bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-domain simulations of sound propagation near a ground surface in comparison with the ANSI impedance measurement models
Authors: Zheng Z. C. , Zhang Junjian , Ke Guoyi
Published: April 2019

Time-domain simulations with the Zwikker-Keston porous-material model are carried out on the geometries specified in the ANSI models for determining the acoustic impedance of ground surfaces (ANSI/ASA S1.18). The comparisons between the simulation results and the results provided in ANSI show very good agreement when the flow resistivity of the ground material is high. The effect of ground roughness is investigated by adding periodic spacing triangular strips on the ground. The numerical method for simulating rough ground surfaces, which combines the time-domain simulation with an immersed-boundary method, is validated by comparing with experimental data in the literature. It is found that when the ground roughness is introduced to the ANSI geometries, the predicted sound level difference between the two microphones in the ANSI geometries tends to shift towards lower frequency ranges with the rough ground, even though the roughness is within the allowed roughness height specified in the ANSI models.
Pitch perception of concurrent high-frequency complex tones
Authors: Guest Daniel , Oxenham Andrew J.
Published: April 2019

Accurate pitch perception is possible for harmonic complex tones with fundamental frequencies (F0s) in the musical range (e.g., 1.4 kHz) but with all harmonics beyond the putative limits of phase locking. However, it is unknown whether pitch perception in more complex scenarios, such as with concurrent complex tones, is possible using these stimuli. To address this question, we measured (1) F0 difference limens (F0DLs) and (2) target-to-masker ratios (TMRs) required to detect a fixed F0 difference in a mixture of complex tones with low F0s (∼280 Hz) or high F0s (∼1400 Hz). The target tones were filtered to ensure that in the high-F0 case, only harmonics beyond the limits of phase locking were present. Pitch perception was poorer for isolated high-F0 tones than for isolated low-F0 tones and adding a masker complex tone with a geometrically centered F0 impaired performance for both high-F0 and low-F0 tones. The TMRs required to achieve good performance in the presence of two complex tone maskers were higher for high-F0 tones than for low-F0 tones. The results should help determine whether different mechanisms underlie the perception of combinations of complex tones at low and high frequencies. [Work supported by Grants NIH R01 DC005216 and NSF NRT-UtB1734815.]
Fundamental frequency (F0) discrimination of one complex tone in the presence of another: The role of excitation pattern and temporal fine structure cues
Authors: Moore Brian C.
Published: April 2019

The perceptual segregation of simultaneous harmonic complex tones depends partly on differences in the fundamental frequency (F0) between those tones. Human listeners have some ability to group together harmonics of a given F0 and segregate them from harmonics of a different F0. This paper reviews studies of the ability to detect changes in F0 of one complex tone in the presence of another complex tone with the same or a different mean F0. The studies include conditions where the harmonics in the complex tones would have been resolved, partially resolved, or completely unresolved. Modeling using excitation patterns and “summary autocorrelation” and “stabilized auditory image” models suggests that while excitation-pattern cues are useful for complex tones with resolved harmonics, the use of temporal fine structure (phase locking) information is required to account for the small F0DLs obtained when harmonics are barely, if at all, resolved.
Human-like pitch perception mechanisms in marmoset monkeys
Authors: Song Xindong , Guo Yueqi , Osmanski Michael , Wang Xiaoqin
Published: April 2019

The perception of the pitch of harmonic complex sounds is a crucial function of human audition, especially in music and speech processing. Whether the underlying mechanisms of pitch perception are unique to humans, however, is unknown. Based on estimates of frequency resolution at the level of the auditory periphery, psychoacoustic studies in humans have revealed several primary features of central pitch mechanisms. It has been shown that (1) the pitch strength of a harmonic tone is dominated by resolved harmonics; (2) pitch of resolved harmonics is sensitive to the quality of spectral harmonicity; and (3) pitch of unresolved harmonics is sensitive to the salience of temporal envelope cues. Here, we show that, for a standard musical tuning fundamental frequency of 440 Hz (ISO 16), the common marmoset (Callithrix jacchus), a New World monkey with a hearing range similar to that of humans, exhibits all the primary features of central pitch mechanisms demonstrated in humans. Thus, marmosets and humans may share similar pitch perception mechanisms, combined with previous findings of a specialized pitch processing region in both marmoset and human auditory cortex, suggesting that these mechanisms may have emerged early in primate evolution.
New developments in acoustofluidics: Understanding and utilization from atomization to nanofluidics
Authors: Friend James
Published: April 2019

