bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Gilmore-Akulichev’s, Keller-Miksis’s and Rayleigh-Plesset’s equations on therapeutic ultrasound bubble cavitation
Authors: Hu Zhong , Xu Jin , Bigelow Timothy A.
Published: October 2014

Many models have been utilized to simulate inertial cavitation for ultrasound therapies such as histotripsy. The models range from the very simple Rayleigh-Plesset model to the complex Gilmore-Akulichev model. The computational time increases with the complexity of the model, so it is important to know when the results from the simpler models are sufficient. In this paper the simulation performance of the widely used Rayleigh-Plesset model, Keller-Miksis model, and Gilmore-Akulichev model both with and without gas diffusion are compared by calculating the bubble radius response and bubble wall velocity as a function the ultrasonic pressure and frequency. The bubble oscillates similarly with the three models within the first collapse for small pressures (<3MPa), but the Keller-Miksis model diverges at higher pressures. In contrast, the maximum expansion radius of the bubble is similar at all pressures with Rayleigh-Plesset and Gilmore-AKulichev although the collapse velocity is unrealistically high with Rayleigh-Plesset model. After multiple cycles, the Rayleigh-Plesset model starts to behave disparately both in the expansion and collapse stages. The inclusion of rectified gas diffusion lengthens the collapse time and increases the expansion radius. However, for frequency smaller than 1 MHz, the impact of gas diffusion is not significant.
Removal of residual bubble nuclei to enhance histotripsy soft tissue fractionation at high rate
Authors: Duryea Alexander P. , Cain Charles A. , Roberts William W. , Hall Timothy L.
Published: October 2014

Previous work has shown that the efficacy of histotripsy soft tissue fractionation is dependent on pulse repetition frequency, with histotripsy delivered at low rates producing more efficient homogenization of the target volume in comparison to histotripsy delivered at high rates. This is attributed to the cavitation memory effect: microscopic residual cavitation nuclei that persist for hundreds of milliseconds following bubble cloud collapse can seed the repetitive nucleation of cavitation at a discrete set of sites within the target volume, producing heterogeneous lesion development. To mitigate this effect, we have developed low amplitude (MI<1) acoustic pulses to actively remove residual nuclei from the field. These bubble removal pulses utilize the Bjerknes forces to stimulate the aggregation and subsequent coalescence of remnant nuclei, consolidating the population from a very large number to a countably small number of remnant bubbles within several milliseconds. The effect is attainable in soft tissue mimicking phantoms following a very minimal degree of fractionation (within the first ten histotripsy pulses). Incorporation of this bubble removal scheme in histotripsy tissue phantom treatments at high rate (100 pulses/second) resulted in highly homogeneous lesions that closely approximated those achieved using an equal number of pulses applied at low rate (1 pulse/second); lesions generated at high rate without bubble removal had heterogeneous structure with increased collateral damage.
Two-dimensional speckle tracking using zero phase crossing with Riesz transform
Authors: Almekkawy Mohamed Khaled , Adibi Yasaman , Zheng Fei , Chirala Mohan , Ebbini Emad S.
Published: October 2014

Ultrasound speckle tracking provides robust estimates of fine tissue displacements along the beam direction due to the analytic nature of echo data. We introduce a new multi-dimensional ST method (MDST) with subsample accuracy in all dimensions. The algorithm based on the gradient of the magnitude and the zero-phase crossing of 2D complex correlation of the generalized analytic signal. The generalization method utilizes the Riesz transform which is the vector extension of the Hilbert transform. Robustness of the tracking algorithm is investigated using a realistic synthetic data sequences created with (Field II) for which the bench mark displacement was known. In addition, the new MDST method is used in the estimation of the flow and surrounding tissue motion on human carotid artery in vivo. The data was collected using a linear array probe of a Sonix RP ultrasound scanner at 325 fps. The vessel diameter has been calculated from the upper and lower vessel walls displacement, and clearly shows a blood pressure wave like pattern. The results obtained show that using Riesz transform produces more robust estimation of the true displacement of the simulated model compared to previously published results. This could have significant impact on strain calculations near vessel walls.
1-MHz ultrasound stimulates in vitro production of cardiac and cerebrovascular endothelial cell vasodilators
Authors: Ammi Azzdine Y. , Davis Catherine M. , Mott Brian , Alkayed Nabil J. , Kaul Sanjiv
Published: October 2014

