Hasil untuk "Acoustics in engineering. Acoustical engineering"

Michael J. Bianco, P. Gerstoft, James Traer et al.

Acoustic data provide scientific and engineering insights in fields ranging from biology and communications to ocean and Earth science. We survey the recent advances and transformative potential of machine learning (ML), including deep learning, in the field of acoustics. ML is a broad family of techniques, which are often based in statistics, for automatically detecting and utilizing patterns in data. Relative to conventional acoustics and signal processing, ML is data-driven. Given sufficient training data, ML can discover complex relationships between features and desired labels or actions, or between features themselves. With large volumes of training data, ML can discover models describing complex acoustic phenomena such as human speech and reverberation. ML in acoustics is rapidly developing with compelling results and significant future promise. We first introduce ML, then highlight ML developments in four acoustics research areas: source localization in speech processing, source localization in ocean acoustics, bioacoustics, and environmental sounds in everyday scenes.

Polack Jean-Dominique

In 1992, the author proposed a generalization of the Sabine formula that develops reverberation time over a series of powers of the reflection coefficient on the boundaries. Some years later, he reduced the development to just two terms that made it possible to monitor reverberation times up to large absorptions. The present paper revisits this development and justifies it with the help of free path statistics in ergodic 2D and 3D circular and rectangular enclosures. It proves that Kuttruff's reverberation formula is a special case of the general formula, but diverges for large absorption. Reverting to Kuttruff's original integration process leads to a formula that does not diverge. The paper further explains the difference between Eyring-type reverberation times that vanish for total absorption, and Sabine-type reverberation times that never vanish even for total absorption, and proposes a simple scheme for evaluating the asymptotic free path statistics and thus improving reverberation time prediction. Lastly, the approach is extended to non-ergodic enclosures.

Rucz Péter, Fontestad Elena Esteve, Angster Judit et al.

Viscothermal effects at the walls are the dominant sources of loss in the air columns of various types of wind instruments. The classical theory of viscous and thermal boundary layers gives an analytical result that allows for computing the wall losses of acoustical wave propagation in cylindrical ducts. Based on theoretical considerations, a simple formula is derived for straight ducts that allows for taking the shape of the cross section into account in the wall loss coefficient. This unidimensional model is compared to three-dimensional finite element computations of different geometries, and an excellent agreement is found. As an application of the theory, a revised scaling method for wooden flue organ pipes with rectangular cross sections is elaborated. In organ building practice, wooden pipes are often made narrower than the reference width because of space limitations. Organ builders reported an undesired change of timbre for narrow pipes, which may be explained by the increased amount of wall losses. The proposed scaling approach enables designing narrower wooden pipes with keeping the amount of wall losses the same as of a reference pipe. Two series of experimental organ pipes designed following the traditional and new scaling rules are examined and compared by means of acoustical measurements and sound analyses, proving the practical applicability of the proposed scaling method.

Xue Kaihang, Zhu Yazhou, Wang Sha et al.

To improve broadband transmission performance of mid-frequency transducers, the finite element method was applied to optimize and analyze the performance of a multi-driven Tonpilz transducer, focusing on excitation methods and structural design. A multi-driven Tonpilz transducer with a radiating head containing concentric-ring cavities was proposed, in which multi-cavity design reduces effective mass and enhances bandwidth. The performance under three excitation methods was evaluated by comparing admittance curves in air and analyzing resonant modes, revealing the effects of excitation methods on electromechanical coupling and resonant peaks. Partial excitation was identified as the optimal approach. The impedance characteristics, vibrational modes, and acoustic directivity in water were further investigated. The effects of the mass block, radiating head containing concentric-ring cavities, and front cover on transmitting voltage response fluctuations were analyzed. After optimization, the transducer operates over 17 kHz–41 kHz, with a −3 dB bandwidth of 24 kHz and a maximum transmitting voltage response of 143.7 dB re 1 μPa/V @ 1 m, providing a foundation for applications in related fields.

Schütze Julia, Kirsch Christoph, Kollmeier Birger et al.

Virtual acoustics enables hearing research and audiology in ecologically relevant and realistic acoustic environments, while offering experimental control and reproducibility of classical psychoacoustics and speech intelligibility tests. Hereby, indoor environments are highly relevant, where listening and speech communication frequently involve multiple targets and interferers, as well as connected adjacent spaces that may create challenging acoustics. Hence, a controllable laboratory environment is evaluated here (by room acoustical parameters and speech intelligibility) which closely resembles a typical German living room with an adjacent kitchen. Target and interferer positions were permuted over four different locations, including an acoustically challenging position of a target in the kitchen with interrupted line of sight. Speech intelligibility was compared in the real room, in virtual acoustic representations, and in standard anechoic audiological configurations. Three presentation modes were tested: headphones, loudspeaker rendering on a small-scale, four-channel loudspeaker array in a sound-attenuated listening booth, and a three-dimensional 86-channel loudspeaker array in an anechoic chamber. The results showed that the target talker in the coupled room requires higher signal to noise ratios (SNRs) at threshold than typical indoor conditions. Moreover, for the stationary speech shaped interferer, effects of room acoustics were negligible. For a majority of target positions, no difference between the four-channel and the large-scale loudspeaker array were found, with an overall good agreement to the real room. This indicates that ecologically valid testing is feasible using a clinically applicable small-scale loudspeaker array.

