bluuebunny/crossref_metadata_2025 huggingface dataset:
Bat-inspired dynamic features and factors that modulate their impact on speech recognition
Authors: Hsu Alexander , Han Jin-Ping , Cui Xiaodong , Audhkhasi Kartik , Gupta Anupam Kumar , Sutlive Joseph , Ahmed Tabassum , Müller Rolf
Published: October 2018

One of the most serious remaining challenges in speech recognition is dealing with corruption of speech signal by other nuisance speech ("babble"). A promising approach to solving the problem of separating the signal of interest from the detractors is to inject direction dependent signatures into all signals received, which has been realized by bat-inspired biomimetic pinna—dynamic periphery. Changing the shape of a biomimetic pinna during the recordings introduces substantial time-variant signatures into speech signals. To investigate the utility of these signatures, we have used bioinspired signal representations (cochleagram and spikegram) as input for speech classifiers based on Gaussian mixture models (GMM) and hidden Markov models (HMM). The speech samples used were obtained from open source databases: spoken digits and alphabets from Carnegie Mellon University were mixed with babble or noise samples from Columbia University. Since the time-variant signatures were found to depend strongly on the direction of the sound source, we attempted to include datasets from different directions for training and testing to feed into the classifiers. The results indicate that dynamic periphery can substantially improve recognition and that these effects depend on the signal representation as well as the angular composition of the training dataset.
Is explicit formant encoding useful for speech perception with cochlear implants?
Authors: Saba Juliana N. , Ali Hussnain , Brochtrup Colin , Hansen John H. L.
Published: October 2018

Earlier generations of cochlear implant (CI) sound processing strategies incorporated explicit encoding of formant frequencies. Many of these CI strategies have yielded higher intelligibility outcomes for CI users due to the pure spectral-based approaches used in contemporary processor today, such as: CIS, ACE, Hi-Res, etc. The aim of the study has been to assess intelligibility due to possible loss in formant frequency encoding and its influence on channel selection in diverse acoustic conditions. Formant accuracy from four computer-aided estimation techniques are compared against hand-marked frequencies derived from phoneme-level transcription with sentences from the IEEE and AzBio databases in three noise types at different SNRs: (a) babble, (b) speech-shaped, and (c) noise and reverb combination. CI speech intelligibility outcomes of the proposed strategy using explicit formant frequency encoding was compared to ACE, the standard energy-based ‘n-of-m’ approach. A relationship between the estimation techniques and differences in channel selection was systematically assessed. Results suggest that minor loss of formant precision does not yield statistically significant differences in resulting speech intelligibility. However, availability of accurate formant cues may help with intelligibility gains in challenging noise such as babble.
Fermat’s principle, Fresnel zones, and ray methods for high-frequency signatures of elastic cylinders in water
Authors: Marston Philip L.
Published: October 2018

Geometric methods are useful for understanding the magnitude and timing of high-frequency echoes from elastic objects in water. This presentation emphasizes, but is not limited to, elastic contributions associated with leaky waves on circular cylinders. The regions of strong coupling between the incident acoustic wave and guided leaky waves can be predicted using Fermat’s principle while the size of the associated Fresnel zones are useful for understanding signal magnitudes [P. L. Marston, J. Acoust. Soc. Am. 102, 1628–1638 (1997); F. J. Blonigen and P. L. Marston, 110, 1764–1769 (2001)]. Ray theory predictions are supported by measurements with tilted cylinders [S. F. Morse, P. L. Marston, and G. Kaduchak, J. Acoust. Soc. Am. 103, 785–794 (1998); K. Gipson and P. L. Marston, J. Acoust. Soc. Am. 106, 1673–1680 (1999); F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 112, 528–536 (2002)]. Related applications include signatures and images of tilted cylinders near flat surfaces [D. S. Plotnick and P. L. Marston, J. Acoust. Soc. Am. 140, 1525–1536 (2016)], time-frequency signatures [S. F. Morse and P. L. Marston, J. Acoust. Soc. Am. 111, 1289–1294 (2002)], and signatures for other targets with corners. [Work supported by ONR.]
Adaptive integration for Capon-type beamformers by exploring Riemannian geometry on covariance matrices
Authors: Nordenvaad Magnus L.
Published: October 2018

Adaptive, or Capon beamformers, offers several advantages compared to standard alternatives in underwater sensing. Furthermore, for hull mounted sensor arrays, adaptive beamformers is a convenient way of mitigating platform induced interference. The underlying difficulty in implementing a data-adaptive approach is how to obtain an accurate estimate of the data covariance matrix, R. The combination of high-dimensionality and time-variation renders significant challenges in maintaining accurate covariance estimates. A common way to approach this issue is to update the covariance matrix using a weighted Euclidean average, Rnew = a Rold + (1-a) Rinst, where Rinst is some instantaneous measurement. Meanwhile, the time-variation naturally form a trajectory on the covariance matrix manifold. With this in mind, it makes much more sense to smooth the trajectory on the space of covariance matrices using proper metrics. The purpose of this paper is to take the geometry of covariance matrices into account while performing adequate covariance matrix estimation. Specifically, we propose a simple and elegant algorithm to track the covariance based on an update through means on Riemannian manifolds. This solution is then incorporated into an adaptive beamformer, and initial evaluations based on both simulated and real data show slight improvements compared to standard approaches.
Characterizing acoustic environments using spherical loudspeaker and microphone arrays
Authors: Gamper Hannes , Godin Keith , Raghuvanshi Nikunj , Tashev Ivan J.
Published: October 2018