Ultrasound exposure of the heart and brain during vessel occlusion reduces infarct size. Our aim was to study the production of vasodilatory compounds by endothelial cells after ultrasound stimulation. A 1.05-MHz single element transducer was used to insonify primary mouse endothelial cells (ECs) from heart and brain with a 50-cycle tone burst at a pulse repetition frequency of 50 Hz. Two time points were studied after ultrasound exposure: 15 and 45 minutes. In heart ECs, EETs levels increased significantly with 0.5 MPa (139 ± 16%, p<0.05) and 0.3 MPa (137 ± 15%, p<0.05) at 15 and 45 min post stimulation, respectively. HETEs and DHETs did not change significantly. There was a trend toward increased adenosine, with maximum release at 0.5 MPa (332 ± 73% vs. 100% control, p<0.05). The trend toward increased eNOS phosphorylation was greater at 15 than 45 min. In brain ECs adenosine release was increased, however increased eNOS phosphorylation was not significant. 11, 12- and 14, 15- EETs were increased while 5- and 15-HETEs were decreased. Pulsed ultrasound at 1.05 MHz has the ability to increase adenosine, p-eNOS, and EET production by cardiac and cerebrovascular ECs. Interestingly, in brain ECs, the vasoconstricting HETEs were decreased.
Vibration sensitivity measurements of silicon and acoustic-gradient microphones
Authors: Reese Marc C.
Published: October 2014

Microphones are often required to record audio while in a vibration environment. Therefore, it is important to maximize the acoustic-to-vibration sensitivity of such microphones. It has previously been shown that the vibration sensitivity of a microphone is, to first order, proportional to the mass per unit area of the diaphragm including the air loading effect. Although the air loading is generally minimal for omnidirectional condenser microphones with thick diaphragms, these measurements show that it cannot be ignored for newer silicon-based micro-electro-mechanical-system (MEMS) and acoustic-gradient microphones. Additionally, since microphone vibration sensitivities are typically not reported by microphone manufacturers, nor measured using standardized equipment, the setup of an inexpensive vibration measurement apparatus and associated challenges are discussed.
An analysis of multi-year acoustic and energy performance data for bathroom and utility residential ventilation fans
Authors: Choi Wongyu , Gomez Antonio , Pate Michael B. , Sweeney James F.
Published: October 2014

Loudness levels have been established as a new requirement in residential ventilation standards and codes including ASHRAE and IECC. Despite the extensive application of various standards and codes, the control of loudness has not been a common target in past whole-house ventilation standards and codes. In order to evaluate the appropriate loudness of ventilation fans, especially in terms of leading standards and codes, a statistical analysis is necessary. Therefore, this paper provides statistical data for bathroom and utility ventilation fans over a nine year period from 2005 to 2013. Specifically, this paper presents an evaluation of changes in fan loudness over the 9 year test period and the relevance of loudness to leading standards including HVI and ASHRAE. The loudness levels of brushless DC-motor fans are also evaluated in comparison to the loudness of AC-motor fans. For AC and DC motor fans, relationships between loudness and efficacy was determined and then explained with regression models. Based on observations, this paper introduces a new “loudness-to-energy ratio” coefficient, L/E, which is a measure of the acoustic and energy performance of a fan. Relationships between acoustic and energy performances are established by using L/E coefficients with supporting statistics for bathroom and utility fans.
New compensation factors for the apparent propagation speed In transmission line matrix uniform grid meshes
Authors: Brandao Alexandre , Cataldo Edson , Leta Fabiana R.
Published: October 2014

Numerical models consisting of two-dimensional (2D) and three-dimensional (3D) uniform grid meshes for the Transmission Line Matrix Method (TLM), use sqrt(2) and sqrt(3), respectively, to compensate for the apparent sound speed. In this work, new compensation factors are determined from a priori simulations, performed without compensation, in 2D and 3D TLM one-section cylindrical waveguide acoustic models. The mistuned resonance peaks obtained from these simulations are substituted in the corresponding equations for the resonance frequencies in one-section cylindrical acoustical waveguides to find the mesh apparent sound speed and, thus, the necessary compensation. The TLM meshes are constructed over the voxels (Volumetric Picture Elements) of segmented MRI volumes, so that the extracted mesh fits the segmented object. The TLM method provides a direct simulation approach instead of solving a PDE by variational methods that must consider the plane wave assumption to run properly. Results confirm the improvement over the conventional compensation factors, particularly for frequencies above 4 kHz, providing a concrete reduction of the topology-dependent numerical dispersion for both 2D and 3D TLM lattices. Since this dispersion problem is common to all TLM applications using uniform grids, investigators in other areas of wave propagation can also benefit from these findings.
A low-cost alternative power supply for integrated electronic piezoelectric transducers
Authors: Brum Ricardo , Aguirre Sergio L. , Paul Stephan , Corrêa Fernando
Published: October 2014

Comercial hardware compatible with IEPE precision sensors normally are expensive and often coupled to proprietary and expensive software packages. commercially available sound cards are a low cost option for AD, but are incompatible with IEPE sensors. To create 4 mA constant current for IEPE transducers commercial solutions are available and labs also have created such solutions, e.g., ITA at RWTH Aachen University. Unfortunately, commercially available circuits are still to expensive for large scale classroom use in Brazil and circuits created elsewhere contain parts subject to US export restrictions or require machines for creation of circuits. Thus, based on a previous project, a new low-cost prototype was mounted on phenolic board. The circuit was tested with an IEPE microphone connected to a commercial soundcard and ITA-Toolbox software and compared to a commercial hardware/software package. The results were very similar in the frequency range between 20 Hz and 10 kHz. The difference below 20 Hz probably occurs due the different high pass filters in the AD-cards. The differences in the high frequency range are very likely due to differences in the electrical background noise. The results suggest the device works well and is a good alternative to make measurements with IEPE sensors.
Investigating the colloquial description of sound by musicians and non-musicians
Authors: Dostal Jack
Published: October 2014

