Acoustic Phenomena Research Articles

An investigation of shock cell-related noise in an installed, full-scale tactical jet engine using acoustical holography

Shock cells in imperfectly expanded supersonic jet flows have been found to contribute to the noise radiated by these jets. Acoustic phenomena such as screech and broadband shock-associated noise have been linked to the shock cell structure in jets. Acoustical holography has been used to study various jet noise source and radiation characteristics. Holography-based reconstructions near the acoustic source in an installed, full-scale tactical jet engine have yielded features indicative of the known shock cell structure in the jet. This paper presents these results and investigates the characteristics of these features, including their distribution and relative amplitudes.

Understanding and applications of striation-based beamforming in underwater acoustics

Utilizing the shallow water acoustic interference phenomenon in the range-frequency domain, striation-based beamforming (SBF) was proposed to estimate waveguide invariant and enhance active sonar output. In the past decade, SBF has also been applied to enhance LOFARgrams to improve tracking performance. In this paper, the correlation theory is used to understand SBF, and some further applications of SBF in underwater acoustic problems are also discussed. It shows that SBF essentially selects the optimal signal components with the best correlation. During the process, the correlation of array signals is improved and the ability to converge signals arriving via different paths is achieved to ensure array gain. The level of gain improvement is related to the direction of striation-based processing. Hence, a cost function can be constructed to facilitate the implementations of SBF in tasks such as striation slope estimation and source range estimation. Additionally, the SBF technique can be further applied to estimate the Green's function by introducing the cross-correlation preprocessing. Utilizing the mathematical connection between SBF and CBF, SBF can also be naturally extended to other beamforming algorithms and improve their performance, such as the subspace algorithms. The above is explained using simulation and experimental results.

Influence of specimen size on granite fracture characteristics and acoustic emission phenomena under mode I loading conditions

The rock mode I fracture characteristics and the size effect are of great significance in understanding the crack initiation, nucleation, propagation, and characterizing the fracture toughness of rocks which is essential for predicting the behavior of rock masses and designing underground structures. In this paper, three-point bending fracture experiments were carried out using single-edge notched beam specimens of different sizes. The fracture characteristics of the entire loading stage, including the post peak stage, were analyzed using digital image correlation (DIC) technology and acoustic emission (AE) technology. Specifically, the calculation of the b value uses the Fisher optimal split and global search algorithm (FGS) method. The results show that both the Fracture process zone (FPZ) length and fracture toughness of granite are size-dependent parameters, and the FPZ length growth rate increases with increasing load level. The failure mode of the source during fracture is mainly tensile failure, and the proportion of tensile failure tends to increase with the increase of specimen size. The temporal b value, average AF value and RA value show corresponding stage changes with time, and the minimum b value, minimum AF value and maximum RA value can characterize the maximum of macroscopic growth rate.

Deep sound-field denoiser: optically-measured sound-field denoising using deep neural network.

This paper proposes a deep sound-field denoiser, a deep neural network (DNN) based denoising of optically measured sound-field images. Sound-field imaging using optical methods has gained considerable attention due to its ability to achieve high-spatial-resolution imaging of acoustic phenomena that conventional acoustic sensors cannot accomplish. However, the optically measured sound-field images are often heavily contaminated by noise because of the low sensitivity of optical interferometric measurements to airborne sound. Here, we propose a DNN-based sound-field denoising method. Time-varying sound-field image sequences are decomposed into harmonic complex-amplitude images by using a time-directional Fourier transform. The complex images are converted into two-channel images consisting of real and imaginary parts and denoised by a nonlinear-activation-free network. The network is trained on a sound-field dataset obtained from numerical acoustic simulations with randomized parameters. We compared the method with conventional ones, such as image filters, a spatiotemporal filter, and other DNN architectures, on numerical and experimental data. The experimental data were measured by parallel phase-shifting interferometry and holographic speckle interferometry. The proposed deep sound-field denoiser significantly outperformed the conventional methods on both the numerical and experimental data. Code is available on GitHub (https://github.com/nttcslab/deep-sound-field-denoiser).

