Hasil untuk "Acoustics in engineering. Acoustical engineering"

Coyle Whitney L., Schefter Lauren K., Cannaday Ashley E. et al.

This study evaluates end-correction behavior in flue organ pipes by comparing two models: the classical low-frequency expression of Levine and Schwinger and the empirical, frequency-dependent refinement of Davies et al. [Journal of Sound Vibration 72 (1980) 543–546], later revisited by Moore et al. [JASA Express Letters 3 (2023) 055002]. Using a Microflown probe, we performed high-resolution pressure measurements inside and outside circular and square pipes to capture the transition from standing-wave to radiating behavior. Sinusoidal variation within the end-correction region and 1/r decay beyond were observed, consistent with theory. A two-region curve-fitting approach quantified each model’s accuracy. In the tested range (0.049 ≤ ka ≤ 0.377), both models reproduced the data with nearly identical accuracy (R2 ≥ 0.997), with only a slight advantage for the classical form in one square-pipe case. Probe interference was evaluated and found negligible. While the analysis employs fixed end-correction values rather than a universal fit, it provides a controlled test of how well existing models capture the spatial pressure field near the pipe termination. Results indicate that both models are adequate in this regime, and that the radiating field beyond δ follows a robust 1/r decay independent of model choice.

De Bie Femke, Denayer Hervé, Deckers Elke

Acoustic metamaterials that consist of multiple λ/4-resonators in series or parallel can be tuned to realise high broadband absorption in a given frequency range. These resonators are often folded to obtain a structure with a (deep) sub-wavelength thickness, which allows an optimal use of the available space and enables low-frequency sound absorption in confined spaces. However, folding a resonator can lead to a significant change in resonance frequency, resulting in an off-design acoustic performance. Hence, in this paper, the effect of a single 90° fold on the resonance frequency of rectangle and slit-like λ/4-resonators is investigated numerically. Based on these numerical simulations, a length correction factor δ is derived to account for this effect in the analytical model. The use of the correction factor is verified for various single-fold resonator configurations and against existing length formulas. The length correction factor is then experimentally validated for rectangle resonators by means of impedance tube measurements on 3D printed samples. It is found that using the proposed length correction factor allows for an accurate prediction of the resonance frequency of the discussed resonator geometries.

Martos Vincent, Boutin Henri, Hélie Thomas et al.

The application of active control to musical instruments brings many benefits to composers and performers, by expanding their sound possibilities. This paper addresses the active control of a brass instrument to design a vocalizing mute. To this end, a sensor (pressure transducer) and an actuator (loudspeaker) with a feedback loop are placed at the bell extremity. A single-input single-output controller is designed to simulate the insertion of a flow-to-flow vocal filter, upstream of the natural radiation impedance load. The vocal transfer function with its target resonances is basically derived using the transfer matrix method for a vocal tract composed of concatenated acoustic cylinders. The loudspeaker model is based on the Thiele and Small description. Numerical experiments are presented on the controller, for a simplified trombone model that admits a Kelly-Lochbaum structure (mouthpiece, bore, bell and radiation are cascaded using the transfer matrix method). Finally, the sensitivity of the control to air temperature, bell opening angle and loudspeakers parameters is studied.

Roland Jacques, Rapin Jean-Marie, Villot Michel et al.

This paper is about the history of the acoustic activities at CSTB, French Center for building Science and Technology. It is an improved and extended version of a paper presented in a structured session on the history of acoustic activities in Europe, at Forum Acusticum 2023 in Torino, Italy. The CSTB Acoustic Department was created in the 1960s around an acoustic test laboratory. From the beginning CSTB has been involved in improving acoustic performance for building occupants. It played an important role in technically supporting the French acoustic regulation (first one in 1968 and last one in 1995) and in developing solutions to reach mandatory building performances in cooperation with the industry. The acoustic department grew fast, mainly supported financially by the government (more than 60% of its budget at the beginning), thus becoming the largest acoustic team in France and worked on 3 main domains: room acoustics, environmental acoustics and building acoustics, in which physical models and calculation tools have been developed to bring science to construction. From the start, CSTB has been involved in standardization at French, European and International levels.

Meza-Pérez Amaury, Stoppani George, Viala Romain et al.

Ryan A. McCarthy, You Zhang, Samuel A. Verburg et al.

