bluuebunny/crossref_metadata_2025 huggingface dataset:
Active control of acoustic scattering from a passively optimised spherical shell
Authors: Elliott Stephen , Orita Mihai , Quaranta Erika , Cheer Jordan
Published: February 2023

At low frequencies, the sound power scattered from a spherical shell can be minimised by designing its material properties and thickness so that the mass and compressibility are the same as that of the displaced fluid. The scattered power is then dominated at higher frequencies by that
due to the resonances of the structural modes of the shell, particularly the ovalling mode. The peaks in the scattered power due to structural resonances can be reduced somewhat by material damping but are more effectively attenuated with active control using structural actuators as secondary
sources. Simulations are presented of the scattered sound power of such a shell when subject to feedforward control, which assumes knowledge of both the incident and scattered acoustic sound fields, and structural feedback control, which only assumes that the velocity on the surface of the
sphere can be measured. The performance of the feedback controller is also examined if the structural actuators and sensors are distributed over the surface of the sphere, rather than just acting at single points.
Analysis of modulating tones in wind farm noise
Authors: Cand Matthew , Norcross Rylan
Published: February 2023

The overall level of the noise from wind turbines generally remains the main regulatory driver for control of this source at neighbouring sensitive receptors. In addition, features sometimes present in the noise can increase its subjective disturbance: these are increasingly recognised
and sometimes penalised. A fluctuating character in the aerodynamic noise is inherent to some degree, due to the rotation of the blades, but in some cases the Amplitude Modulation (AM) of the sound can become stronger. Tonality is another noise feature which can be detected in some cases due
to resonances or emission from specific mechanical/electrical components in the turbine. Objective methods have been developed or adapted over the past years to objectively characterise the magnitude of both features in isolation. This paper considers cases where tones fluctuate, probably
as they are emitted from a rotating component of the turbine. Different numerical quantification methods are compared and investigated and the implications on subjective response are considered.
Simplification of ISO 3744 - Making the Most Important Standard for Determination of Sound Power Levels Easier to Use
Authors: Heisterkamp Fabian , Schmitt Jeff , Hook Joey
Published: February 2023

Sound power level (L_W) is the key quantity to describe the noise emission of products and is needed to reduce noise at work, at home, and in the environment, e.g. for promoting and selecting low noise products (Sell and Buy Quiet). ISO 3744:2010 is the main standard referred to by
most product test codes and regulatory requirements for determining L_W. It is used by laboratories, noise control engineers, and manufacturers. Due to its structure and length, the usability of the current document is limited. The main body of ISO 3744:2010 contains so much information that
the basic concept of sound power is obscured. To improve usability of ISO 3744:2010 three projects were launched: 1. A revision and restructuring of ISO 3744 with a simplified main body and a series of annexes for special cases; 2. A new standard: ISO/CD 5114-1 on the uncertainty of L_W determined
from sound pressure levels; 3. A new standard: ISO/CD 26101-2 to determine the environmental correction used in determining L_W. These new standards contain specific information needed by some users while ISO/CD 3744 focusses on determining L_W. We present key aspects of all three committee
drafts and explain how and why ISO 3744 should be revised.
Vibration and acoustic radiation control of a panel with piezoelectric oscillators.
Authors: Zhang Yongyuan
Published: February 2023

In this paper, the vibration of a thin plate system with piezoelectric sheets attached and its acoustic radiation are modeled theoretically. Then the results are compared with those of finite element simulation, and the results are relatively consistent. Finally, sound absorption and
isolation experiments at non-intrinsic frequencies of the composite plate are conducted in a standing wave tube. Based on the principle of minimum potential energy, the variation equation of a thin plate with a piezoelectric sheet attached are listed, and the impedance matrix of the acoustic
radiation of the plate coupled with each order of the cavity modal is calculated. After the modal displacement response of the plate is obtained, the absorption coefficient and sound insulation volume of the composite plate can be calculated. Through theoretical calculations and finite element
simulations, it is found that the plate has a modal reorganization phenomenon at the peak of sound insulation, and the modal response of each order increases at the peak of sound absorption. After that, the sound absorption and isolation experiments were conducted in the standing wave tube,
and the control effect of the piezoelectric shunt oscillator at the non-intrinsic frequency of the plate was improved by adding negative capacitance.
Design method of asphalt mixture with balanced noise reduction and mechanical properties
Authors: Li Mingliang , Li Yingtao , Li Jun , Zhou Wei , Zu Yaqun
Published: February 2023

