Hasil untuk "Acoustics. Sound"

Slimane Merouani, Aissa Dehane, Oualid Hamdaoui

This review thoroughly examines the potential of water ultrasonication (US) for producing hydrogen. First, it discusses ultrasonication reactor designs and techniques for measuring ultrasonication power and optimizing energy. Then, it explores the results of hydrogen production via ultrasonication experiments, focusing on the impact of processing factors such as ultrasonication frequency, acoustic intensity, dissolved gases, pH, temperature, and static pressure on the process. Additionally, it examines advanced ultrasonication techniques, such as US/photolysis, US/catalysis, and US/photocatalysis, emphasizing how these techniques could increase hydrogen production. Lastly, to progress the efficacy and scalability of hydrogen generation through ultrasonication, the review identifies existing challenges, proposes solutions, and suggests areas for future research.

Xiaoqiang Zhang, Hongyue Chen, Yuhan Wang et al.

We investigate the effect of ultrasound on the evaporation and crystallization of sessile NaCl solution droplets which were positioned in traveling or standing wave ultrasound field. The experimental results indicated that the ultrasound field can significantly accelerate the evaporation rate of the sessile droplets and refine the crystal grains. By adjusting the distance between the sessile droplets and the ultrasound emitter, it is found that, in traveling wave ultrasound field, the sessile droplet evaporation time and the time for the appearance of NaCl grains exhibited a fluctuating increase as the droplet-emitter distance increased. While in the standing wave ultrasound, the sessile droplet evaporation rate increases with the increasing droplet-emitter distance. Overall, the traveling wave ultrasound field has a stronger effect on grain refinement of the sessile droplets than the standing wave ultrasound field. The grain refinement is attributed to the decrease of critical nucleation radius caused by ultrasound energy and the increase of the nucleation rate caused by the accelerated evaporation rate. In addition, the breakage of grains caused by ultrasonic cavitation would also lead to grain refinement.

Robert STĘPIEŃ, Piotr WRZECIONO

Air humidity significantly affects the sound of wooden instruments. The sound quality decreases when the instrument is exposed to low humidity for an extended period. Therefore, the instrument is treated with a humidifier to improve sound quality. This study aimed to verify the effectiveness of the humidification process by analyzing the quality of guitar sound with the methods used in signal complexity studies, such as Higuchi’s fractal dimension (HFD), symbolic analysis, and empirical mode decomposition (EMD). The sound quality was determined by the sound levels measured before, during, and after the guitars’ humidification. The methods used consistently confirmed the improvement of the guitar sound quality after the humidification process. Moreover, it was concluded that the sound quality changes irregularly during the humidification process.

Jianyong Yin, Yongxue Zhang, Xueyu Qi et al.

The solid surface with several cavities containing gas strongly influences the bubble’s dynamical behaviors. To reveal the underlying physical mechanism of the cavitation bubble near a rigid boundary with a gas-entrapping hole, a fully compressible three-phase model, accounting for the three-phase volume transport equation, was implemented in OpenFOAM. The predicted bubble shape was validated with the corresponding experimental photos, and good agreement was achieved. The bubble’s primary physical features (e.g., the expanding shock wave, upward and downward liquid jet, and high-pressure region) are well reproduced, which helps understand the underlying mechanisms. The numerical results show that the solid wall with a gas-entrapping hole could affect the morphology of both the bubble and liquid jet, as well as shortens the bubble's first oscillation period in comparison to an intact rigid wall. The relationship among the prolongation factor, the standoff distance, and the relative size ratio is analyzed. It is found the prolongation factor increases as the relative size ratio decrease. As the standoff distance decreases, the gas entrapping hole plays a significant role in the oscillation period of the bubble. The current model can be further extended to reveal the microscopic mechanism of aeration avoiding cavitation damage and investigate the interaction between air bubbles and cavitation bubbles, which is of great interest to practical applications.