What is meant by the words used in a subjective judgment of sound? Interpreting these words accurately allows these musical descriptions of sound to be related to scientific descriptions of sound. But do musicians, scientists, instrument makers, and others mean the same things by the same words? When these groups converse about qualities of sound, they often use an expansive lexicon of terms (bright, brassy, dark, pointed, muddy, etc.). It may be inaccurate to assume that the same terms and phrases have the same meaning to these different groups of people or even remain self-consistent for a single individual. To investigate the use of words and phrases in this lexicon, subjects with varying musical and scientific backgrounds were surveyed. The subjects were asked to listen to different pieces of recorded music and asked to use their own colloquial language to describe the musical qualities and differences they perceived in these pieces. In this talk, I describe some qualitative results of this survey and identify some of the more problematic terms used by these various groups to describe sound quality.
Experiment to evaluate musical qualities of violin strings
Authors: Baelde Maxime , De Saedeleer Jessica , Hermand Jean-Pierre
Published: October 2014

Most of violin strings on the market are made of different materials and size. They have different musical qualities: full, mellow, warm, and round, for example. Nevertheless, this description is subjective and related to string manufacturers. The aim of this study is to provide an experiment which gives an evaluation of the musical qualities of strings. This study is based on “musical descriptors,” which gives information about a musical sound and psychoacoustics in order to match the musician point of view. “Musical descriptors” are also used for music classification. We use two sets of top-end strings model from two different brands. These strings are mounted on two similar violins and the strings are excited on their normal modes with harpsichord damper mechanism like and other means. The sound radiated is recorded with a microphone and the vibration of the string with a coil-magnet device so as to have intrinsic and extrinsic string properties. Some musicians tried these strings and expressed what they thought about it. These acoustical and psychoacoustical analyzes will give information to the luthiers to know what string property allow one adjustment, in order to provide better advice aside from string manufacturers descriptions.
Vibration study of Indian folk instrument sambal
Authors: Surve Ratnaprabha F. , Desa Keith , Joaj Dilip S.
Published: October 2014

The percussion instruments family, in its folk category has many instruments like Dholki, Dimdi, Duff, Halagi, and Sambal. The Sambal is a folk membranophone made up of wood, played mainly in western India. Sambal a traditional drum, which is used in some religious functions. It is played by the people who are believed to be servants of goddess Mahalaxmi Devi. This instrument is made up of two approximately cylindrical wooden drums united along a common edge, having skin membranes stretched over their mouths. This instrument is played using two wooden sticks, of which one has a curved end. The right hand side drum’s pitch is higher than the left. Its membrane is excited by striking repeatedly to generate sound of a constant pitch. This paper relates to vibrational analysis of the Sambal. A study has been carried out to check it’s vibrational properties like modes of the vibration. The study is done by spectrum analysis (Fast Fourier Transform) using a simple Digital Storage Oscilloscope. The tonal quality of wood used for the cylinders and membrane is compared.
Recent advances in aircraft source noise synthesis
Authors: Rizzi Stephen A. , Palumbo Daniel L. , Hardwick Jonathan R. , Christian Andrew
Published: October 2014

For several decades, research and development has been conducted at the NASA Langley Research Center directed at understanding human response to aircraft flyover noise. More recently, a technology development effort has focused on the simulation of aircraft flyover noise associated with future, large commercial transports. Because recordings of future aircraft are not available, the approach taken utilizes source noise predictions of engine and airframe components which serve as a basis for source noise syntheses. Human subject response studies have been conducted aimed at determining the fidelity of synthesized source noise, and the annoyance and detectability once the noise is propagated (via simulation) to the ground. Driven by various factors, human response to less common noise sources are gaining interest. Some have been around for a long time (rotorcraft), some have come and gone, and are back again (open rotors), and some are entirely new (distributed electric driven propeller systems). Each has unique challenges associated with source noise synthesis. Discussed in this work are some of those challenges including source noise characterization from wind tunnel data, flight data, or prediction; factors affecting perceptual fidelity including tonal/broadband separation, and amplitude and frequency modulation; and a potentially expansive range of operating conditions.
Simulated sound in advanced acoustic model videos
Authors: Plotkin Kenneth
Published: October 2014