A design method of asphalt mixture is proposed for reducing the tyre/road noise while having good mechanical properties. Firstly, by comparing the simulated sound absorption coefficient curve with noise-frequency curve from practical road surface, the target air voids contents are obtained.
Then, models which can predict the texture level and sound absorption coefficient from the given mixture properties, such as porosity, gradation, particle size, asphalt content, etc. as inputs parameters, are used for preliminarily selecting the design parameters of mixture. Test samples are
made according to these selected design parameters in the lab. Test vales of the texture level, sound absorption coefficient and the skid resistance of the mixtures are obtained from laboratory measurements. These measurement values are used for predicting the attenuation of the tyre/road
levels by means of statistical models. Mixtures with superior predicted noise reduction properties are selected for mechanical performance validation. Mixture design which shows the promising noise reduction properties as well as satisfying the mechanical performance requirement are considered
as the optimal one, and it is suggested to be used as the road surface. Road surface designed from this method can both meet the needs of traffic load and noise reduction function.
Numerical modelling of acoustic metamaterial made of periodic Helmholtz resonator containing a damping material in the cavity
Authors: LALY Zacharie , Mechefske Christopher , Ghinet Sebastian , Kone Charly T. , Atalla Noureddine
Published: February 2023

Acoustic metamaterials are frequently used in many fields such as aerospace, buildings and ground transportation industries for low frequency noise control applications. Different solutions based on membrane or Helmholtz resonators have been investigated in the past few years. In the
present study, a numerical design of acoustic metamaterial made of Helmholtz resonator with a membrane in its cavity is presented. The resonator with a neck extended into the cavity is periodically embedded within a porous material. The membrane inside the resonator cavity is modelled as a
linear isotropic elastic material with free and fixed boundary conditions. The transmission loss (TL) of the proposed metamaterial design, predicted by finite element method presents multiple resonant peaks while only one peak is obtained with a conventional resonator. Two TL resonance peaks
are observed when the membrane circumferential boundary is free inside the resonator cavity. For fixed boundary conditions, more than two resonance peaks are obtained. The proposed metamaterial design can therefore be used in many industrial applications for low frequency noise attenuation.
Numerical design of Helmholtz resonators with multiple necks for multi-tonal noise control
Authors: LALY Zacharie , Mechefske Christopher , Ghinet Sebastian , Kone Charly T. , Atalla Noureddine
Published: February 2023

The reduction of multi-tonal noise at multiple frequencies simultaneously is a challenge in many industrial fields. Different solutions such as metamaterials consisting of periodic Helmholtz resonators embedded into a porous layer have been studied in the literature. Generally, a classical
resonator made of a cavity connected to a neck provides only one resonant transmission loss peak. In this study, a design of acoustic metamaterials is proposed numerically using the finite element method for multi-tonal noise reduction. The resonator is made of multiple necks extended into
the cavity and is periodically distributed within a porous material. The cylindrical global cavity of the resonator is partitioned into several sub-cavities, which are separated from one another by a rigid wall, and each sub-cavity is connected to one neck. Helmholtz resonators with 2, 3,
4, and 5 necks are presented, they exhibit multiple resonance transmission loss peaks which correspond respectively to the number of the resonator necks. The proposed acoustic metamaterial designs can be used to reduce multi-total noise at several frequencies simultaneously.
Modelling of acoustic metamaterial sound insulator using a transfer matrix method for aircraft cabin applications
Authors: LALY Zacharie , Mechefske Christopher , Ghinet Sebastian , Kone Charly T. , Atalla Noureddine
Published: February 2023

The incorporation of acoustic metamaterials in the design of aircraft fuselage panels in order to reduce the low frequency noise inside the cabin is nowadays a major research subject in order to offer passengers a comfortable cabin environment. In this study, acoustic metamaterial made
of Helmholtz resonators periodically embedded into a porous material is investigated using a transfer matrix approach combined with finite element calculations. This transfer matrix method is based on the two-load methods where the two loads in the numerical simulations are two different termination
conditions (plane wave radiation and rigid wall) in order to retrieve the equivalent transfer matrix of the porous layer with embedded periodic Helmholtz resonators. The equivalent matrix is then coupled analytically in series with others analytical matrices to model complex multilayer metamaterials.
The results of the transmission loss obtained exclusively using finite element method for single and double wall configurations are compared with the results of the proposed transfer matrix method and good agreements are obtained. It is observed that the frequency band of the transmission
loss of the double wall configuration is larger than the one of the single wall configuration with higher transmission loss peak value. The investigated metamaterial can potentially be used in the design of aircraft cabin panels for low frequency noise reduction.
Impact of Mihrab geometry on the acoustics of the mosque
Authors: Hossam Eldien Hany , M. Bongwirnso Umaru , Hammad Emad
Published: February 2023