Linus Y. S. Chiu, Ying-Tsong Lin

Multipath acoustic arrivals on fixed receivers from a moving source in an underwater waveguide include wide-angle bottom reflections that are affected by sediment properties. Hence, one can use them as input data for seabed geoacoustic parameter estimation. In this study, the effects of seabed properties on such measurements are theoretically analyzed. The result shows that one can utilize time delays and source distances at the critical angle points of multipath arrivals to determine the sediment sound speed. The effect of sediment attenuation is also discussed, and the proposed method is demonstrated with experimental data.

E. Rascevska, L.C.M. Yip, P. Omidi et al.

Approximately 19 % of breast cancer patients undergoing breast conserving surgery (BCS) must return for a secondary surgery due to incomplete tumour removal. Our previous work demonstrated that the lower lipid content, characteristic of tumour tissue, was observed as regions of hypo-intense photoacoustic (PA) contrast. The goal of this work was to evaluate feasibility of a low-frequency, hand-held PA imaging probe for surgical margin assessment based on lipid content differences. Here, we describe (i) the design of a prototype hand-held PA imaging probe, (ii) the effect of limited-bandwidth on image contrast, (iii) accuracy towards hypo-intense contrast detection, (iv) the limited-view characteristics of the single sensor design, and (v) early imaging results of an ex-vivo breast cancer specimen. The probe incorporated a single polyvinylidene fluoride acoustic sensor, a 1-to-4 optical fibre bundle and a polycarbonate axicon lens for light delivery. Imaging results on phantoms designed to mimic positive margins demonstrated the ability to detect gaps in optical absorption as small as 1 mm in width. Compared to images from a near full-view PAI system, the hand-held PAI probe had higher signal to noise ratio but suffered from negativity image artifacts. Lumpectomy specimen imaging showed that strong signals can be obtained from the fatty tissue. Taken together, the results show this imaging approach with a hand-held probe has potential for detection of residual breast cancer tissue during BCS; however, more work is needed to reduce the size of the probe to fit within the surgical cavity.

Gökay Dişken

Detection of audio spoofing attacks has become vital for automatic speaker verification systems. Spoofing attacks can be obtained with several ways, such as speech synthesis, voice conversion, replay, and mimicry. Extracting discriminative features from speech data can improve the accuracy of detecting these attacks. In fact, a frame-wise weighted magnitude spectrum is found to be effective to detect replay attacks recently. In this work, discriminative features are obtained in a similar fashion (frame-wise weighting), however, a cosine normalized phase spectrum is used since phase-based features have shown decent performance for the given task. The extracted features are then fed to a convolutional neural network as input. In the experiments ASVspoof 2015 and 2017 databases are used to investigate the proposed system’s spoof detection performance for both synthetic and replay attacks, respectively. The results showed that the proposed approach achieved 34.5% relative decrease in the average EER for ASVspoof 2015 evaluation set, compared to the ordinary cosine normalized phase features. Furthermore, the proposed system outperformed the others at detecting S10 attack type of ASVspoof 2015 database.

Antonia Tamborrino, Agnese Taticchi, Roberto Romaniello et al.

The objective of this study is to assess the effects of installation and operation of a high-power ultrasound machine (HPU) for the treatment of olive paste by using ultrasound technology in order to evaluate the best way installation and the best definition of the operating conditions of the machine. The study was conducted installing in an industrial olive oil mill a continuous processing ultrasound machine, which used a frequency of 20 kHz able to work at 3200 kg h−1 as feed capacity. Checking of performance has been carried out by the assessment of the different operating and process conditions, assessing in particular the impact of the ultrasound treatment before and after the malaxation phase on performance indicators of the continuous olive oil plant (plant extractability, olive paste rheological characteristic) and on selected chemical properties of the olive oil extracted (quality parameters, antioxidant content, and volatile profiles). In the tested conditions, high-power ultrasound treatment did not produce significant effect on the legal parameters (free acidity, peroxide index and spectrophotometric indexes), while a significant increase in the content of phenolic compounds was generally observed; higher enhancements were more evident when the high-power ultrasound treatment was carried out before the malaxation phase.

