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The audible frequency range covers many octaves in which the wavelength changes from being large with respect to dominant features of a space to being comparatively much smaller. This makes numerical prediction of a space's acoustic response, e.g. for auralisation, extremely challenging if all frequencies are to be represented accurately. Different classes of algorithm give the best balance of accuracy to computational cost in different frequency bands - 'wave solvers' such as Boundary Element Method (BEM) at low frequencies and Geometrical Acoustics (GA) methods at high frequencies. But combining their output data can be an awkward process due to their very different formulations. This is particularly important for early reflections, which give crucial spatial perceptual cues. Hence there is a need for a unified full audible bandwidth algorithm for early reflections. This paper will describe ongoing research to develop such an algorithm by exploiting synergies between high-frequency BEM and GA. It will describe how appropriately chosen oscillatory basis functions in BEM can produce leading-order GA behaviour at high frequencies and explore how interactions between these compare to the same interactions arising in a surface-based Geometrical Acoustics scheme. [ABSTRACT FROM AUTHOR]

The evaluation of urban noise is an important tool in noise control. From existing sources of noise, vehicular traffic is considered the main cause of discomfort in the population. The intensity of the noise that reaches the receiver depends on the level of sound power emitted by the source and the attenuation that occurred in the propagation medium. The analysis of the dispersion of rays in different urban geometries allows the evaluation of parameters that influence the trajectory of noise. The objective of this work is to analyze the contribution of the energy fraction of each path in global noise in different urban configurations, to contribute to the analysis and adoption of mitigating measures. For this, the mathematical model of prediction of noise levels was adopted, which calculates the direct paths and specular (source-image method) and diffuse (radiosity method) paths. The study was applied in two sectors of the city of Maringá, Brazil. In total, 73200 paths were evaluated in 2928 readings of source positions in 54 measured points. The results showed the part of contribution that each path represents in the acoustic field, and the sound decay caused by obstacles, urban geometry, distance and material properties. [ABSTRACT FROM AUTHOR]

Suspended ceilings made of several layers of gypsum boards are a common way to increase the sound insulation of slabs in buildings. The ceiling is typically hanging 100-500 mm below a slab. There are many manufacturers of the hangers and most of them supply elastic hangers, made of rubber or metal springs. The elastic hangers are very costly and there are very little scientific data of the effect of these elastic hangers, especially at low frequencies and especially for concrete slabs, which are the most common slab type. The sound insulation of normal buildings is increasing with frequency and the low frequency region is the most interesting region. The author has for more than 30 years been part of many cinema projects where elastic hangers have not been used. Still, the sound insulation at low frequencies is excellent. What are the most important parameters? Could it be that elastic hangers are even reducing sound insulation due to resonances at low frequencies? In this paper we will discuss measurement data both from laboratory and real buildings with focus on air-borne sound insulation at low frequencies. We will also discuss calculations methods. [ABSTRACT FROM AUTHOR]

Floating floors are a common means of reducing airborne and structure-borne noise, however, prediction of in-situ performance remains a challenge for many consultants. The specification of such floors, usually based on single degree of freedom assumptions, does not account for the influence of floating floor dynamics, dynamics of host structures or interplay/power flow between the two via the isolating mounts. Reliance on single degree of freedom systems tend to over-predict the performance of the floating floor element, often leading to noise/vibration issues in the finished construction. A more robust approach is needed, though is challenging due to complexities in characterising largescale constructions, where source-to-receiver Frequency Response Functions (FRFs) must account for multiple points of contact between floating and structural elements. This paper first presents a hybrid method for evaluating the source-receiver FRF of a simple floating floor via a sub-structured approach and confirms the validity of the method to that of the source-receiver FRF measured directly whilst accounting for real world limitations in a building acoustics consultancy setting. [ABSTRACT FROM AUTHOR]

As with any asset on the highways network, it is common sense to allow for realistic maintenance costs when choosing and procuring a noise barrier system. A short-term approach of focusing on newly installed prices alone creates a false economy and potentially stores up financial hardship for the future. The adverse impact of road traffic noise on public health is also long appreciated. Being able to quantify in financial terms not the only perceived annoyance but also the long-term damage to health due to traffic noise helps to justify why one particular noise barrier design will benefit the community more than another over its life cycle. [ABSTRACT FROM AUTHOR]

An air flow going through an axisymmetric cavity can interact with the acoustic modes of this cavity and produce loud self-sustained acoustic oscillations. Acoustic measurements reveal that the nature of the acoustic mode undergoes complex dynamics. Simultaneously to acoustic measurements, time resolved stereoscopic particle image velocimetry gives the three velocity components in a two-dimensional plane. Although the experimental velocity fields are only two-dimensional, the whole tridimensional phase-averaged velocity field can be reconstructed for the specific case of a spinning aeroacoustic mode. This reconstruction reveals the existence of a helical vortex tube spiralling in the shear layer at the cavity opening. [ABSTRACT FROM AUTHOR]

A major purpose of the European Outdoor Noise Directive (OND) 2000/14/EC is to provide to potential buyers of outdoor machinery relevant noise information to foster the purchase of low noise models, hence incentivizing manufacturers to produce over time quieter machinery. However, the results of this strategy have yet to meet the expectations. Among other issues, the actual noise label for equipment subjected to the OND has been identified as an element that needs to be revised to better fulfill its guidance purpose. This paper proposes a solution to provide meaningful noise information to potential buyers in an effective way by leveraging mobile communication technology and taking in account insights about human buying behavior and habits. This proposal could also benefit market surveillance's effectiveness and assist resellers when advising customers. [ABSTRACT FROM AUTHOR]