Mihrab is a niche in the wall of a mosque that indicates the qibla, the direction of the Kaaba in Mecca towards which Muslims should face when praying. The wall in which a mihrab appears is thus the "qibla wall". Mihrab geometry has an impact on daily prayer recitation and
others. This paper investigates the impact of new type of the Mihrab geometry on the acoustics of the mosque. Flat wall and 7 types of mihrab were modeled. Polar response measurements were carried out using 1:10 scale model. Measurements had been realized using 1:10 omni-directional sound
source and Dirac room acoustics software. It is found that flat wall and Mihrab with trapezium and triangle shapes can generate a uniform polar response over the frequency range we are interested in (500-2000 Hz).
Railway Noise Reduction at the Source only. Is this possible or mandatory?
Authors: Hecht Markus
Published: February 2023

Climate change urges CO2 reduction also in traffic. Electrified Railways are a powerfull CO2 free and energy and space efficient traffic mode already today. Modal shift is demanded but environmental noise of railway hinder rail traffic growth significantly. Noise tunnels are not only
expensive but also reduce energy efficency and increase interior noise. Noise barriers are very costly and optical obstacles. TSI-Noise values have many criticisms. They do not cover the most bothering situations, curve running and severe other critical operation conditions are missing. The
noise limit values are very high. Many standard measures in all other technical fields, construction machines or road vehicles do not exist in the railway context. Even worse is the situation of the track noise. There are nearly no measures except the demand for smooth surfaces. But the noise
radiation of rails and sleepers is not constant but can be reduced significantly. Even good railway practice in other countries does not push the noise reduction without legislatve demands. Exemple are quiet high speed pantographs and tamping machines in Japan. With general measures and low
noise barriers and skirts on each track side the immision limt even at densly operated lines of LDEN 55 dBA is possible.
Pulsed and Continuous Signal Enhancement Based on Improved Noise Power Spectrum Density Estimation in the Passive Underwater Acoustic Data
Authors: Zhong Yun , Wu Qisong
Published: February 2023

The pulsed and continuous narrow-band signal enhancement is quite important for the target detection and recognition in a passive sonar system. In this paper, a novel signal enhancement approach is proposed for both pulsed and continuous narrow-band components in the passive underwater
acoustic data. The short time Fourier transform (STFT) method is firstly used in the time-domain radiated noise data, and then an improved noise power spectrum density (PSD) estimation is proposed to obtain the accurate noise power by using a two-dimension (2-D) sliding window. Finally, the
improved PSD is utilized to enhance both pulsed and continuous narrow-band components. The proposed method has the capability of enhancing pulsed and continuous narrow-band components with avoiding the annoying tuning of the window length. Both simulation and experimental results verify the
effectiveness and robustness of the proposed method.
Flat Fresnel-spiral acoustic metamaterials composed of several arms ventilated metamaterials for simultaneous broadband sound absorption and air circulation
Authors: Singh Sanjeet kumar , Bhattacharya Shantanu
Published: February 2023

With a steep rise in the urban population requiring an increased number of buildings, public and private transport systems, urban noise is posing a serious environmental problem affecting health. To attenuate the effect on the well-being of human health, a variety of conventional sound-absorbing
materials suitable at mid and higher-frequency noise absorption are commonly being used but low and mid-frequency noise remains a challenge. These applications are further limited by the acoustic performance and ventilation efficiency in conventional noise barrier limits of their fields. Acoustic
metamaterial presents a unique solution as an artificially designed material showing low-frequency noise mitigation. A novel subwavelength device having thickness of 15mm (<2 cm) ,with potential application in noise mitigation and air ventilation solution is presented herein. In this study,
the design and fabrication of a small prototype based on a Fresnel-spiral shape composed of several arms are performed. Numerical and experimental investigations were carried out to determine the acoustical properties of the proposed ventilated metamaterial in terms of sound absorption and
sound transmission loss. The experimental investigation shows significant sound absorption with a high bandwidth (more than one octave in the range of > 900 Hz ), acoustic properties leading to potential applications in urban noise control for low and mid-frequency ranges.
Method Implementation Document for BS 4142
Authors: Smyrnowa Julija , Clayton Tony , Tofts Jon , Brown Gillian
Published: February 2023

BS4142:2014+A1:2019 "Methods for rating and assessing industrial and commercial sound" is the standard that the Environment Agency requires to be applied for the assessment of most industrial sound sources. Since its publication in 2014 (in 2019 only some minor updates were
introduced), it has become evident that the standard is prone to misinterpretation, particularly in relation to estimating uncertainty of the assessment and in terms of context at which the sound occurs. As a consequence, quality of most of noise impact assessment reports submitted to the
EA has been very low. In order to improve quality in environmental measurements and assessments of noise impact, the EA has established the Method Implementation Document for BS4142. MID provides details on how the standard shall be used for regulatory monitoring for application for or compliance
with a permit. Where required, MID should be used to supplement the EA`s guidance called up by Noise and vibration management: environmental permits (formerly known as Horizontal Guidance Note H3 which has been withdrawn). However, it does not re-state all the provisions of BS 4142 and organisations
are reminded of the need to comply with the criteria detailed in BS 4142:2014+A1:2019.
A method to quantify the noise annoyance in an airport community
Authors: Gjestland Truls , Granøien Idar L N
Published: February 2023

