Hasil untuk "Acoustics in engineering. Acoustical engineering"

Huisman Thirsa, DeLucia Patricia R., Oberfeld Daniel

To safely cross a street while a vehicle is approaching, pedestrians must estimate how long it will take for the vehicle to reach their position. Recent studies have shown that estimation of a vehicle’s arrival time (i.e., time-to-collision (TTC) estimation) is affected by the intensity of the vehicle’s sound. When presented with the same actual TTC, louder sound sources were perceived as arriving earlier than quieter sources (the so-called “intensity-arrival effect”). However, in these experiments the vehicle sound power (also referred to as source intensity) was varied from trial to trial, potentially directing participants’ attention to the intensity variation. Here, we used high fidelity acoustic simulations of approaching vehicles, to investigate whether the effect of vehicle sound power on auditory TTC estimation persists when it is varied from block to block rather than from trial to trial. Results showed a significant intensity-arrival effect for the blockwise vehicle sound power variation. However, this effect was much weaker compared to a condition where the vehicle sound power varied from trial to trial.

Ohlenbusch Mattes, Rollwage Christian, Doclo Simon et al.

Own voice pickup technology for hearable devices facilitates communication in noisy environments. Own voice reconstruction (OVR) systems enhance the quality and intelligibility of the recorded noisy own voice signals. Since disturbances affecting the recorded own voice signals depend on individual factors, personalized OVR systems have the potential to outperform generic OVR systems. In this paper, we propose personalizing OVR systems through data augmentation and fine-tuning, comparing them to their generic counterparts. We investigate the influence of personalization on speech quality assessed by objective metrics and conduct a subjective listening test to evaluate quality under various conditions. In addition, we assess the prediction accuracy of the objective metrics by comparing predicted quality with subjectively measured quality. Our findings suggest that personalized OVR provides benefits over generic OVR for some talkers only. Our results also indicate that performance comparisons between systems are not always accurately predicted by objective metrics. In particular, certain disturbances lead to a consistent overestimation of quality compared to actual subjective ratings.

Heimes Anne, Vorländer Michael

The prediction and modeling of sound propagation rely heavily on accurate representations of surface scattering. Traditional scattering coefficients, often based on random-incidence assumptions, fail to capture the directional dependence of sound reflections from rough surfaces. This paper introduces a methodology for determining and representing bidirectional surface scattering coefficients, moving beyond the limitations of existing Lambertian-based approaches. We propose a framework that leverages numerical simulations and physical measurements to compute bidirectional scattering coefficients from reflected sound pressure distributions with finite-size samples. The methodology is validated using a well-documented sinusoidal test surface, comparing our results with analytical solutions for infinite-size samples and former random-incidence scattering coefficient measurements. Additionally, we propose a data storage format compatible with the Spatially Oriented Format for Acoustics (SOFA) to facilitate the integration of bidirectional scattering coefficients into sound propagation models. This work provides a foundation for improved acoustic simulations in applications ranging from room acoustics to urban noise control.

Ewert Stephan D., Gößling Nico, Buttler Oliver et al.

Geometrical acoustics is well suited for real-time room acoustics simulation and is often implemented using the image source model (ISM). One drawback of the ISM is its limitation to specular reflections, while sound scattering plays an important role in real environments. Here, computationally-efficient, digital-filter approximations are proposed to account for effects of non-specular scattered reflections in the ISM. For scattering at large surfaces such as room boundaries, each reflection is energetically split into a specular and a scattered part, based on the scattering coefficient. The scattered sound is coupled into a diffuse reverberation model. Temporal effects of the underlying surface scattering for an infinite ideal diffuse (Lambertian) reflector are derived and the resulting monotonic decay is simulated using cascaded all-pass filters. Effects of scattering and multiple (inter-) reflections caused by larger geometric structures at walls, and by objects in the room are accounted for in a highly simplified manner. A single parameter is used to quantify deviations from an empty shoebox room. The cumulated temporal effect of scattering along a reflection path is mimicked using cascaded all-pass filters adjusted to obtain a gamma-distribution-shaped envelope. The proposed method was perceptually evaluated with both music and pulse stimuli against dummy head recordings of real rooms. The results show a better agreement between the recording and the simulation for transient stimuli. In a technical evaluation, the temporal evolution of echo density showed a comparable profile for the suggested method and real rooms.

