centered around the kind of distracting noise generated by other children in adjacent corridors than by mechanical system noise.

Architectural acoustics short course presentation material

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects, called “Architectural Acoustics.” An architect can earn one continuing education unit (CEU) by attending this short course, if it is presented by a qualified member of TCAA. The course covers topics in sound isolation, mechanical system noise control, finish treatments, and implementation of quality acoustical spaces. This paper will cover the course material in order to prepare and qualify potential presenters. In order to qualify as an authorized presenter for this AIA/CES short course, attendance at this special session and membership in TCAA are required.

A Nonlinear Contact Force Model for Revolute Joint with Clearance

ABSTRACTClearances in the joints of mechanism cause vibrations and noise in mechanical systems. The contact force model is the important factor in dynamic analysis of mechanical systems with clearance. This paper presents a nonlinear contact force model for revolute joint with clearance, which is a hybrid model of the Lankarani-Nikravesh model and the improved elastic foundation model. The framework of the Lankarani-Nikravesh model is used with the nonlinear stiffness coefficient derived using the improved elastic foundation model and the damping applied in introducing the ratio of the nonlinear stiffness coefficient of the improved elastic foundation model and contact stiffness of Lankarani-Nikravesh model. Finally, the nonlinear hybrid contact force model is analyzed and discussed. The hybrid contact force model presented in this paper is a nonlinear continuous contact force model, which extends contact modeling of joints with clearance and has a greater applicable scope.