Calculation Of Sound Propagation Research Articles

Uncertainties in numerical predictions and experimental characterization of wind farm noise

Wind Turbine Noise (WTN) variability is often related to the influence of local micrometeorology as well as to space and time variations in the ground properties. Thus, the PIBE Project (2020-2024) aims to estimate these variabilities and their associated uncertainties. Its objective is to enable engineering companies or wind farm developers to estimate more accurately the risk of noise. In the WP2 of the PIBE project, 3 approaches are explored: (i) a NUMerical approach through the development of a metamodel, (ii) an EXPerimental approach through a major in-situ measurement campaign lasting more than 1 year, and (iii) a STATistical approach consisting in the evaluation of WTN variability. The NUM approach consists in sound emission calculation of each wind turbine using the Amiet's theory, and sound propagation calculation using a wide-angle Parabolic Equation (WAPE) modelling. The EXP part of the PIBE project has led to the development of a large database, accessible via a dedicated Shiny application. The last approach (STAT) has been carried out using both an open-access online tool called WindTUNE and an open-source tool based on Code_TYMPANTM, namely OCP. The 3 approaches (NUM + EXP + STAT) are presented and the corresponding results are discussed.

Railway psychoacoustic annoyance - an indicator for planning infrastructure projects

The joint project "Real-time Calculation, Auralization and Visualization of Sound Propagation and Noise Protection Measures for Infrastructure Projects" (EAV-Infra), funded by the German Federal Ministry for Economic Affairs, investigates the potentials of digital infrastructure planning based on Building Information Modeling (BIM) in combination with state-of-the art Auralization and Visualization technology as well as Psychoacoustic Modelling. Currently, log-scaled sound pressure levels, which are only informative to experts, are used to communicate the topic of noise exposure to the public. Auralization, in combination with a hearing-oriented noise index, will constitute a more intuitive and understandable evaluation basis for residents. One focal point of EAV-Infra is the development of a linearly-scaled metric for railway noise, which correlates better with human perception than the LAeq. Binaural recordings of a wide spectrum of different railway pass-by scenarios were presented in listening experiments to obtain semantic-differential information about the sounds as well as global and continuous annoyance ratings for individual passings. Currently, a railway psychoacoustic annoyance metric is being developed by comparing two fitting methods: a classical model based on common psychoacoustic quantities, as well as an AI model with a Mel-log-spectrogram-CRNN architecture. The approach and first results will be discussed in this contribution.

Planning Infrastructure Projects by means of Psychoacoustic Quantities in the Joint Project "EAV-Infra"

Within the joint project "Real-time Calculation, Auralization and Visualization of Sound Propagation and Noise Protection Measures for Infrastructure Projects" (EAV-Infra), funded by the Federal Ministry for Economic Affairs, the potentials of digital infrastructure planning based on Building Information Modelling (BIM) and the auralization of different states of planning will be combined. In this contribution, the objectives of the project will be presented with particular focus on the intended application of psychoacoustics. Currently, planning noise protection measures encompasses an elaborate comparison of various planning alternatives in a time-consuming process. Sound pressure levels, which are only informative to experts, are used to communicate states of planning to the public. Auralized signals of noise immissions and a description of the effectiveness of noise protection measures by hearing-oriented quantities could constitute a more intuitive and intelligible evaluation basis for project managers and residents alike. In EAV-Infra, noise exposure will be evaluated based on psychoacoustic quantities. Both classical quantities and newly developed indices, will be considered. In order to find a suitable psychoacoustic annoyance model for the railway context, listening experiments will be conducted, in which subjects evaluate various noise situations. Typical inner- and outer-city scenarios and various noise protection measures will be assessed.

