Severe Noise Problems Research Articles

Characteristics of community responses to airport noise around Bangkok International Airport

A social noise survey is a study of the community's response to noise. Data from a 2014-2015 noise survey of communities living around Bangkok International Airport is considered a spatial study that is important for the long-term planning of the airport development plan to prevent noise problems from aircraft operations. This paper presents the nature of survey data on airport noise from people living around Suvarnabhumi Airport over a decade after the airport's opening in 2006. It is now planned to expand the airport's capacity to handle more air traffic volume through runway expansion and passenger terminal expansion. The cross-sectional study is thought to be useful in future airport noise planning to avoid severe aircraft noise problems. In addition, it was an appropriate time to collect data from the field as a baseline for future airport noise management before expanding the capacity to handle more air traffic by adding more runways and passenger terminals.

Feasibility verification of reducing the total sound pressure level of multiple cooling fans for fuel cell vehicle

ABSTRACT The high-power operation or generation in fuel cell vehicle (FCV) generates massive heat in the powertrain. Multiple cooling fans are used to ensure the heat dissipation requirement, causing severe fan noise problems. This study aims to analyze the noise characteristics of multiple cooling fans. Hence, the feasibility of reducing the total sound pressure level is verified by cooling fan control strategy. A numerical calculation model of multiple cooling fans is established for the entire vehicle’s internal and external sound fields. Then, this numerical calculation model is verified using experiments. The contribution of multiple cooling fans to the total noise in FCV is analyzed under the same duty cycle of fan. The selection method of cooling fan control strategy is proposed, and the feasibility of reducing noise is verified under three different working conditions. In parking charging working conditions, the total sound pressure level near the driver’s ear decreases by 0.6, 1.9, and 2.8 dBA, respectively. In idling conditions, the total sound pressure level near the driver’s ear decreases by 0.4, 1.6, and 2.4 dBA, respectively. In constant speed working conditions, the total sound pressure level near the driver’s ear decreases by 0.6, 2.2, and 3.1 dBA, respectively.

How the causal structures of noise annoyance and sleep effects changed under the significant decrease of aircraft noise

Many models have been proposed to clarify the interactive effects of acoustic and non-acoustic variables on human perception of noise. Due to the corona pandemic, all flights were closed at the end of March 2020, causing an unprecedented change in the acoustic environment around Tan Son Nhat Airport (TSN). Before the outbreak, TSN was the busiest airport in Vietnam and had severe noise problems. This study focused on determining how acoustic and non-acoustic factors affect community health before and after this change. Approximately 1200 responses were obtained from surveys conducted in 12 residential areas around TSN in 2019 and 2020. Structural equation models (SEM) for noise annoyance and insomnia were developed by linking the questionnaire items of the social surveys. The first effort aims to achieve a common model of noise annoyance and insomnia corresponding to community response to noise before and after the change. It has been found that the degrees of annoyance and insomnia were not reduced, as expected, but increased in 2020. The final constructed SEM indicates that acoustic and non-acoustic factors affected the community health in different structures before and after the noise reduction.

Blind Super-Resolution for SAR Images with Speckle Noise Based on Deep Learning Probabilistic Degradation Model and SAR Priors

As an active microwave coherent imaging technology, synthetic aperture radar (SAR) images suffer from severe speckle noise and low-resolution problems due to the limitations of the imaging system, which cause difficulties in image interpretation and target detection. However, the existing SAR super-resolution (SR) methods usually reconstruct the images by a determined degradation model and hardly consider multiplicative speckle noise, meanwhile, most SR models are trained with synthetic datasets in which the low-resolution (LR) images are down-sampled from their high-resolution (HR) counterparts. These constraints cause a serious domain gap between the synthetic and real SAR images. To solve the above problems, this paper proposes an unsupervised blind SR method for SAR images by introducing SAR priors in a cycle-GAN framework. First, a learnable probabilistic degradation model combined with SAR noise priors was presented to satisfy various SAR images produced from different platforms. Then, a degradation model and a SR model in a unified cycle-GAN framework were trained simultaneously to learn the intrinsic relationship between HR–LR domains. The model was trained with real LR and HR SAR images instead of synthetic paired images to conquer the domain gap. Finally, experimental results on both synthetic and real SAR images demonstrated the high performance of the proposed method in terms of image quality and visual perception. Additionally, we found the proposed SR method demonstrates the tremendous potential for target detection tasks by reducing missed detection and false alarms significantly.