Yahao Zhang, Yixin Yang, Long Yang et al.

This letter solves direction-of-arrival (DOA) estimation of coherent signals for uniform linear array. The proposed method reformulates the covariance matrix as a multiple-snapshot array output model to obtain a high array signal-to-noise ratio. Then the scheme of the atomic norm minimization [Yang and Xie, IEEE Trans. Signal Process. 64(19), 5145–5157 (2016)] is extended to this model, thus estimating the DOAs in a continuous space. The proposed method avoids the condition where DOAs deviate from the discretized grid, i.e., basis mismatch. The simulation and experimental results verify the good performance of the proposed method for coherent signals.

Hongwei Cao, Rulian Sun, Junru Shi et al.

Protein oxidation leads to covalent modification of structure and deterioration of functional properties of quinoa protein. The objective of this study was to investigate the effects of ultrasonic treatment on the functional and physicochemical properties of quinoa protein oxidation aggregates. In this concern, 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was selected as oxidative modification of quinoa protein. The microstructure of quinoa protein displayed by scanning electron microscope (SEM) indicated that oxidation induced extensive aggregation, leading to carbonylation and degradation of sulfhydryl groups. Aggregation induced by oxidation had a negative effect on the solubility, turbidity, emulsifying stability. However, according to the analysis of physicochemical properties, ultrasonic significantly improved the water solubility of quinoa protein. The quinoa protein treated by ultrasonic for 30 min exhibited the best dispersion stability in water, which corresponded to the highest ζ-potential, smallest particle size and most uniform distribution. Based on the FT-IR, SDS-PAGE and surface hydrophobicity analysis, the increase of α-helix, β-turn and surface hydrophobicity caused by cavitation effect appeared to be the main mechanism of quinoa protein solubilization. In addition, the hydrophobic region of the protein was re-buried by excessive ultrasonic treatment, and the protein molecules were reaggregated by disulfide bonds. Microstructural observations further confirmed that ultrasonic treatment effectively inhibited protein aggregation and improved the functional properties of quinoa protein.

A. Merkel, V. Romero-García, J. Groby et al.

In an effective medium description of acoustic metamaterials, the Willis coupling plays the same role as the bianisotropy in electromagnetism. Willis media can be described by a constitutive matrix composed of the classical effective bulk modulus and density and additional cross-coupling terms defining the acoustic bianisotropy. Based on an unifying theoretical model, we unite the properties of acoustic Willis coupling with $\mathcal{PT}$ symmetric systems under the same umbrella and show in either case that an exceptional point hosts a remarkably pronounced scattering asymmetry that is accompanied by one-way zero reflection for sound waves. The analytical treatment is backed up by experimental input in asymmetrically side-loaded wavesguides showing how gauge transformations and loss biasing can embrace both Willis materials and non-Hermitian physics to tailor unidirectional reflectionless acoustics, which is appealing for purposeful sound insulation and steering.

Alvaro E. Lopez Duarte

In this article, I review the concept of algorithmic generative and interactive music and discuss the advantages and challenges of its implementation in videogames. Excessive repetition caused by low interactivity in music sequences through gameplay has been tackled primarily by using random or sequential containers, coupled with overlapping rules and adaptive mix parameters, as demonstrated in the Dynamic Music Units in Audiokinetic’s Wwise middleware. This approach provides a higher variety through re-combinatorial properties of music tracks and also a responsive and interactive music stream. However, it mainly uses prerecorded music sequences that reappear and are easy to recognize throughout gameplay. Generative principles such as single-seed design have been occasionally applied in game music scoring to generate material. Some of them are complemented with rules and are assigned to sections with low emotional requirements, but support for real-time interaction in gameplay situations, although desirable, is rarely found. While algorithmic note-by-note generation can offer interactive flexibility and infinite diversity, it poses significant challenges such as achieving human-like performativity and producing a distinctive narrative style through measurable parameters or program arguments. Starting with music generation, I examine conceptual implementations and technical challenges of algorithmic composition studies that use Markov models, a-life/evolutionary music, generative grammars, agents, and artificial neural networks/deep learning. For each model, I evaluate rule-based strategies for interactive music transformation using parameters provided by contextual gameplay situations. Finally, I propose a compositional tool design based in modular instances of algorithmic music generation, featuring stylistic interactive control in connection with an audio engine rendering system.