Acoustic data provide scientific and engineering insights in fields ranging from bioacoustics and communications to ocean and earth sciences. In this review, we survey recent advances and the transformative potential of machine learning (ML) in acoustics, including deep learning (DL). Using the Python high-level programming language, we demonstrate a broad collection of ML techniques to detect and find patterns for classification, regression, and generation in acoustics data automatically. We have ML examples including acoustic data classification, generative modeling for spatial audio, and physics-informed neural networks. This work includes AcousticsML, a set of practical Jupyter notebook examples on GitHub demonstrating ML benefits and encouraging researchers and practitioners to apply reproducible data-driven approaches to acoustic challenges.

Sonja M. Hyrynsalmi, Grischa Liebel, Ronnie de Souza Santos et al.

The discipline of software engineering (SE) combines social and technological dimensions. It is an interdisciplinary research field. However, interdisciplinary research submitted to software engineering venues may not receive the same level of recognition as more traditional or technical topics such as software testing. For this paper, we conducted an online survey of 73 SE researchers and used a mixed-method data analysis approach to investigate their challenges and recommendations when publishing interdisciplinary research in SE. We found that the challenges of publishing interdisciplinary research in SE can be divided into topic-related and reviewing-related challenges. Furthermore, while our initial focus was on publishing interdisciplinary research, the impact of current reviewing practices on marginalized groups emerged from our data, as we found that marginalized groups are more likely to receive negative feedback. In addition, we found that experienced researchers are less likely to change their research direction due to feedback they receive. To address the identified challenges, our participants emphasize the importance of highlighting the impact and value of interdisciplinary work for SE, collaborating with experienced researchers, and establishing clearer submission guidelines and new interdisciplinary SE publication venues. Our findings contribute to the understanding of the current state of the SE research community and how we could better support interdisciplinary research in our field.

Yining Hong, Christopher S. Timperley, Christian Kästner

Machine learning (ML) components are increasingly integrated into software products, yet their complexity and inherent uncertainty often lead to unintended and hazardous consequences, both for individuals and society at large. Despite these risks, practitioners seldom adopt proactive approaches to anticipate and mitigate hazards before they occur. Traditional safety engineering approaches, such as Failure Mode and Effects Analysis (FMEA) and System Theoretic Process Analysis (STPA), offer systematic frameworks for early risk identification but are rarely adopted. This position paper advocates for integrating hazard analysis into the development of any ML-powered software product and calls for greater support to make this process accessible to developers. By using large language models (LLMs) to partially automate a modified STPA process with human oversight at critical steps, we expect to address two key challenges: the heavy dependency on highly experienced safety engineering experts, and the time-consuming, labor-intensive nature of traditional hazard analysis, which often impedes its integration into real-world development workflows. We illustrate our approach with a running example, demonstrating that many seemingly unanticipated issues can, in fact, be anticipated.

de Reboul Silouane, Perrey-Debain Emmanuel, Ville Jean-Michel et al.

The proximity of obstacles in a ventilation network can result in a significant increase of the noise production. In this paper, a tandem diaphragm inserted in a rigid duct with rectangular cross section is investigated and compared to a single diaphragm obstruction. The disturbed flow which reaches the second obstacle causes an amplification of the radiated noise which goes beyond a simple doubling of the power. Experimental results, carried with various spacing between the two diaphragms and bulk velocity, allows identifying other aeroacoustic source mechanisms which does not appear with a single diaphragm. Depending on the configuration, the broadband level can increase by more than 10 dB and feedback phenomena can appear at low frequency. Explanations and illustrations of those phenomena are given thanks to compressible-fluid simulations.

Hergert Frank

Two simultaneously sounding tones differing in frequency by a few Hertz generate a waveform, whose amplitude modulation is related to the psychoacoustic quantity “fluctuation strength”. In accordance with the widely accepted definitions of consonance, any deviation from a pure interval (a dyad, whose tone frequencies yield a frequency ratio of small integers) generates dissonance. Nevertheless, imperfect intonation is a common occurrence in musical performance. Recent publications have demonstrated that slightly detuned dyads are perceived as more pleasant than their corresponding pure intervals. Some instruments even contain a separate set of tone generators that are intentionally detuned to a slight degree. Examples of instruments that exhibit this feature include various flat and sharp Celeste ranks in the Pipe Organ or the Accordion. The resulting undulating sounds are pictured as pleasant, shimmering, or “celestial”. This work demonstrates that the tonal timbre of two harmonic complex tones, whose fundamental frequencies slightly deviate from ratios of small integers, can undergo notable periodic changes within a beat cycle while maintaining sensory pleasantness. The acceptable limit of detuning unison intervals is related to the frequency difference limen, as evidenced by data on CELESTE ranks in Pipe Organs and Accordions tuned by instrument builders. This allows for the derivation of general tuning progression rules for Celeste ranks in Pipe Organs and Accordions, which can be used to increase the auditory pleasantness of dyads despite their slight detuning.