Highly efficient acoustic absorber designed by backing cavity-like and filled-microperforated plate-like structure

Crowded living conditions and increasingly severe noise problems necessitate the development of a low-thickness sound absorption material with remarkable sound absorption performance. Here, simple materials such as sodium alginate aerogel (SA) and polyurethane (PU) foam are used to combine with special 3D spacer fabric to design an innovative highly-efficient acoustic absorber composite (B&M−L composite). It integrates a “backing cavity-like” (BC-L) structure and “filled-microperforated plate-like” (MPP-L) structure. Thereby, it realizes porous and resonant sound absorption at a small thickness. The superior structure design combining strong resonance with porous structure endows the new type of composite with a remarkable absorption performance. Specifically, the peak absorption coefficient is 0.98, the average absorption coefficient at a thickness of 10 mm is 0.71, and the noise reduction coefficient per unit thickness of B&M−L composites exceeds those of most of the reported sound absorption materials. Based on its remarkable acoustic performance, good mechanical properties, heat insulation performance, and thermal stability, the B&M−L composite provides a convenient and inexpensive method to improve the overall performance of porous sound absorption materials, and displays significant potential for use in the fields of construction, transportation, and large mechanical equipment.

Investigation on Vibration Characteristics of Amorphous Metal Alloy Core Dry-type Distribution Transformer

Large power transformers have severe vibration and noise problems. Thus, as the source of noise, it is vitally important to have accurate core vibration calculations. The calculation of the vibration is incredibly difficult to consider the complex propagation pathway of the vibration in the clamp and the Amorphous Metal Alloy Core Distribution Transformer (AMACDT). To understand the vibration characteristics of AMACDT, this manuscript provides a different approach on investigation of the vibration characteristics of an SCBH15-200/10 type. Based on the vibration characteristics calculation and displacement of an Amorphous Metal Alloy Core Distribution Transformer (AMACDT), they are obtained and solved using Finite Element Analysis software (FEA). Conferring to the outcomes of the vibration analysis, the method by adding bar-reinforcements on the upper clamp of transformer is proposed to lessen the vibration amplitude. To verify the usefulness and application of the suggested approach, the analytical results are obtained. The suggested approach is analyzed with those of experimental.

Cavitation CFD analyses considering the pressure wave propagation within the piping systems

Cavitation surge is a typical unsteady phenomenon and can be a cause of severe noise and vibration problems in hydraulic systems. When the oscillation frequency of the piping systems surrounding the hydraulic devices under cavitation surge is high and/or the pipe length is long, the acoustic wave propagation within the piping systems must be considered. In this study cavitation is computed by two dimensional CFD with cavitation model and the pressure wave in the piping systems is computed by one dimensional distributed model of Method Of Characteristics (MOC). The cavitation CFD and MOC calculations are coupled through boundary conditions. The interactions of cavitation and pressure wave are observed in the computed results.

Effect of rail dynamics on curve squeal under constant friction conditions

Curve squeal noise is a severe railway noise problem that can occur when a railway vehicle negotiates a sharp curve. It is usually characterised by a very loud tonal noise and can be very annoying for people in the vicinity. It is generally attributed to friction-induced instability, either due to a falling friction characteristic with increasing sliding velocity or to a mode coupling mechanism which can lead to instability even for a constant friction coefficient. The squeal frequency is usually associated with one or more wheel modes. However, the wheel is coupled dynamically to the track and insufficient attention has been paid in previous research to the role played by the rail dynamic behaviour. In this paper, the effect of the rail dynamics on curve squeal under constant friction conditions is investigated by means of different modelling approaches. The rail is firstly modelled using a waveguide finite element (WFE) model and it is found that the inclusion of the rail dynamics in the model can lead to squeal in some situations where it would otherwise not occur. Various effects are then considered that may introduce additional resonant behaviour into the rail dynamics. These include the effect of the rail cross mobility, rail cross-section deformation, the influence of the periodic support of the rail and reflections between multiple wheels on the rail. The effect of the rail pad stiffness is also explored. However, the results show that all these factors have little influence on the predicted curve squeal instabilities. By means of a reduced model, the main characteristics of the rail dynamics that can result in squeal are then assessed. It is shown that the mass and damping-like behaviour of the infinite rail are at the origin of the instabilities rather than any modal behaviour of the track. Curve squeal may occur for a single wheel mode even if the rail is represented by a damper, which is a close approximation to the vertical mobility of the track at high frequencies. This forms a third possible mechanism for curve squeal in addition to falling friction and wheel mode coupling.