We report new developments in understanding and utilizing acoustofluidics, including atomization devices and physics, interesting new phenomena observed in nanochannels, and entirely new directions of research. In our atomization effort, we have found an absence of bulk turbulence previously posited responsible for capillary wave phenomena that give rise to atomization and find a complex combination of caustics and nonlinear interfacial deformation to be responsible instead. These phenomena are observed on our completely portable micro-scale atomizer devices potentially useful in pulmonary applications. In extending our previous efforts in nanoslit acoustofluidics, we examine droplet manipulation in two-dimensional nanochannel arrays and observe transport at up to 0.1 m/s. Finally, we describe methods and the underpinning physics to integrate acoustofluidics into energy storage systems for a step change in their performance.
Spoken word segmentation and contextual predictability
Authors: Baese-Berk Melissa M. , Morrill Tuuli
Published: April 2019

During speech perception, listeners rely on context when parsing the speech signal. That is, a listener’s interpretation of the speech signal does not only rely on bottom-up phonetic cues in the signal. Instead, listeners use a variety of cues to interpret the best parse of a speech signal. In the current study, we examine how spoken word segmentation of potentially ambiguous stretches of speech is impacted by a variety of contextually based acoustic-phonetic cues (e.g., speaking rate) and the interactions of these cues with contextually-based linguistic knowledge (e.g., collocation strength). We additionally ask how the strength of these predictive variables varies as a function of native speaker status. That is, do non-native speakers use contextual factors in the same way that native speakers do? Our results suggest that while listeners all use both acoustic-phonetic cues and linguistic knowledge when determining the most likely parse of speech, relianceon these cues varies as a function of language status. We will discuss the implications of these results for our understanding of speech perception, generally speaking.
Diagnostic precision of open- versus closed-set word recognition
Authors: Yu Tzu-Ling J. , Schlauch Robert S.
Published: April 2019

The precision of forced-choice (closed-set) and open-ended (open-set) word recognition (WR) tasks for identifying a change in hearing was examined. WR performance for closed-set (4 and 6 choices) and open-set tasks was obtained from 70 listeners with normal hearing. Speech recognition was degraded by presenting words from the Modified Rhyme Test in speech-shaped noise (-8, -4, 0, and 4 signal-to-noise ratios) or by processing words using a sinewave vocoder (2, 4, 6, and 8 channels). The results for the two degraded listening conditions yielded similarly shaped, monotonically increasing psychometric functions. The closed-set tasks had shallower slopes and higher scores than the open-set task for the same condition. Fitted, average psychometric functions were the input to a computer simulation conducted to assess the ability of each task to identify a change in hearing. Individual data were also analyzed using 95% confidence intervals for significant changes in scores for words and phonemes. These analyses found the following for the most to least efficient condition: open-set (phoneme), open-set (word), 6-choice closed-set, and 4-choice closed-set. Greater than an order of magnitude more trials were needed for the 4-choice condition to equal the precision of the open-set word condition scored by the percentage of correct phonemes.
Propagation and scattering of Lamb waves with infinite wavelength
Authors: Gruensteidl Clemens , Stobbe David , Murray Todd W.
Published: April 2019

The dispersion characteristics of Lamb waves depend on the thickness and the elastic properties of a plate. At the cut-off frequencies (when the wavenumber goes to zero), Lamb waves are standing waves associated with plane longitudinal or shear waves reflecting up and down between the surfaces of the plate at normal incidence. In the general case, these thickness resonances have an infinite wavelength and do not carry energy along the plate. However, if the material properties are selected such that longitudinal and shear thickness mode resonances of the same symmetry coincide, then the elastic fields associated with the resonances couple to produce a wave with an infinite wavelength that propagates energy along the plate surface. Intriguing effects associated with this phenomenon can be observed in aluminum alloy plates where near-degeneracy between resonances occurs. We show that waves generated near the cutoff frequency in such cases spread from the excitation point and produce a spatially uniform oscillation over the plate surface. These infinite wavelength waves show angle independent mode conversion upon encountering the free edge of a plate or thickness step on the surface. Furthermore, we demonstrate that these peculiar waves flow around plate defects and are remarkably insensitive to scattering.
Quadcopter propeller noise and its control
Authors: Brungart Timothy A. , Olson Stephen T. , Kline Brian L. , Yoas Zachary W.
Published: April 2019

Simple scaling analysis is used to show that truly significant reductions in propeller noise are possibly by increasing the propeller diameter while reducing its rotational speed, thereby reducing its blade tip speed, while maintaining a given level of static thrust. The scaling analysis is also used to show that efficiency improvements accompany the reductions in radiated noise. The significant reductions in noise and the increase in efficiency predicted were verified experimentally by measuring the radiated noise and power requirements for both large, slowly rotating propellers and small, high speed propellers, at equivalent static thrusts, where the large propellers serve as possible replacements for the small propellers in typical quadcopter applications. The bulk of the noise reductions offered by large and slowly rotating propellers compared with small, high speed propellers is shown to be maintained at equivalent net force (thrust minus weight conditions), as required for practical implementation into a quadcopter, even using readily available hobby grade components. Further significant noise reductions are possible with lightweight and custom engineered components.
Dysarthric speech perception: Comparison of training effects on human listeners versus automatic speech recognition tools
Authors: Lally Michael F. , Kim Heejin , Moon Lori A.
Published: April 2019

