Hasil untuk "Acoustics in engineering. Acoustical engineering"

Ghouli Zakaria

With the rapid proliferation of unmanned aerial vehicles (UAVs) in both civilian and military domains, the demand for efficient detection and tracking systems has become increasingly critical, particularly in sensitive and strategic areas. Conventional surveillance methods, such as radar and infrared sensing, often struggle to detect low-altitude, low-signature UAVs. This study proposes a real-time acoustic localization system based on a distributed array of MEMS microphones. The approach utilizes Time Difference of Arrival (TDOA) estimations to determine the drone’s angular position, combined with a Random Forest classifier to distinguish drone acoustics from environmental noise. A radar-style interface was developed to provide real-time visualization of detections. Field experiments confirmed the system’s effectiveness under diverse environmental conditions. The solution offers a passive, cost-effective alternative for enhancing situational awareness in maritime and other security-sensitive applications.

Pascal Caroline, Marchand Pierre, Chapoutot Alexandre et al.

The identification and reconstruction of acoustic fields radiated by unknown structures is usually performed using either Sound Field Estimation or Near-field Acoustic Holography techniques. The latter turns out to be especially useful when data is only available close to the source, but information throughout the whole space is needed. Yet, the lack of amendable and efficient implementations of state-of-the-art solutions, as well as the laborious and often lengthy deployment of acoustic measurements continue to be significant obstacles to the practical application of such methods. The purpose of this work is to address both problems. First, a completely automated metrology setup is proposed, in which a robotic arm is used to gather extensive and accurately positioned acoustic data without any human intervention. The impact of the robot on acoustic pressure measurements is cautiously evaluated, and proved to remain limited below 1 kHz. The Sound Field Estimation is then tackled using the Boundary Element Method, and implemented using the FreeFEM software. Numerically simulated measurements have allowed us to assess the method accuracy, which matches theoretically expected results and proves to remain robust against positioning inaccuracies, provided that the robot is carefully calibrated. The overall solution has been successfully tested using actual robotized measurements of an unknown loudspeaker, with a reconstruction error of less than 30%.

Fallah Ali, Nakamura Shun, Gündert Siegfried et al.

When reproducing a virtual acoustic environment over loudspeakers within a reverberant playback room, the acoustics of the playback space can modify the spectral and spatial properties of the virtual environment considerably. Traditionally, optimal loudspeaker rendering of such scenes requires dedicated loudspeaker setups positioned in an anechoic room, employing techniques like Vector-BaseAmplitude Panning (VBAP) to render virtual reverberant sources, or Higher Order Ambisonics (HOA) to render spherical harmonics each using a large number of loudspeakers. In this study we evaluate to what extent it is possible to reproduce virtual acoustic environments using only a limited number of loudspeakers placed within a normal echoic room. Recently, we proposed a perceptually-based method using only four loudspeakers that specifically aims to compensate the detrimental effects of reverberation of the playback room by separately reproducing optimized versions of the direct and reverberant sound fields [Fallah et al., Reproduction of simulated acoustic scenes with limited number of loudspeakers in a reverberant room (2023)]. In this study, this approach is explained in more detail, and specifically an important parameter that controls the power ratio between direct and reverb sounds is investigated in detail using objective and subjective evaluations. In listening tests, the similarity of this proposed Acoustic Room Transformation (ART) method is compared to that of a reference rendering of the virtual acoustic environment within an anechoic room. The results of listening tests show significant improvements in the timbral and spatial characteristics of reproduced sound using the ART method compared to conventional playback without room compensation and show a closer match to the reference simulated environment.

Nyman Birgitta Elise, Nykänen Arne

With electric powertrains quickly advancing in the heavy vehicle sector, there is an increasing interest in the industry to find a general practice for evaluating tonal sounds. The challenge to set requirements is complex. Tonal sounds span from extremely annoying to pleasant. Established methods for prediction of tonal magnitude typically estimate individual tonal components without considering interrelations between the tones. In this study, the loudness perception of continuous complex tones with increasing number of harmonics as well as non-harmonic tone components, is assessed using pink noise as reference. Frequencies studied cover 350–11 000 Hz. These frequencies typically occur in electrified trucks, hitting the most sensitive area of the human hearing. The results show a statistically significant positive linear relationship between perceived loudness and increasing number of harmonics, even with decreasing level of amplitude (−6 dB/oct). Significant differences are seen between harmonic and non-harmonic tonal signals, when the second partial is detuned. Increasing the number of tonal components increases the perceived loudness linearly. Non-harmonic complex tonal sounds are assessed less loud than the corresponding harmonic sounds. In case of complex tonal sounds, models of loudness estimation need to take the number of tone components and their frequency ratios into account.

