Herskindporterfield1826

Waveguides allow grating lobe free beamforming for air-coupled ultrasonic phased-arrays by reducing the effective inter-element spacing to half wavelength. Since the sound waves propagate through the waveguide ducts, additional time delays are introduced. In this work, we present analytical, numerical, and experimental methods to estimate these time delays. Afterwards, two different waveguides are compared. The first one consists of equal-length ducts, requiring a time-consuming assembly process of the ultrasonic phased-array. In contrast, the second waveguide consists of Bézier-shaped ducts of unequal lengths but a planar input port allowing fast assembly. The analytical model is based on the geometric lengths of the waveguide ducts. The numerical model relies on a transient finite element analysis. All simulations are validated in an anechoic chamber using a calibrated microphone. The analytical (7.6% deviation) and numerical (3.2% deviation) propagation time models are in good agreement with the measurements. By using the analyzed propagation times for the compensation of the unequal waveguide duct lengths, we restored the beamforming capability without significant sound pressure level (SPL) loss. This work shows the possibility of reduced transducer assembly time for waveguided air-coupled phased-arrays without a reduced SPL.This paper deals with the solution of the model equations, which describes the propagation of the surface Love-type waves in a waveguide structure consisting of a lossy isotropic inhomogeneous layer placed on a viscoelastic homogeneous substrate. The paper points to the possibility of using the triconfluent Heun differential equation to solve the model equation. The exact analytical solution within the inhomogeneous layer is expressed by the triconfluent Heun functions. The exact solutions are general in the sense that only the internal parameters of the triconfluent Heun functions can change the spatial dependencies of the material parameters in the inhomogeneous layer's thickness direction. Based on the comparison, the limits of the WKB method applicability are discussed. It is further demonstrated that substrate losses affect the dispersion characteristics only to a small extent. Using examples in which the surface layer is represented by functionally graded materials, it was shown that the distance between the modes can be influenced through those materials.The development of stop consonant voicing in English-speaking children has been documented as a progressive mastery of phonological contrast, but implementation of voicing within one voicing category has not been systematically examined. This study provides a comprehensive account of structured variability in phonetic realization of /b/ in running speech by 8-12-year-old American children (n = 48) when compared to adults (n = 36). The stop always occurred word-initially, was followed by either a voiced or voiceless coda, and its position varied in a sentence, which created systematic conditions to examine acoustic variability in closure duration (CD) and voicing during the closure (VDC) stemming from phonetic context and prosodic prominence. Children demonstrated command of long-distance anticipatory coarticulation, providing evidence that information about coda voicing is distributed over an entire monosyllabic word and is available in the onset stop. They also manifested covariation of cues to stop voicing and command of prosodic variation, despite greater random variability, greater CD, reduced VDC, and exaggerated execution of sentential focus when compared to adults. Controlling for regional variation, dialect was a significant predictor for adults but not for children, who no longer adhered to the marked local variants in their implementation of stop voicing.Reflections of low-frequency, broadband airgun signals from ocean water columns have long been collected in modern marine seismic surveys. However, they were barely examined because of their weak amplitude (following from low acoustic impedance contrast in water columns) and the lack of application interests. Nevertheless, in the past decades, a new cross-discipline "seismic oceanography" has developed the interest to use these water-column reflection signals to image the ocean structures. Motivated by seismic oceanography applications, we examined the acoustic multipath structure of marine seismic survey data with a focus on water-column reflections, and developed a two-step matched filtering approach to enhance water-column reflection and suppress the unwanted bubble waves. The approach was applied to process data collected from the Gulf of Mexico and led to an improvement in imaging mesoscale ocean structures when compared with the traditional matched filtering approach. For the specific data we examined, the results reveal a 11.3-dB improvement of signal-to-noise ratio by removing the noise and a 8-dB improvement of signal-to-reverberation ratio by suppressing bubble waves, while not affecting the information of ocean structures embedded in the signals. This study gains insights into features of water-column acoustic reflections and provides better tools for acoustic imaging of mesoscale ocean structures.Estimates of abundance and their changes through time are key elements of marine mammal conservation and management. Absolute marine mammal abundance in a region of the open ocean is often difficult to attain. However, methods of estimating their abundance based on passive acoustic recordings are becoming increasingly employed. This study shows that passive acoustic monitoring of North Atlantic minke whales with a single hydrophone provides sufficient information to estimate relative population abundance. An automated detector was