Dysarthric speech, a motor speech disorder associated with neuro-motor conditions, poses a challenge for automatic speech recognition (ASR) due to its acoustic characteristics and the comparatively limited volume of available data. This study investigates ASR toolkits’ recognition abilities on speech from speakers affected with cerebral palsy (CP) at different intelligibility levels, by comparing them against human listeners’ performance. We ask: (1) how intelligible is speech from CP-affected speakers to ASR toolkits trained on non-dysarthric speech? (2) how does this performance compare to naïve human listeners? and (3) as familiarized human listeners better understand dysarthric speech, to what degree is dysarthric speech more intelligible to similarly familiarized ASR toolkits? Using the UA-Speech Database (Kim et al., 2008), we test the ASR system with two training methods: strong supervision, with both audio and orthography feedback in training, and unsupervised methods, with only audio signals, following Kim and Nanney’s (2014) experiments with human listeners. ASR accuracy is measured by the word error rate in word transcription tests. Findings reveal the extent to which supervision affects ASR models in comparison to human listeners. Implications regarding how to improve the adaptation techniques to dysarthric speech for both ASR and human listeners are presented.
Masking effects of perceptual cues on hearing-impaired ears
Authors: Guo Siyan , Cole Cliston , Allen Jont
Published: April 2019

The most common complaint from hearing-impaired (HI) subjects is "I can hear the speech but I can't understand it." This has led us to investigate the strategy of the HI ear in understanding speech. In this study, the effects of the masking of primary cues in HI ears are analyzed, with and without the presence of conflicting cues. Two consonant-vowel (CV) identification experiments were conducted on 5 normal-hearing (NH) and 10 HI subjects. 4 plosive consonants /t,k,d,g/ paired with vowel /a/ were used as target stimuli. The CVs were presented at SNRs of 0, 9, and 18 dB. In experiment I, the primary cue for each CV was modified in 3 ways: removed, attenuated, and amplified. Experiment II was similar except the conflicting cues were removed. The results for both NH and HI groups show a large increase in probability of error in all SNR levels when the primary cue was removed. The results for Exp II display more variability. The HI subjects were divided into three groups based on their error: low error group (LEG), medium error group (MEG) and high error group (HEG). The analysis shows that HI listeners are using the same primary cue as NH ears. The strength of the primary cue is a critical quality for correct speech perception, especially in the presence of noise. The subjects in MEG and HEG exhibit sensitivity to the presence of conflicting cues. The removal of the conflicting cues demonstrates that HI ears use not only the primary cue but also conflicting cues, for correct speech perception.
Bayesian inference when the physics is not quite right
Authors: Pierce Allan D. , Siegmann William L. , Brown Elisabeth M.
Published: April 2019

Bayesian inference requires a physical and structural model for the portion of the environment being assessed. The model is characterized by a finite number of parameters, and these are assumed to each be a random variable. The forward problem can be solved given a knowldege of these parameters and the governing equations. Bayesian inference begins (prior probability) with some initial broad assumptions about the probability distributions. An intricate (Bayesian) process involving data and solutions to the forward problem leads to a refinement of these probability distributions. The range of possibilities becomes narrower, and one identifies most probable values of the parameters. The present paper raises the question as to what results when the parameterization is capriciously in conflict with what is known about the actual environment. An example from underwater acoustics is the choice of parameters to describe the frequency dependence of attenuation on a sediment layer. What is sometimes done is to assume the attenuation is directly proportional to frequency (just one parameter) or that the attenuation obeys a power law with a constant exponent (two parameters). The intrinsic shear modulus of the sediment is ignored in the numerical solutions of the forward problem, so the physics is incomplete. Some idealized examples are used to explore the consequences of such simplifying assumptions. Improved parameterizations are suggested that will yield more realistic frequency dependences of attenuation.
Localization of a mobile acoustic scatterer from sub-Rayleigh resolved acoustic arrivals in a refractive environment
Authors: Gendron Paul J. , Barros Abner C.
Published: April 2019

Computational Bayesian inference on the state of an underwater mobile object from a continuous active acoustic transmission is presented. The challenge of sub-Rayleigh resolvable wave vectors in refractive environments with uncertainty in ambient acoustic noise power is addressed. The location and speed of the mobile scatterer are inferred under the challenging constraint of a small receive vertical aperture. The need for jointly inferring the vertical angles and Doppler offsets of the arrivals is addressed with a Gibbs sampling approach. The posterior density of the plane wave components is mapped to the object's range, depth, and speed through ray interpolation. A case scenario from an acoustic duct environment in the western Indian ocean is presented.
Broadband design of multilayer micro-slit panel absorbers for improved transparency using Bayesian inference
Authors: Hoeft Michael , Fackler Cameron J. , Xiang Ning
Published: April 2019