The Modal Acoustic Archetype of Japanese Palace-Ceremonial Music Togaku-Kangen

The composite character of the Japanese ethnogenesis manifests itself at the level of culture of social strata including the canonised royal ceremonial complex gagaku (elegant music). Along with sankangaku, the music of the three Korean kingdoms, its essential component is togaku-kangen, the music for string and brass instruments of the Chinese Tang Empire, which is a fusion of intonational forms of China and many peoples of the East including the patterns of the musical thinking and language of the peoples, who had active contacts with the bearers of Greco-Roman culture. Since the musical intonation is a form process aimed to introduce meaning in the acoustic phenomenon making the latter a phenomenon or noumenon both explicitly and implicitly containing the components of comprehending existence in mythological and religious way as well as scientifi c and philosophic one (including terminology tools) and, which is naturally, the notion of the three-pronged-severalty of cosmogenesis/ethnogenesis/culturogenesis/, the systematic structural analysis of the modal acoustic of the intonational canon of the aforementioned Japanese culture makes it possible to identify the archetypical components of the worldconception characteristic not only of the peoples of the Far East, whose handbook was Book of Changes (Yi Jing) popular, in particular, among the scientists of today.

Extensive investigation of geometric effects in sonoreactors: Analysis by luminol mapping and comparison with numerical predictions.

This investigation focuses on the influence of geometric factors on cavitational activity within a 20kHz sonoreactor containing water. Three vessels with different shapes were used, and the transducer immersion depth and liquid height were varied, resulting in a total of 126 experiments conducted under constant driving current. For each one, the dissipated power was quantified using calorimetry, while luminol mapping was employed to identify the shape and location of cavitation zones. The raw images of blueish light emission were transformed into false colors and corrected to compensate for refraction by the water–glass and glass-air interfaces. Additionally, all configurations were simulated using a sonoreactor model that incorporates a nonlinear propagation of acoustic waves in cavitating liquids. A systematic visual comparison between luminol maps and color-plots displaying the computed bubble collapse temperature in bubbly regions was conducted. The calorimetric power exhibited a nearly constant yield of approximately 70% across all experiments, thus validating the transducer command strategy. However, the numerical predictions consistently overestimated the electrical and calorimetric powers by a factor of roughly 2, indicating an overestimation of dissipation in the cavitating liquid model. Geometric variations revealed non-monotonic relationships between transducer immersion depth and dissipated power, emphasizing the importance of geometric effects in sonoreactor. Complex features were revealed by luminol maps, exhibiting appearance, disappearance, and merging of different luminol zones. In certain parametric regions, the luminol bright regions are reminiscent of linear eigenmodes of the water/vessel system. In the complementary parametric space, these structures either combine with, or are obliterated by typical elongated axial structures. The latter were found to coincide with an increased calorimetric power, and are conjectured to result from a strong cavitation field beneath the transducer producing acoustic streaming. Similar methods were applied to an additional set of 57 experiments conducted under constant geometry but with varying current, and suggested that the transition to elongated structures occurs above some amplitude threshold. While the model partially reproduced some experimental observations, further refinement is required to accurately account for the intricate acoustic phenomena involved.

A simulation study on the sensitivity of transcranial ray-tracing ultrasound modeling to skull properties.