Room acoustic parameters, including the reverberation time (T60) and the direct-to-reverberant ratio (DRR), quantitatively describe the behaviour of an acoustic environment. These parameters are typically derived from an acoustic impulse response (AIR) obtained using an omnidirectional sound source and an omnidirectional receiver. However, the acoustic interaction between a source with a complex radiation pattern, for example, a human talker, and a receiver with a complex directivity pattern, for example, a human listener, cannot be accurately described by an omnidirectional AIR or the acoustic parameters derived from it. Here, we propose characterizing acoustic environments while taking the source and receiver directionality into account. A spherical loudspeaker array allows modelling a source with an arbitrary radiation pattern. Analogously, a spherical microphone can be used to describe a receiver with an arbitrary directivity pattern. By combining spherical loudspeaker and microphone arrays, a multiple-input multiple-output (MIMO) AIR of an acoustic environment can be measured to simulate sources and receivers with arbitrary directivities and estimate acoustic parameters accordingly.
Iterative echo labeling technique for room geometry estimation
Authors: Park Soo Yeon , Choi Jung-Woo
Published: October 2018

Room geometry estimation using acoustic room impulse responses (RIRs) has been tackled in various ways. Most of them detect wall locations using the time of arrival (TOA) of echoes between multiple microphones and loudspeakers. To combine TOA information from multiple room impulse responses, echoes from the same walls should be collected and processed together. When multiple microphones are widely distributed in a room, however, it is hard to identify walls responsible for the generation of each echo. In this work, an iterative update algorithm is proposed for resolving the echo labeling problem with low computational complexity. Unlike conventional algorithms utilizing the rank property of Euclidean distance matrix, the proposed algorithm utilizes the property of convex hull formed by ellipses representing individual TOAs. The location of the reflectors are sequentially identified from common tangent lines constituting the convex hull, and the search result is iteratively updated by inspecting later echoes in time. In addition, a termination criterion is also developed in order to enable the geometry estimation without the prior knowledge of the number of the reflectors.
Analysis of sound field isotropy based on directional energy decay curves
Authors: Berzborn Marco , Vorlaender Michael
Published: October 2018

The analysis of the diffuseness of sound fields is of great interest in room acoustic applications ranging from the analysis of concert venues to reverberation room design and calibration. However, a standardized robust diffuseness estimation method is currently lacking. The fundamental definition of the diffuse sound field is that it is isotropic—requiring the sound field to be composed of infinitely many sound waves from uncorrelated sources with directions of arrival uniformly distributed over a sphere. Due to their symmetry, spherical microphone arrays are especially favorable for the analysis of the isotropy requirement. In this work, we propose the directional energy decay curve which we calculate from a directional room impulse response captured with a spherical microphone array. Further, we show how the analysis of the spatial variations of the directional energy decay curve enables examining the isotropy of sound fields in rooms. Finally, we present a simulation study of multiple room configurations with varying degrees of sound field diffuseness.
Postfiltering based on the coherent-to-diffuse power ratio
Authors: Günther Michael , Brendel Andreas , Kellermann Walter
Published: October 2018

In microphone array processing, the availability of multiple sensors observing an acoustic scene allows the extraction of additional spatial sound field properties. The coherent-to-diffuse power ratio (CDR) is a signal-dependent quantity which relates the coherent, typically desired, component and the diffuse, typically undesired, component of a recorded signal and can be employed in different signal enhancement tasks such as dereverberation and noise suppression. Given suitable models for the coherent and diffuse signal components, the complex spatial coherence function of the observed sound field facilitates an efficient estimation of the CDR. Several unbiased CDR estimators can be derived which differ in the sensitivity to estimation errors and the amount of incorporated prior information, e.g., the direction of arrival (DOA) of a desired point-like source. We review popular DOA-dependent and DOA-independent CDR estimators and investigate their efficacy in single-channel postfiltering when multiple point-like acoustic sources, i.e., one target source and at least one coherent interferer, are present.
Measurement of room spatial correlation functions using spherical microphone arrays
Authors: Elko Gary W. , Meyer Jens
Published: October 2018