Auralization and Visualization for Infrastructure Planning in the Joint Project "EAV-Infra"

Within the joint research project "Real-time Calculation, Auralization and Visualization of Sound Propagation and Noise Protection Measures for Infrastructure Projects" (EAV-Infra), funded by the Federal Ministry for Economic Affairs, the potentials of digital infrastructure planning based on Building Information Modeling (BIM) and the auralization of different states of planning will be combined. In this contribution, the objectives of the project will be presented with particular focus on the auralization. Currently, the effectiveness of noise mitigation measures like acoustic barriers or rail dampers is evaluated and communicated mostly by means of SPL values. Through auralization, a more vivid impression of different states of planning can be given during the whole planning process. In EAV-Infra, the auralization will be based on audio data of partial sound sources taken from real train passings. The data will be collected at various sites using a newly developed MEMS microphone array. To achieve a realistic hearing impression at the receiver position, a suitable model of the sound propagation will be implemented, which allows for a simulation in real time. In a last step, the partial sound source's signals will be convolved with the calculated sound propagation to synthesize the signal at the receiver position.

Uncertainties of band sound levels when estimated from monochromatic outdoor sound propagation calculations

Octave band and third octave bands sound levels are widely used in environmental acoustics, and most numerical models for outdoor sound propagation estimate them through the combination of several monochromatic calculations. As some of these models can be very time consuming when long range distance calculations are needed, the number of monochromatic calculations performed for each band is often necessarily very limited. That induces uncertainties on the estimate of the noise level of the band that can be large when the spectrum amplitude varies widely inside a band. This is the case for example when interferences due to ground effects occur. The paper presents estimates of these uncertainties depending on frequency band and on source-receiver locations. The uncertainties are evaluated thanks to a quasi Monte-Carlo technique from many calculations using a Rudnick propagation model and a Latin Hypercube Sampling numerical experimental design for input parameters (source-receiver locations). The results provide practical indications on the minimum number of monochromatic calculations to do per band, in order not to exceed a given uncertainty level.

Numerical study on aerodynamic drag and noise of high-speed pantograph by introducing spanwise waviness

It is noteworthy to explore potential measures for further reducing the aerodynamic drag and noise of high-speed pantographs. This paper proposes a method of introducing spanwise waviness into the upper and lower arms. The improved delayed detached eddy simulation (IDDES) method and the Ffowcs Williams and Hawkings (FW-H) equation are used for flow field simulation and sound propagation calculation, respectively. The effects of wavelength, wave amplitude and inclination on the aerodynamic force and radiated noise of the wave cylinder were firstly investigated, and then the aerodynamic characteristics of the pantograph with and without spanwise waviness configurations were compared. Results show that the appropriate spanwise waviness on the cylinder can diffuse the negative pressure core area in the wake, reduce the negative pressure amplitude, suppress the vortex shedding and weaken the fluctuation amplitude of the aerodynamic force, resulting in the reduction of aerodynamic drag and noise. For the high-speed pantograph by introducing spanwise waviness, when the ratio of wavelength and wave amplitude to cylinder diameter is 1.2 and 1/8 respectively, the aerodynamic drag and noise of the pantograph by introducing spanwise waviness are reduced by 1.58% and 1.16 dBA, respectively.

Calculation of annual aircraft noise exposure for Geneva and Zurich airports with the next-generation program sonAIR - first results

The next-generation aircraft noise simulation program sonAIR was designed to precisely predict single flights with the scope of investigating and optimizing noise abatement flight procedures. Recently, sonAIR was implemented in a geographic information system (GIS) to make it suitable for noise mapping calculations of entire airport scenarios. In this study, we conducted first calculations of annual aircraft noise exposure with sonAIR for Geneva and Zurich airports, Switzerland, for the year 2017, simulating several 10'000 single flights and accounting for real conditions in great detail (e.g., detailed emission modelling and considering ground cover in the sound propagation calculation). Our calculations proved the ability of sonAIR to do annual aircraft noise calculations with many simulated flights. Comparing the results to those obtained with the best-practice program FLULA2, which is currently used for official aircraft noise calculations in Switzerland, we found that the noise contours differ on average little in areas with legally relevant noise exposure. However, locally larger differences may occur, primary due to varying ground cover and more detailed sound emission modelling. In this contribution, we present the process of sonAIR for annual aircraft noise calculations, show the most important results and discuss implications for future aircraft noise calculations around airports.