Shi Tuo, Zhou Pan, Feng Yuxin et al.

Tire cavity noise is becoming more prominent as the speed of electric vehicles is getting higher. This study aims to use a built-in sound-absorbing material to reduce tire cavity noise. First, the radial force was extracted by rolling analysis, and the tire cavity noise was obtained. Then, in order to investigate how the placement of sound-absorbing material affects the noise reduction, sound-absorbing material was applied to the inner side of tire’s side and tread position respectively. Finally, studies were done on the impact of sound-absorbing material’s density, flow resistance, porosity, and thickness on tire noise reduction. The best way to reduce noise with a 215/55R17 tire was to apply sound-absorbing material at side position. The density, porosity, flow resistance and thickness of the sound-absorbing material were 55 kg/m3, 0.95, 5000 Pa·s/m2 and 40 mm, respectively. The A-weighted sound pressure level decreased by 27.7 dB compared with that before the built-in sound-absorbing material. In response to the uncertainties on the reduction achieved by the sound-absorbing material, this study offers some recommendations for noise reduction of tire cavity. The studied effect is limited to the tire cavity, and the effect on the emitted sound energy has not been evaluated.

Adams Christian

Maugeais Sylvain, Terrien Soizic

Self-sustained musical instruments are non-linear dynamical systems that can produce a large number of sound regimes, whose existence and stability depend on both design and a number of control parameters. Determining which regimes exist for given parameters and which one is reached in practice when several stable regimes coexist for identical parameters is of importance from both the making and playing points of view. In this article, we consider a physical model of a trombone, and produce cartographies of the sound regimes in the space of playing parameters associated to the musician, namely the blowing pressure and the lips parameters. In practice, boundaries of the parameters space regions corresponding to different regimes are defined explicitly using Support Vector Machines. This approach is implemented in an open-source python library pyEDSD which is presented here. Importantly, the method is not specific to the considered application and the library may be of interest for other applications, in particular in engineering.

Ronald N. Miles

Nieradka Paweł, Dobrucki Andrzej, Chmielewski Bartosz

Statistical Energy Analysis (SEA) is a well-known numerical method for predicting vibroacoustic phenomena in complex systems. The accuracy of SEA models relies on the precise determination of coupling loss factors and damping loss factors. Experimental SEA (E-SEA) methods, such as the Power Injection Method are commonly employed to measure these parameters. However, these techniques may yield negative loss factors, which are considered measurement errors. Monte Carlo Filtering (MCF) is one of the procedures, that allows the correction of negative loss factors, but the quality of the results remains unknown. The knowledge of the loss factors’ quality is directly related to the practical applications of SEA, where good quality of the input model parameters (coupling and damping loss factors) correspond to good quality and precise simulations of complex vibroacoustic systems (like trains, vehicle, airplanes, buildings) responses. In a previous study, a total loss factor (TLF) criterion was proposed as a quality indicator for the corrected loss factors. The current paper validates the TLF criterion through a comprehensive analysis of various numerical examples. By expanding the Monte Carlo sample’s value range (search area) and using different probability density functions, we intentionally introduced errors in the loss factors. The TLF criterion demonstrated resilience to increasing errors in certain scenarios, raising concerns about its sensitivity. Nevertheless, it seems, that the TLF criterion remains a good indicator of population stability and large error occurrence.

Gölles Lukas, Zotter Franz

Modern large-scale sound reinforcement systems use line-source loudspeaker arrays with the goal to establish a desired direct sound level decay profile along a line into the audience by adjusting the splay angles or delays between the individual enclosures. To design such a profile not only in the depth but also in the width of the audience area, a two-dimensional source would offer sufficiently many degrees of freedom for adaptation. In practical applications, this task is often accomplished with discrete planar loudspeaker arrays. In this work, we suggest employing the stationary-phase approximation to get a continuous symmetric delay length profile, which is then discretized. The aim of the design is to achieve direct sound levels rolling off by −6 ⋅ β dB per distance doubling on the listening area. The efficacy of this method is demonstrated by simulations and measurements of coverage with a small planar array confirming the validity of the proposed theory in practice.

Italy Turin, T. September, •. Politecnico et al.