Exposure-response curves showing the prevalence of high annoyance as a function of the long-term noise exposure level DNL/DENL is the preferred way of presenting the results from surveys on noise annoyance. However, such curves give very little information about the actual extent of
the negative impact in a specific noise situation. The number of impacted people is not known and people that are annoyed to a lesser degree than "highly annoyed" are not counted. A method to quantify the magnitude of noise annoyance in an airport community has been developed.
Measuring the impact force from the ISO impact ball and comparison with the tapping machine and alternate input method
Authors: Girdhar Sunit , Blough Jason , Barnard Andrew , LoVerde John , Dong Wayland
Published: February 2023

The impact ball was recently standardized within the ISO standards as a low-frequency input impact source for impact testing of floor-ceiling assemblies. The input force due to an impact ball is not measured during the tests. A force measurement plate was created with three force transducers
to measure the impact force due to ball drops on six different floor assemblies. The input force showed a really good comparison for heavy and lightweight floors in lower frequency but poor force excitation for all the floors above 100 Hz. The input force values were compared with a modified
tapping machine's force input levels showing the tapping machine has poor low-frequency excitation (in comparison) but an improved high-frequency excitation. An alternate input method was developed where a force transducer is added to the impactor to make live measurements of the input force
and the impact tip can be changed to modify the range of targeted frequencies for any test.
Sound propagation and audibility of train horns
Authors: Toward Martin , Lower Mike , Wiseman Marcus , Thompson David , Ferraby Paul
Published: February 2023

Horn sound levels and sound propagation along the track were investigated to understand the relationship between standardised tests at 25 metres and audibility in practice. Sound levels from a static horn above a test track decayed by 6 dB per doubling of distance (6 dB/dd) up to about
30 or 50 metres, depending on the horn height. At greater distances the level decayed by approximately 12 dB/dd. At 400 metres, the sound level from a horn 2.5 metres above the ground was about 10 dB higher than the level from the horn 0.5 metres above the ground, although the levels at 25
metres were the same. The audibility and the effective range of a horn depends on its height. At two rural mainline sites, with line speeds of 160 km/h and 200 km/h, the mean attenuation rates beyond 90 metres were 10.7 and 9.2 dB/dd respectively. At the first site, horn sound levels were
highly correlated with distance. At the second site, with newer trains, horn levels were poorly correlated, suggesting some variability in horn sound levels at source. Track workers ratings of the audibility of the horns were compared to horn levels recommended by Detectsound and by ISO 7731.
Objective and perceived acoustic environments during the COVID-19 lockdown: An overview of evidence
Authors: Dzhambov Angel
Published: February 2023

The COVID-19 pandemic took a heavy toll on population health directly, but also triggered profound changes to social life, daily mobility patterns, and activity spaces. At the beginning, public health measures for limiting the spread of the virus mandated home confinement and limited
outdoor activities, which in turn reshaped typical acoustic environments for many people. Traffic noise levels reportedly declined across various settings, allowing for nature sounds, hitherto masked, to become more prominent. On the other hand, prolonged home confinement made indoor sounds,
such as mechanical sounds, human voices, and noise generated by neighbors, even more relevant for the well-being of building occupants. This overview will provide a synopsis of the evidence of changes to residential noise exposure and perceived soundscape quality and components across different
contexts, with implications for residents' well-being. The observed changes will be discussed through the lens of stress and restoration theories.
Main flow oriented vorticity noise experiments
Authors: Hirschberg Lionel , Bake Friedrich , Knobloch Karsten , Hulshoff Steven
Published: February 2023

Entropy inhomogeneities and vorticity spots induce so-called indirect combustion noise when passing through a choked nozzle; referred to as entropy noise and vorticity noise, respectively. We note that vorticity noise depends on the orientation of the vorticity; viz., oriented normal
or parallel to the axial main flow. An experimental investigation of parallel component vorticity noise is presented. In the experiment a time- dependent swirling flow was induced by unsteady tangential injection in the pipe upstream of a choked convergent-divergent nozzle. As the resulting
swirling flow passes through the nozzle, the axial stretching of the fluid caused an increase in rotation energy. The steady energy conservation in an isentropic flow implies a Mach number higher than unity at the throat and an associated reduction of density. Ergo, the critical mass-flow
rate (for fixed reservoir pressure and temperature) decreases quadratically with increasing swirl intensity. The acoustic waves radiated downstream of the nozzle are a direct measure for this mass-flow modulation. Using a semi-empirical model, this sound production mechanism is demonstrated
to indeed be quasi steady.
Hybrid space filling curve metamaterials for transmissive flow in Jet Engine inlets
Authors: Glover Jennifer , O'Boy Dan
Published: February 2023