The Advanced Acoustic Model (AAM) and other time-step aircraft noise simulation models developed by Wyle can generate video animations of the noise environment. The animations are valuable for understanding details of noise footprints and for community outreach. Using algorithms developed by NASA, audio simulation for jet aircraft noise has recently been added to the video capability. Input data for the simulations consist of AAM’s one-third octave band sound level time history output, plus flight path geometry and ground properties. Working at an audio sample rate of 44.1 kHz and a sample “hop” period of 0.0116 s, a random phase narrow band sample is shaped to match spectral amplitudes. Ground reflection and low frequency oscillation are added to the hops, which are merged into a WAV file. The WAV file is then mixed with an existing animation generated from the same AAM run. The process takes place in near-real time, based on a location that a user selects from a site map. The presentation includes demonstrations of the results for a simple level flyover and for the departure of a high performance jet aircraft from an airbase.
A comparison of subjects' annoyance ratings of rotorcraft noise in two different testing environments
Authors: McMullen Andrew , Davies Patricia
Published: October 2014

Two subjective tests were conducted to investigate people's responses to rotorcraft noise. In one test subjects heard the sounds in a room designed to simulate aircraft flyovers. The frequency range of the Exterior Effects Room (EER) at NASA Langley is 17 Hz to 18,750 Hz. In the other test, subjects heard the sounds over earphones and the frequency range of the playback was 25 Hz–16 kHz. Some of the sounds in this earphone test, high-pass filtered at 25 Hz, were also played in the EER. Forty subjects participated in each of the tests. Subjects' annoyance responses in each test were highly correlated with EPNL, ASEL, and Loudness exceeded 20% of the time (correlation coefficient close to 0.9). However, at some metric values there was a large variation in response levels, which could be linked to characteristics of harmonic families present in the sound. While the results for both tests are similar, subjects in the EER generally found the sounds less annoying than the subjects who heard the sounds over earphones. Certain groups of signals were rated similarly in one test environment, but differently in the other. This may be due to playback method, subject population, or other factors.
Separation of acoustic waves in isentropic flow perturbations
Authors: Henke Christian
Published: October 2014

The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. It is based on the linearisation of the isentropic Navier-Stokes equation around a new pathline-averaged base flow. As a consequence of this unsteady and non-radiating base flow, the perturbation equations satisfy a conservation law. It is demonstrated that this flow perturbations can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Moreover, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfills Lighthill's acoustic analogy. Therefore, we can define the deviations from the convective wave equation as the “true” sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary.
The sliding mode controller on the rijke-type combustion systems with mean temperature gradients
Authors: Zhao Dan , Li Xinyan
Published: October 2014

Thermoacoustic instabilities are typically generated due to the dynamic coupling between unsteady heat release and acoustic pressure waves. To eliminate thermoacoustic instability, the coupling must be somehow interrupted. In this work, we designed and implemented a sliding mode controller to mitigate self-sustained thermoacoustic oscillations in a Rijke-type combustion system. An acoustically-compact heat source is confined and modeled by using a modified King’s Law. The mean temperature gradient is considered by expanding the acoustic waves via Galerkin series. Coupling the unsteady heat release with the acoustic model enables the flow disturbances to be calculated, thus providing a platform on which to evaluate the performance of the controller. As the controller is actuated, the limit cycle oscillations are quickly dampened and the thermoacoustic system with multiple eigenmodes is stabilized. The successful demonstration indicates that the sliding mode controller can be applied to stabilize unstable thermoacoustic systems.
Feedback control of thermoacoustic oscillation transient growth of a premixed Laminar flame
Authors: Zhao Dan , Li Xy
Published: October 2014

Transient growth of combustion-excited oscillations could trigger thermoacoustic instability in a combustion system with nonorthogonal eigenmodes. In this work, feedback control of transient growth of combustion-excited oscillation in a simplified thermoacoustic system with Dirichlet boundary conditions is considered. For this a thermoacoustic model of a premixed laminar flame with an actuator is developed. It is formulated in state-space by expanding acoustic disturbances via Galerkin series and linearizing flame model and recasting it into the classical time-lag N-τ for controllers implementation. As a linear-quadratic-regulator (LQR) controller is implemented, the system becomes asymptotically stable. However, it is associated with transient growth of thermoacoustic oscillations, which may potentially trigger combustion instability. To eliminate the oscillations transient growth, a strict dissipativity controller is then implemented. Comparison is then made between the performances of these controllers. It is found that the strict dissipativity controller achieves both exponential decay of the oscillations and unity maximum transient growth.
Application of Mach-Zehnder interferometer to measure irregular reflection of a spherically divergent N-wave from a plane surface in air
Authors: Karzova Maria M. , Yuldashev Petr V. , Ollivier Sebastien , Khokhlova Vera A. , Blanc-Benon Philippe
Published: October 2014

Mach stem is a well-known structure typically observed in the process of strong (acoustical Mach numbers greater than 0.4) step-shock waves reflection from a rigid boundary. However, this phenomenon has been much less studied for weak shocks in nonlinear acoustic fields where Mach numbers are in the range from 0.001 to 0.01 and pressure waveforms have more complicated temporal structure than step shocks. In this work, the results are reported for Mach stem formation observed in the experiment of N-wave reflections from a plane surface. Spherically divergent N-waves were generated by a spark source in air and were measured using a Mach-Zehnder interferometer. Pressure waveforms were reconstructed using the inverse Abel transform applied to the phase of the interferometer measurement signal. Temporal resolution of 0.4 μs was achieved. Regular and irregular types of reflection were observed. It was shown that the length of the Mach stem increased linearly while the N-wave propagated along the surface. In addition, preliminary results of the influence of surface roughness on the Mach stem formation will be presented. [Work supported by the President of Russia MK-5895.2013.2 grant, student stipend from the French Government, and by LabEx CeLyA ANR-10-LABX-60/ANR-11-IDEX-0007.]
High temperature resonant ultrasound spectroscopy study on Lead Magnesium Niobate—Lead Titanate (PMN-PT) relaxor ferro-electric material
Authors: Tennakoon Sumudu P. , Gladden Joseph R.
Published: October 2014

