Acoustic Effects Research Articles

An investigation on metallurgical features and joint characteristics of ultrasonic spot welded Al-Ni sheets

Several potential benefits in joining thin, dissimilar and highly conductive metals in a solid-state environment make ultrasonic welding (USW) a popular method for building Li-ion battery packs. The USW method is highly complex and relies on multiple factors. In this study, aluminum (AA1100) and nickel (UNS N02200) dissimilar sheets were ultrasonically welded using various process parameters. Plastic deformation, microstructural development, and the corresponding mechanical characteristics of the joints were evaluated qualitatively and quantitatively. The joint strength and critical intensity factor values seemed to rise until the welding duration of 0.3 s, following which there was a subsequent drop in their values. Based on the mechanical analysis, it is observed that the optimal condition records an amplitude of 68 µm, a weld time of 0.3 s, and a clamping pressure of 0.24 MPa. It showed that the joint performance was significantly impacted by the plastic deformation and microstructural changes at the weld region. On the Al side, substantial plastic deformation was observed, and it was primarily attributed to the sonotrode knurls’ penetration. The Al sheet’s thickness was reduced by more than 40%. The microhardness readings at the welding region experienced diminution due to the acoustic softening effect. The cross-section and fracture surfaces of the Al/Ni weld exhibited several distinct microstructural characteristics, such as atomic diffusion, crimped interface, dimple pattern, and swirl pattern flow. Additionally, the diffusion zone is also investigated using X-ray diffraction analysis. These observations offer valuable insights for enhancing weld quality and controlling the overall welding process.

Acoustic effect of wire mesh liners subjected to grazing flow

The wire mesh liner usually possesses a better acoustic linearity to flow than perforated liners, but it still lacks an impedance model. So, the grazing flow effect of the mesh liner is studied experimentally herein. It reveals that, relative to perforated liners, the mesh liner has qualitatively similar but quantitatively weakened trends in the grazing flow resistance Rg and reactance Xg. As a mesh occurs or as the mesh becomes finer on the flow-saturated perforated surface, Rg is suppressed gradually especially at high frequencies, by lowering its sinking segment, delaying its increasing segment, and decreasing its increasing slope. Furthermore, the effect of a fine mesh can be superimposed with that of a larger orifice diameter dp on lowering the sinking and delaying the increasing, but the former can weaken the effect of the latter on increasing the slope. On another aspect, Xg can also be suppressed evidently by a fine mesh. By contrast, a tested liner with a fine mesh embedded in the middle of perforated plates rather than on the surface exhibits no such a suppressing effect on Rg. Accordingly, a more complete impedance model of the mesh-on-perforated-surface liner considering the grazing flow, mesh type and frequency is established.

Study of the Roman theatre of Volterra: Acoustic effects based on the presence of different architectural construction elements

Roman theatres have always been the subject of research studies, from an architectural perspective and archaeology. The border lines between these and other disciplines is always difficult to be established since the interrelation of various expertise is required to achieve a complete knowledge of ancient buildings, especially when documentations and archaeological sources are limited. The present work deals with the acoustic analysis of the Roman theatre of Volterra, located in northern Italy, which has already been the subject of archaeological and architectural studies since its discovery in 1950. Acoustic measurements have been carried out in line with the standard requirements outlined in ISO 3382. After model calibration, the acoustic simulations have been carried out using four specific scenarios, highlighting the contribution that different construction elements can have on the acoustic response of this open-air theatre in comparison with the existing conditions. The results were evaluated assuming that light music (classical quartets, unamplified) and prose are the main functions of the space, as this case was in the past. The simulated results show that the values for the main acoustic parameters are better than the measured values, to be closer to the optimal ranges of the criteria borrowed from studies on enclosed spaces, since there are no criteria for Roman theatres. The good acoustic response of the Roman theatre of Volterra raises new doubts about the function of the vessels that were located under the steps of the cavea, as mentioned by Vitruvius.