Multilayer Micro-Slit panels (MSP) are assessed for their potential as broadband absorbers that simultaneously maintain visual transparency. The late Dah-You Maa introduced micro-Slit panel absorbers as a continuation of his previously developed Micro-Perforated panel (MPP) absorbers. Like MPPs, Micro-Slit panels allow high absorption coefficients to be achieved without using fibrous materials but are limited to a narrow frequency bandwidth. Broadband absorption can be achieved by combining panels into a multilayer absorber. The complexity of determining the optimum set of parameters required to fulfill a design scheme necessitates implementation of the Bayesian framework. This probabilistic method automatically determines the most concise number of layers required and gives parameters for each layer of the resulting composite. Various slit patterns and algorithms introduce a family of solutions, which satisfy the design scheme, for optimization of visual transparency. The Micro-Slit samples can be fabricated and tested to validate acoustic performance and assess visual properties.
Bald eagles (Haliaeetus leucocephalus) monitor their immediate acoustic environment vigilantly
Authors: McGee JoAnn , Nelson Peggy B. , Marr Jeff , Ponder Julia , Milliren Christopher , Feist Christopher , Byrne Andrew , Walsh Edward J.
Published: April 2019

As part of an initial effort to determine if acoustic signals can be used to discourage eagles from entering wind turbine facility airspaces and thereby reduce morbidity/mortality collision rates, behavioral responses of bald eagles (Haliaeetus leucocephalus) to a battery of both natural and synthetic acoustic stimuli of varying spectral complexities were studied. Each signal was directed randomly to one of two loudspeakers in a sequence of ~10 trials, and the stimulus order was randomized for each bird. A variant of an observer-based psychoacoustic protocol was implemented, and judges were instructed to report the absence or presence of a response, response strength, and other distinctive response attributes. In pilot studies, subjects responded to ~74% of trials across all stimuli. Responsivity was greater to spectrally complex stimuli (~80% vs 59%), and greater responsivity was observed to natural stimuli than to synthetic stimuli (~82% vs 69%). Responsive subjects oriented correctly in the direction of the signal source in ~74% of trials. A significant difference in overall responsivity was not observed across stimulus sets, although habituation was observed across repeated trials when responses to all stimulus types were combined. The relevance of findings in relation to the design of deterrence/alerting protocols will be discussed. [Work supported by DOE Grant No. DE-EE0007881.]
The effects of age and sex on rates of hearing loss for pure tones varying in duration
Authors: Kobrina Anastasiya , Dent Micheal L.
Published: April 2019

Mice are frequently used to study and model presbycusis due to similarities in the human and mouse cochleae and in genetic makeup. Most of the previous research on presbycusis used electrophysiological measures of hearing in mice, leading to an underrepresentation of behavioral experiments in the literature on mouse aging. The goal of the current research was to fill this gap by behaviorally measuring audiograms and temporal summation functions in aging mice. Adult mice were trained and tested using an accelerated longitudinal design. Mice were trained on a detection task using operant conditioning procedures with positive reinforcement. Audiograms were constructed using thresholds for 8, 16, 24, 42, and 64 kHz pure tones. Temporal summation functions were constructed for 16 and 64 kHz pure tones ranging from 20 to 800 ms in duration. The results revealed that mice retain pure tone hearing late into their lifespan, with high-frequency hearing loss preceding low-frequency hearing loss. Mice also benefit from increases in the duration of pure tones; however. this benefit decreases with age. Generally, male mice lose hearing at a faster rate than females. These results highlight the importance of measuring hearing in awake, trained, behaving subjects when comparing presbycusis across species.
Evaluation of a potential medical diagnosis application of sonoluminescence
Authors: Casacchia Alicia , George Parker , Wilson Preston S. , Hamilton Mark F.
Published: April 2019

Sonoluminescence (SL) is a phenomenon in which light is produced via violent collapse of a gas-filled cavity under excitation by a varying pressure field. Although the precise mechanism of this light production is not yet agreed upon in the literature, various applications of this effect have been established and are continually being developed. One such example of an application of this phenomenon that has not been extensively studied is the production of SL in biological fluids as a method for medical diagnostics. Measurements performed by Chernov et al. [in Proceedings of 14th International Symposium on Nonlinear Acoustics (1996), pp. 219–223] revealed varied intensities of SL emissions in blood plasma samples from groups of patients diagnosed with different diseases. We present an experimental apparatus for the production of single bubble sonoluminescence (SBSL) and subsequent measurement of radial oscillations using optical scattering techniques. This system will allow for characterization of the effects of both the biological fluid content and viscoelasticity on the spectra of SBSL light emissions. Additionally, these experimental results can be used to inform future computational models of this behavior. [This is a Plan II SAWIAGOS project.]
Racial categorization and word identification: The influence of sex, race and regional dialect
Authors: Holt Yolanda F. , Bent Tessa
Published: April 2019