The study of acoustic spatial correlation functions has been ongoing since early analytical development and experiments were done by Farran and Hills in 1952. The measurement of sound diffuseness using spatial correlation functions has been discussed previously by the authors in 2009. It has been conjectured that audio rendering of the spatial impression of a soundfield is related to the degree of correlation between the microphones used to record the soundfield. The correlation between the recorded channels is related to the diffuseness of the sound field. Many different models of diffuse fields have been described and are based on a definition that involves incoherent sound coming uniformly from all directions. Schroeder surmised that as the modal density exceeds three overlapping modes in one modal bandwidth that the random uniform model can be utilized in practice. In order to obtain measured room spatial correlation functions one has to ensemble average either multiple source or receiver positions. With eigenbeamforming spherical microphone arrays these functions can be ensemble averaged by utilizing multiple steered beampatterns with at least two spaced arrays. We will show some theoretical spatial correlation functions for different beampatterns and orientations and compare these to measurements made in a real room.
Effects of vessels and noise on the subsurface behavior of endangered killer whales (Orcinus orca)
Authors: Holt Marla M. , Hanson Brad , Emmons Candice , Tennessen Jennifer B. , Giles Deborah , Hogan Jeffery
Published: October 2018

Prey availability and disturbance from vessels and noise are identified threats to endangered Southern Resident killer whales. Vessel noise can mask echolocation signals used for hunting and/or disrupt foraging with implications for energy acquisition in a likely prey-limited population. We utilized suction cup-attached digital acoustic recording tags (DTAGs), to measure received noise levels, understand killer whales’ use of sound, and determine effects of vessels/noise on subsurface behavior. During the 28 tag deployments, we collected vessel data concurrently along with opportunistic predation observations to validate feeding. Broadband received levels (dB re 1μPa) were significantly different across years. Of the vessel factors considered, both vessel count and speed were significant explanatory variables of received levels. Vessels emitting echosounder signals were commonly received by the DTAGs and overlapped with the echolocation frequencies use to hunt fish. Additionally, different phases of foraging were differentiated from the acoustic record, including the detection of crunching sounds after fish kills. Together with movement data analysis, these results allow the identification of different whale activities, including prey capture dives, to test hypotheses of vessel/noise effects on behavior. This work, along with a comparative investigation involving Northern Resident DTAG data, inform killer whale conservation and management measures.
Attenuation compensation of ultrasound backscatter from human carotid plaque
Authors: James Sheronica L. , Fedewa Russell , Gornik Heather , Lyden Sean , Vince D. Geoffrey
Published: October 2018

Carotid atherosclerotic plaque composition may be a valuable predictor of stroke risk. Here, a patient adaptive attenuation compensation technique is introduced. A Siemens S3000, 9L4 probe and Axius Direct software were used to acquire radiofrequency (RF) data from 19 subjects prior to carotid endarterectomy. Histology slices of the excised plaque were prepared and matched to ultrasound frames. Regions of interest (ROI) were selected from a homogeneous area within the slide stack and matched to corresponding ROI’s in the RF data. ROI’s were categorized as fibrous (n = 32), hemorrhagic and/or necrotic core (n = 74), or calcium (n = 32). Additionally, 209 adventitia ROI’s were obtained from six normal subjects. ROI power spectra were computed and normalized to a uniform phantom. Five attenuation compensation methods were applied to the spectra: (1) reference phantom with 0.5 dB/cm-MHz attenuation; (2) nominal power spectral shift estimator; (3) optimum power spectral shift estimator; (4) normalized backscatter from adventitia; and (5) patient adaptive two-step attenuation compensation. A linear fit of the resulting estimated backscatter transfer functions (eBTF) was performed over the fundamental bandwidth of 3–7 MHz. Only the patient adaptive two-step attenuation compensation distinguished among the means of all four tissue types for the linear mid-band fit parameter.
Experimental reconstruction of sound speed and attenuation profiles
Authors: Mojabi Pedram , LoVetri Joe
Published: October 2018

Quantitative reconstruction of sound speed and attenuation profiles using ray-based approaches are considered. To this end, experimental datasets from two different ultrasound imaging systems are utilized. The first is our in-house system that is composed of a relatively small number of co-resident fixed piezo-electric transducers. The second, referred to as the MUBI system [Camacho, Archives of Acoustics, 2012], is equipped with many more transducers that can be rotated around the object-of-interest, allowing higher resolution reconstructions. The raw data collected from our system cannot be directly used in the reconstruction algorithms because various sources of noise and systematic errors corrupt the data. We compare the image reconstruction performance when different preprocessing techniques are applied to the raw data, as well as when various techniques of determining the time-of-arrival, such as the Akaike information criterion (AIC), are employed. The quantitative ray-based reconstruction algorithms are tested on simplistic tissue-mimicking phantoms [Mojabi & LoVetri, Submitted to IEEE UFFC, 2018].
Characterization of perfluorocarbon nanodrops with 18-MHz plane waves
Authors: Ketterling Jeffrey A. , Nguyen Tiffany-Trang , Fabiilli Mario L.
Published: October 2018