TDR measures the rate of vibration decay along rail in dB/m. Higher TDR leads to lower noise radiation. However, new railways are often having low TDR due to the use of resilient fasteners (to provide vibration isolation between rail and supporting structure for ground borne noise concerns), which leads to high noise radiation. Rail damper is used to increase TDR (thus reduces railway noise), where TMD is an efficient damping mechanism dissipating the vibration energy of the rail. TMD provides reactive damping force, maximised after a few cycles of oscillations. TMD force is stronger with continuous excitation than impulse excitation. For convenient purposes in the industry, TDR measurements are primarily conducted by impulse method, which do not allow sufficient time to include reactive TMD force. Therefore, impulse excitation TDR is smaller than continuous excitation TDR. Continuous excitation TDR is considered to reflect more of the real case of wheel/rail interaction excitation during train running. Besides, TDR in terms of time decay in dB/s is an alternative approach for evaluating noise performance of the rail. This paper presents TDR measurement results of short rail (~6m) with resilient fastener support in a laboratory setting. [ABSTRACT FROM AUTHOR]

Construction noise is one of the major noise pollution sources in urban area. In Hong Kong, the Noise Control Ordinance (NCO) states that construction works at night time and holiday with Powered Mechanical Equipment (PME) are only allowed if the PME noise levels are controlled within the Acceptable Noise Level (ANL) calculated at nearby Noise Sensitive Receivers (NSRs). In many cases, night work required noise barrier to minimize the PME noise levels. However, conventional noise barriers of 3m to 6m height required a heavy base in order to sustain occasional heavy gust wind loading. Those heavy base required cranes to install and relocate which may not feasible under some site constraints. SilentUP® Retractable Noise Barrier has been invented in Hong Kong to meet this demand. It is a 7m high noise barrier without concrete foundation. The modular design and magnet connecting mechanism allows SilentUP® to form a continuous wall. It can be installed, uninstalled and relocated by people without using any machines. The entire process is quiet enough to be completed at night. To enhance the stability and safety features, a patented automatic wind load relieving mechanism is incorporated so that the lightweight structure remains safe during occasional gusts. It reduces up to 95% structural loading requirement and hence a lightweight design can be adopted. The on-site insertion loss performance of SilentUP® Retractable Noise Barrier is varied from 11-21 dB(A) depending on the noise source and size of barrier / enclosure. [ABSTRACT FROM AUTHOR]

Noise impact from sheet piling by vibratory hammer is one of the major concerns during the basements construction. It is also a challenge to conventional mitigation methods such as noise barrier or enclosure due to the size of the sheet piling wall. The results from acoustic imaging by acoustics camera shows that the major noise source of sheet piling event is the radiated noise from a row of sheet piles vibration with dominant frequencies were ranged from 630Hz to 2000Hz. Vibration frequency response of sheet pile is also measured with handheld force hammer. A tailor made Sheet Pile Tuned Mass Damper (Sheet Pile TMD) is invented to dissipate vibration energy of sheet pile by tuned mass damping mechanism hence the noise raising from the sheet piling work would be mitigated. The on-site noise and vibration reduction performance of total 6 sets of 5m long Sheet Pile TMD, installed on 12m high x 4m wide sheet pile wall driven by vibratory hammer, were determined. The Sheet Pile TMDs was tuned to absorb vibration energy from 630 Hz to 1250 Hz by adjusting the stiffness of the resilient layer and the size of the oscillation masses. From the on-site trial results, the Sheet Pile TMDs achieved ~9-14dB vibration reduction at the 1st, 2nd and 3rd piles next to the driven pile and ~7dB noise reduction at distance 7m and 22m from pile. [ABSTRACT FROM AUTHOR]

With the increasing use of wood also for multistory dwellings, a wide variety of timber construction systems have been developed in Austria, of which in particular timber post and beam construction and solid timber construction in cross-laminated timber have become established. During the Internoise 2006, thefirst session on sound insulation in timber construction was initiated by Jean-Luc Koiumji. Within this session Austrian experiences with CLT could be presented for thefirst time, using the example of the first multistory CLT apartment houses in Austria, that even high sound insulation requirements can be wed met. However, it also became apparent that there is still a great need for research, especially in the low-frequency range, in flanking transmission and optimization. In the last years, within the ongoing Sound.Wood.Austria research project, acoustic laboratory measurements of typical Austrian wooden building components were carried out in order to determine the effect of various design measures on sound insulation in a systematic approach and to identify possible optimization potential. Exterior walls, apartment partition walls and apartment partition ceilings were investigated, but also effects from flanking transmission. In this talk, selected measurement results are presented and discussed. However, the results pointed out, that further research work and developments, preferably internationally networked, are desirable in order to exploit the acousticpotential of timber buildings in the sense of'Green Deal". [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration has made a commitment to deliver to the International Civil Aviation Organization's Committee on Aviation Environmental Protection (ICAO CAEP) data defining community response to sounds from supersonic aircraft designed such that their sonic boom is replaced with a soft "thump" sound. The dataset will be a correlation of public perceptions of these sounds to the corresponding acoustic levels. The data will support efforts to develop international standards for permissible noise from supersonic overflight. NASA is planning andpreparing for a series of community overflight tests with the X-59, a unique research aircraft capable of generating the "sonic thump". NASA svill begin these tests in 2024. With an eye toward achieving global consensus for noise standards, NASA's goal is that the community response data be as broadly representative of the response of the international population as possible. As such, NASA is engaging the international regulatory and research communities in both the planning and execution of these tests, through status briefings at ICAO CAEP-sponsored meetings and through workshops with international participation. As part of this outreach NASA held a virtual workshop in December 2021 focused on strategies and considerations for estimating noise exposure levels and conducting surveys to characterize community annoyance levels relative to the "thump" sounds. This paper will present an overview of NASA's effort, with a focus on the plans and technical goals for the community response tests. In addition, results of the recent workshop will be briefed, including considerations and approaches for ensuring broad representativeness of results and approaches for estimation of the sound levels across the test community. Participant feedback from both the workshop and previous engagements will be discussed, along with how it is being addressed in NASA's ongoingplanning efforts. [ABSTRACT FROM AUTHOR]