The speech signal provides information on talker characteristics including socio-ethnic affiliation and racial identity. Regional variation, both similar and divergent from White American English, has been described in African American English. However, it is unknown if such regional dialect variation influences listeners’ racial categorization or word identification accuracy. This work evaluated the influence of listeners’ sex, race, and regional dialect on racial categorization and word identification for Black and White talkers from two dialect regions within North Carolina. Black and White listeners (n = 23) from eastern and central North Carolina participated. In the racial categorization task, listeners heard /hVd/ words produced by male and female Black and White talkers from eastern and western North Carolina. Listeners categorized the perceived talker race for each token as Black or White. In the word identification task, the same listeners matched the speech tokens from the same talkers to one of fourteen /hVd/ words. Results showed an effect of listener sex on word identification accuracy such that female listeners were more accurate than male listeners. No effect of listener race or regional dialect was observed for either task. Follow-up analyses will investigate the interaction between listener and talker sex, race, and regional dialect.
The southern shift and regional identity in Appalachia
Authors: Reed Paul E.
Published: April 2019

The Southern Vowel Shift (SVS) historically occurred across the Southern U.S. (e.g., Labov et al., 1972; Feagin, 1986). Several recent studies document the retreat of the SVS in the urban South (Fridland, 1999; Prichard, 2010; Dodsworth and Kohn, 2012). However, Irons (2007) found the SVS advancing in rural Kentucky. Thus, Fridland notes the SVS might not be "a supra-regional norm," serving rather as "an ecological distinction within the South" (2012:187). As an ecological distinction, SVS features might reflect a speaker’s orientation toward differing ecologies. Thus, a speaker with a rural orientation might use more SVS features than a speaker who is less rurally oriented. The present paper investigates the SVS in rural speech examining three features: monophthongization of /aI/, rotation of /E/ and /e/, and rotation of /I/ and /i/. Data come from sociolinguistic interviews, reading passages, and words lists from 25 speakers from rural northeast Tennessee. Additionally, every participant completed a Rootedness Metric, a psychometric survey that quantifies place-based orientation. Results indicate that speakers exhibit SVS features, with reversals of the relative front vowel positions and monophthongization of /aI/ in all positions (cf. Irons, 2007). However, more rooted speakers exhibited the most advanced SVS features. Thus, the central difference of SVS features may not merely be "ecological," rather the speaker’s relationship to the differing regional ecologies.
Proactive neural processing of native and non-native speech
Authors: Llanos Fernando , Reetzke Rachel , Chandrasekaran Bharath
Published: April 2019

The impact of attention and language-experience in neural speech processing is typically assessed using sentences, words, and syllables that, when presented in isolation, may not engage the cortical speech network as well as more realistic continuous speech. Here, we explore the neuromodulatory effects of attention and language experience using continuous speech. We recorded electroencephalographic responses from native speakers of English and late Chinese-English bilinguals while listening to a story recorded in English. The story was mixed with a tone sequence, and listeners were instructed to focus either on the speech (attended speech condition) or the tone sequence (ignored speech condition). We used the multivariate temporal response function and the accuracy of a machine-learning based brain-to-speech decoder to quantify differences in cortical entrainment and speech-sound category processing. Our analyses revealed a more robust, context-independent neural encoding of speech-sound categories when they were attended and native. Interestingly, while cortical entrainment to speech was also enhanced by attention, the enhancement was stronger among non-native speakers. Our results suggest that while listeners can manage attention to improve the neural parsing of continuous speech via cortical entrainment, the benefits of attention for speech-sound category processing can be attenuated when the sounds are not native.
Broadband elastic black hole and vibration isolator based on the transformation method
Authors: Gao Hexuan , Xiang Zhihai
Published: April 2019

The transformation method has stimulated many interesting applications of manipulating electromagnetic and acoustic waves by using metamaterials, such as super-lens imaging and cloaking. These successes are mainly due to the form-invariant property of the Maxwell equations and acoustic equations. However, the similar progress in manipulating elastic waves is very slow, because the elastodynamic equations are not form-invariant. Here, we show that the expression of the elastodynamic potential energy can approximately retain its form under two restrictions: conformal mapping and using the material whose longitudinal wave velocity is much larger than the transverse wave velocity. Based on this finding, we use inhomogeneous isotropic material to design and fabricate an efficient 180-deg wave bender acting as vibration isolator, in which the incident elastic waves turn around and make little disturbance on the item being supported. In addition, an elastic black hole is designed in the same way, so that the elastic energy propagating near the black hole is mostly absorbed into the center and dissipated by the damping material.
Laser Doppler vibrometer and bending wave based dynamic material characterization of organic aerogel panels
Authors: Miller Max , Malakooti Sadeq , Xiang Ning , Leventis Nicholas , Lu Hongbing
Published: April 2019