Zachos Panagiotis, Moiragias George, Mourjopoulos John

This work proposes a headphone Active Noise Control (ANC) scheme based on the targeted attenuation of sources that are deemed disturbing for listeners. Initially, a listening test determines the disturbance of distinct noises that coexist within background noise based on their class and their direction of arrival. The listening test is based on such predetermined spatial scenes, binaurally auralized and presented via headphones. The derived disturbance metric, guides the operation of the proposed headphone ANC: any complex auditory scene is subsequently analyzed and via a Sound Event Localization and Detection Neural Network, a beamformer is steered to the source deemed to be the most disturbing. A Time-Domain Beamformer, driven by a phased array formed by the two already existing reference microphones commonly found in the outer shell of ANC-enabled headphones and guides the multi-reference ANC controller in order to provide an improved attenuation of the primary disturbing source, while also significantly attenuating the background noise field to acceptable levels.

Červenka Milan, Bednařík Michal

This article presents a systematic numerical study of the absorbing properties of acoustic black holes (ABHs) serving as an anechoic termination of waveguides. The study focuses on the sensitivity of ABHs’ absorbing performance to their profile and internal-structure parameters. The article compares numerical predictions from 1D model based on the Riccati equation with a detailed 2D model based on the linearized Navier-Stokes equations and the finite element method, finding good agreement among all results, especially for ABHs with fine internal structures. The mean value of the reflection coefficient modulus is used to quantify the ABH’s absorbing performance, and the article introduces the use of power-law functions and cubic splines to define the ABH’s shape function. An evolutionary algorithm is employed to optimize the ABH’s profile, resulting in improved absorbing performance. The numerical results suggest that the optimum shape is simple and more-or-less insensitive to other geometrical and internal-structure parameters.

Penelet Guillaume, Ablitzer Frédéric, Dalmont Jean-Pierre

This paper describes a toy device, namely an electroacoustic clarinet, which was designed for educational purposes. It consists of a loudspeaker connected through a cavity to a duct drilled with several side holes. Unlike what happens in a clarinet where the emitted sound is caused by the motion of a reed and the blowing of a musician, the present system is excited by the loudspeaker through a positive feedback mechanism giving rise to self-oscillations. This feedback is achieved by placing a microphone in the cavity, and connecting it to the loudspeaker through an audio amplifier. It is shown that, by adjusting the gain of the amplifier and by opening/closing the side holes to control the pitch of the emitted sound, the system can spontaneously play all the notes of a scale. The dynamics of the system beyond the threshold of self-oscillations is also studied both experimentally and theoretically. This simple system can be easily reproduced with minimum equipment and it may have some merits for educational purpose, because its understanding requires some basic knowledge of electroacoustics, guided wave theory and nonlinear dynamics.

B. Schnitta, Joanne Solet, F. Pitts et al.

This diverse panel of experts will discuss the impact and challenges associated with acoustics in healthcare from multiple perspectives: design, regulation, clinical care, research, and engineering, and will entertain questions from participants.

Benjamin R. Thompson, Sarah R. Smith

A challenge in designing first-year engineering curriculum is meeting the needs of a group of students with diverse academic backgrounds. Educators in the field of audio and acoustical engineering are often tasked with simultaneously preparing majors to be successful in their subsequent coursework while delivering a course that is both accessible to and exciting for all students. At the University of Rochester, we offer a survey course that introduces students to fundamental concepts in acoustics, signals, and audio electronics in which we leverage students’ existing experiences with sound and music in a project-based environment. Students complete a series of laboratory exercises where they interact with the science of audio by building a guitar amplifier circuit from scratch. Analyzing a schematic, soldering components, solving equations, seeing waveforms, and HEARING the results of their work, allows all students to engage in the content more deeply than any of these activities in isolation. In this presentation, we will share the specifics of our approach, and provide open-source curriculum in the form of lab manuals, supporting files, and sample PCBs.