Pinhède Cédric, Boulandet Romain, Friot Emmanuel et al.

Semi-anechoic rooms are used for the acoustic characterisation of noise sources. They involve heavy infrastructures and thick absorbent lining. The aim of this work is to demonstrate a less expensive alternative by complementing a thin passive coating with an active technology. Previous work has achieved the active reduction of the pressure scattered by the reflective wall of a semi-anechoic room, in the 80–200 Hz frequency band. This work validated an innovative approach allowing to control the scattered pressure throughout the measurement volume, using a setup located over its periphery. This paper extends a previous presentation at Forum Acusticum dealing with the active control of the low-frequency reflections on the walls and ceiling of a semi-anechoic room [Pinhède et al., Forum Acusticum 2023, Torino, Italy, 11–15 September, 2023, https://doi.org/10.61782/fa.2023.0399]. We describe the design principles and the 2D semi-analytical and 3D finite element simulations of the control system that help optimise parameters such as the transducers number and locations. A full-scale demonstrator has been built to validate the control strategy. Acoustics measurements, which have been used to characterise the room acoustics and to update the simulation parameters are also presented and compared to an updated numerical model.

Lampis Alessio, Mayer Alexander, Chatziioannou Vasileios

Understanding the dynamics of bowed-string attacks involves exploring the relationship between bow acceleration, bow force, and the generation of Helmholtz motion during transients. This study addresses the following research question: How do theoretical limits of “playability” predict these parameters? Motivated by the need for experimental evidence in this domain, we present a comprehensive investigation into bowed-string transients within the bow acceleration and bow force parameter space, known as the Guettler diagram. This study exclusively employs an experimental methodology. The setup, employing a robotic arm, permits the collection of transient data under varying bowing conditions. Analysis of the bridge force waveform allows for the extraction of pre-Helmholtz transient times. Our results reveal a triangular playable region in the Guettler diagram, consistent with theoretical predictions and previous experimental findings. However, Guettler’s analytical limits for playable regions during transients show limitations. We investigate the role of friction, a key parameter idealized in the model used for obtaining these limits. Measured friction coefficients from transients reveal discrepancies with prior experimental studies, highlighting the need for further investigations in this direction.

Berchtenbreiter Benedikt, Renz Andreas, Becker Stefan

Microperforated absorbers (MPA) are a well-established technology for attenuating sound in flow carrying ducts. MPAs usually consist of a microperforated panel (MPP) in combination with a cavity as back volume. The damping maxima of MPAs occur in the range of their resonant frequencies and the effect is narrowband compared to porous or fibrous absorbers, which damp broadband at high frequencies. The resonant frequencies of MPAs decrease with increasing back volume. This provides a challenge, especially in applications with limited installation space when the damping of low frequencies is required. In the literature, the combination of MPPs and porous or fibrous absorbers is reported to reduce the required back volume. Therefore, double-layer MPAs with an additively manufactured porous absorber underneath the MPP are introduced in this work. The advantage of using additively manufactured porous absorbers as an acoustic metamaterial over conventional absorbers is that the acoustic properties can be specifically adapted to the required impedance boundary conditions. The results of this work show that the additively manufactured absorbers reduce the required back volume by up to 13% compared with liners without absorber underneath the MPP. Experimental validation underscores the robustness of the chosen design approach for double-layer MPAs.

Maugeais Sylvain, Dalmont Jean-Pierre

The duduk is a double reed instrument with cylindrical bore originating from Armenia. It is characterized by a deep and melancholic sound that has become one of the characteristics of Armenian music. Although its physical characteristics bring it close to the oboe (double reed) and the clarinet (cylindrical bore), its timbre make the duduk a distinct instrument. The present article aims at explaining this particularity by calibrating the parameters of a reed wind instrument model adapted for the duduk that can capture the main characteristics of the duduk sound. For this, physical measurements are made using an artificial mouth. Simulations are in good agreement with experiments and show that a clarinet model with a low reed resonance frequency is able to reproduce the main features of the duduk. This low reed frequency appears to be the main specificity of the duduk.