Perfluorocarbon (PF) nanodrops (NDs) undergo a phase change from liquid to vapor with an acoustic stimulation. Activation thresholds are established with relatively high-concentrations of NDs. Activating single NDs with high-frequency plane waves without the need to switch between transmit waveforms would allow uninterrupted high-speed imaging studies to be undertaken in microvasculature. Lipid-coated perfluoropentane (PFP) or perfluorohexane (PFH) NDs were made via sonication (S) or sonication and extrusion (SE). A control sample consisted of lipid blend (LB) without PF. A Verasonics Vantage with an 18-MHz array was used to acquire backscatter data from activated NDs. A test tank with a 200-μm diameter input flow channel was used to pass a diluted concentration of NDs into the image plane of the array. The injection flow rate was 55 mL/hr. Batches of 5 plane waves were transmitted over ± 5 degrees at an effective PRF of 1000 Hz. Data were collected over 10 s intervals and then processed to count activation events. An event was defined as a backscatter signal 25 dB above background noise. PFPSE showed the highest counts at a given pressure. Agents appeared to be activated prior to entering the image plane. PFPS cases showed a reduced rate of activation but with a similar linear rise. PFH and LB had minimal to no events. The data indicate a small fraction of the injected agents were activated but do not indicate a distinct activation threshold was reached.
Are phantom partials produced in piano strings?
Authors: Moore Thomas , Neldner Lauren , Rokni Eric
Published: October 2018

The anomalous frequency components in the sound from a piano, often referred to as phantom partials, were first noted almost 75 years ago. They occur at the sums and differences of the frequencies generated by the transverse motion of the string, and it is generally accepted that they are produced by longitudinal motion of the string that is associated with the normal transverse motion. Experimental evidence will be presented demonstrating that while some of the power in a phantom partial may originate in the string, most of it does not. A simple theory explaining how phantom partials may originate in the wooden components of the piano will be presented.
Overtone series in variable density strings
Authors: Elliott Greg S. , Jackson Martin , Russell Ethan
Published: October 2018

The vibrational mode frequencies of a taut string depend on the form of its mass distribution. To lowest order, deviations away from a uniform mass density that are even about the center of the string cause shifts in the overtones away from harmonic, while deviations that are odd do not. The problem of determining the overtone series for a given mass distribution is formulated and a full solution is derived for variations in the inverse mass density that are expressed as a Fourier cosine series. Variations arising from a single Fourier component predominantly shift the relative frequency of a single mode, with the 2nth Fourier component shifting the frequency of the nth mode. For a physically reasonable range of mass density variations, the frequency of a mode can typically be shifted by two semitones. Wrapped metal strings with variations in inverse mass density with different Fourier components have been fabricated, characterized, and tested. Light plucking produces overtones in agreement with the model; ordinary plucking produces incommensurate tones at sum and difference frequencies. Overtone series with several different major and minor tones are possible for variations involving more than one Fourier component.
How different strings affect violin qualities
Authors: Fu Lei , Scavone Gary , Fritz Claudia
Published: October 2018

The brand and model of strings used on violins are considered to play a significant role in their playability and sound quality. An experiment was designed to test the perceptual quality of different violin strings. A professional violinist selected two violins, from a set of the same make/model, that had similar sound and playing qualities. Three different types of strings were chosen for this study: Dominant, Kaplan, and Pro-Arté strings. Professional and advanced student violinists were invited to play and evaluate the violins. The experiment involved three phases: in the first phase, the two violins were strung with the same types of strings; in the last two phases, the strings of one of the violins was changed to the other two different types of strings (in a random manner). Violinists were asked to freely describe the differences of the two violins in each phase and rate them on eight specified criteria. Preliminary results indicate that the violin with Dominant strings was perceived as being more responsive and having a brighter sound, while that with the Pro-Arté strings was considered to have a richer sound and better overall quality.
Kuramoto and Sommerfeld: Toward comprehension of symphony orchestras in concert halls
Authors: Lee James B.
Published: October 2018

Given comprehension of physical acoustics in concert halls, an accurate replacement to the inadequate concatenation of reverberation theory, geometric acoustics, and Beranek’s “perceptual categories” that long has held the field in architectural acoustics, it remains to explain how the symphony orchestra couples to the space. Individual instruments do not couple to the space directly, but first to others in their respective sections: first violins to first violins, second violins to second violins, violas to violas, cellos to cellos, basses to basses, and so on through the winds, and others. Each section is synchronized in phase by a Kuramoto mean-field. Then the coherently radiating sections couple to each other asynchronously and create a unique propagating field according to the Sommerfield radiation condition. Kuramoto mean-field coupling is key, for absent that a section’s individual instruments would tend to randomize in phase and sum to zero power. The Sommerfeld radiation condition does not guarantee such a uniform field, only a unique one, the power and information of which are conveyed to the audience as constrained by the usual Gabor-Huygens principle: proximity effects and resonant scattering are essential.
Spatial release from masking in reverberation for children and adults with normal hearing
Authors: Peng Z. Ellen , Pausch Florian , Fels Janina
Published: October 2018