In transcranial focused ultrasound therapies, such as treating essential tremor via thermal ablation in the thalamus, acoustic energy is focused through the skull using a phased-array transducer. Ray tracing is a computationally efficient method that can correct skull-induced phase aberrations via per-element phase delay calculations using patient-specific computed tomography (CT) data. However, recent studies show that variations in CT-derived Hounsfield unit may account for only 50% of the speed of sound variability in human skull specimens, potentially limiting clinical transcranial ultrasound applications. Therefore, understanding the sensitivity of treatment planning methods to material parameter variations is essential. The present work uses a ray-tracing simulation model to explore how imprecision in model inputs, arising from clinically significant uncertainties in skull properties or considerations of acoustic phenomena, affects acoustic focusing quality through the skull. We propose and validate new methods to optimize ray-tracing skull simulations for clinical treatment planning, relevant for predicting intracranial target's thermal rise, using experimental data from ex-vivo human skulls.

Developing Assumptions for the Tram Noise Attenuation Passive System Using the Noise Maps Analysis Method

The paper presents experimental research carried out to determine the possible actions to reduce the noise generated by trams in a highly urbanised area. A few design strategies affecting tram ride quality have been presented – especially in the aspect of the acoustic phenomena. Main sources of the noise in trams were characterised. The paper includes selected results of comprehensive studies of tram noise in the pass-by test based on the authors’ research methodology. The tests were carried out on various types of trams to recognise the acoustic phenomena characteristic for the rolling stock in a selected tram system. The results of the measurements were analysed both in the field of amplitudes based on noise maps and in respect to frequencies based on noise spectra. The results indicated the rolling noise as important issue demanding taking some actions in order to reduce its level. In this area, elements for the application of individual attenuation solutions, i.e. at the source and during propagation, were presented. The results of the measurements were used as input data to the assumptions of the noise attenuation passive system, which was the final outcome of the study. Dedicated external dampers were used in the case of wheel and rail pairs, where the dominant power of the noise is emitted. The acoustic properties of the bogie area and the bogie side covers were redeveloped to hamper the noise propagation, which is a novel application. The presented results indicate measurable benefits from the applied solutions on the tram noise reduction.

Acoustic softening – investigation of the volume effect and introduction of amplitude strain parameter

Acoustic softening is a phenomenon where metals exhibit a lower flow stress when excited by a vibration at ultrasonic frequencies. This softening effect has been well documented in the literature, however, there are two areas that require further in-depth analysis. The first relates to the wide range of reported softening responses for the same alloy. The second relates to the use of coefficients and compensation factors when modeling the acoustic softening phenomenon in a complex forming processes. This study investigates the changes in softening response when altering specimen dimensions in ultrasonic assisted compression tests. Aluminum alloys (AA) 2024-O and AA7075-O were machined to different dimensions and compressed with ultrasonic assistance, to investigate the relationship between specimen volume and softening response. An inverse relationship between softening magnitude and sample volume was found. When relating this to acoustic energy density and stress, the values are invariant because the standard acoustic equations cannot account for changes in specimen height. The amplitude strain parameter, amplitude divided by the current specimen height, is introduced, and shown to account for changes in specimen dimensions. In addition, the softening effect diminishes relative to the state of strain. The results suggest acoustic softening is a function of the amplitude strain parameter and strain history.

Implications of liquid impurities filled in breaking cracks on nonlinear acoustic modulation response: Mechanisms, phenomena and potential applications