Adaptive Control of a Piezoelectric Valve for Fluid-Borne Noise Reduction in a Hydraulic Buck Converter

The hydraulic buck converter (HBC) is a novel high-bandwidth and energy-efficient device which can adjust or control flow and pressure by a means that does not rely on throttling the flow and dissipation of power. However, the nature of a HBC can cause severe fluid-borne noise (FBN), which is the unsteady pressure or flow in the fluid-filled hydraulic circuit. This is due to the operation nature of a high-speed switching valve of the device. The FBN creates fluctuating forces on the pipes which lead to system structure-borne noise that develops air-borne noise reaching to 85 dB. Thus, there is a need for an effective method that does not impair the system performance and efficiency to reduce the FBN. This paper describes the first investigation of an active controller for FBN cancellation in a HBC based on in-series and by-pass structures. The dynamics and the noise problem of the HBC are investigated using the analytical models. A piezoelectrically actuated hydraulic valve with a fast response and high force is applied as the adaptive FBN attenuator. The performance and robustness of the designed noise controller were studied with different operating conditions of a HBC. Simulated and experimental results show that excellent noise cancellation (30 dB) was achieved. The proposed active attenuator is a very promising solution for FBN attenuation in modern digital hydraulic systems which promise high energy efficiency but suffer severe noise or vibration problems in practice.

Dynamic numerical analysis of single-support modular bridge expansion joints

Severe fatigue and noise problems of modular bridge expansion joints (MBEJs) are often induced by vehicle loads. However, the dynamic characteristics of single-support MBEJs have yet to be further investigated. To better understand the vibration mechanism of single-support MBEJs under vehicle loads, a 3D finite element model of single-support MBEJ with five center beams is built. Successive vehicle loads are given out and the vertical dynamic responses of each center beams are analyzed under the successive loads. Dynamic amplification factors (DAFs) are also calculated along with increasing vehicle velocities from 20 km/h to 120 km/h with an interval 20 km/h. The research reveals the vibration mechanism of the single-support MBEJs considering coupled center beam resonance, which shows that dynamic responses of a given center beam will be influenced by the neighboring center beams due to their rebound after the vehicle wheels depart. Maximal DAF 1.5 appears at 120 km/h on the second center beam. The research results can be utilized for reference in the design, operation and maintenance of singlesupport MBEJs.

Flow-Excited Acoustic Resonance Excitation Mechanism, Design Guidelines, and Counter Measures

The excitation mechanism of acoustic resonances has long been recognized, but the industry continues to be plagued by its undesirable consequences, manifested in severe vibration and noise problems in a wide range of industrial applications. This paper focuses on the nature of the excitation mechanism of acoustic resonances in piping systems containing impinging shear flows, such as flow over shallow and deep cavities. Since this feedback mechanism is caused by the coupling between acoustic resonators and shear flow instabilities, attention is focused first on the nature of various types of acoustic resonance modes and then on the aeroacoustic sound sources, which result from the interaction of the inherently unstable shear flow with the sound field generated by the resonant acoustic modes. Various flow-sound interaction patterns are discussed, in which the resonant sound field can be predominantly parallel or normal to the mean flow direction and the acoustic wavelength can be an order of magnitude longer than the length scale of the separated shear flow or as short as the cavity length scale. Since the state of knowledge in this field has been recently reviewed by Tonon et al. (2011, “Aeroacoustics of Pipe Systems With Closed Branches”, Int. J. Aeroacoust., 10(2), pp. 201–276), this article focuses on the more practical aspects of the phenomenon, including various flow-sound interaction patterns and the resulting aeroacoustic sources, which are relevant to industrial applications. A general design guide proposal and practical means to alleviate the excitation mechanism are also presented. These are demonstrated by two examples of recent industrial case histories dealing with acoustic fatigue failure of the steam dryer in a boiling water reactor (BWR) due to acoustic resonance in the main steam piping and acoustic resonances in the roll posts of the Short Take-Off and Vertical Lift Joint Strike Fighter (JSF).

Acoustics of Corrugated Pipes: A Review

Corrugated pipes and tubes are commonly used in many engineering and industrial applications because they offer global flexibility combined with local rigidity. Some of the engineering systems which use the corrugated pipes are Liquefied Natural Gas (LNG) storage systems, risers for offshore oil and gas industries, heat, ventilation, and air conditioning systems (HVAC), aerospace and automobile cabin cooling systems, and certain domestic appliances such as vacuum cleaners. Air flow through a short or a long length of corrugated pipes can cause the pipes to emit loud and clear “tonal” sounds or “whistling” at some critical flow conditions. Interaction and coupling of these acoustic waves with vortex shedding-flow instability can result in severe noise and structural vibration problems. A phenomenon of sound generation in corrugated pipes is also observed in a children's toy called “Hummer,” “Voice of the Dragon,” or “Magic Whistle.” This review paper focuses on the research work carried out to date to study the sound generation mechanism and its reduction methodology in corrugated pipes with air flow. This paper reviews and summarizes the various theoretical, experimental and computational work carried out in relation to acoustics of corrugated pipes.