Strongly enhanced nonlinear acoustic valley Hall effect in tilted Dirac materials

Strongly enhanced nonlinear acoustic valley Hall effect in tilted Dirac materials

Acoustic characteristics of voice production in virtual reality-simulated and physical environments: a comparative study in university professors

This study investigated the reliability of a virtual reality-simulated classroom to generate a comparable self-perception of voice quality and acoustic effects of phonation to a real classroom in a group of teachers, and sense of presence. Thirty university professors participated in the study and were required to produce loud connected speech by reading a 100-word text in two conditions: (1) in a real classroom including a group of students, and (2) in a virtual replica of the classroom consisting of a 360-degree video of the same classroom and students, which was displayed using a head mounted display. Ambient noise was controlled in both conditions by playing classroom noise through headphones. The self-perception of voice quality, the long-term average spectrum and smooth cepstral peak prominence were estimated in both conditions. The sense of presence generated by virtual reality was measured after interacting with the virtual classroom. There were no statistically significant differences in the self-perception of voice quality or in the acoustic measures of voice production between conditions. The sense of presence in the virtual classroom was high. Our findings suggest that a virtual reality-simulated classroom generate comparable self-perception of voice quality and acoustic effects of phonation to the real classroom, and a high sense of presence, in a group of teachers. Additionally, it is important to highlight the potential of virtual reality to enhance the ecological validity of acoustic assessment of voice production in laboratories and clinical settings.

Acoustic Effects of Speaker Sex, Speech Sample, and Mandarin Tone on Vowel Production of Poststroke Spastic Dysarthria

Plain Language SummaryMandarin speakers with poststroke spastic dysarthria often have vowel production deficits that affect articulation and speech intelligibility. Vowel production is influenced by many factors. This study explored the acoustic effects of speaker sex, tones, and speech samples and their interactions on vowel production in Mandarin speakers with poststroke spastic dysarthria and confirmed the existence of these effects. We found that regardless of the speech samples or tones, there were the reduced range of articulatory movements, centralized vowel production, and prolonged vowel duration in dysarthria compared to healthy people. The most sensitive and useful analysis measures were the vowel articulation index and vowel duration. Specific influencing factors (speaker sex, speech sample, and tone) of vowel production need to be taken seriously by speech and language pathologists and considered in the assessment and rehabilitation.

Strategic Integration of a Vegetative Component on a Metal Roof Base: An Evaluation of Its Impacts on Thermal and Acoustic Performance in the Tropics

This paper attempts to ascertain the thermal and acoustic impacts of introducing a vegetative roof layer on insulated and uninsulated metal roofs for tropical climates, through field measurements in Skudai, Johor, Malaysia, that were conducted for both dry and wet days. Four small-scale roof modules were tested, namely an uninsulated metal roof (uiMDR), an insulated metal roof (iMDR), and two identical corresponding modules with an additional vegetative component (uiGR and iGR, respectively). Outdoor ambient temperature (Tamb) was the most influential correlated variable affecting the roof outer surface temperature (RTOS) in 50% of the assessed scenarios. On the selected dry day, the inter-quartile ranges (IQR) of iGR, iMDR, uiGR, and uiMDR were 6.21 °C, 8.32 °C, 6.69 °C, and 1.66 °C, respectively; the IQRs were 1.6 °C, 4.11 °C, 2.59 °C, and 1.78 °C, respectively, on the selected wet day. Based on design U-value calculations, iGR was better than iMDR and uiMDR for both dry and wet days. The U-value of uiGR was also better than iMDR under dry-day conditions. The Wilcoxon signed-rank test also indicated a statistically significant difference in the roof inner surface temperature (RTIS) measurements (p-value = 0.00) during Malaysian daylight hours, between 8.00 a.m. and 6.00 p.m., regardless of the weather. In terms of sound level reduction under dry-day conditions, the Kruskal–Wallis and Wilcoxon signed-rank tests showed statistically significant differences in sound level reductions, with iGR and uiGR performing better than iMDR and uiMDR (p-values = 0.00). The sound level reductions for iGR, iMDR, and uiGR were 51%, 32%, and 31%, respectively, while uiMDR experienced sound level amplifications by 6%, possibly due to the acoustic resonance effect. This proof of concept may encourage a broader application of extensive GRs in Malaysia using metal roofs, beyond the conventional RC base construction method.

Numerical investigation of the thermal and acoustic effect of material variations on the exhaust muffler

Exhaust mufflers are used in automobiles to prevent the noise arising from exhaust gases resulting from internal combustion engines. With the advancement of the automotive industry, exhaust mufflers have become more complex over time to reduce noise and increase driving comfort. Within the scope of this study, exhaust muffler geometries with different geometries have been designed, and harmonic acoustic analyses have been carried out. In the analysis, the airflow speed has been accepted as 30 m/s. Acoustic pressure and transmission loss data obtained because of analyses performed with 1Pa pressure input have been evaluated. As a result of the evaluations, it has been concluded that the muffler modeled in a complex structure has been better acoustically. Although the main task of exhaust muffler is to reduce the sound level at the exit of exhaust gases, it is also important to reduce the temperature of the air in the exhaust system and have good thermal conductivity so as not to jeopardize the thermal safety of the system. For this reason, CFD thermal flow analysis has been carried out with 4 different materials using a complex design with high acoustic efficiency. Gray cast iron, stainless steel, 1020 steel, and aluminum have been used as materials. In this part of the study, it has been determined that the use of aluminum material has been better in terms of thermal efficiency.

