Acoustic Level Research Articles

Graphene-based stand-alone nanomechanical membrane production and mass-acoustic hybrid-sensor application

In this article, experimental studies were carried out for the preparation, characterization, and nanomechanical membrane application of Graphene-based nanomechanical mass and acoustic hybrid sensors. The purpose of this study was to prepare facile and low-cost nanomechanical membrane-based mass-acoustic hybrid sensors by set-ups developed on the exfoliation and membrane transfer methods, and to examine their morphological, spectroscopical, and nanomechanical-vibrational properties, as well as the membrane characteristics like mass and acoustic sensitivities and durability over time. For the experiments, equipment and items such as optical, digital, atomic force and scanning electron microscopes, Raman spectroscope, acoustic signal source and amplifier, data-logger, sound pressure level meter, and laser Doppler vibrometer were used. Graphene-based nanomechanical membrane sensor chips with varying acoustic pressure levels and mass-loadings were tested. It was observed that the acoustic sensitivity of the produced 706.5 µm2 nanomechanical membranes increased with increasing sound pressure levels and decreased with increasing mass-loads. With 67.8 ± 5 nm/Pa, the unloaded nanomechanical membrane was the most sensitive sample. Experimental challenges and sensor development solutions were discussed. Existing application examples were examined and discussions were made on the current challenges and the future prospects of the nanomechanical membrane sensors.

Two-photon 3D printing diaphragm-integrated ring waveguide coupler for ultrasound detection.

We demonstrate a diaphragm-integrated ring waveguide coupler fabricated by the two-photon direct laser wring technique as an ultrasonic sensor, which is integrated on an optical fiber tip. The device consists of a micro-ring waveguide with a diameter of 5 µm functionalized as an optical fiber tip light reflection mirror and a straight waveguide connecting a diaphragm. The evanescent field coupling can be realized between the two waveguides, and the coupling efficiency can be changed due to the variation of the coupling gap induced by ultrasound. Accordingly, the light reflection can be changed. Based on the plate vibration theory, the vibration frequency can be changed through optimizing the diaphragm size. The experiments show that the device exhibits a high sensitivity and low noise equivalent acoustic signal level of 1.07 mPa/Hz1/2 at 100 kHz, which has great potential in various acoustic wave sensing applications.

Numerical Study of Comparison of Thrust Bearing Slip - No Slip Condition on Acoustic Performance

The acoustic power level (APL) produced by a thrust bearing during operation has a major effect on its performance. Therefore, this research aimed to investigate the impact of slip engineered on the noise generated by thrust bearings. A numerical approach was used to simulate open pocket bearings with varying film thickness depths. At the initial location of the slip area, three bearing models were analyzed: pocket slip, pocket no slip, and smooth slip. The results show that implementing slip can reduce noise levels, turbulence kinetic energy (TKE), and turbulence eddy dissipation (TED) rate. The average APL, TKE, and TED values were the lowest at the high film thickness

Impact of acoustic intensity on melting behavior of ice cream

Ice cream mixes (407 ± 12 total solids g/kg and 115 ± 14 fat g/kg) were subjected to power ultrasound at different acoustic intensity (11-18 W/cm2), and the resulting ice creams were evaluated for melting (oscillatory rheology from −20 to 10 °C) and meltdown (gravimetrical test) behavior. All samples showed a sigmoidal melting curve characterized by two plateaus and a linear segment between the plateaus. A dominant solid behavior (G′ >G″) was observed in ice creams made with sonicated mixes (11 and 18 W/cm2). Acoustic levels of 14.4 ± 0.5 and 18.4 ± 0.8 W/cm2 delayed the onset of meltdown by about 3.0-fold and increased the maximum meltdown compared with the control ice creams. Sonicated samples resulted in approximately 2.0-fold viscosity increment within the high spectrum of shear rate compared with the control samples. Dynamic rheology showed a gel-like and strain-thinning behavior of sonicated mixes. The control ice cream displayed moderate hardness (91 ± 9 N) and an onset of meltdown of 642 ± 45 s, whereas the sonicated samples exhibited hardness of 156–218 N and onset of meltdown values of 1900–2200 s. The outcomes of this study demonstrate the ability of power ultrasound to delay the onset of meltdown, providing processing strategies for structuring frozen desserts with delayed meltdown.