Pike Xander, Cheer Jordan

Advances in digital technologies have allowed for the development of complex active noise and vibration control solutions that have been utilised in a wide range of applications. Such control systems are commonly designed using linear filters, which cannot fully capture the dynamics of nonlinear systems. To overcome such issues, it has been shown that replacing linear controllers with Neural Networks (NNs) can improve control performance in the presence of nonlinearities. Many real systems are subject to non-stationary disturbances where the magnitude of the system excitation time dependent. However, within the literature, the performance of single NN controllers across different excitation levels has not been thoroughly explored. In this paper, a method of training Multilayer Perceptrons (MLPs) for single-input-single-output (SISO) feedforward acoustic noise control is presented. In a simple time-discrete simulation, the performance of the trained NNs is investigated for different excitation levels. The effects of the properties of the training data and NN controller on generalised performance are explored. It is demonstrated that the generalised control performance of the MLP controllers falls as the range of magnitudes included in the training data is increased, and that this performance can be recovered by increasing the number of hidden nodes within the controller.

Lincke Dorothea, Pieren Reto

Atmospheric turbulence causes well-audible fluctuations in sound amplitude as it propagates through the atmospheric boundary layer. However, the best currently available theoretical model describing amplitude fluctuations is limited to relatively short propagation distances and weak turbulence. This article presents a semi-empirical model for predicting the standard deviation of amplitude fluctuations, combining the existing theoretical model of Ostashev and Wilson with empirical data. Leveraging a dataset of over 5000 aircraft flyovers across diverse meteorological conditions, the model incorporates factors such as frequency- and distance-dependent saturation of amplitude fluctuations, an effective propagation length based on the boundary layer height, turbulence decay time during transitional states of the atmosphere, and turbulence production by nocturnal low-level-jets. The mean absolute error of the semi-empirical model compared to the measurements is 0.4 dB. The application of the semi-empirical model to aircraft auralization is demonstrated for a flyover in two meteorological conditions. The findings will enhance the modeling of outdoor sound propagation for elevated sound sources like aircraft and wind turbines. Enhanced modeling of these fluctuations can considerably improve the realism of the listening experience in aircraft flyover auralization. Further, it helps estimating the measurement uncertainty in measured aircraft noise, particularly for maximum levels.

Rychtáriková Monika, Zelem Lukáš, Chmelík Vojtech et al.

The development and validation of single number quantities that are meant to serve for straightforward assessment and comparison of airborne sound insulation properties of partition walls are typically challenged by the necessity to perform large numbers of laboratory listening tests with human subjects. This is because a reliable validation of a single number quantity requires testing for many different wall types with multiple real-life stimuli that are representative for daily life soundscapes. In this article, an alternative approach is presented that allows to test a large number of “partition wall – real-life sound stimuli” combinations. This approach uses the well-established and nowadays generally accepted Zwicker’s Loudness for quantifying the subjective loudness of sound passing through a wall, and derive from that the subjectively perceived sound insulation. Using the proposed assessment method, the adequacy of single number quantities that are currently in use, and a number of newly proposed single number quantities, are compared.

Steve Barbar

In 1990, we presented a technical paper at the Audio Engineering Society that described a new and unique system that enables microphones to be positioned as much as 50 feet from the sound source while producing high reverberation level without coloration from acoustic feedback. Since that time, hundreds of these systems have been installed throughout the world in both a wide range of applications, as well as wide variety of venues. We will discuss successful solutions for acoustical problems that are difficult to address using conventional architecture.

Ferina Saati, Karl-Alexander Hoppe, Steffen Marburg et al.

A. Dell, A. Krynkin, K.V. Horoshenkov

Josh Thede, Nick Boyts, J. Teel et al.

There are several established procedures and design tools for estimating the background sound levels from heating, ventilation and air-conditioning (HVAC) building systems. Building Information Modeling (BIM) is a process commonly used in architecture, engineering, and construction that uses data to generate digital representations of a building’s physical and functional characteristics. We will demonstrate a BIM-automated design tool which uses a Dynamo script and a Revit model duct layout to estimate HVAC noise levels in buildings. With just a few inputs in the model, the script calculates the sound attenuation of each duct element and receiver room sound correction to estimate the HVAC background sound level in any space or building type. Leveraging existing data through BIM automation can help create efficient, optimized designs and improve coordination between mechanical engineers, architects, and acoustical consultants to meet acoustical design criteria.