Railway GBN impact has raised increasing concerns due to underground metro expansion. Reducing train speed or replacing standard baseplates with high resilient baseplates are sometimes adopted for GBN control. Both mitigations are not satisfactory considering the installation difficulty and limited performance, e.g. only ~3dB noise reduction for 30% train speed reduction. On the other hand, FST (Floating Slab Track) are commonly used. In many cases, to accommodate the FST, tunnel diameter is enlarged for the TBM (Tunnel Boring Machine) tunnel section. Also, rail dampers are used for air-borne noise control, but never used for GBN control due to its relatively small mass. P2 resonance is a main cause of railway GBN. It is a simple harmonic motion of a lump mass (wheel and rail combined) oscillating on top of resilient baseplates. Laboratory test with a 6m fastened rail and a ~450kg weight to simulate train wheel and track system. A retrofit rail damper with TMD (Tuned Mass Damping) oscillators is tested. The mass TMD oscillators along the rail with ~2m effective length of P2 resonance is more than 10% of the wheel mass. Around 7dB vibration reduction is recorded at the rail and floor when allowing the TMD oscillation. [ABSTRACT FROM AUTHOR]

A lot of work was spent by acousticians the last decades to reduce the noise caused by technical products. Important steps on that way were the description of the sound emission of these products and facilities by unambiguously defined quantities - the A-weighted sound power level and the emission sound pressure level. With a framework of standards for measurement and declaration we supported the buyer of such products in his purchase decision. The emission values of different machine groups were published - in standards and guidelines in anonymous form - and the buyers were encouraged to select from possible alternatives those that offer the lower noise emission in their declaration. But since many years we hear in this buy quiet sessions that the declared emission values are often not very reliable - and they are not understandable for those affected by the noise. This can be improved by establishing a strong link between the emission and the noise impact. Some strategies and tools are shown and recommendations for the development of supporting standards are given. Some examples about the advantageous use of emission values are demonstrated. [ABSTRACT FROM AUTHOR]

As London's extensive underground network passenger communication is highly dependent on its Public Address/Voice Alarm (PA / VA) system, attention to its efficacy is of great importance. In its current state, the system lacks 21st-century performance regarding modern technological capabilities. It has not been able to overcome the difficult acoustic challenge that an underground station represents, struggling to achieve the minimal life safety intelligibility requirements established by the British standard and bringing an uncomfortable experience to its millions of daily passengers. A reinterpretation of the line array / planar source concept has been proven to raise the intelligibility beyond the minimal requirements by achieving a homogeneous sound distribution close to the public, with minimal room excitation thus minimising reverberations destructive interference to intelligibility. [ABSTRACT FROM AUTHOR]

Aircraft designs may include an engine that exhausts over the upper fuselage of the aircraft. This design has many benefits including reduced noise below the aircraft. However, the scrubbing of the high-speed turbulent jet flow over the fuselage has the potential to cause structural fatigue. This paper describes an experimental/computational study of the surface pressure fluctuations induced by the supersonic jet flow. The model configuration consists of a rectangular convergent-divergent nozzle that exhausts over a flat plate. The plate is a continuation of the lower lip of the nozzle. Pressure measurements are made at several locations on the plate surface. In addition, schlieren visualization is used to identify the jet's shock cell structure. Numerical simulations are performed using hybrid RANS/Large Eddy Simulation (LES). Results are compared between the simulations and the experiments. The importance of shock turbulent boundary layer interaction to the surface loading is identified. [ABSTRACT FROM AUTHOR]

Assessment of annoyance "at home" from environmental noises has been widely investigated so far and the ISO/TS 15666:2021 was developed to lead the socio-acoustic surveys. On the other hand, the rating of buildings' acoustical performance considering the indoor noise levels, has also been well researched in building acoustics and the studies have ended up with the ISO/TS 19488:2021 covering the acoustic classification system for buildings. Basically the rating system needs to be supported by the subjective tests in the field or in laboratories, to acquire data about the annoyance/disturbance or satisfaction of residents. If the target is to design the healthy, comfortable and sustainable acoustical environment, both technical standards might be harmonized in the future, particularly with respect to survey methodologies and evaluations. In this paper, based on the dose/response relationships with respect to the indoor noise levels, an approach is proposed to translate the acoustic classes proposed in ISO/TS 19488, into the annoyance boundaries in terms of different scales (verbal/numerical and the HA%) referred in ISO/TS 15666. The results from the previous laboratory and the field studies conducted by the authors, were used for verification of this approach. [ABSTRACT FROM AUTHOR]

Roughness in rail surface accumulates with train operations and grows faster on curved tracks than tangent tracks. Higher roughness leads to higher noise radiation. In Hong Kong, railway noise prediction includes a 3dB correction for rail surface deterioration. Depending on rate of deterioration, different rail grinding cycles (typically between 3 and 24 months) are scheduled to ensure train operations without excessive noise radiation. Before rail dampers installation, noise levels were monitored for 1.5 years and around the noise limit with variation +/- 3dB(A) due to rail roughness variation. After installation of rail damper, railway noise was generally maintained at 7dB(A) below the noise limit with variation +/-1.5dB(A) for more than 3 years. Noise reduction at dominant frequencies 630 Hz and 800 Hz were more than 10dB in 1/3 Octave analysis. The rail dampers were installed at alternative spaces such that additional rail dampers can be installed to double the amount in case further noise reduction is required. This paper examines the five years' monitoring data in detail, showing the noise levels with smaller variations over grinding cycles after rail damper installation, and explores rail damper potential ability to slow down the growth rate of rail roughness levels. [ABSTRACT FROM AUTHOR]