To what extent aerogels are useful in noise and vibration control applications remains an open question. With the advent of low cost, facile synthesis, ductile, and purely polymeric aerogels, the prospects are alluring. Within the polyurea family of aerogels, multiple nanomorphologies exist with some being amenable to rheological paradigms. An inverse problem approach is applied to tease out material parameters with the aid of viscoelastic models and a pair of dynamic characterization techniques. A specialized transfer function driven, quasi-longitudinal wave eliciting, material characterization setup is refined and augmented with laser Doppler vibrometry. This effort seeks to improve repeatability and increase frequency limits, two factors whose absences plague many schemas. Intriguing properties previously uncovered with this method, such as broadband negative dynamic mass, are reexamined. In tandem, a bending wave excitation arrangement and characterization method is introduced. Low bending and quasi-longitudinal phase speeds in addition to high static and low dynamic moduli shed light on the enhanced noise and vibration control performance reported in the literature. This paper discusses the dynamic measurement method and possible applications which may benefit from this unique combination of properties.
A generational acoustic analysis of Mexican Spanish and English vowels
Authors: Reyes Herrera Edwin D.
Published: April 2019

Multiple studies have suggested that the Spanish vowel system is stable, with little to no variation (Delattre, 1996; Quillis and Esgueva, 1983), while others have also noted variation in monolingual Spanish (Boyd-Bowman, 1952; Canellada and Vicente, 1960; Delforge, 2008; Lipski, 1990; Lope-Blanch, 1964; Marín Galvés, 1995; Matluck, 1952; Quilis, 1999; Quilis and Esgueva, 1983) and bilingual Spanish in the United States (Fought, 1999; Godinez and Maddieson, 1985; Konopka and Pierrehumbert, 2008; Konopka, 2011; Ronquest, 2013; Willis, 2005). This study analyzes the vowel quality and duration of Spanish and English vowels by Mexican and Mexican-American speakers across different sociolinguistic generations in the United States (Silva-Corvalan, 1994), which has been absent from previous literature. An examination of the different generations is needed to account for the differing levels of Spanish and English use in the United States, as well as to examine how production of speech may change across generations. Results indicate all generations exhibit significant unstressed vowel reduction, though there is variation across the different groups. The amount of centralization and reduction also increases for each subsequent generation. In addition, Spanish influence is evident in the production of both G1 and G3 groups, though there is also evidence for acquired English speech.
Effects of perceptual training in Mandarin tone sandhi production
Authors: Chen Si , Chen Shuwen , He Yunjuan , LI Bei , Yang Yike , Wayland Ratree
Published: April 2019

It is well-established that the production of non-native lexical tone poses a great challenge to adult L2 learners (Hao,2012; Chang and Yao, 2016; Mok et al., 2018). The production of tonal patterns on disyllabic words is more challenging for non-native speakers because additional computational and/or lexical mechanisms are involved in correctly applying the tone sandhi rules in languages like Mandarin (Chen et al., 2017). Previous speech training studies have shown that perceptual training could improve both perception and production of non-native tones in isolation (Wang et al., 1999, 2003; Wayland and Li, 2008). The current study aims to further examine if perceptual training promotes learning of tonal patterns on disyllabic words by examining the production of two Mandarin Tone sandhi rules—the third tone sandhi and half-third tone sandhi by Cantonese learners. Native Cantonese speakers were trained with an identification task and a same/different discrimination task with both real and wug words. Their pre- and post-training production was compared with native speakers’ production, and it showed that perceptual training can lead to more successful learning of Mandarin tone sandhi rules based on acoustic and statistical analyses of tonal contours.
Interplay of native and non-native vowels in Japanese late learners of English
Authors: Takahashi Chikako
Published: April 2019

This study investigates perception of native (/i/-/e/) and non-native (/i/-/ɪ/) contrasts by Japanese late learners of English (N = 40). We hypothesized that speakers with greater proficiency in L2 might show more effects of L2 learning on L1 perception than speakers with lower L2 proficiency. We found first that self-rated proficiency correlated relatively well with L2 vowel contrast categorization (r = 0.622) indicating that late bilinguals can achieve more nativelike categorization of L2 vowels (/i/-/ɪ/) as their overall proficiency improves. Turning to the effect of L2 proficiency on L1 perception, we found that the bilinguals who exhibited more nativelike English /i/-/ɪ/ categorization in their L2 were more likely to have a broader /i/ category when identifying /i/vs./e/ in Japanese (compared to monolingual Japanese controls). We argue that while L2 English learners may be improving in identifying English /i/vs./ɪ/, the non-native /ɪ/ is not fully differentiated from their Japanese /i/ category, possibly providing atypical exemplars that influence the perceptual boundary of /i/ in their L1. The complex interplay of L1 and L2 vowels will be further discussed by reference to production data for the learners and native speaker controls for Japanese and English.
Helmholtz-Rayleigh Interdisciplinary Silver Medal in Psychological and Physiological Acoustics, Speech Communication, and Architectural Acoustics 2019: Barbara G. Shinn-Cunningham
Authors: Shinn-Cunningham Barbara G.
Published: April 2019