Supervised strategies for ultrasonic-based cracks detection in existing structures has been one of particular concerns in the engineering community. However, current researches mostly focus on the clean microcracks, while ignoring the fact that such cracks will be contaminated with liquid impurities (lubricants, silicone oil, etc.) due to its exposure to the operational environment. Actually, the presence of liquid may lead to a non-negligible change in the acoustic performance and interfere with damage diagnosis. The central contribution of this work is to reveal the nonlinear acoustic mechanisms and phenomena induced by the gas–liquid–solid coupling interfaces in such liquid-filled cracks and investigate their potential applications for such crack detection. Firstly, the state equation for a liquid-filled cavity in beams is established to determine the nonlinear dependences of stress–strain relationship at crack wall on the viscous and capillary pressure in liquid. Secondly, a modified acoustic modulation method, in which swept signal is used as the pumping wave to sufficiently trigger and enhance the nonlinear behaviours at the gas–liquid–solid interfaces without requiring exact reference information, is utilized for detecting sub-millimeter cracks filled with different liquid. The results suggest that the liquid fillers may cause considerable increase of the damage-related acoustic nonlinearities involving hysteresis nonlinearity, nonlinear elastic behavior and dissipative nonlinearity. Additional analysis provides compelling evidence for the following valuable conclusions: 1) the capillary pressure is a key factor that promotes conducive to the nonlinear elastic behavior that is the primary source of the first-order sum-difference frequency; 2) the viscous pressure contributes to hysteresis as well as the nonlinear dissipation, and the latter promotes the second-order sum frequency. Further, such nonlinear performance especially dissipation offer promising prospects for nonlinear acoustic diagnostic of such cracks. All results obtained in this study will aid in understanding the nonlinear wave processes and further improving the reliability of crack detection in engineering.

Auditorium Acoustics and Architectural Design

The effectiveness of the acoustic treatment in any auditorium or a performing space has a direct impact on how clearly people can communicate and perform there. This quality is defined by several characteristics in Acoustical architecture. This research seeks to clarify the acoustical phenomena and defects that provide the basis for acoustical designing and material choice. The paper includes fundamental guidelines and methods for planning auditorium acoustics, as well as fundamental criteria for material selection in relation to the NRC values needed in a space. Overall, this research emphasizes the importance of an integrated approach to auditorium design that considers both acoustic and architectural design elements to create optimal auditory experiences for the audience.

A second wave of topological phenomena in photonics and acoustics.

Light and sound are the most ubiquitous forms of waves, associated with a variety of phenomena and physical effects such as rainbows and echoes. Light and sound, both categorized as classical waves, have lately been brought into unexpected connections with exotic topological phases of matter. We are currently witnessing the onset of a second wave of active research into this topic. The past decade has been marked by fundamental advances comprising two-dimensional quantum Hall insulators and quantum spin and valley Hall insulators, whose topological properties are characterized using linear band topology. Here, going beyond these conventional topological systems, we focus on the latest frontiers, including non-Hermitian, nonlinear and non-Abelian topology as well as topological defects, for which the characterization of the topological features goes beyond the standard band-topology language. In addition to an overview of the current state of the art, we also survey future research directions for valuable applications.

Superior broadband sound absorption in hierarchical ultralight graphene oxide aerogels achieved through emulsion freeze-casting

Ultra-lightweight aerogels have profound applications as advanced multi-functional sound-absorbing materials. At present, conventional aerogels are associated with pores with sizes too small for effective sound absorption in the audible range. In this work, we fabricated a hierarchically porous ultralight graphene oxide (GO) aerogel through a novel emulsion freeze-casting process of an air-in-water emulsion. Microstructural analysis of the aerogels reveals a hierarchical pore morphology consisting of highly inter-connected pores produced from the emulsion bubbles and the micro-pores produced by freeze-casting. Sound absorption measurements revealed that an aerogel with a surfactant-to-GO weight ratio of 1:1 displays an average absorption coefficient of up to 0.86 at a broadband frequency range between 250 Hz and 6300 Hz, a vast improvement by up to 58% as compared to conventional GO aerogels. Numerical microstructural models were developed to model the acoustic absorption phenomenon and understand the mechanisms behind enhanced sound absorption. These models identified the enhanced acoustic absorption as attributed to the increased air-wetting area as derived from the high reticulation rate in this hierarchical microstructure. Overall, we demonstrate the potential of leveraging the highly inter-dependent material-process-structure relationships of GO aerogel production to achieve hierarchical GO aerogels as advanced ultralight sound-absorbing materials.