Although the need to consider acoustics in the built environment is well-accepted, an understanding of 'what' constitutes 'good acoustics' is not. The authors present posteriori--reviews of historical events and of empirical evidence--to develop an understanding of the current landscape of Standards, Guidelines, and Codes. More specifically, special attention is devoted to the development of speech privacy metrics, as well as that of auditory and non-auditory effects of noise and sound on health. With a refreshed understanding of theory, a priori--i.e., an acoustical framework for design and/or performance verification with a special interest in speech privacy--is renewed and its impacts on the ongoing development of Standards, Guidelines and Codes is discussed. [ABSTRACT FROM AUTHOR]

The need has been identified for an overall outcome of any co-ordinated airport research programme to work towards a better understanding of airports impact on QoL with a requirement to better understand the value (in terms of noise reduction and health outcomes) and effectiveness of the interventions airports make - this includes the provision of respite. Anderson Acoustics Ltd (funded by Heathrow Airport Ltd) has been consolidating current knowledge on respite, particularly in relation to airspace design. That work has essentially continued the journey towards understanding respite and its effective implementation, linking together past, current, and potentially future activities, providing timelines, signposting to other reports and work. This paper presents a highlevel overview of HAL's journey to date on building knowledge on respite. [ABSTRACT FROM AUTHOR]

Aircraft noise prediction models traditionally omit buildings to optimize speed. Buildings and vertical surfaces scatter and reflect incident sound, affecting sound levels around buildings and within streets. Previous studies showed the impact of buildings on aircraft noise, based on a small number of measurements. Based on additional numerical models, it was found that the shape of buildings, i.e. a slanted or overhanging roof, lead to lower sound levels compared to streets comprised of vertical and flat surfaces. To examine these findings, a fullscale field lab was built near Amsterdam Schiphol Airport, comprised of shipping containers. The experiment consists of three courtyards, in which ten microphones measure sound levels from aircraft flyovers, near facades facing towards and away from the sound source (airplanes). Measurements are matched with meteorological and radar data, which gives information about the position of aircraft and the local weather conditions. The measurements show substantial differences depending on the position, ranging between 8/9dB(A) for a courtyard with straight facades, up to 14dB(A) for facades in a courtyard with a slanted facade and a building inset. Results can be used to rethink the way areas near airports are designed. [ABSTRACT FROM AUTHOR]

A human listener embedded in a sonic environment will rely on meaning given to sound events as well as on general acoustic features to analyse and appraise its soundscape. However, currently used measurable indicators for soundscape mainly focus on the latter and meaning is only included indirectly. Yet, today's artificial intelligence (AI) techniques allow to recognise a variety of sounds and thus assign meaning to them. Hence, we propose to combine a model for acoustic event classification trained on the large-scale environmental sound database AudioSet, with a scene classification algorithm that couples direct identification of acoustic features with these recognised sound for scene recognition. The combined model is trained on TUT2018, a database containing ten everyday scenes. Applying the resulting AI-model to the soundscapes of the world database without further training shows that the classification that is obtained correlates to perceived calmness and liveliness evaluated by a test panel. It also allows to unravel why an acoustic environment sounds like a lively square or a calm park by analysing the type of sounds and their occurrence pattern over time. Moreover, disturbance of the acoustic environment that is expected based on visual clues, by e.g. traffic can easily be recognised. [ABSTRACT FROM AUTHOR]

Wearing face masks (alongside physical distancing) provides some protection against COVID-19. Face masks can also change how people communicate and subsequently affect speech signal quality. This study investigated how two common face mask types affect acoustic analysis of speech perception. Quantitative and qualitative assessments were carried out in terms of measuring the sound pressure levels and playing back to a group of people. The responses gauged proved that masks alter the speech signal with downstream effects on speech intelligibility of a speaker. Masks muffle speech sounds at higher frequencies and hence the acoustic effect of a speaker wearing a face mask is equivalent to the listener having slight high frequency hearing loss. When asked on the perception of audibility, over 83% of the participants were able to clearly hear the no mask audio clip, however, 41% of the participants thought it was moderately audible with N95 and face shield masks. Due to no visual access, face masks act as communication barriers with 50% of the people finding to understand people because they could not read their lips. Nevertheless, based on these findings it is reasonable to hypothesize that wearing a mask would attenuate speech spectra at similar frequency bands. [ABSTRACT FROM AUTHOR]

This paper aims to introduce preliminary statement of methods of a computationally efficient and user-friendly toolbox, called VIBWAY, able to predict vibration and re-radiated noise levels in two situations. On the one hand, it can predict levels in existing buildings due to new lines or after the application of mitigation measures in existing operational railway infrastructures. Thus, it can be used to assess the performance of vibration countermeasures applied at the track, at the soil and/or at the building. On the other hand, it can predict levels in new buildings to be constructed close to an existing railway line from vibration measurements in the surface of the ground where the building will be constructed. The VIBWAY toolbox is based on a non-interface 2.5D FEM-SBM approach for the wave propagation on the soil, on semi-analytical approaches for the track and the building and on rigid multibody dynamics modelling of the train vehicle. [ABSTRACT FROM AUTHOR]

In industry, the use of blocked forces for the characterisation of structure borne sound sources is now common practice, whereas the sound power is typically used for airborne sound sources. It should also be possible to use blocked forces (or blocked pressures) to predict airborne sound radiation using a similar approach and measurement methodology as the in-situ blocked force method. This is achieved by discretising the surface of the source into small unit cells, and measuring the vibration velocity whilst operational. To convert these velocities to blocked forces, the mobility of the source for each of the positions must also be known: and to predict the radiated sound, a measured vibro-acoustic frequency response function is also required. Typically, vibro-acoustic FRFs are measured by exciting the structure with an instrumented hammer or shaker, but they may also be measured reciprocally using a volume velocity source. Described in the paper is an experiment conducted in a fully anechoic chamber to investigate the feasibility of the above approach, i.e. using blocked pressures and reciprocally measured vibro-acoustic FRFs to characterise and predict airborne sound. The method is validated by comparing the directly measured radiated sound pressure to the predicted pressures, according to the above. [ABSTRACT FROM AUTHOR]