Lead magnesium niobate-lead titanate [(1-x)PbMg1/3Nb2/3O3-xPbTiO3] is a perovskite relaxor ferroelectric material exhibiting superior electromechanical coupling compared to the conventional piezoelectric materials. In this work, non-poled single crystal PMN-PT material with the composition near morphotropic phase boundary (MPB) was investigated in the temperature range of 400 K—800 K where the material is reported to be in the cubic phase. High temperature resonant ultrasound spectroscopy (HT-RUS) technique was used to probe temperature dependency of elastic constants derived from the measured resonant modes. Non-monotonic resonant frequency trends in the temperature regime indicate stiffening of the material, followed by gradual softening typically observed in heated materials. Elastic constants confirmed this stiffening in the temperature range of 400 K—673 K, where the stiffness constants C11 and C44 increased approximately by 40% and 33% respectively. Acoustic attenuation, derived from the quality factor (Q), exhibits a minimum around the temperature where the stiffness is maximum and, significantly higher attenuation observed at temperatures below 400 K. The temperature range 395 K—405 K was identified as a transition temperature range, where the material showed an abrupt change in the resonant spectrum and, the material emerges from the MPB characterized by this very high acoustic attenuation. This transition temperature compares favorably with dielectric constant measurements reported in the literature.
Structure of cavitation zones in a heavy magma under explosive character of its decompression
Authors: Kedrinskiy Valeriy
Published: October 2014

The paper is devoted to the investigation of a dynamics of state and structure of compressed magma flow saturated by gas and microcrystallites which is characterized by phase transitions, diffusive processes, by increase of a magma viscosity magnitude by the orders and bubbly cavitation development behind the decompression wave front formed in the result of volcanic channel depressurization. The multi-phase mathematical model, which includes well-known conservation laws for mean pressure, mass velocity, and density as well as the system of the kinetic equations describing the physical processes that occur in a compressed magma during its explosive decompression, is considered. The results of numerical analysis show that the processes of a magma saturation by cavitation nuclei as their density magnitude increases by a few orders lead to the formation of separate zone with anomalously high values of the flow parameters. As it has turned out the abnormal zone is located in the vicinity of a free surface of a cavitating magma column. The mechanism of its formation is determined by diffusion flows redistribution as the nuclei density increases as well as by the change of the distribution character of main flow parameters in the abnormal zone from a gradual to an abrupt increase of their values on the lower zone bound. Note, the mass velocity jump by the order magnitude relatively main flow allows to conclude that the flow disintegration on the lower bound of the zone is quite probable. [Supp. RAS Presidium Program, Project 2.6].
Aging as a window into central auditory dysfunction: Combining behavioral and electrophysiological approaches
Authors: Eddins David A. , Ozmeral Erol J. , Eddins Ann C.
Published: October 2014

Central auditory processing involves a complex set of feed-forward and feedback processes governed by a cascade of dynamic neuro-chemical mechanisms. Central auditory dysfunction can arise from disruption of one or more of these processes. With hearing loss, dysfunction may begin with reduced and/or altered input to the central auditory system followed by peripherally induced central plasticity. Similar central changes may occur with advancing age and neurological disorders even in the absence of hearing loss. Understanding the behavioral and physiological consequences of this plasticity on the processing of basic acoustic features is critical for effective clinical management. Major central auditory processing deficits include reduced temporal processing, impaired binaural hearing, and altered coding of spectro-temporal features. These basic deficits are thought to be primary contributing factors to the common complaint of difficulty understanding speech in noisy environments in persons with hearing loss, brain injury, and advanced age. The results of investigations of temporal, spectral, and spectro-temporal processing, binaural hearing, and loudness perception will be presented with a focus on central auditory deficits that occur with advancing age and hearing loss. Such deficits can be tied to reduced peripheral input, altered central coding, and complex changes in cortical representations.
Auditory processing demands and working memory span
Authors: Pichora-Fuller Margaret K. , Smith Sherri L.
Published: October 2014