Ultrasonic Decontamination of Chemical Warfare Agents

Abstract Sonochemistry studies the physical and molecular level changes induced by ultrasonic energy on solutions. Sonochemical degradation of the chemical warfare agents (CWA) may occur due to three successive phenomena based on the principles of acoustic cavitation phenomena: nucleation, growth, and implosive collapse of microbubbles. The sonolytic degradation of CWA was quantified by GC-MS technique, considering the variation of some parameters such as frequency of ultrasonic waves, power control, temperature, and addition of nanoparticles as catalysts to the solution.

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

Analyzing the acoustic behavior of gamelan music performance in different environments

This study examines the acoustic characteristics of Gamelan music performances in various settings, explicitly emphasizing the disparity between enclosed auditoriums and open spaces. Given the growing frequency of Gamelan performances in varied contexts, the comprehension of how diverse environments impact acoustic qualities is of utmost importance to enhance audience experience and safeguard the authenticity of traditional musical forms. The significance of this study arises from the increasing prevalence of Gamelan music in non-traditional contexts, such as outdoor festivals, prompting inquiries into the variations in acoustic properties across different situations. This research endeavor aims to fill the existing gap in knowledge by undertaking a qualitative examination of acoustic phenomena in enclosed and unobstructed environments. The research presented in this study is notable for its extensive investigation into acoustic phenomena across many settings, considering several aspects, including sound reflection, absorption, and reverberation. Qualitative analytical techniques were applied to evaluate the acoustic characteristics within each respective setting by utilizing a comprehensive examination of pertinent scholarly works pertaining to acoustics and Gamelan music. The findings suggest that closed auditoriums, which have controlled sound distribution and little interference, exhibit unique acoustic characteristics compared to open spaces. In open spaces, sound propagation is affected by ambient elements and the audience's presence. The research underscores the significance of architectural design in influencing acoustic surroundings and the necessity for flexible performance venues that can handle the intricacies of Gamelan music. This study makes a valuable contribution to the existing body of knowledge by providing a more comprehensive understanding of the impact of contextual elements on the acoustic characteristics of Gamelan music. The findings of this research have implications for the improvement of performance venues and the promotion of audience involvement in various contexts.

Churches Acoustics as Intangible Cultural Heritage: Experimental and Numerical Characterization of the Temple of San Biagio

ABSTRACT The acoustic properties of churches are, to date, as much a cultural asset as their architectural features. The study, understanding and conservation of acoustic phenomena that characterize liturgical spaces, to date, make use of new technologies and methodologies that facilitate their practice. The study presented here analyzes the acoustic phenomena that characterize the Temple of San Biagio (Montepulciano, Tuscany, Italy). It makes use of experimental acoustic surveying and the aid of the laser scanning surveying technique for the creation of the geometry, subsequently adopted for numerical acoustic modeling of the church in Odeon Acoustics software, used for the study of its acoustic characteristics. The selected methodology allowed us to delve into dynamics often encountered in acoustic simulations, such as the calibration of numerical models and the influence of the mesh number of the generated geometric models, and to understand the acoustic characteristics of the church.