Active control of pressure pulsation in a switched inertance hydraulic system

The nature of digital hydraulic systems may cause severe pressure pulsation problems. For example, switched inertance hydraulic systems can be used to adjust or control flow and pressure by a means that does not rely on dissipation of power, but they have noise problems because of the pulsed nature of the flow. An effective method to reduce the noise is needed that does not impair the system performance and efficiency. This article reports on an initial investigation of an active attenuator for pressure pulsation cancellation in a switched inertance hydraulic system. Using the designed noise attenuator, the pressure pulsation can be decreased effectively by superimposing an anti-phase control signal. A high-performance piezoelectric valve was selected and used as the secondary path actuator in terms of its fast response and wide bandwidth. Adaptive notch filters with the filtered-X least mean square algorithm were applied for pressure pulsation attenuation, while a frequency-domain least mean square filter was used for secondary path identification. A ‘switched inertance hydraulic system’ in a flow booster configuration was used as the test rig. Experimental results show that excellent cancellation was achieved using the proposed method, which has several advantages over passive noise control systems, being effective for a wide range of frequencies without impairing the system’s dynamic response. The method is a very promising solution for pressure pulsation cancellation in hydraulic systems with severe noise or vibration problems.

Investigation on Technology of Automobile Vibration and Noise Reduction Based on Body-In-White Structure

The automotive body system is not only a source for directly radiating noise into the vehicle interior space, but also a key component for transmitting various vibrations and noise. The optimization of the modes for body-in-white has significant meanings for improving the reliability and NVH (Noise, Vibration and Harshness) performance of the whole vehicle. Based on the current situation that there is more severe interior vibration and noise problem occurring in driving for a light passenger vehicle, a hybrid modal analysis method combined with experiment and simulation methods is applied to investigate the vibration and noise characteristics of the whole vehicle body. By performing such modal analysis, the modal frequencies of the auto-body are improved effectively by strengthening the vibration sensitive regions in the body structure. The experiment for measuring interior vibration and noise levels under cruise condition is conducted to validate that the structural optimization for body-in-white has significant contribution for improving the whole vehicle NVH performance.

Flow-Excited Acoustic Resonance in Industry

The excitation mechanism of acoustic resonances has long been recognized, but the industry continues to be plagued by its undesirable consequences; manifested in severe vibration and noise problems in a wide range of industrial applications. This paper focuses on the nature of the acoustic resonance excitation mechanism for the case of closed side branches because of its relative importance to industrial applications. Design charts are presented for the Strouhal number at the onset of acoustic resonance and for the acoustic source strength representing the integral effect of the shear layer at the mouth of the side branch. Because these design charts are developed from tests of cylindrical pipes conveying turbulent flow at high Reynolds numbers, they can be used in industrial applications to predict the onset flow velocity and the intensity of acoustic resonances in side branches. Two industrial examples involving flow-excited acoustic resonance of closed side branches are presented. The first example deals with acoustic fatigue failure of the steam dryer in a boiling water reactor due to acoustic resonance in the main steam piping system, whereas the second example considers acoustic resonances in the roll posts of the short take-off vertical lift (STOVL) joint strike fighter. In both examples, effective means to alleviate the acoustic resonance mechanism are discussed.

Well Test Analysis of Naturally Fractured Reservoirs with Unsteady State Behavior Using Direct Synthesis Technique

This study proposes a new method for analyzing pressure transient in naturally fractured reservoirs (NFR). Parameter estimation is based on the direct synthesis technique. The direct synthesis technique utilizes the characteristic intersection, maximum and minimum points, slopes, and starting time of various straight lines from a log–log plot of pressure and pressure derivative data. Applicability of the empirical expressions developed as a result of this work is demonstrated by successfully analyzing actual pressure transient data. The main advantage of direct synthesis method is for a case where there is no guarantee on the existence of an early-time unit slope line, and/or the late-time infinite acting radial flow line has not been seen due to inner and outer boundaries, lack of points, and severe noise problems. Application of this technique is presented for well test analysis in infinite-acting naturally fractured reservoirs with an unsteady state flow model. Both the effects of wellbore storage and skin are included in the analysis. Comparison between the results obtained in this work and already published results indicates good agreement.