Rainbow Capture Based on Underwater Gradient Phononic Crystals

Waves of different frequencies are located and captured at different positions, giving rainbow capture a wide range of potential applications in filtering, buffering, energy collection, and other fields. In this paper, we design a rainbow capture structure based on gradient phonon crystals. The edge states change due to the different structural parameters. By designing a gradient structure, the sound waves of different frequencies are separated and trapped at different boundary positions to form the acoustic rainbow effect. Incident waves from different directions produce significantly distinct rainbow trapping effect. The distance sound propagates when excited from the left is increasingly further, while the distance when excited from the right is increasingly shorter. Besides, the symmetrical rainbow effect has also been demonstrated in symmetrical gradient phonon crystals. This work provides a theoretical reference for achieving diverse multiwavelength devices in acoustic systems.

Smart Blade Count Selection to Align Modal Propagation Angle with Stator Stagger Angle for Low-Noise Ducted Fan Designs

The rotor–stator interaction noise is a major source of fan noise. Especially for low-speed fan stages, the tonal component is typically a dominant noise source. A challenge is to reduce this tonal noise, as it is typically perceived as unpleasant. Therefore, in this paper, we analytically, numerically and experimentally investigate an acoustic effect to lower the tonal noise excitation. Our study on an existing low-speed fan indicates a reduction in tonal interaction noise of more than 9 dB at the source if the excited acoustic modes propagate parallel to the stator leading edge angle. Moreover, a design-to-low-noise approach is demonstrated in order to apply this effect to two new fan stages with fewer stator than rotor blades. The acoustic design of both fans is determined by an appropriate choice of the rotor and stator blade numbers in order to align the modal propagation angle with the stator stagger angle. The blade geometries are obtained from aerodynamic optimization. Both fans provide similar aerodynamic but opposing acoustic radiation characteristics compared to the baseline fan and a significant tonal noise reduction resulting from the impact of the modal propagation angle on noise excitation. To ensure that this effect can also be applied to other low-speed fans, a design rule is derived and validated.

A high-intensity low-frequency acoustic generator based on the Helmholtz resonator and airflow modulator.

The high-intensity low-frequency acoustic sources have essential applications in acoustic biological effects research, airport bird repelling, and boiler ash removal. However, generating high-intensity low-frequency acoustic waves in open space is difficult. In this paper, a low-frequency acoustic generator with a resonant cavity used to enhance the acoustic intensity in open space was developed, which is an aerodynamic acoustic generator to radiates a high-intensity acoustic wave of 52Hz. Some experiments were carried out to measure this generator's internal flow field and radiated acoustic field characteristics, including the propagation characteristics at 100m. The experimental results show that the resonant enhancement effect is presented near the predetermined resonance frequency, and the enhanced value is about 4dB. The acoustic intensity for 52Hz at 1m position is 124dB. By combining the Helmholtz resonator with the airflow modulator, the airflow resonance in the resonator enhances the air pressure pulsation inside the chamber and increases the disturbance of acoustic radiation to the air. So as to improve the sound intensity and radiation efficiency in the low-frequency range.

Development of prominent bonding strength in Al/Mg bimetal composites prepared by ultrasonic vibration-assisted compound casting: Effects of ultrasonic powers

In this work, the A356/AZ91D bimetal composites were prepared by ultrasonic vibration-assisted lost foam compound casting, and the effects of ultrasonic powers on interfacial microstructures and mechanical properties of the Al/Mg interfaces were investigated. Results revealed that the Al/Mg bimetal composites without ultrasonic vibration treatment (UVT) were heterogeneous, and the Al/Mg interface was composed of Al-Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) area and Al-Mg eutectic structures (δ-Mg+Al12Mg17) area. The Mg2Si particles were gathered at the IMCs area and an oxide film that mainly composed of Al2O3 was existed between the IMCs area and eutectic structures area. With UVT, the oxide film was eliminated and the gathered Mg2Si particles were refined and dispersed by the acoustic cavitation effect, and part of the Al3Mg2 and Al-Mg eutectic structures were transformed into the Al12Mg17 due to the promoted solute interdiffusion, which improved the homogeneity of the Al/Mg interfaces. Besides, the grains of the Al/Mg interface with UVT under ultrasonic power of 75 W were significantly refined. The thickness of Al/Mg interface was increased with the increase of the ultrasonic power. Due to the excessive heat induced by UVT under the further increased ultrasonic power, the cooling rates and the degree of supercooling were reduced, resulting in the coarsening of interfacial grains. The microhardness of the Al/Mg interfaces was increased and got more uniform by UVT. The shear strengths of the Al/Mg bimetal composites with UVT were enhanced to 61.4 MPa from 32.4 MPa, with an increase of 89.5 % compared with that of the Al/Mg bimetal without UVT. This could be ascribed to the removal of the oxide film, the refinement of the interfacial grains and the dispersed and refined Mg2Si particles achieved by UVT, which hindered the crack propagation during deformation.