Study on the influence pattern and efficiency enhanced mechanism of acoustic–chemical spray dust reduction

To study the influence pattern and efficiency enhanced mechanism of acoustic–chemical spray method on dust reduction, a self-developed acoustic excitation test platform, viscosity test, surface tension experiment and sinking experiments were used to investigate the chemical spray properties and the wetting behavior of coal dust excited by acoustic waves. The self-developed acoustic–chemical spray dust reduction simulation platform was used to study the influence of acoustic waves on coal dust reduction effect and its efficiency enhanced mechanism. The results showed that the surface tension and viscosity of the chemical spray solution fluctuated between 0.4 mN/m and 0.4 mPa·s along with the variations in acoustic wave frequency and sound pressure level (SPL), thereby confirming that acoustic waves had on effected on chemical spray solution properties. However, the wetting time of the chemical spray solution on coal dust increased by 33.64 % at an acoustic frequency (f) of 1300 Hz and SPL of 120 dB because of the liquid interface vibrations caused by acoustic waves. With an increasing of acoustic frequency, the dust reduction efficiency demonstrated a parabolic trend and reached its maximum value at f = 1300 Hz. The dust reduction efficiency also increased exponentially along with increasing SPL. Acoustic waves not only increased the collision frequency between particles and droplets by changing the trajectory of dust but also accelerated the wetting and agglomeration effect of chemical spray reagents on coal dust by causing vibrations at the gas–liquid interface, thereby enhancing the dust reduction efficiency. Compared to the dust reduction efficiency of chemical spray technology, the total dust reduction efficiency was increased by 8.53 %, and the respirable dust reduction efficiency was increased by 21.93 %. The effect of acoustic waves on the respirable dust reduction efficiency was more significant than that on total dust.

Interlingual Subtitling of Ethno/Cultural Representation in Selected Episodes of Yahya and Kunooz Animated TV Series (2022)

The present study examines Audiovisual Translation (AVT) strategies in selected episodes of Yahya and Kunooz animated TV Series (2022). AVT is quite a unique sub-discipline of Translation Studies (TS) due to its polysemiotic nature in which it functions on verbal, acoustic and visual levels. Within this rationale, the study conducts an interrogation of the verbal auditory or acoustic channel, the non-verbal auditory channel, the verbal visual channel, e.g. written signs on the screen and the non-verbal visual channel. As such, the aim of the study is to scrutinize the constraints and challenges that the AVT translators face during the subtitling process within the paradigm of translation strategies. The present study is carried out within the boundaries of the target-oriented approach developed by Gideon Toury and the foreignization/domestication approaches developed by Lawrence Venuti to interrogate culture-bound characteristics. Foreignization as a translation strategy seems principally appropriate for a historical and cultural text to recreate the source text in target language in such a way that the reader or the audience would feel the cultural effect of the source text. The contribution of the research is hopefully twofold. One, it is the first-ever study of Yahay and Kunooz Series in the academia; the other, this study incites further studies in the future to develop a comprehensive and sound-based theoretical frame for AVT.

Experimental evidences of nonlinear programmable electroacoustic loudspeaker

A two degrees-of-freedom system coupling an acoustical mode of a closed tube to an electroacoustic loudspeaker is considered. A model-inversion technique is presented to digitally program the impedance of the loudspeaker for reaching a targeted nonlinear behavior. Experimental results show that the programed nonlinearity can guide the system to both periodic and non-periodic responses while acoustical levels for activation of the nonlinearity are less than the ones for systems with passive nonlinear oscillators (94 and 100 dB in this paper compared to 138 dB in previous papers), allowing building applications. Moreover, it is spotted that the programed nonlinearity of the electroacoustic loudspeaker, even in its non-optimized form, performs nonlinear noise control for some frequency ranges. The main objective of this article is to show that it is possible to program the behavior of an electroacoustic loudspeaker.