Extracting boundary conditions for sound propagation calculations using augmented reality

The number of air-to-water heat pumps has increased over the last years, resulting in a rising number of installed outdoor units. These objects constantly emit noise into the environment during the heat pumps’ runtime. To avoid conflicts with neighbors or even a relocation of the already placed heat pump, an app is developed to estimate the emitted sound of the virtual heat pump on site. This publication presents adapted sound calculation methods suitable for outdoor use and on mobile devices. Based on this, boundary conditions are specified that must be met by the sound data of the respective sound source and the objects recorded on site using augmented reality in real time. Both the determination of the sound data and the identification of objects using AR are explained in detail. Furthermore, different virtual objects that alter the sound propagation can be placed in the real environment and configured with sound-relevant properties. This allows the estimation of the usefulness of sound-reducing measures already before realization. An example of the identification of individual objects, the placement of virtual walls and heat pumps, and the final visualization of the sound propagation in different ways on the mobile device is presented.

SOFTWARE DEVELOPMENT FOR ESTIMATION OF LOW FREQUENCY SOUND PROPAGATION IN GAS GUIDES OF POWER PLANTS TAKING TO ACCOUNT ACTIVE SOUND SOURCES

This paper is devoted to the problems of modelling and calculation of propagation of low frequency sound in gas guides of power plants taking to account active sound sources. The structure of software for prediction and calculation of low-frequency sound propagation in gas guides have described. Software uses four-pole method and takes to account radiation from additional (active) sound course. By using software it is possible to estimate sound source parameters to provide efficient sound attenuation. Examples of software application to calculation of intake and exhaust noise of internal combustion engine are described. The results of calculations show the possibilities of four-pole method software using to design acoustically the parameters of gas guides and mufflers for the different fields of applications.

Noise predictions of sound systems using system data and complex summation

As the number and size of amplified outdoor events in urban areas is increasing, so are the challenges with accompanied noise immissions and therefore the need for accurate noise predictions. An advanced method for predictions of sound systems is introduced, that uses specific system data and applies complex summation. The system data, including all acoustically relevant characteristics, such as positioning, orientation and directivity of loudspeakers, delays and electronic filters, are simply imported with a system design file already in use by the system provider (d&b’s ArrayCalc simulation software). This procedure eliminates any inaccuracies and inefficiencies because it spares the process of re-modeling a sound system in the noise prediction software and ensures predictions using the actual system design. Also, and with increasing importance, advanced electronic filtering (e.g., IIR, FIR) is automatically included. Environmental noise modelling software usually does not consider complex summation between sources because they are assumed to be un-correlated with one another (as in traffic and industry). However, in sound systems, the signals sent to the loudspeakers are mostly correlated. Furthermore, modern line-array systems use coherence effects to further tailor directivity. Therefore, the sound propagation calculation was extended for complex summation and the method was implemented in SoundPLAN software and in NoizCalc (d&b audiotechnik).

Sound-Source Localization in Range-Dependent Shallow-Water Environments Using a Four-Layer Model

Sound-source localization in shallow water is a difficult task due to the complicated environment, e.g., complex sound-speed profile and irregular water bottom reflections. Full-wave numerical techniques are currently able to accurately simulate the propagation of sound waves in such complex environments. However, the source localization problem, which generally involves a large number of sound propagation calculations, still requires a fast computation of the wave equation, and thus a simplified model is well advised. In this paper, a four-layer model is considered, which is able to approximate a wide range of shallow-water environments, particularly those in summer conditions. More specifically, the medium is assumed to be horizontally stratified and vertically divided into four layers, and the sound speed in each layer is assumed to be constant or varying linearly. Under this assumption, the wave propagation can be rapidly computed via a classical wave number integration method. The main contribution of this paper is to show the suitability of the four-layer model in terms of source localization in a complex (range-dependent) environment. The sound-speed profile is assumed to be vertically irregular and horizontally slowly varying and the bottom is nonflat. In the forward problem, sound propagation in complex underwater environments is simulated via a time-domain full-wave simulation approach called the spectral-element method. The source localization error due to model imprecision is analyzed.