The ability to perform spatial release from masking (SRM), i.e., benefiting from a spatial separation between target and distracting talkers, is an important developmental skill for children to navigate noisy environments such as classrooms. While studies on children’s SRM were mostly conducted in anechoic rooms or sound booths to date, little is yet known how realistic room acoustics including reverberation in everyday listening affect this ability. In this study, we measured SRM from children and adults with normal hearing in virtual acoustic environments that mimic typical classrooms with different acoustic conditions. Two virtual classrooms were simulated with mean mid-frequency reverberation times (RTs) of 0.4 and 1.1 s, one within and the other poorer than the recommendation of classroom acoustics standard (ANSI S12.60). Overall, children performed more poorly than adults on both speech intelligibility and SRM. Children’s speech intelligibility of the target speech masked by distractor voices was better under the less reverberant condition. Interestingly, while adults showed better SRM under RT = 0.4 s, children did not perform any differently between the two RT conditions. The findings will be discussed for further investigation and implications for classroom acoustic designs. [Work supported by the EU 7th Framework Programme, ITN FP7-607139.]
Effects of measured acoustic and other indoor environment factors on student achievement in K-12 classrooms
Authors: Smith Kieren H. , Arthur Ann , Bovaird James , Wang Lily M.
Published: October 2018

Students can be affected by what they hear, see, and feel within the indoor classroom environment, whether or not it is cognizantly perceived by them. To understand how the indoor environment affects students' performance, measurements were logged in 220 K-12 classrooms in two Midwestern states during three seasons with two occupied days per season. Measurements of acoustics, indoor air quality, thermal comfort, and lighting were taken and a variety of metrics were calculated. For example, acoustic measurements provided reverberation time, clarity index, and equivalent sound levels during both active and inactive portions of the occupied school day. Achievement data in the form of percentile ranks on math and reading tests were also collected for the students who received instruction in each classroom. Structural equation models and multivariate linear regression models were utilized to analyze the effect of the indoor environment factors on student math and reading achievement. Significant findings, particularly in the area of acoustics, are presented and related to previous work in this area. [Work supported by the United States Environmental Protection Agency Grant Number R835633.]
Lombard effect in restaurant setting: How much would you spend to eat at this restaurant?
Authors: Bottalico Pasquale
Published: October 2018

The objective of this study is to determine the minimum level of noise in a restaurant that starts the Lombard effect, and how it relates to the perceived communication disturbance and the willingness to spend time and money for a meal. Twenty-eight participants were instructed to read a passage in the presence of restaurant noise from 35 dB(A) to 85 dB(A). As the noise level increased, participants began to be disturbed by the noise at 52 dB(A) and began to raise their voice at 57 dB(A). The willingness to spend time and money decreased starting at 52 dB(A).
Acoustic tweezer and its biomedical applications
Authors: Shung K. K.
Published: October 2018

Acoustic tweezer, the counterpart of optical tweezer in acoustics, was developed more than 10 years later than optical tweezer. It has been found to be capable of performing many tasks similar to optical tweezer but substantial differences also exist. Because of its larger wavelength, acoustic tweezer manipulates larger particles and yields larger forces in the nanonewton range. A number of biomedical applications have been studied including measuring intercellular forces and cellular mechanical properties. These results along with its physical principles will reviewed in this paper.
Applications of acoustic radiation force for material characterization and imaging
Authors: Fatemi Mostafa , Alizad Azra
Published: October 2018

Acoustic radiation force has been used in many interesting medical and industrial applications in the past two decades. The fact that radiation stress can be confined to a small focal area and exerted remotely inside or on an object allows one to use this phenomenon in a variety of ways to explore properties of the object. Vibro-acoustography is a material characterization and imaging method that uses harmonic or impulsive acoustic radiation force to stimulate the targeted material and receives the resulting acoustic response. The output acoustic signal is then used to extract important information about the object. Biomedical applications of vibro-acoustography and its closely related methods include imaging, flow detection, and tissue characterization. Other applications include non-destructive evaluation/testing of materials, modal analysis of small structures, and microscopy. This talk presents an overview of vibro-acoustography and its closely related techniques over the past 20 years. Various biomedical and industrial applications will be presented. The talk will conclude with a discussion on potential future applications of this technology.
Importance of translational research in audiology
Authors: Diedesch Anna C.
Published: October 2018