Modelling underwater noise mitigation of a bubble curtain using a coupled-oscillator model

Bubbles can inhibit underwater sound transmission, owing to density and acoustic-impedance mismatches and associated reflection and absorption of sound waves, and also scattering due to bubble-acoustic resonances. Thus, bubble curtains have been used to reduce underwater noise propagation. For the present study, a discrete bubble model (DBM) utilising self-consistent coupled-oscillator theory was developed to model noise mitigation by bubble curtains. The DBM is inherently able to handle polydisperse-sized and anisotropically-distributed bubbles. The DBM was shown to accurately predict the bubble collective resonance frequencies of 1D line, 2D planar and 3D complex bubble cloud configurations. Subsequently, the model demonstrated that the collective resonance frequency decreases as the inter-bubble spacing was reduced in 2D planar bubble screens and 3D cylindrical bubble curtains. Modal analysis indicated that the fundamental mode in both configurations dominated the vibration of bubble clouds when subjected to an external acoustic source. The broadband acoustic pulse levels were able to be reduced by approximately 17 dB using realistic cylindrical bubble curtain configurations with a diameter of 5 m and two different gas volume fraction values of 1% and 2%. Variations in the sizes of bubbles within a curtain were shown to have a significant impact on curtain performance, whereas variations in inter-bubble spacing had no significant impact, implying that bubble-curtain operators should focus on controlling the size of the bubbles.

Humans recognize affective cues in primate vocalizations: acoustic and phylogenetic perspectives

Humans are adept at extracting affective information from vocalizations of humans and other animals. However, the extent to which human recognition of vocal affective cues of other species is due to cross-taxa similarities in acoustic parameters or the phylogenetic closeness between species is currently unclear. To address this, we first analyzed acoustic variation in 96 affective vocalizations, taken from agonistic and affiliative contexts, of humans and three other primates—rhesus macaques (Macaca mulatta), chimpanzees and bonobos (Pan troglodytes and Pan paniscus). Acoustic analyses revealed that agonistic chimpanzee and bonobo vocalizations were similarly distant from agonistic human voices, but chimpanzee affiliative vocalizations were significantly closer to human affiliative vocalizations, than those of bonobos, indicating a potential derived vocal evolution in the bonobo lineage. Second, we asked 68 human participants to categorize and also discriminate vocalizations based on their presumed affective content. Results showed that participants reliably categorized human and chimpanzee vocalizations according to affective content, but not bonobo threat vocalizations nor any macaque vocalizations. Participants discriminated all species calls above chance level except for threat calls by bonobos and macaques. Our results highlight the importance of both phylogenetic and acoustic parameter level explanations in cross-species affective perception, drawing a more complex picture to the origin of vocal emotions.

Acoustic Noise Levels in High-field Magnetic Resonance Imaging Scanners.

7-Tesla (T) magnetic resonance imaging may allow for higher resolution images but may produce greater acoustic noise than 1.5- and 3-T scanners. We sought to characterize the intensity of acoustic noise from 7- versus 3-T scanners. A-weighted sound pressure levels from 5 types of pulse sequences used for brain and inner ear imaging in 3- and 7-T scanners were measured. Time-averaged sound level and maximum sound levels generated for each sequence were compared. Time-averaged sound levels exceeded 95 dB and reached maximums above 105 dB on the majority of 3- and 7-T scans. The mean time-averaged sound level and maximum sound level across pulse sequences were greater in 7- than 3-T (105.6 vs 91.4, P = .01; 114.0 vs. 96.5 dB, P < .01). 7- and 3-T magnetic resonance imaging scanners produce high levels of acoustic noise that exceed acceptable safety limits, emphasizing the need for active and passive noise protection.