IV 道路交通騒音予測における伝搬計算方法 ( 道路騒音の予測 : 道路一般部を対象としたエネルギーベース騒音予測法 : (日本音響学会道路交通騒音調査研究委員会報告))

IV 道路交通騒音予測における伝搬計算方法 ( 道路騒音の予測 : 道路一般部を対象としたエネルギーベース騒音予測法 : (日本音響学会道路交通騒音調査研究委員会報告))

Aerial and underwater sound of unmanned aerial vehicles (UAV, drones)

Unmanned aerial vehicles/systems (UAV/UAS, drones) are increasingly being used for terrestrial and marine ecological surveying and research. Studies on the potential disturbance of fauna by UAVs have been sparse, with most reports on the behavioral responses of birds. Responses of marine mammals have been reported in the case of pinnipeds on land, with very limited information on marine mammals at sea. Whether the stimulus was visual (the UAV or its shadow) or acoustic (noise) is unknown. While UAV technology is developing fast, guidelines for the responsible use of UAVs around fauna are lagging behind. We recorded aerial and underwater sound from four aerial drones in different environments. Sound spectra exhibited distinct tones <2 kHz. Median broadband source levels were 77–89 dB re 20 μPa rms at 1 m in air. Under water, median broadband received levels were <100 dB re 1 μPa rms varying with drone altitude, flight mode, and recorder depth. Drone power spectral density exceeded underwater ambient levels by up to 30 dB between 100 and 10 000 Hz. Drone levels were well below those commonly considered in underwater noise regulations. Simple sound propagation and transmission calculations predicted underwater levels within −3.2 to +6.2 dB of measured levels.

Uncertainty quantification, turbulent scattering, and random sampling in outdoor sound propagation calculations

Although the fundamental physics of sound propagation outdoors (e.g., absorption, ground interactions, refraction, and scattering) are well understood, modeling capabilities are typically inadequate to capture the many intricate interactions with the atmosphere, ground, and natural and man-made terrain features. Furthermore, environmental data are rarely available at the sub-wavelength resolution needed to accurately predict the sound field in the audible range, in a deterministic sense. Fortunately, advances in computing capabilities and statistical sampling methods provide new opportunities for quantifying the inherent uncertainties of sound propagation predictions. Among the sampling techniques considered in this presentation are ordinary Monte Carlo sampling, Latin hypercube sampling, stratified sampling based on meteorological classes, importance sampling, and adaptive importance sampling. When uncertainties in the atmospheric and ground properties dominate, importance sampling is found to converge t...

Description and quantification of uncertainty in outdoor sound propagation calculations.

The accuracy of outdoor sound propagation predictions is often limited by imperfect knowledge of the atmospheric and ground properties, and random environmental variations such as turbulence. This article describes the impact of such uncertainties, and how they can be efficiently addressed and quantified with stochastic sampling techniques such as Monte Carlo and Latin hypercube sampling (LHS). Extensions to these techniques, such as importance sampling based on simpler, more efficient propagation models, and adaptive importance sampling, are described. A relatively simple example problem involving the Lloyd's mirror effect for an elevated sound source in a homogeneous atmosphere is considered first, followed by a more complicated example involving near-ground sound propagation with refraction and scattering by turbulence. When uncertainties in the atmospheric and ground properties dominate, LHS with importance sampling is found to converge to an accurate estimate with the fewest samples. When random turbulent scattering dominates, the sampling method has little impact. A comprehensive computational approach is demonstrated that is both efficient and accurate, while simultaneously incorporating broadband sources, turbulent scattering, and uncertainty in the environmental properties.

Virtual reality for architectural acoustics

Over the last decades, powerful prediction models have been developed in architectural acoustics, which are used for the calculation of sound propagation in indoor and/or outdoor scenarios. Sound insulation is predicted rather precisely by using direct and flanking transmission models of sound and vibration propagation. These prediction tools are already in use in architectural design and consulting. For the extension towards virtual reality (VR) systems, it is required to accelerate the prediction and simulation tools significantly and to allow an adaptive and interactive data processing during the simulation and 3D audio stimulus presentation. This article gives an overview on the current state-of-the-art of acoustic VR and discusses all relevant components in terms of accuracy, implementation and computational effort. With the progress in processing power, it is already possible to apply such VR concepts for architectural acoustics and to start perceptual studies in integrated architectural design processes.