Yingqun Ma, Qingjun Zhao, Kai Zhang et al.

The main goal of the study is to apply the structural intensity method to analyze the effects of positions of the main-mount and the sub-mount on the vibrational energy flow transmission characteristics in aero-engine casing structures, so as to attenuate the vibration of the casing and the whole aero-engine. Structural intensity method, indicating magnitude and direction of the vibrational energy flow, is a powerful tool to study vibration problems from the perspective of energy. In this paper, a casing-support-rotor coupling model subjected to the rotor unbalanced forces is established by the finite element method. Formulations of the structural intensity of a shell element and the structural intensity streamline are given. A simulation system consisting of the finite element tool and the in-house program is developed to carry out forced vibration analysis and structural intensity calculation. The structural intensity field of the casing is visualized in the forms of vector diagram and streamline representation. The vibrational energy flow behaviors of the casing at the rotor design rotating speed are analyzed, and the vibrational energy flow transmission characteristics of the casing with different axial positions of the main-mount and the sub-mount are investigated. Moreover, some measures to attenuate the vibration of the casing are obtained from the numerical results, and their effectiveness is verified in the frequency domain and the time domain. The results shed new light on the effects of the mount positions on the vibration energy transmission behaviors of the casing structure. The structural intensity method is a more advanced tool for solving vibration problems in engineering. Furthermore, it may provide some guidance for the vibration attenuation of the casing and the whole aero-engine.

Mojtaba Navvab, Fabio Bisegna, Franco Gugliermetti

These paper present accurate reconstructions and virtual representations of buildings of cultural heritage, which have been developed techniques of visualization and auralization in virtual environment. Computer graphics allows to reconstruct and experience the visual and acoustic conditions of the past with a high degree of realism and to deepen the knowledge of cultural heritage.

M. Ainslie

Narendiranath Babu THAMBA, Himamshu H S, Prabin Kumar NAYAK et al.

Journal bearings are widely used to support the shafts in industrial machinery involving heavy loads, such as compressors, turbines and centrifugal pumps. The major problem that could arise in journal bearings is catastrophic failure due to corrosion or erosion and fatigue, which results in economic loss and creates major safety risks. Thus, it is necessary to provide suitable condition monitoring technique to detect and diagnose failures, and achieve cost savings to the industry. Therefore, this paper focuses on fault diagnosis on journal bearing using Debauchies Wavelet-02 (DB-02). Nowadays, wavelet transformation is one of the most popular technique of the time-frequency-transformations. An experimental setup was used to diagnose the faults in the journal bearing. The accelerometer is used to collect vibration data, from the journal bearing in the form of time domain. This was then used as input for a MATLAB code that could plot the time domain signal. This signal was then decomposed based on the wavelet transform. The fast Fourier transform is then used to obtain the frequency domain, which gives us the frequency having the highest amplitude. To diagnose the faults various operating conditions are used in the journal bearing such as Full oil, half loose, half oil, fault 1, fault 2, fault 3 and full loose. Then the Artificial Neural Networks (ANN) is used to classify faults. The network is trained based on data already collected and then it is tested based on random data points. ANN was able to classify the faults with the classification rate of 85.7%. Thus, the test process for unseen vibration data of the trained ANN combined with ideal output target values indicates high success rate for utomated bearing fault detection.