Rüdiger Hoffmann

At the TU (formerly TH) Dresden, acoustics is part of the faculty of electrical engineering. Its development started in 1911 when \textsc{Heinrich Barkhausen} was appointed Professor for ``low-current technology'', which was an umbrella for both, acoustics and communications engineering. \textsc{Barkhausen} contributed to the field of acoustics, e. g., with the first device for loudness measurement.  After the war and the retirement of \textsc{Barkhausen}, several new institutes were established from which we mention: (1) the Institute of Electro- and Building Acoustics led by \textsc{Walter Reichardt}, contributing to many fields of technical acoustics, and (2) the Institute of Telecommunications Engineering supervised by \textsc{Kurt Freitag}, contributing to speech acoustics with the design of a vocoder and the measurement of speech quality. When the GDR performed a ``higher education reform'' in 1969, the acoustical activities were concentrated in a laboratory for ``communications and data acquisition'' which included five chairs in acoustics, sensors, speech, and measurement. This step took into account the growing role of computer technology. After the political changes in 1990, the number of chairs was reduced to two which is expressed by the today's name ``Institute of Acoustics and Speech Communications''. The paper is finished by an overview on the recent activities of the institute.

P. Gerstoft, Michael J. Bianco, Ryan A. McCarthy et al.

Acoustic data provide scientific and engineering insights in fields ranging from biology and communications to ocean and Earth science. We survey the recent advances and transformative potential of machine learning (ML), including deep learning, in the field of acoustics. ML is a broad family of techniques, which are often based in statistics, for automatically detecting and utilizing patterns in data. We have ML examples from ocean acoustics, room acoustics, and personalized spatial audio. For room acoustics, we take room impulse responses (RIR) generation as an example application. For personalized spatial audio, we take head-related transfer function (HRTF) up-sampling as examples. The tutorial will conclude with a set of Jupiter notebook examples on GitHub demonstrating ML benefits.

Lafarge D.

This study extends efforts to incorporate spatial dispersion into Biot-Allard’s theory, with a focus on poroelastic media with intricate microgeometries where spatial dispersion effects play a significant role. While preserving Biot’s small-scale quasi-“en-bloc” frame motion to keep the structure of Biot-Allard’s theory intact, the paper challenges Biot’s quasi-incompressibility of fluid motion at that scale by introducing structurations in the form of Helmholtz’s resonators. Consequently, Biot-Allard’s theory undergoes a significant augmentation, marked by the arising of non-local dynamic tortuosity and compliability, which are associated with potentially resonant fluid behavior. Building on an acoustic-electromagnetic analogy, the study defines these non-local responses and suggests simplifying them into pseudo-local ones, now potentially resonant and reminiscent of Veselago-type phenomena. In the high-frequency limit of small boundary layers and as an extension of the classical Johnson-Allard’s findings, simple field-averaged formulas are demonstrated for pseudo-local ideal-fluid tortuosity and compliability (complex frequency-dependent) and viscous and thermal characteristic lengths (positive frequency-dependent). These formulations are grounded in the Umov-Heaviside-Poynting thermodynamic macroscopic acoustic stress concept, suggested by the analogy. Future computational investigations, spanning various fundamental microgeometries, are planned to assess assumed pseudo-local simplifications, encompass low- and intermediate frequencies, and unveil potential behavioral outcomes resulting from the incorporation of spatial dispersion effects.

Schäfer Philipp, Fatela João, Vorländer Michael

A central part of auralization is the consideration of realistic sound propagation effects. This can be achieved using computationally efficient physics-based simulations based on the principle geometrical acoustics. When considering complex effects, e.g. curved propagation due to atmospheric refraction, those simulations can be computationally demanding. This can become the bottleneck for real-time auralizations, as the run-time exceeds the duration of one audio block even for large block sizes. A solution is to schedule the simulations into a separate thread. However, this leads to an irregular update rate which is lower than the rate of the audio blocks. Consequently, the output signal can contain audible artifacts. This especially holds when considering the Doppler effect for dynamic scenarios with fast moving sources, like aircraft. This paper introduces a method for interpolating, and thereby upsampling, the results of scheduled simulations in an auralization context in order to avoid such artifacts. The method is applied to an aircraft flyover auralization considering curved sound propagation in an inhomogeneous, moving atmosphere. Using this method, it is possible to auralize such scenarios in real time.