Acoustic metamaterials research has grown exponentially in the past 10 years driven by the advances in manufacturing and an increased understanding of damaging environment noise. 2050 was the first noise reduction target as set by Advisory Council for Aircraft Research and Innovation
in Europe with a relative 65% decrease. This ambitions target will not be met by current engine noise control technology; however, metamaterials offer an encouraging alternative. Space Filling Curves (SFC) have the potential to provide a lightweight, thin, high performance acoustic liner.
SFC have a history in mathematical geometry dating back to the 1890's but are a comparatively new addition to acoustics. They are designed with a sub-wavelength curled cross-section creating a maze-like pattern which slows acoustic wave propagation through the liner, enabling characteristics
such as negative refraction and low frequency attenuation. This paper contains unique hybrid designs combining some of the most promising SFC metamaterial acoustic liner designs, in terms of the fundamental theory of the design category and a discussion of the reflection, absorption and transmission
characteristics in terms of a grazing flow conditions. Experimental impedance tube testing compares 3D printed designs to the traditional Helmholtz resonator. The paper concludes with future application for aeroacoustics with particular focus on the engine inlet.
Noise in restorative environments - Perceptions, positive and negative environmental components in Tyrolean children
Authors: Dzhambov Angel , Lercher Peter , Rüdisser Johannes
Published: February 2023

Background: Annoyance is regarded as the most common adverse reaction to environmental noise, and yet, relatively little is known of noise annoyance in children, even though children find themselves in a vulnerable developmental period. Noise perception is usually studied as a unidimensional
phenomenon with an emphasis on annoyance, disregarding positive appraisals of the acoustic environment. This study aims to explore the joint relationships between traffic noise, other built and natural environment indicators and children's perception of noise and associated environmental restorative
quality. Methods: Data are gathered from a cross-section survey among 1251 children (8 - 12 years old) in the cross-border Tyrol area (Austria/Italy). Children and their mothers completed questionnaires on sociodemographics, living conditions, perceived neighborhood quality, and noise annoyance
in different situations. Children's residential locations were assigned traffic noise, air pollution, and built environment/natural landscape indicators, including imperviousness density, greenness, and the composite indicator distance to nature (D2N; Rüdisser et al., 2012), which are
aimed to allow an integrated prediction of noise perception and restorative quality in these children. Results: This paper will present findings on the association between contextual influences and noise perception in children, with a focus on both positive and negative appraisals of the environment.
Relationship between vortex shedding noise and remotely-sensed surface pressure fluctuations of a structured porous-coated cylinder
Authors: Maryami Reza , Arcondoulis Elias J. G. , Yang Chenghao , Liu Yu
Published: February 2023

Tonal noise suppression of a cylinder placed in uniform flow has been achieved, to some extent, by coating it with a structured porous material as a form of passive flow and noise control. A previously studied structured porous-coated cylinder is investigated in an anechoic wind tunnel
to determine the relationship between the far-field vortex shedding noise and the pressure recorded on the outer porous surface. To date, no experimental studies have been conducted on the surface pressure of any type of porous-coated cylinder. Acoustic measurements are obtained using an equispaced
microphone arc array and simultaneously unsteady surface pressure fluctuations are obtained around the cylinder mid-span circumference using remote-sensing techniques. By obtaining simultaneous time-dependent signals, more light is shed on the underlying noise-reduction mechanism of the structured
porous-coated cylinder. In this paper, strong relationships between surface pressures and acoustic signals are revealed at the vortex shedding frequency. A spatio-temporal relationship between surface pressure and vortex shedding phenomena is also presented that helps explain the role of the
structured porous media in passive flow and noise control.
A prediction method for indoor vibration over metro depot throat area based on coupled interactions of wheel-rail
Authors: Lei He , Song Ruixiang , Wu Yubin , Wu Yanan
Published: February 2023

Environmental vibration pollution is the primary environmental problem faced by the superstructure of metro depots. The throat area is especially prone to high wheel-rail impact vibration due to multiple joints and turnouts, which may cause high annoyance to the residents in the superstructures
both on the upper cover and surrounding areas. In this paper, based on the coupled dynamic analysis of wheel-turnout, a prediction method to evaluate the indoor vibration of over-track building is established. Firstly, subway turnout with variable sections on switch, connection part and frog
and vehicle models are established, and wheel-rail force is obtained through multibody dynamics calculation. Secondly, the track-foundation-structure finite element numerical model was built, loading the wheel-rail force excitation, then the indoor vibration could be obtained. The accuracy
of this method is verified taking a 32 story residential superstructure in North China as an example. The vertical vibration accelerations were measured on every other floor when a A-type train travelled on a 7-turnout. The error between the measured data and the calculated results was within
5%, indicating that this prediction method has certain accuracy. The research results have certain guiding significance for the prediction and control of vibration in metro depot.
Strategic Modelling of Industrial Noise with Limited Input Datav
Authors: Skinner Chris , Basturk Seckin , Notley Hilary
Published: February 2023