Motorcyclists are among the most vulnerable road users globally, they enjoy less protection than car drivers and experience higher speed collisions than cyclists, with less mobility and spatial awareness to avoid crashes. Sound localisation (SL) while wearing military and ski helmets has been a significant area of research to improve spatial awareness, but no research has been completed thus far on the impact of motorcycle helmets on SL. This research aims to examine experimentally the impact of a motorcycle helmet on the Head Related Impulse Response, and therefore determine the extent of the impact on SL ability of a user. A database of HRIRs was established as a function of position in the horizontal plane with and without a motorcycle helmet. The variation in the signals was evaluated and it was found that the helmet results in a significant alteration to the HRIR at higher frequencies, important for resolving front-back confusions. It is also demonstrated that the overall sound attenuation would result in reduced SL ability of the rider. A novel system to compensate for changes in the HRIR was developed and experimentally tested to mitigate the impact on SL ability for the wearer. [ABSTRACT FROM AUTHOR]

Train Activated Warning System (TAWS) is a railway safety system which uses an audible warning to alert track workers of an oncoming train. When the system is active, a safe-tone sound is emitted to indicate the system is active. Activated by the train signalling system, the safe tone switches to a warning-tone when a train approaches, in enough time to allow rail workers to reach a position of safety. There is currently no specific methodology for designing a new TAWS to achieve the required audibility over a defined area of track. This paper discusses the approach to the design and specification of the TAWS audibility over lengths of track where different prevailing acoustic environment conditions need to be considered. The challenges encountered and the limitations of the resulting approach are also discussed. [ABSTRACT FROM AUTHOR]

The global COVID-19 pandemic has resulted in social distance restrictions that have limited the ability for transport authorities to undertake in-person community engagement activities and consult on proposed local infrastructure developments. Potential increases in noise levels or change in acoustic environment can often be a key concern for residents living close to a proposed development. This paper documents the approach taken to engage with local stakeholders regarding a proposed new light rail metro line in Toronto, Ontario, Canada, using an innovative online web-based auralization tool. The tool allows the existing trains and planned new metro trains to be compared interactively in an environmental context and with and without acoustic mitigation interventions. The paper discusses the benefits, challenges and limitations associated with the delivery method and provides an overview of the auralization approach of the proposed new metro line. [ABSTRACT FROM AUTHOR]

The properties of the materials used in underwater acoustics are important for applications such as acoustic windows, reflectors and baffles, acoustic barriers or screens, decoupling materials, and anechoic coatings. To characterise the performance of such materials at frequencies above 1 kHz, measurements are typically undertaken on samples of the material in the form of finite sized panels. Such measurements suffer from uncertainty due to the finite size of the panel (leading to contaminating signals from edge diffraction), and the difficulty in simulating the ideal plane-wave insonification. This paper describes work at the UK National Physical Laboratory to minimise these effects by use of: (i) a parametric array as a sound source that provides a directional beam and short broadband pulses; and (ii) nearfield scanning using a hydrophone to sample the complex sound pressure field interacting with the test sample, decomposing the sound field into its plane-wave components. Results are presented of these techniques applied to measurements in laboratory test tanks at frequencies between a few kilohertz and a few hundred kilohertz to determine the reflection and transmission performance of a range of test samples, including panels consisting of homogeneous polymers and materials with regular periodic structure. [ABSTRACT FROM AUTHOR]

Indoor soundscaping is a multi-disciplinary field that integrates, sound, user experience, and architecture. At its core, it has the potential to redefine any enclosed acoustic environment. Listening to spaces should be an active act of an interior architect; an awareness that should be gained during the early years of interior architecture undergraduate education. The elective course with the same name, 'Listening to Spaces' has been offered to interior architecture students since 2015 at Çankaya University, Ankara, Turkey under the Department of Interior Architecture, with the aim of implementing an important additional topic specific course to the present education curriculum of the Department as the course combines architectural, spatial and functional analysis methods from an acoustical perspective, in order to raise awareness on conscious listening of spaces with different functions. The course is conducted through interactive learning bases and the orientation is more research-based than teaching-based, although basic acoustical and soundscape theoretical knowledge is given. Students are expected to accomplish 6 tasks progressively following the cognitive process dimensions parallel to Bloom's taxonomy. The outcomes of the tasks and the final spatial design proposals has been evaluated and discussed as part of this study to highlight the importance of topic specific course integration to architectural design education. [ABSTRACT FROM AUTHOR]

Measurement methods with multiple sensors are powerful tools in assessing and diagnosing noise. As sensor counts increase, the number of sensors can exceed the number of available channels in a single data acquisition system. In these cases, multiple data acquisition systems can be used, but synchronizing the sampling of each system is critical for an accurate measurement. In this tutorial, different methods of synchronization are discussed, along with the benefits and drawbacks of each. Additionally, methods of post-processing data to synchronize measurements are presented for use in cases where hardware-based synchronization is not feasible. [ABSTRACT FROM AUTHOR]