Causes and evolution of asymmetric polygonal wear of metro train wheelsets

Wheel acoustic roughness of one metro line in China shows that the wheel polygonal wear (WPW) on both sides of the wheelset is asymmetrical. The dominant harmonics of the left and right wheels are 12–13, but with large differences in acoustic roughness levels. To analyse the causes of the asymmetrical WPW (AWPW), an investigation of the acoustic roughness of the wheels and rails and a modal analysis of the wheelset–track system are carried out. In addition, a long-term wear model considering the flexibility of the wheelset and track is established to provide insight into the initiation and evolution of the AWPW. The results of the experiments and simulations show that the natural asymmetric vibration mode in the wheelset–track system with a frequency of 83 Hz is the main cause of WPW, which can be excited on sharp curves. The difference between the lengths of the left and right curved tracks with small radius is the cause of AWPW. The residual WPW after reprofiling and rail corrugation with a wavelength of about 200 mm are the main sources of excitation for the asymmetric natural vibration.

Investigation on aerodynamic noise for leading edge erosion of wind turbine blade

Wind turbine blade is extremely prone to leading edge erosion under complicated operation conditions. This decreases the aerodynamic performance and power generation efficiency of wind turbine. Currently acoustic-based erosion detection of the blade still faces a significant challenge. Consequently, this paper presents aerodynamic noise mechanism of the eroded blade using the computational fluid dynamics method. The Zonal Detached Delay Eddy Simulation turbulence model is applied to obtain the three-dimensional instantaneous turbulent flow field. Then the far-field aerodynamic noise is carried out using the Ffowcs Williams and Hawkings approach. Simulations are performed for the erosion condition that determined by the length and depth at leading edge of 5-MW National Renewable Laboratory wind turbine. Results indicate that erosion leads to unsteady pressure pulsation near the leading edge, decrease of surface pressure difference in tip area, increase of airflow separation region and forward movement of separation point. Furthermore, the eroded blade achieves higher acoustic level than that of the normal one. From the noise directivity of wind turbine blade, erosion causes obvious asymmetry of noise pattern in the upwind and downwind directions.

Acoustic noise reduction for spiral MRI by gradient derating.

To show that the acoustic noise of spiral MRI can be reduced by derating the gradients with minimal penalty to image quality and scan time, and to illustrate an algorithm for optimal choice of derating parameters. Acoustic noise level was measured and compared for various values of maximum gradient amplitude and slew rate for T1 -weighted spin-echo spiral scans while maintaining image contrast, FOV and resolution, and readout time. A full gradient trajectory and a derated gradient (undersampled) trajectory were chosen for a volunteer scan followed by parallel imaging-aided reconstruction to illustrate comparable image SNR. Two auto-derating methods, which prioritize slew rate and gradient amplitude, respectively, were derived using analytical results from the WHIRLED PEAS variant of spiral waveforms and compared in their acoustic noise level under test use cases. Derating the gradients made the scan quieter by 16.6 dB(A) on average than a full gradient trajectory and required an undersampling factor R = 2 in order to maintain scan time, with no appreciable penalty in image SNR. Prioritizing reduced slew rate resulted in maximal loudness reduction. Scanner gradients can often be derated to reduce the acoustic noise for spiral MRI with minimal penalty in scan time and image quality with the help of parallel imaging. An automatic slew-priority derating method that maximizes loudness reduction is given.

Communicating Emotion: Vocal Expression of Linguistic and Emotional Prosody in Children With Mild to Profound Hearing Loss Compared With That of Normal Hearing Peers.