Effects of cup, cushion, headband force, and foam lining on the attenuation of an earmuff

The use of hearing protectors is considered the only short-term solution available to severe noise problems. In this paper the noise leak pathways through the protector to the ear channel were investigated. Noise attenuation measurements were carried out for a circumaural earmuff protector to quantify the effect of various parameters and modifications on the earmuffs, such as: internal foam lining, vibration of earmuff cover, type and force of contact between the earmuff and the head face. The assays were undertaken using an artificial head according to ANSI S12.42-1995 and a diffuse sound field according to ISO 4869-1. The coherence function between cup vibration and sound pressure inside the cup has shown that a great amount of sound energy is transmitted to the inside of the cup at low frequencies: 100–320 Hz. The foam lining of the cup clearly attenuated the sound in the frequency range between 2000 and 8000 Hz. The attenuation measured with a complete earmuff and the same without the cushion has shown that sound leakage occurs at frequencies ranging from 125 to 2000 Hz. A Vaseline coating between the head surface and the cushion improved the attenuation by less than 5 dB (100–200 Hz). As the headband force increases to a maximal deformation of the cushion, attenuation reaches 20 dB at 200 Hz. The increase in the headband force is however a limiting factor to the use of the earmuff, as it can get too uncomfortable. In this work the bone conduction is negligible.

Analysis of friction-induced vibration leading to "EEK" noise in a dry friction clutch

This study deals with a severe noise problem (Eek) that arises during the engagement of a dry friction clutch in a vehicle with manual transmission. Measurements have shown that near the full engagement the pressure plate suddenly starts vibrating (rigid body wobbling mode) with a frequency close to the first natural frequency of the rotational sub-system. This self-excited vibration problem exhibits typical signs of a dynamic instability associated with a constant friction coefficient. The transient event results in the generation of high transient noise levels and often consumers will change clutches prematurely in an effort to eliminate this noise. Our work focuses on developing a linearized lumped-parameter model of the clutch. The effect of key parameters on the system stability is examined by calculating complex eigensolutions. Results of this analytical study are in agreement with experimental observations. It is seen that the instability of the rigid body wobbling mode is controlled by the friction forces. This mode may, however, be also affected by the first bending mode of the pressure plate. Therefore, a stiffer plate could lead to a design with a reduced tendency to Eek.

Inspection of Tooth Surface Geometry by Means of Vibration Measurement(Assessment of Tooth Surface Undulation from Synchronous Averaged Signal and Application of Frequency Response Function)

Tooth surface undulation is one of the important sources of gear noise and vibration. The vibration caused by this source is observed as the occurrence of non-meshing vibration component or ghost noise on a vibration spectrum. Frequently ghost noise occurs at the same frequency with natural frequency of a gear pair, consequently its amplitude is amplified to the considerable level and lead to unexpected and severe noise and vibration problems. In this paper a method for inspecting tooth surface undulation is proposed and applied to a helical gear pair. Vibration characteristics of individual gear are extracted from the vibration signal of a gear by synchronous averaging technique, then a frequency response function that can be determined experimentally is applied to the individual averaged signal to assess the tooth surface undulation. The undulations are evaluated by applying this method to the measured vibration signals of the gear pair operated at various speeds and various torques, and show good agreement with each other regardless of operating conditions and also with the expectation by precise tooth surface measurement, even though the undulation is very small in the level of 0.1µm. These results suggest the ability of this method to assess the tooth surface geometry relevant to vibration.

An Application of the Acoustic Similarity Law to the Numerical Analysis of Centrifugal Fan Noise

Centrifugal fans, which are frequently used in our daily lives and various industries, usually make severe noise problems. Generally, the centrifugal fan noise consists of tones at the blade passing frequency and its higher harmonics. These tonal sounds come from the interaction between the flow discharged from the impeller and the cutoff in the casing. Prediction of the noise from a centrifugal fan becomes more necessary to optimize the design to meet both the performance and noise criteria. However, only some limited studies on noise prediction method exist because there are difficulties in obtaining detailed information about the flow field and casing effect on noise radiation. This paper aims to investigate the noise generation mechanism of a centrifugal fan and to develop a prediction method for the unsteady flow and acoustic pressure fields. In order to do this, a numerical analysis method using acoustic similarity law is proposed, and it is verified that the method can predict the noise generation mechanism very well by comparing the predicted results with available experimental results.