Historically, strategic modelling of industrial noise exposure on a national scale has taken a wide range of approaches. Where sound emission data of industrial sites are not available, numerous assumptions are often made. These include simplified modelling of industrial sites and adoption
of generic sound power levels for different industry types. In most cases such assumptions significantly increase the uncertainty in strategic noise mapping outcomes. This paper presents an alternative approach to strategic modelling of industrial sound which is based on the environmental
permitting practice of large industrial sites in England. Drawing on this approach, a cost-effective and scalable modelling procedure has been developed to estimate sound emission levels and radiation patterns of industrial activities accounting for the local context of the site. This paper
details the alternative modelling approach along with example prediction outputs. Potential future refinements to improve the modelling accuracy and opportunities to enhance site-specific input data in collaboration with national authorities are also discussed.
Vibroacoustic simulations with non-homogeneous TBL excitations: Synthesis of wall pressure fields with the Continuously-varying Uncorrelated Wall Plane Waves approach
Authors: Guillon Corentin , Redon Emmanuel , Maxit Laurent
Published: February 2023

A numerical method is presented to predict the vibro-acoustic response of a vibrating structure excited by a spatially inhomogeneous turbulent boundary layer(TBL). It is based on the synthesis of different realizations of the random pressure fluctuations that can be introduced as loadings
of a vibro-acoustic model (such as a finite element model). To generate the pressures of the non-homogeneous turbulent boundary layer, the Uncorrelated Wall Plane Wave(UWPW) approach used so far for homogeneous TBL is extended. On a first step, this extension is based on a decomposition of
the excited surface into sub-areas and on the averaged TBL parameters for each sub-area. In a second step, it consists in taking into account the interaction between the sub-areas and a refinement of the sub-area decomposition. This leads to the Continuously-varying Uncorrelated Wall Plane
Waves (C-UWPW) approach. The accuracy of the proposed approach is investigated on a panel with a varying thickness and excited by a growing TBL triggered at one edge of the plate. The interests of the proposed approach in terms of accuracy and computation time are discussed. Finally, an illustration
of the proposed approach to predict the radiated noise from a blade immersed in a water flow is proposed.
Optimization of a thermoacoustic system
Authors: Wei Jiasen , Pralits Jan Oscar , Bottaro Alessandro
Published: February 2023

Clean combustion such as hydrogen combustion for the reduction of NOx emission is prone to thermoacoustic instabilities, which may cause structural vibrations and equipment failures. In the present work, an adjoint-based sensitivity analysis is applied to a low-order thermoacoustic
model with a non-zero mean flow. The adjoint-based analysis can be a powerful tool to yield information for optimization techniques to eliminate or control such instabilities. With quick and low-cost calculations, structural sensitivity and base-state sensitivity are achieved and the conditions
most sensitive to instabilities are identified.
Constrained layer damping concept used on isolated gym floors. Better than Concrete?
Authors: Rodrigues Marina
Published: February 2023

As the global fitness trends continues in a post-pandemic world, intra-building disruptions from high-energy fitness create serious acoustical challenges. Solutions from simple roll-out mats and rubber tiles to concrete floating floors supported by spring jack-up isolators are used
to achieve acoustical separation for gyms. Understanding the sources of sound and vibration produced in fitness environments and finding effective solutions was a journey that CDM Stravitec began in the 1970s and this area of the acoustics industry has been intensively researched as part of
the development of our range of lightweight floating floors. As part of this research, we extensively investigated how the concept of constrained layer damping (CLD) could be employed to mitigate vibration radiation through structures. In the application of fitness flooring, the CLD functions
to restrict the physical movement between the rigid board layers decreases the area of influence from the impact, reduces the energy radiation through the composite panel system to its support and subsequently reduces the energy transfer into the structure. Our research has also shown that
elastomeric supports balance low-resonant frequency performance to prevent energy build-up at the driving frequencies and can achieve high levels of transmission loss which are comparable to concrete based solutions.
Validation of three inherently different aircraft noise calculation programs
Authors: Meister Jonas , Schalcher Stefan , Wunderli Jean-Marc , Schäffer Beat
Published: February 2023