The purpose was to compare the acoustic performance of commercial thermal insulators. Thirteen insulator types were studied. Six acoustic quantities were determined: sound reduction index of bare insulator, sound reduction index of encapsulated insulator (insulator between two boards), normal incidence sound absorption coefficient, airflow resistivity, dynamic stiffness per unit area, and reduction of impact sound pressure level in a floating floor. The ranges were 10-27 dB, 33-52 dB, 0.20-0.78, 3.0-2700 kPa-s/m2, 1.5-730 MN/m3, and 15-36 dB, respectively, when the thickness of the insulator was 100 mm. Closed-pore insulator types usually carried worse acoustic properties than open-pore insulator types. Lower thermal conductivity was associated with worse acoustic performance of two acoustic quantities. Insulator manufacturers should consider to better declare the acoustic properties of insulator products, because this knowledge is needed in the acoustic design of building constructions and other applications. [ABSTRACT FROM AUTHOR]

Controlling impact noise from heavy weight drops continues to be a challenging design issue in new and existing gyms. Within the design and prediction phases, in-situ measurements on bare slab and flooring test samples are often required to reduce uncertainty. However, these can be intrusive, and there is no consistent test methodology within the industry as of yet. This is further complicated by the nature of problem - a large number of source mass and height combinations and potential flooring test samples to be tested with such source combinations. Emerging guidance within the UK is likely to fill gaps on predictions for typical gym floors with reliance on engineering grade assumptions and empirical limits. However, this does not necessarily subside the need for robust in-situ test data to complement such predictive approaches. As such, there is a need for a methodology which bridges the gap between prediction and in-situ test elements which is reliable, time efficient and can be used for predictions on wider source cases and in varied locations or structures. The paper discusses potential ways of simplifying prediction and testing strategies with a view to estimating the noise and vibration levels from gym floors with resilient layer. It is shown that if certain quantities can be independently characterized in a laboratory, then this would avoid the need of weight drop testing in-situ. [ABSTRACT FROM AUTHOR]

Mobile enclosures (booths, pods) or partially enclosed furniture ensembles are increasingly used in offices, hospitals, education buildings, traffic centers and other public places to provide spaces for conversations, meetings, or private work. International standard ISO 23351-1:2020 describes a laboratory method for determining the speech level reduction DS,A of such mobile products. DS,A describes how much the product reduces the A-weighted sound power level of standard speech to the exterior space. The method is based on repeated application of ISO 3741 standard. The purpose of our study was to determine the precision of the ISO 23351-1 for two extreme kinds of mobile products that the method covers: a workstation and a phone booth. Eight laboratories from six countries participated in the accuracy experiment. Two specimens were circulated in these laboratories and tested according to ISO 23351-1. The measured DS,A values varied from 3.7 to 5.5 for the workstation and from 27.2 to 30.3 dB for the booth. The corresponding reproducibility standard deviations were 0.6 and 1.1 dB, respectively. The results show that the precision of ISO 23351-1 is high and in good agreement with ISO 3741 standard. The results have been published in Annex C of ISO 23351-1 standard. [ABSTRACT FROM AUTHOR]

The aim was to determine how the sound levels of wind turbines and road traffic are associated with stress, diseases, and symptoms in a wind turbine area. Case-control design included a wind power area and a control area farther away not exposed to wind turbine noise nor visibility of turbines. Sound levels were modeled to the yard or all potential respondents. Road traffic and wind turbine sound level varied between 32-64 dB and 17-39 dB LAeq, respectively. Altogether 684 residents responded to a living environment questionnaire. No associations with wind turbine sound level were found for symptoms, diseases, nor stress. Unexpectedly, prevalence of several symptoms and prevalence of heart disease were higher if road traffic sound level was higher. Wind turbine sound level did not exceed the Finnish regulated value of 40 dB LAeq in any residential yard. Therefore, the findings can be applied to existing and future areas where the regulated value is applied. Our study emphasizes that road traffic noise can be a larger problem than wind turbine noise even in wind power areas, not to mention areas where the road traffic noise is higher than in our study. [ABSTRACT FROM AUTHOR]

A feedforward active noise control system represents a valid solution whenever it is necessary to attenuate a disturbing noise at low frequencies. One example of application is the case of tractors, in which the agricultural operators are exposed for a prolonged time to loud low-frequency noise, mainly generated by the engine. Generally, the feedforward systems make use of one reference sensor to measure the noise produced by the main source. However, this way of proceeding could be inadequate to describe the disturbing noise, especially when the noise consists of both structureborne and air-borne components. In this article, a comparison between the use of single and multiple reference signals, processed in a multichannel active noise control system applied to the cabin of a motionless tractor, is proposed. In particular, an accelerometer positioned on the turbocharger is used to sense the vibration generated by the engine, while a microphone placed near the cooling fan is used to sense the air-borne noise. The active system implements the filtered-X least mean squares (FXLMS) algorithm to produce the anti-noise signals. The results show that the use of two simultaneously acquired reference signals generates only small benefits in the performance of the active system. [ABSTRACT FROM AUTHOR]

Although the demands and sales of cordless vacuum cleaners are on the rise in the global home appliance markets, some consumers are still complaining of the inconvenience such as short battery life and frequent emptying of a dust box. To resolve such inconvenience, a suction station tower that can automatically charge the battery and empty the dust box has been developed and is now on the market. However, aerodynamic noise generated when the station tower sucks dust in the vacuum cleaner causes another inconvenience. The purpose of this study is to identify the major aerodynamic noise sources in the complex internal flow passage which forms when the station tower is connected to a wireless vacuum cleaner and to develop a low-noise design based on the identified noise sources. First, the entire flow path through the cordless vacuum cleaner and the station tower was simulated using the unsteady compressible Reynolds-Averaged Navier-Stokes equations. Then, the main aerodynamic noise sources were identified using the vortex sound sources. From these results, the flow region through the head nozzle throat of the cordless vacuum cleaner was identified as one of the most significant aerodynamic noise sources. Based on the identified noise source mechanism, two new throat designs named Model A and B were proposed, and their validity was investigated using a high-resolution Large Eddy Simulation technique. It was found that the strength of the vortex sound source of pipe flow through Model B was much less than the others. This result well matched the predicted and measured sound pressure levels according to the different shapes of the head nozzle throats. [ABSTRACT FROM AUTHOR]