The (in)dependence of auditory and cognitive processing abilities is a controversial topic for hearing researchers and clinicians. Some advocate for the need to isolate auditory and cognitive factors. In contrast, we argue for the need to understand how they interact. Working memory span (WMS) is a cognitive measure that has been related to language comprehension in general and also to speech understanding in noise. In healthy adults with normal hearing, there is typically a strong correlation between reading and listening measures of WMS. Some investigators have opted to use visually presented stimuli when testing people who do not have normal hearing in order to avoid the influence of modality-specific auditory processing deficits on WMS. However, tests conducted using auditory stimuli are necessary to evaluate how cognitive processing is affected by the auditory processing demands experienced by different individuals over a range of conditions in which the tasks to be performed, the availability of supportive context, and the acoustical and linguistic characteristics of targets and maskers are varied. Attempts to measure auditory processing independent of cognitive processing will fall short in assessing listening function in realistic conditions.
Auditory perceptual learning as a gateway to rehabilitation
Authors: Wright Beverly A.
Published: October 2014

A crucial aspect of the central nervous system is that it can be modified through experience. Such changes are thought to occur in two learning phases: acquisition—the actual period of training—and consolidation—a post-training period during which the acquired information is transferred to long-term memory. My coworkers and I have been addressing these principles in auditory perceptual learning by characterizing the factors that induce and those that prevent learning during the acquisition and consolidation phases. We also have been examining how these factors change during development and aging and are affected by hearing loss and other conditions that alter auditory perception. Application of these principles could improve clinical training strategies. Further, though learning is the foundation for behavioral rehabilitation, the capacity to learn can itself be impaired. Therefore, an individual’s response to perceptual training could be used as an objective, clinical measure to guide diagnosis and treatment of a cognitive disorder. [Work supported by NIH.]
Perception of breathiness in pediatric speakers
Authors: Kopf Lisa M. , Shrivastav Rahul , Eddins David A. , Skowronski Mark D.
Published: October 2014

Extensive research has been done to determine acoustic metrics for voice quality. However, few studies have focused on voice quality in the pediatric population. Instead, metrics evaluated on adults have directly been applied to children’s voices. Some variables, such as pitch, that differ between adult and pediatric voices, have been shown to be critical in the perception of breathiness. Furthermore, it is not known whether adults perceive voice quality similarly for pediatric and adult speakers. In this experiment, 10 listeners judged breathiness for 28 stimuli using a single-variable matching task. The stimuli were modeled after four pediatric speakers and synthesized using a Klatt-synthesizer to have a wide range of aspiration noise and open quotient. Both of these variables have been shown to influence the perception of breathiness. The resulting data were compared to that previously obtained for adult speakers using the same matching task. Comparison of adult and pediatric voices will help identify differences in the perception of breathiness for these groups of speakers and to develop more accurate metrics for voice quality in children. [Research supported by NIH (R01 DC009029).]
Combining differentiated electroglottograph and differentiated audio signals to reliably measure vocal fold closed quotient
Authors: Morris Richard J. , Bernadin Shonda , Okerlund David , Wright Lindsay B.
Published: October 2014

Over the past few decades researchers have explored the use of the electroglottograph (EGG) as a non-invasive method for representing vocal fold contact during vowel production and to measure the closed quotient (CQ) and open quotient (OQ) of the glottal cycle. The first derivative of the EGG signal (dEGG) can be used to indicate these moments (Childers & Krishnamurthy, 1985). However, there can be double positive peaks in the dEGG as well as a variety of negative peak patterns (Herbst et al., 2010). Obviously these variations will alter any measurements made from the signal. Recently, the use of the dEGG with dAudio signal was reported as a means for more reliable measurement of the CQ from the EGG signal in combination with a time synchronized audio signal. The purpose of this study is to demonstrate the reliability of the dEGG and dAudio for determining CQ across a variety of vocal conditions. Files recorded from group of 15 trained females singing an octave that included their primo passaggio provided the data. Preliminary results indicate high reliability of the CQ measurements in both the chest and middle registers of all of the singers.
The influence of attentional focus on voice control
Authors: Zaheer Eesha A. , Larson Charles R.
Published: October 2014

The present study tested the role of attentional focus on control of voice fundamental frequency (F0). Subjects vocalized an “ah” sound while hearing their voice auditory feedback randomly shifted upwards or downwards in pitch. In the “UP” condition, subjects vocalized, listened for and pressed a button for each upward pitch shift stimulus. In the “DOWN” condition, subjects listened for and pressed a button for each downward shift. In the CONTROL condition, subjects vocalized without paying attention to the stimulus direction or pressing a button. Data were analyzed by averaging voice F0 contours across several trials for each pitch shift stimulus in all conditions. Response magnitudes were larger for the CONTROL than for the UP or DOWN conditions. Responses for the UP and DOWN conditions did not differ. Results suggest that when subjects focus their attention to identify specific stimuli and produce a non-vocal motor response conditional upon the identification, the neural mechanisms involved in voice control are reduced, possibly because of a reduction in the error signal resulting from the comparison of the efference copy of voice output with auditory feedback. Thus, focusing attention away from vocal control reduces neural resources involved in control of voice F0.
Attention-related modulation of involuntary audio-vocal response to pitch feedback errors
Authors: Liu Hanjun , Hu Huijing , Liu Ying
Published: October 2014