Xu Jingcheng, Chen Changzheng

Considering that thin film acoustic metamaterials have many special properties that natural materials and traditional materials do not possess, the low-frequency attenuation signal absorption performance of thin film acoustic metamaterials is studied. Prepare thin film acoustic metamaterials using raw materials such as silicone, calculate the basic law of low-frequency attenuation signal absorption based on this material, and determine the acoustic parameters of thin film acoustic metamaterials through calculation. Using the obtained acoustic parameters as inputs, a finite element numerical model of thin film acoustic metamaterials is used to analyze the low-frequency attenuation signal absorption performance under changes in porosity, thickness, density, size, tension, parameter error, and frame material and mass width in contact area with the thin film. The experimental results show that when the porosity is 95%, the thickness is 11, the variable length is 16 mm, the tension force is 160 N/m, and the contact area between the mass block and the film is 5.5 mm2, the absorption effect of low-frequency attenuation signals is the best. The frame material and elastic modulus have little effect on the absorption performance of the thin film acoustic material.

Andrea Giglio, Marcella Benini, Jonathan M Broyles et al.

Nowadays, the Architectural-Engineering-Construction (AEC) market requests buildings with both low CO2 emissions and high performance across all building disciplines, including architectural acoustic systems, to satisfy design regulations and protocols. However, not all acoustic material systems guarantee both of them. Previous research has suggested that design trade-offs exist when reducing CO2 emissions and achieving high-performing room acoustics but a study on a case study is absent. In response, this paper analyses the carbon data set and material quantities of the acoustic systems of a 7-story office building in Milan, Italy. The data are gathered by outsourcing them from the LCA and further analyzed by considering the technical data sheets of the as-built products. The analysis highlights the important role of acoustics in the total amount of CO2 emissions of the building. In particular, horizontal and vertical partitions have the highest impact due to the large material intensities. In conclusion, this research demonstrates that a performance-based LCA analysis is needed to better evaluate the relationship between acoustic performance and CO2 emissions, with future research needed to understand these complex design trade-offs further.

M. Ballard, Preston S. Wilson, Mark F. Hamilton

The acoustical oceanography (AO) curriculum at The University of Texas at Austin (UT) consists a number of courses and thesis research, which often includes field work. The core course is EE/ME 384N-5, Underwater Acoustics, which covers acoustic properties of the ocean, propagation, reflection, reverberation, scattering and target strength, ocean noise, array and signal processing and basic sonar design. The course is offered in alternate years and is cross-listed as both an electrical and mechanical engineering course. Prior to this, students usually take two semesters of physical acoustics: EE/ME 384N-1 and 2, Acoustics I and II, which covers plane waves in fluids, transient and steady-state reflection and transmission, lumped elements, refraction, ray acoustics, absorption and dispersion, spherical and cylindrical waves, radiation and scattering, multipole expansions, Green’s functions, waveguides, Fourier acoustics, and Kirchhoff theory of diffraction. Both are offered every year. Another course commonly taken by AO students is EE/ME 384N-3: Electromechanical Transducers, which covers basic modeling, analysis and design of acoustics and vibration transducers, including calibration. Recent student thesis topics have included marine acoustic ecology, the investigation of methane seeps, acoustic seagrass monitoring, and the assessment of glacial processes. Appropriate courses in UT’s natural and earth sciences departments supplement the acoustics courses.

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

J. Lewis

Sonos’ office in downtown Boston is home to a variety of audio and acoustics labs where smart speakers, soundbars, subwoofers, headphones and installed speaker solutions are developed. This tour will show the 4-pi and 2-pi anechoic chambers, transducer development labs, and listening rooms. This is where the audio, microphone, and acoustical engineering teams develop, measure and listen to these products. In these labs, high-precision measurements are balanced with subjective listening evaluations to develop speaker products.

J. Bonnel, A. Lavery, J. Colosi

The Massachusetts Institute of Technology (MIT) - Woods Hole Oceanographic Institution (WHOI) Joint Program (JP) is a five-year doctoral program conferring a PhD degree awarded by both institutions. It is organized in five disciplines: Applied Ocean Science and Engineering (AOSE), Biological Oceanography, Chemical Oceanography, Marine Geology and Geophysics, and Physical Oceanography. Because the MIT-WHOI JP is so broad in scope, it is an ideal place for advanced studies in acoustical oceanography. The MIT-WHOI acoustic curriculum falls mostly under the AOSE umbrella. Students can take classes both at WHOI and MIT and can do research on a variety of topics covering acoustic propagation and scattering, undersea navigation/communication, remote sensing and environmental inversion, bioacoustics, robotics, and high latitude acoustics. JP students have access to courses, programs and resources at one of the top oceanographic research institutions in the world (WHOI) and one of the top research universities in the world (MIT). By benefiting from the best of these two institutions theoretical and sea going strengths, JP students can become part of the next generation of ocean science leaders, allowing them to pursue careers all over the world in diverse areas including universities, research institutions, government, private industry or NGOs.