This article provides a broad overview of the recent advances in the field of spatial active noise control techniques to reduce unwanted noise over a certain region of interest. Thanks to overview of the recent advances in the field of spatial active noise control techniques in local active noise control systems extending the size of the quiet zone seems to be a crucial step to developing the next generation of active control systems for a more personalized and quieter audio product. In this review article, the advances over the past decade in the design and development of spatial active noise control techniques to enlarge the controlled sound zone are reviewed. The study has paid specific attention to measures such as convergence rate, stability and robustness of the algorithms, the size of the quiet zone and how it can be enlarged by configuring the loudspeaker and microphone array geometries. Finally, the authors will discuss the current and future challenges that should be overcome to improve the effectiveness of the recently proposed methods to expand the silence zone. [ABSTRACT FROM AUTHOR]

Absorbing sound almost completely at specific frequencies with conventional acoustic materials whose thickness is much smaller than the wavelength is a challenge, particularly at low frequencies. For this purpose, acoustic metamaterials are of great interest. The metamaterial studied in this research is called multi-pancake cavities. It is composed of a main pore with a repetition of thin annular cavities (pancake cavities). Previous research has shown that this repetition increases the effective compressibility of the main pore. This increase makes it possible to decrease the effective sound speed in the material and, consequently, the main pore resonance frequencies. At these resonances, the metamaterial presents absorption peaks, the first one can have a wavelength to material thickness ratio of more than dozens of times (subwavelength material). To complete the analysis and prediction of absorption peaks (especially secondary peaks) of these metamaterials, this study proposes to adapt a conventional mass-spring model to this metamaterial. Due to the small cavity length-to-diameter ratios, radial propagation is considered inside the annular cavities. This model shows a good agreement with results obtained by finite element method and impedance tube measurements. Finally, comparisons with previous theoretical approaches are presented and discussed. [ABSTRACT FROM AUTHOR]

Porous materials with energy absorption characteristics have been used for attenuation against hazardous vibrations and noises. The intrusion of liquid water and aqueous solutions into hydrophobic nanoporous materials such as metal-organic frameworks (MOFs) present an attractive pathway to engineering new attenuation technologies. In this process, hydrostatic pressure forces water to intrude hydrophobic nanopores, thereby converting mechanical work into interfacial energy through nanoscale interfacial interactions. Once the external pressure is removed, water molecules can flow out of the nanopores spontaneously, making the system reversible. We envision that this mechanism has the potential of innovating attenuation technologies, so in this work we provide a preliminary study in this direction. We investigate a material system consisting of water and a commonly used MOF, zeolitic imidazolate framework-8 (ZIF-8) and demonstrate its reversibility and stability under cyclic pressurization, considering its performance at various peak pressures and frequencies, its tunability in terms of intrusion pressure, and its potential in hydrogel forms. These features are important for potential attenuation technologies based on this novel mechanism. [ABSTRACT FROM AUTHOR]

The LIFE SNEAK project, started in September 2021, aims at the reduction of noise in densely populated urban areas where noise and vibrations produced by the tram overlap with noise produced by road traffic. Applicative measures will be designed and tested in a pilot case of the city of Florence, such as lownoise and vibration surfaces, with life cycle costs comparable to those of traditional surfaces, and measures to reduce tram noise aiming to obtain substantial reductions in noise and annoyance. Referring to tram noise, in the first phase of the project, specific attention has been dedicated to the state-of-the-art analysis concerning possible measures to perform noise reduction with specific attention to noise due to wheel-rail contact and "squeal noise" phenomena that mainly occur in urban environments close to curves with small radius. In this paper, the results of the state-of-the-art analysis are presented with particular attention to the use of sound-absorbing panels to be applied on the tram (bogie skirts). [ABSTRACT FROM AUTHOR]

Flame transfer functions (FTF) of laminar premixed flames are analytically investigated and modelled. The study is based on the linearised G-equation, which is used to kinematically track the flame front. In order to incorporate combustion properties, the laminar consumption speed is considered to vary with the flame front stretch. Written in dimensionless form, the G-equation reveals that the FTF depends on three dimensionless parameters: a Strouhal number (St*) that accounts for the convective time of the flow perturbation along the flame-front, the flame aspect-ratio (Λ) and the dimensionless Markstein length (Ma), adimensionalized by the injector radius. It is shown that the latter term is responsible for an additional mechanism that acts as damper or amplifier of the flame perturbation, respectively, for thermodiffusively stable or unstable flames. A LOM FTF is derived both for Conical and V-flames which accounts for this effect and includes a different scaling term for each configuration. The obtained FTFs are compared to previously proposed analytical models from the literature, discussing the conditions where stretch effects are not negligible. [ABSTRACT FROM AUTHOR]

The round-trip method enables the indirect determination of point mobilities along interfaces that cannot be easily excited. One embodiment of the method requires excitation at a subset of points either side of the interface, while responses are measured along it. This is typically done by instrumented hammer or shaker. In the present paper, we investigate the sensitivity of the round-trip method with respect to the number of remote measurement positions used, and the geometry of the structure. Numerical and experimental examples are provided which demonstrate that there exists an optimum number of excitation and response positions for the accurate reproduction of point FRFs. [ABSTRACT FROM AUTHOR]