Long term estimations of low frequency noise levels over water from an off-shore wind farm

This article focuses on computations of low frequency sound propagation from an off-shore wind farm. Two different methods for sound propagation calculations are combined with meteorological data for every 3 hours in the year 2010 to examine the varying noise levels at a reception point at 13 km distance. It is shown that sound propagation conditions play a vital role in the noise impact from the off-shore wind farm and ordinary assessment methods can become inaccurate at longer propagation distances over water. Therefore, this paper suggests that methodologies to calculate noise immission with realistic sound speed profiles need to be combined with meteorological data over extended time periods to evaluate the impact of low frequency noise from modern off-shore wind farms.

Acoustic mode coupling induced by nonlinear internal waves: evaluation of the mode coupling matrices and applications.

This paper applies the mode coupling equation to calculate the mode-coupling matrix for nonlinear internal waves appearing as a train of solitons. The calculation is applied to an individual soliton up to second order expansion in sound speed perturbation in the Dyson series. The expansion is valid so long as the fractional sound speed change due to a single soliton, integrated over range and depth, times the wavenumber is smaller than unity. Scattering between the solitons are included by coupling the mode coupling matrices between the solitons. Acoustic fields calculated using this mode-coupling matrix formulation are compared with that obtained using a parabolic equation (PE) code. The results agree very well in terms of the depth integrated acoustic energy at the receivers for moving solitary internal waves. The advantages of using the proposed approach are: (1) The effects of mode coupling can be studied as a function of range and time as the solitons travel along the propagation path, and (2) it allows speedy calculations of sound propagation through a packet or packets of solitons saving orders of magnitude computations compared with the PE code. The mode coupling theory is applied to at-sea data to illustrate the underlying physics.

Linearized Euler simulations of sound propagation with wind effects over a reconstructed urban terrain using digital geographic information

The procedure of sound propagation calculation employing the linearized Euler (LE) model has been known to be complex because the procedure requires a chaining of two distinct simulations, namely a fluid dynamics simulation (CFD) in order to solve the background flow field, and a succeeding sound propagation simulation using the LE model over the flow field. The complexity is considered one of the main reasons why the most of the applications of the model remain in investigations assuming highly abstract geometries. In the study, a streamlined workflow is established for LE simulations over a complex urban terrain with its reconstruction utilizing digital geographic models which provide building outline maps and digital surface elevation information. Focus is given to automatic geometry reconstruction and mesh generations of realistic urban terrain. Subsequent processes of CFD and LE simulations are validated through comparisons with published results of wind-tunnel tests and with theoretical solutions. The workflow is deployed to an actual urban terrain of Nagaoka, Japan. The present technique generates a good reconstruction of urban geometry and subsequent split-hexahedral unstructured grid for CFD software and uniform structured mesh for finite-difference LE simulation. The numerical experiments show differences of up to 5dB between sound pressure levels obtained by the present reconstruction technique and those by a flat-roof geometry. Also, the wind effects are mostly representable in terms of the source-observation point distance in spite of the complex urban configuration. Subtle wind effects of less than 0.5dB are observed in crosswind condition as well.

Influence of Real Atmospheric Conditions on Free Propagation of Aircraft Noise

The propagation of sound in the atmosphere is influenced by meteorological conditions. During computation a detailed description of meteorological conditions takes a lot of time but principally the needed meteorological data are not available in most cases. That is why the sound propagation calculation of common tools, like the German AzB or the Integrated Noise Model, is based on standardised meteorological conditions. The main objective of this study is to quantify the noise level differences between common propagation and propagation considering real weather conditions. Therefore the two important sound propagation effects for free sound propagation (atmospheric attenuation and geometrical spreading) are investigated for sources in higher altitudes. A ray-tracing algorithm is used to model the refractions of sound due to wind, wind gradients, and temperature gradients. The atmospheric attenuation is calculated by ISO 9613-1. The used meteorological conditions based on the parameters, i.e. temperature, wind, and relative humidity, from one year radiosonde measurements taken at the meteorological observatory Lindenberg in Germany. All in all, for long-term periods all these calculated average sound pressure levels and the levels calculated for standardised atmospheric conditions are similar in size. Furthermore, common noise calculations overestimate the meteorological influence on sound propagation slightly.