Students, postdocs, and junior research-faculty in audiology all face an interesting challenge: which conferences should I attend, and can I afford the time and likely financial burden associated with attending several meetings in one year? As research shifts towards translational topics, it becomes difficult to remain siloed within our respective fields. It is increasingly important for clinical researchers in audiology to communicate with specialized medical doctors, physiologists, engineers, psychoacousticians, etc. An example of such technological advancements that may contribute to the field of audiology are neuroimaging techniques and signal processing capabilities. For instance, enhanced imaging techniques allow for mapping the auditory pathway for different spatial cue information and auditory prostheses are now capable of retaining or supplementing binaural information through signal processing. But how many patients visit an audiologist with complaints of sound localization ability? In this example, it is critical for clinical researchers to be aware of physiological and technological advancements in order to appropriately translate spatial hearing research to the clinic. Here, I will discuss the benefit of clinicians attending translational auditory conferences by highlighting binaural hearing research and why attendance at translational conferences such as the Acoustical Society of America is essential for clinical research in audiology.
Blast exposure impairs sensory gating: Evidence from measures of acoustic startle and auditory event-related potentials
Authors: Papesh Melissa A. , Gallun Frederick J.
Published: October 2018

Many military Veterans who have been exposed to high-intensity blast waves suffer from traumatic brain injury (TBI), resulting in chronic auditory deficits despite normal hearing sensitivity. The current study examined the neurological cause of this chronic dysfunction by testing the hypothesis that blast exposure leads to impaired filtering of sensory information at brainstem and early cortical levels. Groups of blast-exposed and non-blast-exposed participants completed self-report measures of auditory status, auditory perceptual tasks, and physiological measures of sensory gating, including prepulse-inhibition and habituation of the acoustic startle reflex and electrophysiological assessment of a paired-click sensory gating paradigm. Blast-exposed participants showed significantly reduced habituation to acoustic startle stimuli and impaired filtering of redundant sensory information at the level the auditory cortex. Linear regression analyses revealed that poorer sensory gating at the cortical level was primarily influenced by a diagnosis of TBI, while reduced habituation was primarily influenced by a diagnosis of posttraumatic stress disorder. A statistical model was created including cortical sensory gating and habituation to acoustic startle, which strongly predicted performance on a degraded speech task. These results support the hypothesis that blast exposure impairs central auditory processing via impairment of neural mechanisms underlying habituation and sensory gating.
Subcortical neural correlates of behavior in the auditory system
Authors: Ramachandran Ramnarayan
Published: October 2018

One of the biggest open questions in neuroscience is the relationship between neuronal activity and behavior. Little is known in the auditory system about the nature of the relationship between stimulus encoding and perception. To shed light on this topic, we recorded responses of single neurons in the central nucleus of the inferior colliculus (CNIC) and cochlear nucleus (CN) of macaques that were trained to detect tones or vowels during behavioral performance. Using signal detection theoretic methods, we determined that neurometric tone and vowel detection thresholds based on rate measures in CNIC matched behavioral thresholds, while thresholds of CN neurons were higher than behavior. Additionally, the response magnitudes of a majority of the CNIC neurons varied significantly depending on the behavioral accuracy, compared to a much smaller proportion of CN neurons. Analysis of temporal patterns of response (e.g., phase locking) suggests that neurometric thresholds of all CN and most CNIC neurons matched behavioral thresholds during vowel detection. Additionally, every CNIC and CN neuron showed significant response pattern differences based on behavioral accuracy. These results suggest that behaviorally relevant coding early in the pathway is temporal in nature and is transformed to more rate based measures at higher levels of processing.
The role of central processing in modulation masking release
Authors: Alamatsaz Nima , Ihlefeld Antje
Published: October 2018

When background sound is present, hearing impaired (HI) individuals and cochlear-implant (CI) listeners typically are worse at hearing out target sound as compared to normal-hearing (NH) listeners. This perceptual deficit occurs both when the background consists of noise that fluctuates over time (“modulated”) and for stationary background noise (“unmodulated”). In addition, the difference in thresholds between tone detection in modulated and unmodulated noise, referred to as modulation masking release (MMR), is much reduced or absent in HI and CI as compared to NH. Both peripheral and central processing mechanisms contribute to MMR. We previously showed that central MMR is reduced in human CI listeners, and that sound deprivation reduces central MMR in Mongolian gerbils. Here, we began to explore the neurobiological basis of central MMR. NH gerbils were trained to hear out target tones (1 kHz) in modulated (10-Hz rectangularly gated) versus unmodulated bandlimited background noise, and chronically implanted with recording electrodes in core auditory cortex. Neural discharge was analyzed as a function of the broadband energy ratio between target and background sound to determine how different types of background sound affect neural information transmission in awake behaving gerbil. Preliminary results will be discussed in the context of how hearing loss may affect central MMR.
Neighborhood-conditioned coarticulation effects in French listener-directed speech
Authors: Scarborough Rebecca , Fougeron Cécile , Marques Luciana
Published: October 2018