Noise pollution has been one of the main causes of citizens' discomfort in the urban centers in Brazil, an issue enhanced by the Covid pandemic that resulted in an increase of noise complaints, especially those related to noise from construction sites. This context triggered the construction industry to pursue solutions to understand the acoustic reality and minimize the impacts through regulations that require long-term noise measurements. Due to the necessity of a comprehensive evaluation in several locations, class 1 Sound Level Meters measurement systems can hardly be considered because of their high costs. This paper discusses the practical implementation of MEMs in a low-cost monitoring system for urban noise, focusing on construction sites. The prototype, based on a Raspberry Pi (a single-board computer model widely used in IoT projects) and a MEMs microphone with I²S interface for high-fidelity digital audio communication, was compared in a controlled environment to a Sound Level Meter of Class 1 through validation tests, such as calibration, frequency response, and dynamic range. Field measurements were also carried out in typical urban noise-generating sound environments. [ABSTRACT FROM AUTHOR]

Under the Environmental Noise Directive (END), the Round 4 strategic noise maps are to be calculated using the methodology set out in Directive 2015/996 (as amended) (CNOSSOS-EU). As part of the road traffic source emission model, a correction for the effect on noise levels due to the acceleration and deceleration of vehicles shall be applied near crossings with traffic lights and roundabouts. As part of the revision of the EPA guidelines on strategic noise mapping in Ireland, a technical investigation was carried out to identify the effect of the correction factor on road traffic noise emissions, and determine whether there was a practical approach to implement the correction factor within the upcoming noise mapping. This paper will provide an overview of the results, including the change in noise level emissions for low-speed low flow roads, and high-speed high flow road. It will also present a practical approach to preparing the road traffic flow models in GIS based on available datasets. [ABSTRACT FROM AUTHOR]

Ahead of the Round 4 strategic noise mapping under the END, TII commissioned a research project to determine the meteorological correction factors required for CNOSSOS-EU road and railway traffic noise calculations across Ireland. Methodologies for determining the percentage favourable propagation were identified under NMPB2008 and NORD2000, and the input data requirements of the methods assessed. Meteo data available from Met Eireann and TII weather stations was collected and collated and compared with the requirements of the two methodologies. The data available in from Irish met stations led to the selection of the methodology from NORD2000 being selected. Thirty years of hourly data was analysed for 26 counties to provide long term weather data for temperature, relative humidity, mean sea level pressure, and percentage of favourable propagation suitable for calculations under CNOSSOS-EU. This paper will present an overview of the methodology, available data and results obtained. [ABSTRACT FROM AUTHOR]

In most countries in Europe, regulatory noise limits apply for service equipment in housing. During the last few decades, mechanical ventilation with heat recovery (MVHR) has become increasingly prevalent in new and retrofitted housing in Europe. The MVHR systems supply fresh air to obtain good indoor air quality, with minimal heat losses. However, the systems may operate continuously 24 hours/day and transmit noise into and between rooms by many possible paths. In practice, many people get annoyed or disturbed by the noise, especially during nighttime or when having quiet activities. Some countries have stricter service equipment noise limits for continuous sources, and stricter limits also apply for upper quality classes in acoustic classification schemes. Thus, both design and measurements become challenging. The aim of this paper is to investigate the noise limit values and descriptors applied to ventilation systems in housing in selected countries in Europe and to compare and discuss the field test procedures typically applied. [ABSTRACT FROM AUTHOR]

The LIFE SNEAK project, started in September 2021, aims at the reduction of noise from road traffic that mainly affects densely populated urban areas where the noise and vibrations produced by the tram overlap with noise produced by road traffic. Applicative measures will be designed and tested in a pilot case of the city of Florence, such as lownoise and vibration surfaces with life cycle costs comparable to those of traditional surfaces, and measures to reduce tram noise aiming to obtain substantial reductions in noise and annoyance. In the first phase, specific attention was dedicated to the state-of-the-art analysis concerning prediction and monitoring of the level of noise and ground-borne vibrations in urban environments. Moreover, the impacts of road traffic and tramway in terms of noise and vibrations on people annoyance in urban context have been investigated to design appropriate questionnaires for citizens. In fact, the exploration of any combined effect of vibration and noise on annoyance is also suggested by recent guidelines for designing dedicated social surveys. In this paper the procedure to design a noise and vibration measurements and survey campaign oriented to support an evaluation of effective reductions in terms of both levels and annoyance is presented. [ABSTRACT FROM AUTHOR]

Sound is the only one of our senses that remains active while we sleep. Through hearing we test our safety at distance and in the dark. It can also condition the way we feel. Noise can affect our health and well-being negatively but sound may do so positively. Acousticians are used to measuring noise but the more positive effects of sound less well understood. The idea that sound can reduce stress and enhance our sense of wellbeing and even improve our health is a tantalising target for soundscape designs in the future but we need more fully to understand how to achieve it in a scientific way. We know that a tranquil place does not need to be quiet for instance, and that context and non-acoustic factors are important in the perception of tranquillity. We know that natural sounds: waves breaking, rain, leaves rustling, water babbling, birdsong; and some anthropogenic sounds: a familiar voice, the murmur of conversation, music; can contribute to a positive soundscape. Some examples and the current understanding of why this is, taking in cues from neuroscience, medicine and psychoacoustics are explored leading to quantification of these benefits for application in soundscape analysis and, ultimately, design. [ABSTRACT FROM AUTHOR]

Squeal noise occurring in narrow curves is one of the most annoying noise issues for people living alongside the railway track. When vehicles pass through those curves, squeal noise is mainly generated due to the large, high-frequency, lateral sliding friction force. To investigate generation mechanism of curve squeal, a three-dimensional (3D) vehicle-track interaction model with a flexible wheelset and a flexible curved track is built in a multi-body simulation tool. Compared to conventional rigid models, this model allows to obtain the high frequency friction force between wheel and rail. Then, friction force in the frequency domain is analyzed to identify the major modes. Those modes are compared with the modal properties of the wheelsets and rails in order to determine which modes have the main sensitivity to the friction force and the squeal noise. [ABSTRACT FROM AUTHOR]