Bischof Norbert F., Aublin Pierre G., Seeber Bernhard U.

Sound reflections and late reverberation alter energetic and binaural cues of a target source, thereby affecting its detection in noise. Two experiments investigated detection of harmonic complex tones, centered around 500 Hz, in noise, in a virtual room with different modifications of simulated room impulse responses (RIRs). Stimuli were auralized using the Simulated Open Field Environment’s (SOFE’s) loudspeakers in anechoic space. The target was presented from the front (0°) or 60° azimuth, while an anechoic noise masker was simultaneously presented at 0°. In the first experiment, early reflections were progressively added to the RIR and detection thresholds of the reverberant target were measured. For a frontal sound source, detection thresholds decreased while adding early reflections within the first 45 ms, whereas for a lateral sound source, thresholds remained constant. In the second experiment, early reflections were removed while late reflections were kept along with the direct sound. Results for a target at 0° show that even reflections as late as 150 ms reduce detection thresholds compared to only the direct sound. A binaural model with a sluggishness component following the computation of binaural unmasking in short windows predicts measured and literature results better than when large windows are used.

Couineaux Audrey, Ablitzer Frédéric, Gautier François

The cristal Baschet is a musical instrument created during the 1950’s by Bernard and Francois Baschet. It is composed of a large number of glass rods arranged in a chromatic scale. The sound produced results of vibrations induced by friction between wet fingers and the glass rods. Each glass rod is connected to an assembly of threaded shafts and a mass. Mechanical properties of this assembly determine the pitch of the note. Then vibrations are transmitted to large metal panels or cones that act as radiating elements. The manufacturing and tuning of this instrument is based on empirical knowledge and involves many parameters whose effects are not clearly understood. One of the encountered problems is the difficulty to produce sound in the high register of the instrument. In an attempt to understand the influences of these parameters on playability, a minimal physical model of the cristal Baschet is developed. It focuses on the interaction between the finger and the isolated resonator. The dynamic behavior is described by a set of modes obtained from a finite element model or from experimental modal analysis. The musician’s gesture is described by two control parameters: the velocity of the finger along the glass rod and the normal force applied by the finger on the rod. To describe the interaction between the finger and the resonator, a friction law is implemented. The influence of different parameters is studied by means of linear stability analysis and time-domain simulations. Specific criteria are developed to highlight the role of design parameters on playability.

Ford Courtney, Pereira Antonio, Bailly Christophe

This work aims to predict the transfer function of a given modal content inside a circular duct with a bellmouth inlet in the presence of a mean flow. The transfer function is the relation in amplitude and phase between a given mode inside the duct and an observer located in the far-field. The numerical solution is obtained by finite element simulation in which the mean flow is input data. Verification is provided by comparison to the analytical solution of an unbaffled circular duct with uniform flow. Influence from various parameters such as the geometry and mean Mach number on the radiated pressure field is investigated. The analytical solution is a good approximation for finding the radiated principal lobe, and the inlet geometry is found to be more important than other parameters such as mean flow when static inlet configuration is studied.

Volery Maxime, Guo Xinxin, Lissek Hervé

This paper presents an acoustic impedance control architecture for an electroacoustic absorber combining both feedforward and feedback microphone-based strategies on a current-driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passivity, which can cause unstable behaviour. The feedback contribution allows the absorber to better handle model errors and still achieve an accurate impedance, preserving passivity. Numerical and experimental studies were conducted to compare this new architecture against a state-of-the-art feedforward control method.

Martin S. Lawless, Michael Giglia, David Wootton

Hands-on, project-based learning was difficult to achieve in online classes during the COVID-19 pandemic. The Engineering Experimentation course at Cooper Union teaches third-year mechanical engineering students practical experimental skills to measure physical phenomenon, which typically requires in-person laboratory classes. In response to COVID, a low-cost, at-home laboratory kit was devised to give students tools to conduct experiments. The kit included a microcontroller acting as a data-acquisition device and custom software to facilitate data transfer. A speed of sound laboratory was designed with the kit to teach skills in data collection, signal processing, and error analysis. The students derived the sound speed by placing two microphones a known distance apart and measuring the time for an impulsive signal to travel from one to the other. The students reported sound speeds from 180.7-477.8 m/s in a temperature range from 273.7-315.9 K. While these reported speeds contained a large amount of error, the exercise allowed the students to learn how to account for sources of error within experiments. This paper also presents final projects designed by the students at home, an impedance tube and two Doppler shift experiments, that exhibit successful and effective low-cost solutions to demonstrate and measure acoustic phenomenon.