* Mr Paavo Arni (1905 – 1969) was a central influencer in the field of acoustics in Finland since the 1940’s until his death. Paavo Arni ran an engineering office specialized in acoustics, but he was also active in education, founding of the Acoustical Society of Finland, preparing regulation concerning sound insulation of apartment buildings as well as occupational noise. He also supported research on acoustics in Finland and internationally, too. In addition, he was the author of the first Finnish handbook on acoustics published in 1949. The base of the wide range of activities of Paavo Arni was possible because of his main work at the Finnish Broadcasting Company YLE. He began as a studio manager in 1931 and ended his career as a technical director of YLE. Construction of studios provoked a need for knowledge on acoustics. Paavo Arni started to form international connections with other broadcasting companies and with acousticians in the 1930s by making visits, attending conferences and hosting international experts’ visits in Finland.

Megan S. Anderson

Acoustic behavior of metamaterials. Oceanic stratification characterization. Foraging behavior of whales. These are just a few of the many research areas explored by our fellow and former members of the Acoustical Society of America (ASA) Student Council (see bit.ly/3GF5jPr ). In this essay, we highlight several of our peers who inspire us, all of whom are either nearing graduation or recently graduated. See other Acoustics Today essays about students and the Student Council in “ AT Collections” at bit.ly/3m5kMyP . possible career path identified acoustics as a con-nector between Colby’s undergraduate major aerospace engineering and his for music. A conversation with in graduate relationships the acoustics were crucial explains his research as motivated by acoustic metamaterials.

Aulitto Alessia, Hirschberg Avraham, Arteaga Ines Lopez et al.

The effect of the slit length on the acoustic transfer impedance of micro-slit plates (MSPs) is investigated in the linear and non-linear regime for a specific slit geometry. This geometry is inspired by slits obtained by cutting and bending the plate. MSPs are plates with arrays of slit-shaped perforations, with the width of the order of the acoustic viscous boundary layer thickness. Impedance tube measurements on two accurately manufactured plates are compared to numerical solution of the Linearized Navier-Stokes equations and to analytical limits. The impedance of the plate is obtained by the impedance of a single slit divided by the plate porosity. The resistance of a slit is independent on the slit length and on the plate porosity. In the linear regime the resistance is accurately predicted by a two-dimensional numerical model. In the non-linear regime, the resistance is strongly dependent on the amplitude of the acoustic waves. The inertance of the slit is weakly dependent on the slit length and on the plate porosity, for low and moderate amplitudes. For high amplitudes, a complicated amplitude dependency of the inertia of short slits is found. One expects that most of the conclusions obtained can be generalised to other slit geometries.

Fréour Vincent, Guillot Louis, Masuda Hideyuki et al.

Numerical continuation using the Asymptotic Numerical Method (ANM), together with the Harmonic Balance Method (HBM), makes it possible to follow the periodic solutions of non-linear dynamical systems such as physical models of wind instruments. This has been recently applied to practical problems such as the categorization of musical instruments from the calculated bifurcation diagrams [V. Fréour et al. Journal of the Acoustical Society of America 148 (2020) https://doi.org/10.1121/10.0001603]. Nevertheless, one problem often encountered concerns the uncertainty on some parameters of the model (reed parameters in particular), the values of which are set almost arbitrarily because they are too difficult to measure experimentally. In this work we propose a novel approach where constraints, defined from experimental measurements, are added to the system. This operation allows uncertain parameters of the model to be relaxed and the continuation of the periodic solution with constraints to be performed. It is thus possible to quantify the variations of the relaxed parameters along the solution branch. The application of this technique to a physical model of a trumpet is presented in this paper, with constraints derived from experimental measurements on a trumpet player.

Schneehagen Erik W., Geyer Thomas F., Sarradj Ennes

The tonal noise generated at the tip is a major contribution to the aerodynamic noise generated by three-dimensional airfoils. One way to reduce this noise is the use of end plates, which was investigated in the present study for three different circular end plate geometries applied to a cambered NACA 4412 airfoil with aspect ratio 2 and forced boundary layer transition. Microphone array measurements were performed in a small aeroacoustic wind tunnel for chord based Reynolds numbers between 75,000 and 200,000 and geometric angles of attack between 0° and 20°. The acoustic far-field noise spectra obtained for the baseline configuration show a broadband hump centered at a chord based Strouhal number of 13 that is associated with the noise generation at the tip and scales with the third power of the flow velocity. The application of end plates reduces this peak and is most effective for end plates which bound the flow on the suction side of the airfoil. Hot-wire measurements taken for one configuration show that the end plates diffuse the turbulence intensity in the relevant frequency range and reduce the fluid transfer along the pressure gradient at the tip. The suction side end plate additionally prevents the interaction of turbulent structures with the trailing edge and is therefore more effective in reducing noise. Surface flow visualizations for this configuration reveal a separation line extending along the full span up to the tip while the surface flow of the baseline and pressure configuration is strongly affected by the flow swept around the tip. Therefore, the placement of the end plate on the suction side is more effective in reducing tip noise.