Words from dense phonological neighborhoods (Hi-ND words) are realized with greater vowel hyperarticulation and increased coarticulation in English, relative to words from sparser neighborhoods (Lo-ND words) [e.g., Wright 2004]. Here, the relation between coarticulation and neighborhood density is investigated for French by looking at patterns for anticipatory and carryover nasal coarticulation, coronal and uvular CV coarticulation, and V-to-C rounding coarticulation. Twelve native French speakers (northern France) produced 82 disyllabic words of French containing a context for one of these 5 types of coarticulation in phonetically similar high-low ND pairs. Test words were produced to a real listener who had to transcribe them in the instructed positions on a grid. F1, F2, and A1-P0 (a spectral measure of nasality) were measured at 5 timepoints across each test vowel. In addition to having more hyperarticulated (peripheral) vowel midpoints, Hi-ND words showed greater anticipatory nasality and stronger coronal transitions in appropriate contexts than Lo-ND words. Carryover nasality and uvular and rounding coarticulation did not differ across NDs. These results can be interpreted in light of the relation between coarticulation and contrast and the role these effects may serve in making Hi-ND words, which are subject to greater lexical competition, easier to perceive.
Speech-like movements emerge from simulated peri-oral muscle activation space without neural control
Authors: de Vries Jonathan M. , Stavness Ian , Fels Sid , Gick Bryan
Published: October 2018

Muscle synergies have been proposed as a solution to the degrees of freedom problem inherent in the biomechanics of speech production [Gick & Stavness, 2013, Front. Psych, 4, 977]. However, the majority of experiments involving the extraction of muscle synergies prove theoretically insufficient to determine whether such synergies are of neural origin or simply reflect the lower dimensionality of an under-sampled biomechanical/neural task space [Kutch & Valero-Cuevas, 2012, PLoS computational biology, 8(5), e1002434]. Therefore, to what extent biomechanics of the human vocal tract may constrain the “ecological state space” of a speaker during locution remains uninvestigated. As a proof of concept, we created a simplified version of the peri-oral region using FEM modeling in a physics-based simulator (ArtiSynth [Lloyd et al., 2012, Soft tissue biomech…surgery, pp. 355]). Systematic simulations enabled us to model the full kinematic/biomechanical space. Visualization of the resulting biomechanical state space using t-SNE [van der Maaten & Hinton, 2008, J.MLR., 9, 2579] illustrates that speech-like movements (e.g., lip rounding or spreading) emerge as self-organizing structures (muscle synergies) critically without a direct neural controller. These results are discussed in the context of current and future explorations of motor control of speech. [Funded by NSERC.]
Differences in clear speech strategies across read and spontaneous speech produced in interactive tasks for young and older adults
Authors: Hazan Valerie , Tuomainen Outi
Published: October 2018

This study investigates whether clear speech strategies vary according to the demands of the task used for eliciting clear speech. Spontaneous speech involves greater planning than sentence reading and this might particularly affect talkers who find communication more effortful. 77 talkers (24 young and 53 older adults) carried out two collaborative tasks with a conversational partner in two listening conditions. The “read” task involved reading a sentence to the partner who repeated it back; the “spontaneous” task involved completing the diapix problem-solving task. Partners either heard each other easily (NORM) or communicated with the partner having a simulated profound loss, naturally eliciting clear speech (CLEAR). The percentage relative change between NORM and CLEAR was calculated for articulation rate, long-term average spectrum, fundamental frequency, vowel formant ranges. Analyses focus on task and age effects. There were significant task [F(1,75) = 10.27;p = 0.002, η2 = 0.886] and task by measure effects [F(5,375) = 17.97;p<0.001, η2 = 0.193], with a greater reduction in articulation rate for read (M = -27.3%) than spontaneous (M=-9.2%) speech, p<0.001. Task effects did not vary significantly with talker age. In summary, the use of read speech may over-emphasise the role of articulation rate as a clear speaking style strategy but this was the case for young and older talkers.
Do speakers maintain clear speech throughout natural conversation?
Authors: Lee Dae-yong , Baese-Berk Melissa M.
Published: October 2018

Previous studies have shown that speakers tend to speak more clearly when they speak with a listener in adverse listening conditions in naturalistic settings. Most previous studies assumed that when speakers speak more clearly, they maintain the style throughout the conversation. However, a clear speech style deviates from speakers’ conversational speaking style, and extra effort is required in order to produce clear speech. Therefore, it is possible that speakers begin a conversation in a clear speaking style and revert back to a conversational style at some point during the conversation. This study aims to examine whether native English speakers use and maintain a clear speaking style while participating in a conversation with non-native speakers in naturalistic settings. Native English listeners will respond to sentences from naturalistic conversations. The sentences are from either a conversation between two native English speakers or a conversation between a native English speaker and a non-native English speaker. Intelligibility (typing what the listeners heard) and comprehensibility (rating how easy it is to understand the sentences) are measured to examine the usage of clear speech throughout the conversations. The results of this study will provide a better understanding of the circumstances under which speakers use clear speech.
The role of vertical larynx movement in the tense-lax contrast of Seoul Korean stops across phrasal position
Authors: Lee Yoonjeong , Goldstein Louis
Published: October 2018