Revealing the Incidence-Angle-Independent Frequency Shift in the Acoustic Rotational Doppler Effect.

The Doppler effect is a universal wave phenomenon that has inspired various applications due to the induced frequency shift. In the case of the linear Doppler effect, the frequency shift depends on the incident frequency and angle. Here, we unveil the frequency shift dependence induced by the acoustic rotational Doppler effect in the wave-object scattering process. We experimentally demonstrate that this frequency shift is exclusively determined by the angular speed and rotational symmetry of the spinning scatterer while remaining independent of the incident angular momentum and angle. We derive the analytical relationship between the frequency shift and the scatterer's helicity, presenting a novel approach for helical feature recognition. The angle-independent nature of the frequency shift inherently prevents spectrum broadening and offers a solution for precise motion measurement through the rotational Doppler effect. This work provides a rigorous and comprehensive understanding of the acoustic Doppler effect, enriching its applications in helicity and motion detection.

Suppression of dendrite formation via ultrasonic stimulation

This research introduces a chemistry-agnostic approach to achieve rapid and degradation-free battery charging via ultrasonic agitation. An ultrasonic device operating in the megahertz range was used to stimulate electrolyte flow from outside the cell. The acoustic streaming effect accelerates ion transport from the bulk electrolyte to the electrode surface and suppresses the formation of an ion depletion zone. An experimental setup was used to optically observe the formation of dendrites when the current imposed across two zinc electrodes exceeded the limiting current. Beyond this limit, diffusion alone cannot provide sufficient ions, resulting in an ion depletion zone. It was subsequently shown that dendrite formation was reduced by over 98% when 15x the limiting current was forced across the electrodes and acoustic stimulation was delivered. Furthermore, it was shown that compared to the scenario without ultrasonic stimulation, the steady state potential was also reduced by 29%, indicating much better ion exchange between the electrodes. These findings suggest that ultrasonic stimulation can be a tool for enhancing electrochemical processes such as battery charging and discharging.

Acoustically enhanced porous media enables dramatic improvements in filtration performance

Indoor air pollution affects millions of people worldwide. Conventional air purification techniques struggle to balance between safety, power consumption, efficacy, and cost. Acoustics have previously been leveraged to improve air purification with fiber filters, but little is known about how the arrangement of the fibers influences the acoustic effects, particularly for non-agglomerative purification performance relevant to fine and ultrafine pollutants. Here, we explore performance enhancements to fiber filters by applying external standing acoustic waves. We investigate the effects of the porous media arrangement in ordered (aligned and staggered) and disordered fiber media by building a multiphysics model, incorporating thermos-viscous acoustics, laminar flow, and particle tracing. Particles are modeled as point forces to isolate acoustic radiation forces and streaming. Attractive acoustic radiation forces dominate in the porous domain, leading to increased particle/boundary interactions. We find that the average acoustic radiation forces scale linearly with the average scattered acoustic pressure by the fiber medium. The scattered pressure varies depending on the fiber arrangement, indicating that there is an optimal design to increase the performance of acoustic-induced effects. We show a dramatic increase in performance efficiency, up to two orders of magnitude (123 times) for a staggered domain. This work has important applications to further advance acoustically enhanced filtration as a compelling solution for micro/nanoparticle separation processes.

Acoustic ground effects simulations from asteroid disruption via the “Pulverize It” method

Our simulations show that PI (“Pulverize It”), a NASA Phase II NIAC study, is an effective multi-modal approach for planetary defense that can operate in extremely short interdiction modes (with intercepts as short as hours prior to atmospheric entry) as well as long interdiction time scales with months to years of warning. The basic process is complete disruption of the threat via fragmentation. In long warning time cases, the fragment cloud spreads enough to miss Earth, resulting in no ground effects. In cases where the warning time is short, the fragments (typically <10 m in diameter) will enter Earth’s atmosphere where their energy is dissipated in a series of ground-level optical pulses and de-correlated shock waves, mitigating any significant damage. We investigate the acoustic ground effects through a set of simulation codes that model the interaction of asteroid fragments with the Earth’s atmosphere following threat interception. Even in the short warning time cases where the fragments enter the atmosphere, our simulations show that threats mitigated by the PI method produce vastly less damage on the ground when compared to the same unfragmented case, yielding shock wave over-pressures under 3 kPa. Our simulations support the proposition that threats sized 20 m—1000 m in diameter can be effectively mitigated through fragmentation, resulting in acoustic ground effects that are below estimated damage thresholds and yield short- and long-term non-lethal effects.