Christopher M. Jasinski, R. Celmer

The University of Hartford is home to two unique undergraduate engineering majors in acoustics, both sharing a core course layout of acoustics, vibrations, and projects. The Bachelor of Science in Mechanical Engineering with an Acoustics Concentration and the Bachelor of Science in Engineering in Acoustical Engineering and Music programs allow for two complementary tracks within the acoustics field, providing cohesive plans of study on many facets of listening and design. All Mechanical Engineering majors (regardless of concentration) are required to take Vibrations I and a course in Engineering and Environmental Acoustics. The department philosophy for this inclusion is that acoustics and vibration design considerations are an essential component for the development of the complete mechanical engineer. This paper outlines program educational goals and outcomes, along with pedagogical adjustments made based on continuous assessment and evaluation of select courses, including recent changes to adapt to measured deficiencies. The paper also details the historical development of the acoustics program, components of the Vibrations I and Engineering & Environmental Acoustics courses, and example research and design projects based on work in these courses. Among the included projects are modal analysis, community room acoustics assessment, and an open access computational room acoustics simulator for use and collaboration with colleagues in acoustics education.

Schäfer Philipp, Reich Lennart, Vorländer Michael

In a recent publication, we presented an efficient method to find eigenrays in a stratified, moving medium. The simulation framework is designed to auralize aircraft flyovers. However, the method is restricted to the direct sound and a ground reflection. When dealing with flyover scenarios close to residential areas, the interaction of sound with urban structures, especially reflection and diffraction, should be considered. Typical models for auralization in urban areas in fact do consider those interactions but neglect the inhomogeneity of the atmosphere. Thus, in this paper, the two models are combined in an approach to link between atmospheric models using curved propagation paths and urban models using straight paths but handling structure interaction.

Ruan Yongdu, Liang Xu

Phononic crystals are well known for acoustic wave manipulation which may have potential application in an underwater acoustic detection system. In this work, we design and simulate a two-dimensional Luneburg lens based on gradient-index (GRIN) phononic crystal that is composed of PLA-Air inclusion, and a novel application of GRIN phononic crystals is proposed to sound localization. The Luneburg lens has a broadband working range, from 1500 Hz to 7500 Hz, for acoustic wave focusing with sensitive directivity and signal-to-noise improvement. By searching maximum wave intensity’s position of the focusing beam, the propagating direction of an unknown sound wave can be directly recognized covering 360°. Besides, we redesign the conventional square-lattice Luneburg lenses using annular lattices for better performance. The annular-lattice Luneburg lens overcomes the weakness of configuration defect due to the square lattice. The numerical results show that the redesign Luneburg lenses have high accuracy for distance measurement from 5 m to 35 m through the triangulation location. In a word, this work tries to explore a novel application of phononic crystals in underwater acoustic positioning and navigation technology.

Andrew Barnard, Daniel A. Russell

The Graduate Program in Acoustics at Penn State offers graduate degrees (M.Eng., M.S., Ph.D.) in Acoustics, with courses and research opportunities in a wide variety of subfields. Our 820 alumni are employed around the world in a wide variety of military and government labs, academic institutions, consulting firms, and consumer audio and related industries. Our 40+ faculty from several disciplines conduct research and teach courses in structural acoustics, nonlinear acoustics, architectural acoustics, signal processing, aeroacoustics, biomedical ultrasound, transducers, computational acoustics, noise and vibration control, acoustic metamaterials, psychoacoustics, and underwater acoustics. Course offerings include fundamentals of acoustics and vibration, electroacoustic transducers, signal processing, acoustics in fluid media, sound and structure interaction, digital signal processing, experimental techniques, acoustic measurements and data analysis, ocean acoustics, architectural acoustics, noise control engineering, nonlinear acoustics, outdoor sound propagation, computational acoustics, biomedical ultrasound, flow induced noise, spatial sound and three-dimensional audio, and the acoustics of musical instruments. This poster highlights faculty research areas, laboratory facilities, student demographics, successful graduates, and recent enrollment and employment trends for the Graduate Program in Acoustics at Penn State.

Arthur W. van der Harten

Pachyderm Acoustic Simulation is a professional tool for geometrical and numerical simulation of acoustics in the built environment that happens to be open source under the General Public License. Over the course of the 14 year life of the open-source acoustics simulation project, Pachyderm Acoustic has had the privilege of partnering with numerous academic institutions worldwide to educate architecture and engineering students in acoustics. This has been in the form of support for student projects, lectures and workshops on acoustics simulation and other topics, and, in some cases, PHD advice. This session will explore several notable examples of successful pedagogy using the open source software as a tool for higher education. There will also be some discussion of approaches to pedagogy that have not been as successful, in an effort to further discussion regarding an appropriate approach to higher learning in acoustics.