It has been demonstrated that unexpected alterations in auditory feedback elicit fast compensatory adjustments in vocal production. Although generally thought to be involuntary in nature, whether these adjustments can be influenced by cognitive function such as attention remains unknown. The present event-related potential (ERP) study investigated whether neurobehavioral processing of auditory-vocal integration can be affected by attention. While sustaining a vowel phonation and hearing pitch-shifted feedback, participants were required to either ignore the auditory feedback perturbation, or attend to it with two levels of attention load. The results revealed enhancement of P2 response to the attended auditory perturbation with the low load level as compared to the unattended auditory perturbation. Moreover, increased auditory attention load led to a significant decrease of P2 response. By contrast, there was no attention-related change of vocal response. These findings provide the first neurophysiological evidence that involuntary auditory-vocal integration can be modulated as a function of auditory attention. Furthermore, it is suggested that auditory attention load can result in a decrease of the cortical processing of auditory-vocal integration in pitch regulation.
A study on the effect of intraglottal vortical structures on vocal fold vibration
Authors: H Farahani Mehrdad , Zhang Zhaoyan
Published: October 2014

Recent investigations suggested possible formation of the vortical structures in the intraglottal region during the closing phase of the phonation cycle. Vortical regions in the flow field are locations of negative pressure, and it has been hypothesized that this negative pressure might facilitate the glottal closure and thus affects the vibration pattern and voice production for high subglottal pressures. However, it is unclear whether the vortex-induced negative pressure is large enough, compared with vocal fold inertia and elastic recoil, to have a noticeable effect on glottal closure. In addition, the intraglottal vortical structures generally exist only for a small fraction of the closing phase when the glottis becomes divergent enough to induce flow separation. In the current work, oscillation of the vocal folds and the flow field are modeled using a non-linear finite element solver and a reduced order flow solver, respectively. The effect of vortical structures is modeled as a sinusoidal negative pressure wave applied to vocal fold surface between the flow separation point and the superior edge of the vocal folds. The effects of this vortex-induced negative pressure are quantified at different conditions of vocal fold stiffness and subglottal pressures. [Work supported by NIH.]
Effects of thyroarytenoid muscle activation on phonation in an in vivo canine larynx model
Authors: Luegmair Georg , Chhetri Dinesh , Zhang Zhaoyan
Published: October 2014

Previous studies have shown that the thyroarytenoid (TA) muscle plays an important role in the control of vocal fold adduction and stiffness. The effects of TA stimulation on vocal fold vibration, however, are still unclear. In this study, the effects of TA muscle activation on phonation were investigated in an in vivo canine larynx model. Laryngeal muscle activation was achieved through parametric stimulation of the thyroarytenoid, the lateral cricoarytenoid (LCA), and the cricothyroid (CT) muscles. For each stimulation level, the subglottal pressure was gradually increased to produce phonation. The subglottal pressure, the volume flow, and the outside acoustic pressure were measured together with high-speed recording of vocal fold vibration from a superior view. The results show that, without TA activation, phonation was limited to conditions of medium to high levels of LCA and CT activations. TA activation allowed phonation to occur at a much lower activation level of the LCA and CT muscles. Compared to conditions of no TA activation, TA activation led to decreased open quotient. Increasing TA activation also allow phonation to occur at a much larger range of the subglottal pressure while still maintaining certain degree of glottal closure during vibration. [Work supported by NIH.]
Voice accumulation and voice disorders in primary school teachers
Authors: Bottalico Pasquale , Pavese Lorenzo , Astolfi Arianna , Hunter Eric J.
Published: October 2014

Statistics on professional voice users with vocal health issues demonstrate the significance of the problem. However, such disorders are not currently recognized as an occupational disease in Italy. Conducting studies examining the vocal health of occupational voice users is an important step in identifying this as an important public health issue. The current study was conducted in six primary schools in Italy with 25 teachers, one of the most affected occupational categories. A clinical examination was conducted (consisting of hearing and voice screening, a VHI, etc.). On this basis, teachers were divided into three groups: healthy subjects, subject with logopaedic disorders, and subjects with objectively measured pathological symptoms. The distributions of voicing and silence periods for the teachers at work were collected using the Ambulatory Phonation Monitor (APM3200), a device for long-term monitoring of vocal parameters. The APM senses the vocal fold vibrations at the base of the neck by means of a small accelerometer. Correlations were calculated between the voice accumulation slope (obtained by multiplying the number of occurrences for each period by the corresponding duration) and the clinical status of the teachers. The differences in voice accumulation distributions among the three groups were analyzed.
Room acoustics and vocal comfort in untrained vocalists
Authors: Hunter Eric J. , Bottalico Pasquale , Graetzer Simone , Banks Russell
Published: October 2014