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Level of detail in room-acoustic simulation
Authors: Vorlaender Michael
Published: April 2019

The quality of present-day room acoustic simulations depends on the quality of the boundary conditions and of the underlying CAD room models. A “high-resolution” room model does not mean that it needs to have a visually perfect geometrical fine structure. To our experience, the required resolution of objects or surfaces does not need to be higher than about 1 m. In this presentation, an auralization engine is briefly introduced which uses a set of models of the same room but with a graduated level of detail (LOD). These different models can account for more physical correctness especially for very low-frequency specular reflections. Furthermore, a good estimate of scattering coefficients is essential. The relevance of the uncertainty of scattering coefficient data is discussed in a review on perception tests with varied surface scattering. Finally, guidelines for creation of CAD models are proposed.
Best available science? Are NOAA fisheries marine mammal exposure noise guidelines up to date?
Authors: Stocker Michael A.
Published: April 2019

NOAA fisheries employs a set of in-water noise exposure guidelines that establish regulatory thresholds for ocean actions that impact marine mammals. These are established based on two impact criteria: level A—a physiological impact including “Permanent Threshold Shift” (PTS) and level B—a behavioral impact or disruption. Recently, the level A exposure thresholds were reconciled to the frequency-dependent hearing sensitivities of five classes of marine mammals based on the work done more than a decade ago (Southall et al., 2007). Since that time, much more work has been published on behavioral impacts of various noise exposures, and consideration of more variables such as frequency-dependent noise propagation characteristics, cumulative, concurrent, and continuous exposures, and noise impacts on marine soundscapes has entered into the discussion—but have not been incorporated into the NOAA Fisheries guidelines. Some of these variables will be highlighted, suggesting that it may be time to reevaluate the thresholds for level B exposures.
Human auditory discrimination of bottlenose dolphin signature whistles masked by noise: Investigating perceptual strategies for anthropogenic noise pollution
Authors: Morrison Evan L. , DeLong Caroline M.
Published: April 2019

Anthropogenic masking noise in the world’s oceans is known to impede many species ability to perceive acoustic signals, but little research has addressed how this noise pollution affects the detection of bioacoustic signals used for communication. Bottlenose dolphins use signature whistles which contain identification information. Past studies have shown that human participants can be used as models for dolphin hearing, but most previous research investigated echolocation. In experiment 1, human participants were tested on their ability to discriminate among signature whistles from three dolphins. Participants’ performance was nearly errorless (M = 98.8%). In experiment 2, participants identified signature whistles masked by five different samples of boat noise, with different signals to noise ratios. Preliminary results suggest that participants perform worse in lower ratios of signal to noise, that some signature whistles are easier to identify in the presence of noise, and that some noises have more detrimental impacts on whistle recognition. The presence of boat noise may cause participants to use more auditory cues in order to identify whistles, although participants always relied most heavily on frequency contour and duration. This study may provide insight into the impacts of different types of boat noise on dolphin whistle perception.
Power law attenuation modeled as multiple relaxation
Authors: Holm Sverre
Published: April 2019

Wave equations with non-integer order derivatives may model power law behavior in medical and sediment acoustics. As experiments only support a finite bandwidth, there is a limit to how much physical insight that can be gained from such models. Other ways to model a power law are with a fractional heat law, hierarchical ladder models for polymer chains, and the non-Newtonian rheology of grain shearing. Multiple relaxation processes may be motivated by a hierarchy of substructures at different scales. It is also inherent in soft glassy materials, such as cells, with disordering and metastability. Even the Biot model with contact squirt flow and shear drag (BICSQS) may be interpreted as a multiple relaxation model. A weighted sum of relaxation processes will approximate a power law over a limited band, and an even distribution of relaxation frequencies on a logarithmic frequency axis, and with equal relaxation strengths, will give a power law attenuation with unit power, y = 1. This can be generalized to other power laws if the contribution from each relaxation process varies in proportion to the relaxation frequency to the power of y - 1. This scale-invariant distribution may hint at some fractal medium properties.
Validity of Independent Scattering Approximation (ISA) to measure ultrasonic attenuation in porous structures with mono-disperse random pore distribution
Authors: Yousefian Omid , Karbalaeisadegh Yasamin , Muller Marie M.
Published: April 2019