Acoustics Features of Voice in Adolescent Females With Anorexia Nervosa

The process of human voice production is a complex physiological and acoustic phenomenon that depends on many structural, physical, and hormonal factors, systemic diseases as well as emotional states. All these factors can be present in eating disorders. However, studies on eating disorders and voice problems have usually been evaluated in terms of bulimia. Chronic starvation and emotional problems in the course of anorexia nervosa (AN) appear to be under-researched, despite various biochemical, metabolic, and hormonal changes. The purpose of this study was to evaluate voice quality, specifically acoustic analysis, in adolescent female with AN from the point of view of the possible influence on the function and structure of the larynx, low body mass accompanying AN, as well as energy deficiency, hormonal and emotional disturbances. A total of 84 girls diagnosed with AN (Gr.A) (15.32 years, SD=2.12; range 12-19, BMI=14.11±1.72)were assessed for the condition of the voice such as perceptual voice evaluation on the GRBAS scale, maximal phonation time (MPT), laryngoscopy, with special attention to voice acoustic analysis - Multi-Dimensional Voice Program (MDVP). The control group (Gr.C) included 62 girls without eating disturbances (aged 12-19, mean age 15.41±2.40, BMI=21.60±1.92). Perceptual voice assessment, aerodynamic test MPT, and acoustic parameters were analyzed according to girls' age. Total GRBAS scale was higher in girls with AN compared to the control group mainly for two parameters: breathiness (B) (P=0.00015) and asthenia (A) (P<0.05). TheMPT for Gr.A was significantly shorter compared to Gr.C (15.40±3.51seconds vs. 23.19±5.17seconds) (P<0.001), and a correlation of MPT values with the age of the adolescent female was observed: Spearman's coefficient for Gr.A=(-)0.5378, for Gr.C=0.5516 (P=0.0012). Acoustic analysis revealed the decrease in the basic frequency F0 in Gr.A compared to Gr.C (231.08Hz vs. 242.30Hz), and narrowing of the voice scale was observed, resulting mainly from a reduction in the upper limit. Significant differences were found for measures of frequency perturbations (Jita, Jitter, RPA, PPQ, sPPR), with Gr.A scoring significantly higher than Gr.C (P<0.05 for all). Significant changes in voice acoustic analysis parameters were found with age. Negative correlations were found for measures of F0 for Gr.A to a much greater extent compared to Gr.C. Positive correlations were found with measures of tremor assessment (SPI, FTRI, ATRI) for Gr.A.

Effects of un-parallel notches on the granite fracture properties and acoustic emission phenomena under biaxial test: PFC computation and experimental verification

To assess connections between these notches throughout fracture formation under stress, the mechanical performance of granite specimens with two non-parallel notches underwent a biaxial compression test. The first notch had a 45° angle, whereas the second had a variable angle (0°, 45°, 90°, 130°, and 180°). Three ligament angles (0°, 45°, and 90°) were measured between the inner tips of two notches and the horizontal axis. The ligament length, distance between the inner tips of the two notches, and both notch lengths were each 2 cm. These samples were examined at 0, 1, and 3 MPa confining pressures. By using the particle flow code (PFC), simulated results of the evaluations were run after the trials. It was discovered that the specimens’ failure strengths were influenced by the notch’s geometric characteristics, which in turn impacted the failure mechanism as well as fracture geometry. The number of tensile fractures had an impact on the specimens’ failure strengths. Whilst also increasing the ligament angle, more induced tensile cracks were produced. In the early stages of loading, just a few AE events were found, but after that, they multiplied quickly before approaching the peak stress. By raising the confining pressure, the AE hits were increased and delay failure was occured. The failure strength and AE hits are significantly impacted by the second notch’s angle. In constant ligament angel, the compressive strength of models containing overlapped joint were more than that with non-overlapped joints. In models containing non-overlapped notches, the model with ligament angles of 0° and 45° had maximum and minimum compressive strength, respectively. In models containing overlapped notches, the model with ligament angles of 90° and 45° had maximum compressive strength and minimum compressive strength, respectively. In all ligament angles, minimum compressive strength was occurred when the upper joint angle was 45°. Both the computational and experimental methodologies showed that the specimens’ failure pattern and compressive strength were very comparable.

Analysis of the combustion engine exhaust system structure in aspect of shaping acoustic energy

The flow of exhaust gases is the source of many physical processes, including thermal, acoustic, mechanical and chemical phenomena with high dynamics of changes. The study analyzes the impact of the entire structure of the exhaust system on the formation of acoustic energy, determining the transmission loss characteristics of its individual components and the entire system. On the example of a structure based on a proprietary solution of an adjustable reactive muffler, the possibilities of shaping the flow of acoustic waves in the process of designing and selecting exhaust systems for internal combustion engines were determined. The study was carried out with the use of the CFD method and a specialized package for advanced simulations AVL AST.