Sogand Okhovatian, Viken N. Koukounian

The purpose of utilizing higher level of understanding techniques is to improve the overall outcome of any process. As a full-service provider of complex engineering solutions to environmental noise problems, there is a need to house specialized knowledge to design and deliver bespoke solutions that are compatible with various constraints that implicate numerous subjects (acoustics, aerodynamics, structural, materials/chemical compatibility). The physics associated with seemingly simple products, such as an industrial acoustic silencer, is often complex. More specifically, its study should be described as aero-vibro-acoustical—whereby (1) airflow causes vibrations in the structure of the silencer, (2) the vibrations generate airborne and structureborne noise, and (3) components of the silencer (i.e., baffles) attenuate noise propagating through the duct. Motivated to expand our understanding of our products’ performances, we are using Siemens software to circumvent exhaustive laboratory testing that is cost-prohibitive, and which is, generally, limited to common geometries and parameters. A systematic approach is necessary to validate correlations between simulated results with empirical data. This is accomplished by, first, correlating the aerodynamic performance of products using computational fluid dynamics (CFD) to predict pressure drop values and the distribution of forces on the structure, to then leverage additional solvers to assess the vibro-acoustical stage of the analysis.

Yangfan Liu

Yangfan Liu received his Mechanical Engineering bachelor’s degree in China in 2009 and joined Purdue University in United States for Master and PhD degrees in Acoustics and Noise Control right after that. His PhD degree was earned in 2016, he continued to work as a post-doc researcher for two years at the same lab, Ray W. Herrick Lab, at Purdue. Dr. Liu was hired as an Assistant Professor by Purdue School of Mechanical Engineering in 2018 after his Post-doc. His research was focused on sound field reconstruction and room acoustics simulation during his graduate school study, he then established many other research areas later on, such as active noise control, multi-physics simulation, sound perception, vibroacoustic signal based fault diagnosis, etc. Dr. Liu is also very active in academic organizations, such as the Acoustical Society of America (ASA) and the Institute of Noise Control Engineering (INCE) USA, with multiple serving and leading roles. In this presentation, Dr. Liu will share his experiences in his career pathway, lessons he learned as well as opinions on the key skills and mindsets for an academic career preparation and development based on his personal experiences.

A. Adetu, C. Adetu, Daniel Bosniceanu et al.

Engineering acoustics is a multidisciplinary field that involves the use of mathematical and physical principles to model, analyze, design, develop, and test engineering systems, with the goal of ensuring that these systems exhibit desirable acoustical behavior. This study aimed to investigate the acoustic performance of a steel insulation panel using experimental and numerical methods. The experimental investigation involved measuring the sound pressure level at different distances and frequencies. The numerical investigation involved creating finite element models of the acoustic panel and analyzing the pressure distribution field for different frequencies and sound pressure levels. The results showed a good correlation between the numerical and experimental data. The study provides valuable insights into the acoustic behavior of steel insulation panels and demonstrates the effectiveness of combining experimental and numerical methods in acoustic research. The findings can be used to optimize the design of steel insulation panels for better sound insulation performance in various applications, such as building construction and industrial noise control.

David A. Brown

Students have observational experience with waves by speaking and hearing, seeing, and feeling but their use of mathematics may be delayed until introductory physics at middle school, high school, and/or college. Students following a university physics or engineering bachelor’s degree are usually required to take a course on electromagnetic wave theory because of the foundational science and/or applications such as communications and observation. Regrettably, it is common that a mathematical description of various wave propagations may be acquired but without a thorough understanding of the underlying physics – especially in electromagnetics. Thus, we have tried to develop an introductory graduate level course that teaches electromagnetics and optic waves and its applications on the foundation of first understanding acoustics. This serves as a preparation for research or vocation. Topics include traveling waves, standing waves, wave impedance, radiation patterns, interference, interferometry, sonar and radar, imaging, waveguides in more. Examples of introducing the mathematics of solution first and then derivations of wave equation is presented. The goal is that mathematics should be a useful language to communicate physical information and that acoustic demonstrations should reinforce learning in multiple physical modalities.

David Manley

Mass timber commercial buildings can significantly shift the building and design industry to a more sustainable path, but integrating architectural, engineering, and acoustic systems within this relatively new superstructure presents many challenges for designers. This talk will discuss DLR Group’s integrated design approach and mass timber research including architectural design, structures, and acoustics.