Understanding speech in everyday conditions—Effects of room acoustics and noise

Understanding speech in noisy, indoor settings is a considerable challenge for listeners. Room acoustics, such as reverberation and heating, ventilation, and air conditioning (HVAC) noise, all contribute to such challenges. In the current study, the effects of different backgrounds were examined in anechoic versus reverberant conditions at two different signal-to-noise ratios (SNRs) were examined. 60 monolingual American English listeners transcribed spoken English sentences under different noisy conditions. Overall, we tested two acoustic conditions: anechoic and reverberant, reverberation time = 1.5 s, with four speech conditions (target speech only, or combined with HVAC noise, two-talker babble, or both) and two different SNRs (0 dB and -3 dB). Both the target and babble speech were female voices speaking in English. Complex backgrounds resulted in decreased performance, and the detrimental effects of such masking were accentuated by reverberation and lower SNR. This study serves as a basis for future research exploring the effects of room acoustics on speech intelligibility to gain a more wholistic understanding of speech perception under realistic conditions.

What do voices contribute to acoustic context effects in speech perception?

All perception takes place in context, and speech perception is no exception. Surrounding sounds form a context that guides speech perception. This is particularly true when earlier sounds inform the perception and/or recognition of later sounds. Several lines of research have advanced models where listeners use preceding context to account for characteristics of the talker’s voice, such as vocal tract properties, articulatory maneuvers, or the speaker’s identity. Conversely, research with nonspeech sounds and/or nonhuman animals has advanced alternative models where perception is responding more to signal acoustics than to vocal characteristics. In this talk, I will review recent evidence from our research on acoustic context effects and talker normalization when hearing speech and nonspeech (music) sounds. Parallel patterns of performance across speech and music domains are conducive to, but not definitive evidence of, acoustic context being utilized according to general signal acoustics, with speech- and voice-specific contributions coming later in the processing stream.

Broad and fine acoustic categories in bod, bond, bald, and bard: A step toward acoustic phonology

Acoustics is central to the study of speech communication, but it is conspicuously under-represented in abstract representations of speech. Many flavors of phonological analysis tend toward articulatory descriptions, and transcriptions focus on strings of articulatory actions. All this is despite acoustics being easier to measure than articulation with current technology. The present study explores basic concepts for an acoustic phonology, with two types of postulated categories: broad and fine. Resonant, turbulent, transient, and occludent types of sounds comprise the broad categories, as general methods of filtering the speech source. Fine categories are conceptualized as specific types of acoustic actions within a broad category. These acoustic actions are goal-oriented, as for achieving a particular acoustic effect like the presence of antiformants or a lowered F2 or F3. However, these actions are not explicitly restricted to manipulating traditional phonetic features like formants. By default, fine categories are assumed to be produced in parallel when possible, yielding overlap effects like anticipatory nasalization, lateralization, and rhotacization. These concepts are explored in a microanalysis of bod, bond, bald, and bard from the speaker in the Massive Auditory Lexical Decision data set, with an eye to seeding the ground for a future acoustic phonology.

“I feel like a pack a day smoker”: Teacher and student voices from noisy classrooms

Concerns about the effects of poor classroom acoustics on student learning (particularly on students who are deaf or hard of hearing) have been expressed since the 1950s, yet research continues to indicate that poor classroom acoustics are both common, and related to poorer student outcomes in academic achievement, attention, behavior, and most recently, mental health. Teachers are not immune to the detrimental effects of noise; for them, research indicates a higher incidence of voice problems, absenteeism and job stress. However, little is reported about what teachers and students themselves have to say about their experiences attempting to learn under adverse listening conditions, and what changes for them when acoustical conditions improve. Their voices are largely missing from the research literature but they illuminate the problem in ways that quantitative data does not always capture. This presentation by an educational audiologist with over 35 years of experience in classrooms will provide an overview of the research on learning under adverse listening conditions, with a focus on representing teacher and student voices through qualitative research and anecdotal reports. The title is a quote from a teacher describing her voice problems and fatigue after a day of teaching.