Krzysztof JASEK, Mateusz PASTERNAK, Michał GRABKA et al.

One of the most important problems with regard to the Surface Acoustic Wave (SAW) gas sensors technology is the deposition of chemosensitive films exhibiting desirable chemical and physical properties. The electrospraying technology seems to be a very promising method of the film deposition in this case. It allows the chemosensitive layers to be obtained out of almost any chemicals and their mixtures in a controllable way. The process gives the possibility to generate specific films with properties unattainable if other methods were to be applied. For example, it allows to deposit solutions of polymers and suspensions of solids in polymer solutions which can degrade in the process of thermal evaporation deposition. The paper describes the results of experiments with electrospraying technique in order to obtain Nafion® films. The influence of the process parameters on film sensitivity has been studied.

Jiří ADLER, Ivo HRAZDIRA, Jitka HANZLOVÁ et al.

In the present paper bovine kidney cell cultures were used as an experimental model for the study of the biophysical mechanism of ultrasonic action. In the first series of experiments functional and morphological changes in the cells immediately after sonication were evaluated. A decrease in viability and degenerative morphological changes in the cells were found. In the second series the sonicated cells were seeded in Roux bottles and grown in the optimal conditions. The growth properties of the cells were evaluated at different time intervals after sonication. Significant stimulation of the cell growth was demonstrated after the action of ultrasound intensity of 1.0 kWm^{-2}. However, after the action of ultrasound intensities above 3.0 kWm^{-2} the inhibition of the cell growth was found.

Carlo ALVISI, Marco GIULIONI, Marziano CERISOLI et al.

The Authors present different experimental models performed in the attempt to determine whether the alterations of brain circulation following an increase in the intracranial impedance can be estimated by systolic and diastolic common carotid artery (CCA) velocity Doppler signals recorded at 15-minute intervals until 60 minutes and 10 hours. In model 1 both jugular veins (JV) were ligated and Doppler signals were recorded at 15-minute intervals until 60 minutes. In model 2 ipsilateral external carotid artery (ECA) ligation was added to JV occlusion. In model 3 recording of Doppler signals was performed at 15-minute intervals until 60 minutes and 10 hours in the presence of ipsilateral ECA and bilateral JV occlusion. In model 4 Doppler signals were recorded in the presence of ipsilateral ECA occlusion alone. Statistically significant results confirming the well-known theoretical relationship between increased encephalic impedance and flow velocity Doppler signals were obtained in model 3. The results demonstrated that a sudden increase in the encephalic impedance can affect both systolic and diastolic flow velocities in afferent vessels. Later (from 60 minutes to 10 hours), systolic values tend to increase and at 10 hours are always higher than starting values. The diastolic values, however, remain inferior to the starting values, although showing a slight tendency to rise. The Authors conclude that significative alterations of cerebrovascular impedance can be obtained by clamping both JV. However, these alterations can be recorded on the CCA only if the ipsilateral ECA is occluded, thus eliminating the risk of run-off across it, or if recordings are taken from the internal carotid artery.

A. RAKOWSKI

Three musicians not possessing absolute pitch repeated vocally five standard tones played on the guitar. The repetition was completed over various periods of delay ranging from 10 seconds to 6 minutes. Periods of delay were: a) silent, b) filled with cognitive activity (counting backward in threes) or c) filled with interfering tonal stimuli (an endless, ascending chromatic scale). The frequencies of tones sung by the subjects were measured and compared to those of standard tones. Standard deviations of the sets of frequency differences were taken as measures of the inaccuracy of pitch memory trace. The obtained "forgetting curves" show that at concentrated attention subjects could retain the memory for pitch of a standard with accuracy better than a quartertone for three minutes. With cognitive interference the same was possible for two minutes, and with tonal interference for thirty seconds. Conclusions may be drawn concerning the hypothetical time constant for short-term auditory memory.