Emotional prosody is known to play an important role in social communication. Research has shown that children with cochlear implants (CCIs) may face challenges in their ability to express prosody, as their expressions may have less distinct acoustic contrasts and therefore may be judged less accurately. The prosody of children with milder degrees of hearing loss, wearing hearing aids, has sparsely been investigated. More understanding of the prosodic expression by children with hearing loss, hearing aid users in particular, could create more awareness among healthcare professionals and parents on limitations in social communication, which awareness may lead to more targeted rehabilitation. This study aimed to compare the prosodic expression potential of children wearing hearing aids (CHA) with that of CCIs and children with normal hearing (CNH). In this prospective experimental study, utterances of pediatric hearing aid users, cochlear implant users, and CNH containing emotional expressions (happy, sad, and angry) were recorded during a reading task. Of the utterances, three acoustic properties were calculated: fundamental frequency (F0), variance in fundamental frequency (SD of F0), and intensity. Acoustic properties of the utterances were compared within subjects and between groups. A total of 75 children were included (CHA: 26, CCI: 23, and CNH: 26). Participants were between 7 and 13 years of age. The 15 CCI with congenital hearing loss had received the cochlear implant at median age of 8 months. The acoustic patterns of emotions uttered by CHA were similar to those of CCI and CNH. Only in CCI, we found no difference in F0 variation between happiness and anger, although an intensity difference was present. In addition, CCI and CHA produced poorer happy-sad contrasts than did CNH. The findings of this study suggest that on a fundamental, acoustic level, both CHA and CCI have a prosodic expression potential that is almost on par with normal hearing peers. However, there were some minor limitations observed in the prosodic expression of these children, it is important to determine whether these differences are perceptible to listeners and could affect social communication. This study sets the groundwork for more research that will help us fully understand the implications of these findings and how they may affect the communication abilities of these children. With a clearer understanding of these factors, we can develop effective ways to help improve their communication skills.

Case study on the audibility of siren-driven alert systems

Abstract The civil security sirens are used by the authorities in a wide range of countries to signal an imminent or ongoing threat. Even if their sound level is known, it is nevertheless difficult to evaluate their audibility across a given zone, especially in complex urban environments. An experimental protocol was deployed around a siren installed in a town in France, to assess its audibility perceptually and through modeling. Sound level measurements during source activation were made with the NoiseCapture smartphone application at different distances and on several axes by a group of 25 participants. They were also asked to fill in a questionnaire on perceptual information about the siren such as its audibility, the perceived sound level, or the masking of the siren by passing vehicles. A comparison between acoustic measurement levels using NoiseCapture and simulated sound levels using NoiseModelling was performed. The results of this study validate the use of the Common Noise Assessment Methods in Europe model to evaluate the audibility of a warning system located in an urban environment within a radius of 2.8 km around the siren. Finally, a metric linking audibility to modeled sound level is proposed, enabling the development of siren audibility maps in the study area.

Sonochemical formation of peroxynitrite in water: Impact of ultrasonic frequency and power

There is a lack of literature on peroxynitrite formation due to sonolysis of aerated water. In this work, the impact of sonication parameters, frequency and power, on ultrasonic peroxynitrite production in aerated alkaline water was investigated. Peroxynitrite formation was clearly established with undeniable evidence at all the tested frequencies in the range of 516–1140 kHz with a typical G-value (energy-specific yield) of 0.777 × 10−10, 0.627 × 10−10, 0.425 × 10−10 and 0.194 × 10−10 mol/J at 516, 558, 860 and 1140 kHz, respectively. The ultrasonication frequency has a direct impact on the sonochemical peroxynitrite production. Increasing the ultrasonication frequency in the interval 321–1140 kHz reduces peroxynitrite formation. The most practical sonochemistry dosimetries, including hydrogen peroxide production, triiodide dosimetry, Fricke dosimetry, and 4-nitrocatechol formation, were compared with the sonochemical efficiency of the reactors used to produce peroxynitrite. The G-value, energy specific yield, for the tested dosimetries was higher than that for peroxynitrite formation, regardless of frequency. For all chemical dosimetries investigated, the same trend of frequency dependence was found as for peroxynitrite generation. The influence of ultrasonication power on peroxynitrite formation by sonication at diverse frequencies in the interval 585–1140 kHz was studied. No peroxynitrite was formed at lower acoustic power levels, regardless of frequency. As the frequency increases, more power is required for peroxynitrite formation. The production of peroxynitrite increased as the acoustic power increased, despite the frequency of ultrasonic waves. Ultrasonic power is a key factor in the production of peroxynitrite by sonolysis. Since peroxynitrite is uniformly distributed in the bulk solution, peroxynitrite-sensitive solutes can be transformed both in the bulk of the solution and in the surfacial region (shell) of the cavitation bubble. The formation of peroxynitrite should be taken into account in sonochemistry, especially at higher pH values. Ultrasonic peroxynitrite formation in alkaline solution (pH 12) can be considered as a kind of chemical dosimetry in sonochemistry.