In contemporary Seoul Korean (SK), phrasal tone patterns are co-active with tone patterns that distinguish tense and lax stops. Utilizing real-time MRI, the current investigation of the SK stops elucidates the articulatory synergies that distinguish tense versus lax and how they function within SK’s Accentual Phrase (AP) prosodic system. The f0 and corresponding larynx height values were measured from sequences containing the three oral stops of SK placed in AP-initial and AP-internal prosodic positions. Larynx height was obtained by finding the intensity centroid within a locally selected region in the MR image around the larynx. We find a strong positive correlation between f0 and larynx height, indicating that vertical larynx movement is engaged in some tonal manipulation. We confirm the categorical consonant effect on f0 AP-initially (tense >> lax), compared to a gradient effect AP-internally (tense >= lax). In AP-initial position, the larynx height results mirror the f0 results, suggesting that the f0 goals associated with tenseness result in large part from a vertical larynx position manipulation. In AP-internal position, however, larynx height does not differentiate tense versus lax consonants, suggesting that some other articulatory activity, such as vocal fold stretching, is responsible for its f0 variations. [Work supported by NIH.]
A computational study of the role of laryngeal muscles in vocal fold posturing
Authors: Zheng Xudong , Pham Ngoc , Geng Biao , Xue Qian
Published: October 2018

This work aims at using a three-dimensional finite element method to simulate the contraction of different laryngeal muscles, and to study the role of each or groups of muscles in vocal fold posturing. A Hill-based contractile model is coupled in the finite element analysis to capture the active response of the vocal folds, and a fiber-reinforced model is employed to model the passive response. A 1D flow model and 1D acoustic solver are coupled with the vocal fold model to simulate the flow-structure-acoustics interaction. In the simulation, the geometry of the vocal folds and cartilages is reconstructed from a MRI scan. The coupled Hill-based contractile model and fiber-reinforced tissue model shows good agreement with literature data for simulating dynamics, concurrent tissue stimulation and stretching. It is found that the contraction of cricothyroid (CT) muscle alone lengthens the vocal folds by rotating the thyroid cartilage clockwise, around the cricoid-thyroid joint, whereas the contraction of cricoarytenoid (CA) muscle causes vocal fold abduction. The contraction of TA muscle and arytenoid muscles, on the other hand, adduct the vocal folds. The effect of muscle contraction on subglottic pressure during voice production is also shown in flow-structure-acoustics interaction simulations.
Using ultrasound to examine contrastive hyperarticulation
Authors: Hall Kathleen C. , Fullerton Geoff , McMullin Kevin
Published: October 2018

The current paper examines the extent to which there is cross-linguistic evidence for the hyperarticulation of more phonologically contrastive vowel sounds. Hall et al. [2017, JCAA 45: 15] found that tense vowels in English are produced with more total tongue movement when in positions where they are more phonologically contrastive. This finding was established through the use of Optical Flow Analysis [Horn & Schunck 1981] on ultrasound videos of the tongue. The “more contrastive” positions were those in which the vowels could contrast with their lax vowel counterparts, while the “less contrastive” positions were those in which no such contrast was possible. While there was evidence that the degree of contrast affected the tongue movements, the data were somewhat confounded by the fact that the more contrastive positions were largely closed syllables, while the less contrastive positions were largely open syllables. In the current paper, we first replicate the original results with more tightly controlled phonetic contexts in English and then examine analogous results for Canadian French. Crucially, in Canadian French, [e] vs. [ɛ] contrast in open syllables and not in closed, such that the effects of syllable position and phonological contrast can be teased apart. [Funded by SSHRC.]
Towards higher precision in vocal tract length estimation
Authors: Flego Stefon M.
Published: October 2018

Approaches to vocal tract length (VTL) estimation typically differ in how much credibility is allocated to certain formants as predictors of length, but are alike in allocating equal credibility to all vowel spectra. The latter may be problematic, as asymmetries in the phonotactic frequency of certain vowels and measurement errors for higher formants can influence VTL estimates. Herein, an additional parameter is proposed which privileges vowel spectra that approximate a uniform tube. The proposed metric for this proximity is standard variance (σ) in Φ, where Φ=Fn/(2n-1), n represents the integer label of the formant, and σΦ for a uniform tube is 0. The five estimators detailed in Lammert & Narayanan (2015) were tested on the speech of two adult males. Each of the estimators were run using all vowel spectra as well as only those for which σΦ < 50 Hz. Estimates from all vowel spectra had σVTL well above 1 cm, which is undesirably large, given that the adult vocal tract only ranges from 13 to 20 cm. However, estimates from vowel spectra with σΦ < 50Hz had σVTL less than 1 cm. This higher precision is especially striking since spectra with σΦ < 50 Hz constituted a small fraction of the total.