developed for minke whale pulse trains and an approach for converting its output into a relative abundance index is proposed by accounting for detectability as well as false positives and negatives. To demonstrate this technique, a 2 y dataset from the seven sites of the Atlantic Deepwater Ecosystem Observatory Network project on the U.S. east coast was analyzed. Resulting relative abundance indices confirm pulse train-calling minke whale presence in the deep waters of the outer continental shelf. The minkes are present December through April annually with the highest abundance near the site offshore of Savannah, Georgia.A three-dimensional (3D) hybrid modeling method is used to study the generation and propagation of T waves in the ocean triggered by a Southern Mid-Atlantic Ridge earthquake. First, a finite-element method model named SPECFEM3D is used to propagate seismic waves in the crust and acoustic waves in the ocean for the T-wave generation in a 200 × 50 km area near the epicenter. A 3D parabolic equation (PE) method is then used to propagate the T waves in the ocean for about 850 km further to the hydrophone stations deployed by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) near Ascension Island. All of the simulations considered the realistic bathymetry and water sound speed profile. The SPECFEM3D results suggest that T waves with clear modal features could be generated by the concentration of reflected head waves in two depressions 40 km away from the epicenter. CI-1040 To compare with the hybrid modeling method for calculating T-wave propagation losses and arrival azimuths at the CTBTO hydrophones, point source simulations using the 3D PE model from the T waves source locations, identified with SPECFEM3D, were also implemented. The advantages and limitations of each approach are discussed.Temporal audio features play an important role in timbre perception and sound identification. An experiment was conducted to test whether listeners are able to rank order synthesized stimuli over a wide range of feature values restricted within the range of instrument sounds. The following audio descriptors were tested attack and decay time, temporal centroid with fixed attack and decay time, and inharmonicity. The results indicate that these descriptors are susceptible to ordinal scaling. The spectral envelope played an important role when ordering stimuli with various inharmonicity levels, whereas the shape of the amplitude envelope was an important parameter when ordering stimuli with different attack and decay times. Linear amplitude envelopes made the ordering of attack times easier and caused the least amount of confusion among listeners, whereas exponential envelopes were more effective when ordering decay times. Although there were many confusions in ordering short attack and decay times, listeners performed well in ordering temporal centroids even at very short attack and decay times. A meta-analysis of six timbre spaces was therefore conducted to test the explanatory power of attack time versus the attack temporal centroid along a perceptual dimension. The results indicate that attack temporal centroid has greater overall explanatory power than attack time itself.The interfacial tension (IFT) of fluids plays an essential role in industrial, biomedical, and synthetic chemistry applications; however, measuring IFT at ultralow volumes is challenging. Here, we report a novel method for sessile drop tensiometry using surface acoustic waves (SAWs). The IFT of the fluids was determined by acquiring the silhouette of an axisymmetric sessile drop and applying iterative fitting using Taylor's deformation equation. Owing to physiochemical differences, upon interacting with acoustic waves, each microfluid has a different streaming velocity. This streaming velocity dictates any subsequent changes in droplet shape (i.e., height and width). We demonstrate the effectiveness of the proposed SAW-based tensiometry technique using blood plasma to screen for high leptin levels. The proposed device can measure the IFT of microscale liquid volumes (up to 1 μL) with an error margin of only ±5% (at 25 °C), which deviates from previous reported results. As such, this method provides pathologists with a solution for the pre-diagnosis of various blood-related diseases.A difference in fundamental frequency (F0) between two vowels is an important segregation cue prior to identifying concurrent vowels. To understand the effects of this cue on identification due to age and hearing loss, Chintanpalli, Ahlstrom, and Dubno [(2016). J. Acoust. Soc. Am. 140, 4142-4153] collected concurrent vowel scores across F0 differences for younger adults with normal hearing (YNH), older adults with normal hearing (ONH), and older adults with hearing loss (OHI). The current modeling study predicts these concurrent vowel scores to understand age and hearing loss effects. The YNH model cascaded the temporal responses of an auditory-nerve model from Bruce, Efrani, and Zilany [(2018). Hear. Res. 360, 40-45] with a modified F0-guided segregation algorithm from Meddis and Hewitt [(1992). J. Acoust. Soc. Am. 91, 233-245] to predict concurrent vowel scores. The ONH model included endocochlear-potential loss, while the OHI model also included hair cell damage; however, both models incorporated cochlear synaptopathy, with a larger effect for OHI. Compared with the YNH model, concurrent vowel scores were reduced across F0 differences for ONH and OHI models, with the lowest scores for OHI. These patterns successfully captured the age and hearing loss effects in the concurrent-vowel data. The predictions suggest that the inability to utilize an F0-guided segregation cue, resulting from peripheral changes, may reduce scores for ONH and OHI listeners.