The goal of this study is to assess the validity of the Independent Scattering Approximation (ISA) for predicting ultrasonic attenuation in structures mimicking simplified geometries of cortical bone. Finite Difference Time Domain (FDTD) methods were used to assess the ultrasound attenuation in porous media with a monodisperse distribution of pores, with pore diameters, density, and frequency in the range of ϕ = 40–120μm, 3–16 pore/mm2, and 1–8 MHz, respectively. The attenuation values obtained from the FDTD simulations were compared to attenuation values predicted by the ISA. The results indicate that the ISA reliably predicts the attenuation for kϕ<1 and ϕ∈[100,120] μm, with less than 15% error. The error increases up to 26% as ϕ decreases. The reason that ISA fails to predict accurate values for lower ϕ is investigated through the quantification of multiple scattering (MS). This is done by MS assessment in which the effect of multiple versus single scattering (SS) is compared by measuring the backscattered signals on a simulated linear array transducer. The results revealed that MS is dominant at ϕ = 120, but that SS is dominant for ϕ = 60 μm. Assuming that the attenuation is a function of kϕ, the ISA is modified to test its applicability where single scattering is dominant. The results using the modified ISA showed that it can predict the attenuation in monodisperse porous structures for kϕ < 1 and ϕ∈[40–100] μm with less than 10% error.
Miniature fiber optic acoustic pressure sensors with air-backed graphene diaphragms
Authors: Dong Qian , Liu Haijun
Published: April 2019

Graphene has been known to possess exceptional mechanical properties, including its extremely high Young’s modulus and atomic-layer thickness. Although there are several reported fiber optic pressure sensors using a graphene film, a key question that is not well understood is how the suspended graphene film interacts with the backing air cavity and affects sensor performance. Based on our previously analytical model, we will show that sensor performance suffers due to the significantly reduced mechanical sensitivity by the backing cavity. To remedy this limitation, we will, through experimental and numerical methods, investigate two approaches to enhance the sensitivity of fiber optic acoustic pressure sensors using the graphene film. First, a graphene-silver composite diaphragm is used to enhance the optical sensitivity by increasing the reflectivity. Compared with a sensor with pure graphene diaphragm, a graphene-silver composite can enhance the sensitivity by three-fold, while the mechanical sensitivity is largely unchanged. Second, a fiber optic sensor is developed with enlarged backing air volume through the gap between an optical fiber and a silica capillary tube. Experimental results show that the mechanical sensitivity is increased by 10xfrom the case where the gap side space is filled.
A bio-inspired sound source localization sensor with internal coupling
Authors: Dong Qian , Liu Haijun
Published: April 2019

The mechanism of using internal coupling to enhance directional hearing has been found in various animals across multiple length scales, including crickets, lizards, frogs, birds, and alligators. For each eardrum, the acoustic stimuli impinge not only on the front side but also on the opposing side via the connecting cavity. The combination of these two stimuli renders a much higher directional sensitivity than the case with two uncoupled independent receivers. Inspired by this mechanism found in Nature, here we present a bio-inspired sound source localization sensor which consists of two pre-tensioned membranes on a three-dimensional printed housing. The vibration of the two membranes is detected by a low coherence fiber optic interferometric system. The experimental results from this prototype will be demonstrated to validate the feasibility of developing miniature bio-inspired devices for sound source localization.
Design of a conformal acoustic parametric array
Authors: Malone Matthew , Dieckman Eric A.
Published: April 2019

The acoustic parametric array exploits the nonlinearity of air to create an audible sound beam that can propagate long distances. Transmitted signals are modulated around a nominal 40 kHz carrier, creating sum and difference components as the signal propagates through air. Since attenuation is proportional to frequency squared only the low-frequency difference component remains at long distances. Current commercially available parametric arrays arrange ultrasonic transducers in a planar array to create a beam of sound that is audible at distances up to 100 m. Our goal is to create a concave parametric array to determine if the added geometrical focusing allows for tighter spatial control of the audible signal. Ultrasonic transducers were mounted on a flexible three-dimensional printed structure to create an array with a variable curvature. Simulation and experimental results are presented comparing our conformal array to two commercially available planar arrays.
Acoustic radiation characteristics improvement according to the shape change of flat-plate display exciter speaker
Authors: Park Hyung Woo , Lee SungTae , Park Kwanho
Published: April 2019

For human, sound and video are evolving as the information transmission method. People are quick and easy to understand when sound and video are transmitted at the same time. In previous studies, we introduced a study to increase the quality of sound by equalizing the position of sound and sound in a flat panel display such as OLED (organic light emitting diode) TV. In that, we have implemented a sound field by separating two or more channels by vibrating the display panel of an OLED display. In this study, we investigated the effect of the variation of the shape of the pole piece on the radiation characteristics of the exciter speaker. In dynamic speakers, a pole piece guides the voice coil. However, in the exciter, the Pole Pieces excite the diaphragm directly. Initially, due to the limitations of exciter manufacturing technology, two exciters were placed separately. The first improvement was arranged on the same axis, and the sound was implemented by twin structure. However, because of the use of two pole pieces, the subtle phase difference of the two influenced the radiation pattern. In this study, the elliptical pole piece was introduced to improve the radiation characteristics in the transverse axis direction. The use of a single pole piece not only improves acoustical characteristics in the longer radius direction; furthermore, it is confirmed that the sound quality is improved by reducing manufacturing and driving errors even in the radial direction.