Talkers have long been studied in their speech accommodation strategies in noise. Vocal effort and comfort within noisy situations have also been studied. In this study, untrained vocalists were exposed to a range of room acoustic conditions. In each environment, the subject performed a vocal task, with a goal of being “heard” by a listener 5 m away. After each task, the subject completed a series of questions addressing vocal effort and comfort. Additionally, using a head and torso simulator (HATS), the environment was assessed using a sine sweep presented at the HATS mouth and recorded at the ears. It was found that vocal clarity (C50) and the initial reflection related to vocal comfort. The results are not only relevant to room design but also to understanding talkers’ acuity to acoustic conditions and their adjustments to them.
Flow vibrato in singers
Authors: Nandamudi Srihimaja , Scherer Ronald C.
Published: October 2014

Frequency (F0) vibrato is commonly known, but not so for flow vibrato, the mean flow variation that accompanies frequency vibrato. Two classically trained singers, each with over 20 years professional experience, a soprano and a tenor, recorded /pa:pa:pa:/ sequences on three pitches (C4, A4, and G5 for the soprano, D3, D4, and G4 for the tenor) and three loudness levels (p, mf, and f) at each pitch. Each vowel had 3–6 frequency vibrato cycles. For both singers, flow vibrato (obtained using the Glottal Enterprises aerodynamic system) was present, and the lowest pitch had the most variability; otherwise, flow vibrato was fairly sinusoidal in shape. For the soprano, flow vibrato cycle extents were: 21–88 cc/s, lowest pitch; 60–147 cc/s, middle pitch; 115–214 cc/s, highest pitch, across loudness levels. For the soprano, the phase difference for the flow was 120–180 degrees ahead of the F0 vibrato. For the tenor, the flow vibrato cycle extents were: 32–85 cc/s, lowest pitch; 98–113 cc/s, middle pitch; 76–240 cc/s, highest pitch, across loudness levels. Flow vibrato for the tenor led the F0 vibrato typically by 40–120 degrees. For both subjects, some flow vibrato cycles had double peaks. Flow vibrato needs further study to determine its origin, shapes, and magnitudes.
Perceptual differences among models of the voice source: Further evidence
Authors: Garellek Marc , Chen Gang , Gerratt Bruce R. , Alwan Abeer , Kreiman Jody
Published: October 2014

Models of the voice source differ in how they fit natural voices, but it is still unclear which differences in fit are perceptually salient. This study describes ongoing analyses of differences in the fit of six voice source models to 40 natural voices, and how these differences relate to perceptual similarities among stimuli. Listeners completed a visual sort-and-rate task to compare versions of each voice created with the different source models, and the results were analyzed using multi-dimensional scaling (MDS). Perceptual spaces were interpreted in terms of variations in model fit in both the time and spectral domains. The discussion will focus on the perceptual importance of matches to both time-domain and spectral features of the voice. [Work supported by NIH/NIDCD grant DC01797 and NSF grant IIS-1018863.]
Towards standard scales for dysphonic voice quality: Magnitude estimation of reference stimuli
Authors: Eddins David A. , Shrivastav Rahul
Published: October 2014

This work represents a critical step in developing standard measurement scales for the dysphonic voice qualities of breathiness and roughness. Methods such as Likert ratings, visual analog scales and magnitude estimation result in arbitrary units, limiting their clinical usefulness. A single-variable matching task can quantifying voice quality in terms of physical units but is too time consuming for clinical use. None of these methods result in information that has a direct or intuitive relationship with the underlying percept. A proven approach for the perception of loudness is the Sone scale which ties physical units to the perceptual estimates of loudness magnitude. As a first step in developing such a scale for breathiness and roughness, here we establish the relationship between the change in perceived VQ magnitude and the change in physical units along the continuum of each VQ dimension. A group of 25 listeners engaged in a magnitude estimation task to determine perceived magnitude associated with the comparison stimuli used in our single-variable matching tasks. This relationship is analogous to mapping intensity in dB to perceived loudness in Phons and is a critical step in developing a Sone-like scale for breathiness and roughness.
Divergent or convergent glottal angles: Which give greater flow?
Authors: Scherer Ronald
Published: October 2014

During phonation, the glottis alters between convergent and divergent angles. For the same angle value, diameter, and transglottal pressure, which angle, divergent or convergent, results in greater flow? The symmetric glottal angles of the physical static model M5 were used. Characteristics (life-size) of the model were: axial glottal length 0.30 cm; angles of 5, 10, 20, and 40 degrees; diameters of 0.005, 0.01, 0.02, 0.04, 0.08, 0.16, and 0.32 cm; transglottal pressures from 1 to 25 cm H2O; resulting in flows from 2.7 to 1536 cc/s and Reynolds number from 29.4 to 13,058. Results: (1) For diameters of 0.04, 0.08 and 0.16 cm, the divergent angle always gave more flow than the convergent angle (about 5–25%); (2) for the smallest (0.005 cm) and largest diameter (0.32 cm), the divergent angles always gave less flow (10–30%); (3) for diameters of 0.01 and 0.02 cm, flow was greater for divergent 5 and 10 degrees, and less for divergent 20 and 40 degrees. These results suggest that the divergent glottal angle will increase the glottal flow for midrange glottal diameters (skewing the glottal flow further “to the right”?), and create less flow at very small diameters (increasing energy in the higher harmonics?).