Freidhager Clemens, Schoder Stefan, Maurerlehner Paul et al.

We analyze the differences between the Ffowcs–Williams and Hawking’s approach and a new sound propagation approach based on the finite element method used for solving Lighthill’s aeroacoustic wave equation for compressible flows. In addition, we discuss the applicability of both methods. The sound propagation approach based on Lighthill’s equation introduces a flow-interface boundary condition, similar to permeable boundaries in the Ffowcs–Williams and Hawking’s analogy, which allows the omission of complex geometries in propagation domains. This enables to reduce numeric effort and storage requirements. Thereby, the hybrid aeroacoustic workflow is considered, for which aeroacoustic source terms are computed to couple a flow and a separated acoustic propagation simulation. We present an extensive investigation of Lighthill’s source terms in the sense of the proposed weak formulation of Lighthill’s equation. For validation, measurements from a cold gas test rig are used. In addition, the possibilities of applying both sound propagation methods for investigating the influence of resonators and sound absorbers are discussed.

Tur Bogac, Echternach Matthias, Turowski Stefan et al.

Wearing face coverings became one essential tool in order to prohibit virus transmission during the COVID-19 pandemic. In comparison to speaking and breathing, singing emits a much higher amount of aerosol particles. Therefore, there are situations in which singers can perform or rehearse only if they are using protective masks. However, such masks have a more or less adverse effect not only on the singer’s comfort and tightness of the mask but also on the radiated sound. For this reason, the spectral filtering and directivity of masks designed specifically for professional singing was measured. The tests were performed with a head phantom. Over most of the spectrum, attenuation is observed, although amplification happens at some low frequency bands for different mask types and directions. Especially singing masks with a plastic face shield showed partial amplification of up to +10 dB below a frequency of 2 kHz, while only slight significant attenuation and no amplification (minimal acoustic loss) were seen for woven fabric masks. Above 2.5 kHz, the transparent masks showed the greatest sound attenuation up to −30 dB, while woven fabric masks produced an overall lower sound attenuation of up to −5 dB. In addition at low frequencies, the sound was amplified or attenuated equally in all directions for masks with a stiff plastic face shield. At higher frequencies, the attenuation is higher to the frontal than to the backward direction.

Bailhache Simon, Maillard Julien, Guigou-Carter Catherine

The purpose of this investigation is to propose an alternative indoor sound spectrum based on objective and verifiable data, representative for an average household in Europe. It is obtained from the energetic sum of the emission spectra of sound sources commonly found in residential buildings, each weighted by its estimated occurrence time. Such a spectrum could then be used to evaluate airborne sound transmission performance.

Deng Jin-Jie, Yu Ming, Yang Ri-Fu

A dynamic model for a double-bubble system in compressible liquid under the coupling effect of ultrasound and electrostatic field was developed here. In this study, we mainly discussed the effect of the interaction on the investigated bubble using the numerical solutions to the theoretic model. The variable parameters are the distance between bubble centers and the initial radius of the adjacent bubble. In addition, we applied approximate equations to analyse variations of the internal gas pressure and temperature of a bubble. We found that, the oscillation amplitude of a bubble with an adjacent bubble significantly reduces, compared to that of an isolated bubble.

Béquin Philippe, Nanda Tonlio Adalbert, Durand Stéphane

It is shown experimentally that a microplasma created by a microstructured electrode array is sensitive to sound pressure. In this paper, two electrode architectures are used to create the microplasma. The sensitivity of these microplasma microphones, close to 0.4 nA/Pa, is estimated using a waveguide and a calibration method by comparison with a reference microphone. An empirical expression of the acoustic pressure sensitivity of microdischarges is proposed. The predictions of this empirical model are in good agreement with the experimental data.