Aircraft noise affects large areas around airports. Noise calculation programs therefore need to account for air operations with high accuracy. In this contribution, we simulated several thousand single flights with the three aircraft noise calculation programs FLULA2, sonAIR and AEDT,
and compared the results among each other and with corresponding noise measurements to evaluate their accuracy. While FLULA2 and sonAIR calculations are adjusted to local conditions, AEDT was run with default settings (NPD data and standard procedural profiles) to assess its performance when
using unadjusted input data. We found that results of all three programs on average agree well with measurements and with each other. sonAIR is more accurate when using flight configuration data, but also in greater distances to the airports. Exemplarily adaptations of AEDT input data to local
conditions showed that such adaptations clearly improve its calculation results. It was shown that, despite their inherently different modelling approaches, (a) all three programs are on average equally capable of reproducing the sound exposure in the vicinity of airports, (b) adaptions of
input data to local conditions substantially improve results and (c) sonAIR is able to reproduce single flights with higher accuracy when provided with flight configuration data.
Thermoacoustic stability prediction using Deep Learning
Authors: Gaudron Renaud , Morgans Aimee S.
Published: February 2023

Thermoacoustic instabilities are an undesirable physical phenomenon that can occur in a wide range of combustors such as gas turbines, rocket engines, and boilers. These instabilities are typically loud, vibration-inducing, and can increase parietal heat transfer in the combustion chamber.
As a consequence, mechanical fatigue increases and can sometimes lead to a catastrophic failure of the combustor. A well-established formalism to predict thermoacoustic stability is based on network models where the combustor is represented by a sequence of connected acoustic modules. The
frequency of the modes appearing inside the combustor are then given by the eigenvalues of a characteristic equation obtained using conservation equations. This approach has been successfully used to predict the stability of a variety of combustors. However, this operation needs to be repeated
many times in order to optimise the shape of an unstable combustor at an early design stage. One option to reduce the computational cost of predicting the thermoacoustic stability of a given configuration is to use a data-driven approach as opposed to a physics-based approach. In the former
approach, a Machine Learning algorithm is trained to discriminate between thermoacoustically stable and unstable combustors using examples generated by a (physics-based) acoustic network model. The ML model is then able to predict the thermoacoustic stability of an unknown configuration much
faster than a traditional acoustic network model and with a very high accuracy. This approach has been validated in a previous study using classical Machine Learning algorithms, but it is restricted to somewhat simple geometries. The objective of this study is to investigate whether Deep Learning
architectures can be used to generalise those results to complex geometries with a large number of elements.
Optimisation of a Multi-Material Acoustic Black Hole
Authors: Austin Beth , Cheer Jordan
Published: February 2023

Acoustic black holes (ABHs) have been proven as an effective passive vibration control measure. Typically, they are realised by introducing a geometric taper into the structure. This approach introduces thin structural sections which leaves the ABH prone to damage through fatigue. An
alternative approach has been suggested in which the material properties vary within the structure, which can be realised through multi-material additive manufacturing. This allows the structure to maintain a constant thickness and this may reduce the effect of fatigue. Prior work has been
performed to characterise the materials currently available that would be suitable for the ABH application. This paper investigates methods of optimising the design of the multi-material ABH, in order to minimise the reflection coefficient in a beam termination application.
Numerical and experimental analysis on helicopter's main rotor transmission for predicting structure-borne noise (SBN) using CB-TPA methods
Authors: El Khatiri Wafaa , Cherif Raef , El Bikri Khalid , Atalla Noureddine
Published: February 2023

A large number of a vehicle's mechanical systems are responsible for tonal vibrations, which propagate through the connected structures to radiate structure-borne noise into the cabin. In the literature, transfer path analysis (TPA) methods make it possible to solve vibro-acoustic problems
using sub-structuring applications. This paper presents a case study of a heavy-active component connected to a plate backed cavity, using Component-Based transfer path analysis methods. The studied academic system is representative of a helicopter's main transmission. Both numerical and the
experimental characterization are used to discuss the effect of several parameters, such as coupling (in-situ) vs decoupling (sub-structuring), completeness of the used transfer function matrix, the accuracy of the inversion method, as well as the rigidity of the test bench used to identify
the equivalent forces. It is shown both numerically and experimentally that by using part of the frequency response functions matrix, one can reconstruct the response of both vibration and acoustic targets locations, even by decoupling the system and characterizing the equivalent forces on
a test bench.
Automating the assessment of sound power levels of running vehicles using information extracted from a static video
Authors: Takai Marjorie , Yonemura Miki , Lee Hyojin , Sakamoto Shinichi
Published: February 2023