Sensitivity-enhanced Fabry-Perot interferometric fiber-optic microphone using hollow cantilever.

Transducer components are crucial in optimizing the sensitivity of microphones. Cantilever structure is commonly used as a structural optimization technique. Here, we present a novel Fabry-Perot (F-P) interferometric fiber-optic microphone (FOM) using a hollow cantilever structure. The proposed hollow cantilever aims to reduce the effective mass and spring constant of the cantilever, thereby enhancing the sensitivity of the FOM. Experimental results demonstrate that the proposed structure outperforms the original cantilever design in terms of sensitivity. The sensitivity and minimum detectable acoustic pressure level (MDP) can reach 91.40 mV/Pa and 6.20 µPa/Hz at 1.7 kHz, respectively. Notably, the hollow cantilever provides an optimization framework for highly sensitive FOMs.

Compensatory articulatory mechanisms preserve intelligibility in prodromal Parkinson's disease

IntroductionDysarthria is highly prevalent in patients with Parkinson's disease (PD) and speech changes have already been detected in patients with prodromal PD on the acoustic level. However, the present study directly tracks underlying articulatory movements with electromagnetic articulography to investigate early speech alterations on the kinematic level in isolated REM sleep behavior disorder (iRBD) and compares them to PD and control speakers. MethodsKinematic data of 23 control speakers, 22 speakers with iRBD, and 23 speakers with PD were collected. Amplitude, duration, and average speed of lower lip, tongue tip, and tongue body movements were analyzed. Naive listeners rated the intelligibility of all speakers. ResultsPatients with iRBD produced tongue tip and tongue body movements that were larger in amplitude and longer in duration compared to control speakers, while remaining intelligible. Compared to patients with iRBD, patients with PD had smaller, longer and slower tongue tip and lower lip movements, accompanied by lower intelligibility. Thus, the data indicate that the lingual system is already affected in prodromal PD. Furthermore, lower lip and especially tongue tip movements slow down and speech intelligibility decreases if motor impairment is more pronounced. ConclusionPatients with iRBD adjust articulatory patterns to counteract incipient motor detriment on speech to maintain their intelligibility level.

On the noise generation and unsteady performance of combined heaving and pitching foils

A transient two-dimensional acoustic boundary element solver is coupled to a potential flow boundary element solver via Powell’s acoustic analogy to determine the acoustic emission of isolated hydrofoils performing biologically-inspired motions. The flow-acoustic boundary element framework is validated against experimental and asymptotic solutions for the noise produced by canonical vortex-body interactions. The numerical framework then characterizes the noise production of an oscillating foil, which is a simple representation of a fish caudal fin. A rigid NACA 0012 hydrofoil is subjected to combined heaving and pitching motions for Strouhal numbers () based on peak-to-peak amplitudes and chord-based reduced frequencies () that span the parameter space of many swimming fish species. A dipolar acoustic directivity is found for all motions, frequencies, and amplitudes considered, and the peak noise level increases with both the reduced frequency and the Strouhal number. A combined heaving and pitching motion produces less noise than either a purely pitching or purely heaving foil at a fixed reduced frequency and amplitude of motion. Correlations of the lift and power coefficients with the peak root-mean-square acoustic pressure levels are determined, which could be utilized to develop long-range, quiet swimmers.

Quiet Spacecraft Cabin Ventilation Fan: Wake Measurements Results

A spacecraft cabin ventilation fan suitable for aerodynamic and acoustic ground tests was designed and two copies of the fan assembly were fabricated - designated as Quiet Space Fan. Both fans were tested for aerodynamic performance and acoustic levels in the NASA Glenn Research Center Acoustical Testing Laboratory. A new test rig for small axial flow fans was designed to accommodate the instrumentation and back-pressure adjustments. Measurements acquired were - static pressures for measuring performance, a 72-channel in-duct microphone array, external microphone measurements for acoustics, and inter-stage hot wire measurements of the fan wake. This report documents the wake velocity and turbulence measurements as part of a series of reports.