Noise has become a ubiquitous pollutant in big cities, especially Road Traffic Noise compared with other means of transportation. Several countries/regions have developed road noise prediction models based on local measurements, adjusting their requirements and goals for evaluating
this pollutant. Differently than most developed countries, industrializing countries have different characteristics of noise generation due to implied differences, such as degree of maintenance (both vehicle and road conditions) and the driving behavior, for instance. The data acquisition
needed for evaluating the vehicle fleet's sound power emission is expensive and time-consuming. This research proposes using a video camera close to the microphone to automate the data gathering and analysis. Using a Python script, this system extracts the sound pressure, estimates the running
speed, assesses the distance from the receiver point, and classifies the vehicle under investigation. In addition, to discard inaccurate data, the expected trajectory and sound pressure are evaluated. The proposed system's performance was compared against manual measurements. The resulting
sound levels differ less than 0.2 dB for most cases. Thus, acquired 3.4 times the amount of data in the same time interval. After this verification, measurements in different conditions and vehicle fleet were tested in Hokkaido, Oita, and São Paulo cities.
A Study on the Noise Optimization through the Analysis of Electric Vehicle Noise Paths
Authors: Yang Yoon-Sang , Lee Seung
Published: February 2023

Since an internal combustion engine is not required for electric vehicle, the electric vehicle's noise is much lower than that of conventional internal combustion engine based vehicle. However, a road noise and wind noise that used to be masked by engine noise became the critical noise
factors. Moreover, the electric vehicle generates a specific current conversion noise and motor high frequency noise that provides an unpleasant sound environment for drivers and passengers. In this study, therefore, the noise path of the electric vehicle was identified through Power Based
Noise Reduction (PBNR) and Acoustic Transfer Function (ATF) tests. As a result of analyzing the noise path, it was confirmed that the rear side of vehicle was weak in terms of noise. As a countermeasure against this, it was confirmed that interior noise level could be improved by reinforcing
the luggage side.
Multi-directional active vibration control of 1D smart structure inspired by automotive engine mounting system
Authors: Hojoon Moon , Qiu Yang , Byeongil Kim
Published: February 2023

Recently, active mounting system is being gradually applied to automotive engine mounts for mitigating structure-borne vibration effectively throughout the whole vehicle chassis. This paper presents modeling, analysis, and control of a source structure with an active mounting system
in multi-directions, considering position and direction of actual automotive engine mounts. The active mount consists of a piezoelectric stack actuator in series with an elastomeric (rubber) mount. When harmonic excitation forces are employed, secondary force required for each active mount
is calculated mathematically and the control signal can reduce the vibration through the destructive interference with input signal. In addition, the horizontal vibration can also be mitigated by setting a variable parameter through the dynamic relation of source structure. A series of simulation
results demonstrate that the excitation vibration could be reduced along with this multi-directional (vertical and horizontal) active mounts. Based on this result, it can be expected that noise vibration harshness(NVH) performance can be improved by controlling the vibration of the actual
automotive engine structure with rubber mount and secondary force of actuators in both vertical and horizontal directions.
Validation of target tracking performance through signal feature extraction method based on 1D convolutional neural network
Authors: Hong Dongwoo , Kwon Junhee , Kim Byeongil
Published: February 2023

In order to perform active vibration and noise control, a variety of adaptive algorithms have been investigated and developed. Especially, neural network-based signal tracking algorithms, such as the radial basis function neural network (RBFNN), are being widely utilized. For signal
tracking problems, a reference signal has a significantly important role, while it is difficult to determine the reference signal when it has relatively complex spectrum. Thus, this study focuses on the signal feature extraction for manipulating appropriate reference signals easily and validation
of signal tracking performance with it. In order to carried out the signal feature extraction, 1D convolutional neural network (1D CNN) is implemented and trained based on the CWRU bearing dataset. In addition, multi normalized least mean square (NLMS), neural network-based signal tracking
algorithm, and diagonal recurrent neural network (DRNN) is employed to confirm the signal tracking performance. The proposed method shows that the 1D CNN-based signal feature extraction method could find the signal feature properly and the reference signal obtained from this methodology is
employed to a target tracking problem, which shows a great performance.
Modeling, analysis, and control of shaft transverse vibration from rotating systems through active bearing concept
Authors: Kwon Junhee , Hong Dongwoo , Kim Byeongil
Published: February 2023

Rotating parts are widely applied to mechanical systems such as pumped-storage hydroelectricity, nuclear power plant, machining tools and so on. While operating, they can be easily damaged or destroyed by unbalanced mass, bending, torsion and misalignment. In order to solve this problem,
rotor vibration control can be conducted through active bearing concept. In this work, active bearing system which consists of piezo actuators and rubber grommets is proposed and applied to a rotating system motivated from a pumped-storage hydroelectricity, for performing active vibration
control. The main point of this paper is to prevent damage or failure caused by harsh transverse vibration through active bearings. First, the rotating system is modeled by transfer matrix method (TMM) based on Euler-Bernoulli beam theory and in order to check accuracy of this model, the responses
of TMM are compared with the responses from the finite element method (FEM). For implementing active control in real time, normalized least mean square (NLMS) algorithm is utilized. The results show that the proposed active bearing concept shows great performance on the attenuation of shaft
transverse vibration.