Tissue Vibration Research Articles

Velar flutter does not Occur on Persian radico-uvular /G/ sound: Case reports

Nasal turbulence with velar flutter is an obligatory symptom that occurs during production of high-pressure sounds due to a partially closed velopharyngeal (VP) port. A small VP gap creates air-pressure high enough to set the marginal edges of the velum into vibration. The flutter component is characterized spectrally by low frequencies (Zajac & Preisser, 2015) and vibratory activity through auto-correlation functions (Eshghi et al., 2015). In this study, two speech-language pathologists independently listened to the audio recordings of stops produced by two Persian-speaking children (1 male, 8 yrs and 1 female, 9 yrs) with repaired cleft palate. Speech samples consisted of Persian plosives including /p, b, t, d, k, g, G/. The two listeners achieved 100% agreement that velar flutter occurred on all stops except /G/, a voiced radico-uvular sound. Spectral evaluation indicated characteristics of flutter were present during all stops except for /G/. It is hypothesized that tissue vibration was inhibited during the production of /G/ due to the the tongue making contact with the posterior part of the soft palate and/or uvula. The findings provide cross-linguistic evidence in support of tissue vibration (velar flutter) rather than displacement of mucous (bubbling) as the primary perceptual component of nasal turbulence.

Visualizing the Vibration of Laryngeal Tissue during Phonation Using Ultrafast Plane Wave Ultrasonography

Ultrafast plane wave ultrasonography is employed in this study to visualize the vibration of the larynx and quantify the vibration phase as well as the vibration amplitude of the laryngeal tissue. Ultrasonic images were obtained at 5000 to 10,000 frames/s in the coronal plane at the level of the glottis. Although the image quality degraded when the imaging mode was switched from conventional ultrasonography to ultrafast plane wave ultrasonography, certain anatomic structures such as the vocal folds, as well as the sub- and supraglottic structures, including the false vocal folds, can be identified in the ultrafast plane wave ultrasonic image. The periodic vibration of the vocal fold edge could be visualized in the recorded image sequence during phonation. Furthermore, a motion estimation method was used to quantify the displacement of laryngeal tissue from hundreds of frames of ultrasonic data acquired. Vibratory displacement waveforms of the sub- and supraglottic structures were successfully obtained at a high level of ultrasonic signal correlation. Moreover, statistically significant differences in vibration pattern between the sub- and supraglottic structures were found. Variation of vibration amplitude along the subglottic mucosal surface is significantly smaller than that along the supraglottic mucosal surface. Phase delay of vibration along the subglottic mucosal surface is significantly smaller than that along the supraglottic mucosal surface.

Dynamic analysis of the human brain with complex cerebral sulci

ABSTRACTThe brain is one of the most vulnerable organs inside the human body. Head accidents often appear in daily life and are easy to cause different level of brain damage inside the skull. Once the brain suffered intense locomotive impact, external injuries, falls, or other accidents, it will result in different degrees of concussion. This study employs finite element analysis to compare the dynamic characteristics between the geometric models of an assumed simple brain tissue and a brain tissue with complex cerebral sulci. It is aimed to understand the free vibration of the internal brain tissue and then to protect the brain from injury caused by external influences. Reverse engineering method is used for a Classic 5-Part Brain (C18) model produced by 3B Scientific Corporation. 3D optical scanner is employed to scan the human brain structure model with complex cerebral sulci and imported into 3D graphics software to construct a solid brain model to simulate the real complex brain tissue. Obtaining the normal mode analysis by inputting the material properties of the true human brain into finite element analysis software, and then to compare the simplified and the complex of brain models.

Er:Yag Laser Treatment of Simple Snorers in an Outpatient Setting

Objective: Snoring occurs as a result of soft tissue vibration caused by a partial upper airway collapse during sleep. This study evaluated the effectiveness and potential adverse side effects associated with the use of a nonsurgical, erbium-doped yttrium aluminum garnet (Er:YAG) laser treatment for patients with snoring conditions. Materials and Methods: In total, 33 patients with different degrees of snoring were analyzed retrospectively. All patients received three NightLase™ Er:YAG laser treatments. Results were measured using a follow-up questionnaire and then statistically analyzed. Any effects that occurred during the first year after treatment (i.e., short-term effects) were followed up with interviews. Results: Laser treatment effectively reduced patients' snoring and achieved a 65% satisfaction rate after three treatments. The greatest improvement and satisfaction were experienced by patients aged ≥50 years. Patients reported additional benefits from this treatment including easier breathing, higher alertness, and increased focus. Conclusion: Nonsurgical Er:YAG laser treatment is an effective and minimally invasive procedure to reduce patient snoring and other sleep-disordered breathing symptoms. Patients reported minimal disadvantages including minor discomfort and a low risk of side effects.

Source and Filter Estimation for Throat-Microphone Speech Enhancement

In this paper, we propose a new statistical enhancement system for throat microphone recordings through source and filter separation. Throat microphones (TM) are skin-attached piezoelectric sensors that can capture speech sound signals in the form of tissue vibrations. Due to their limited bandwidth, TM recorded speech suffers from intelligibility and naturalness. In this paper, we investigate learning phone-dependent Gaussian mixture model (GMM)-based statistical mappings using parallel recordings of acoustic microphone (AM) and TM for enhancement of the spectral envelope and excitation signals of the TM speech. The proposed mappings address the phone-dependent variability of tissue conduction with TM recordings. While the spectral envelope mapping estimates the line spectral frequency (LSF) representation of AM from TM recordings, the excitation mapping is constructed based on the spectral energy difference (SED) of AM and TM excitation signals. The excitation enhancement is modeled as an estimation of the SED features from the TM signal. The proposed enhancement system is evaluated using both objective and subjective tests. Objective evaluations are performed with the log-spectral distortion (LSD), the wideband perceptual evaluation of speech quality (PESQ) and mean-squared error (MSE) metrics. Subjective evaluations are performed with an A/B comparison test. Experimental results indicate that the proposed phone-dependent mappings exhibit enhancements over phone-independent mappings. Furthermore enhancement of the TM excitation through statistical mappings of the SED features introduces significant objective and subjective performance improvements to the enhancement of TM recordings.

Fatigue and soft tissue vibration during prolonged running

Muscle tuning paradigm proposes that the mechanical properties of soft tissues are tuned in such a way that its vibration amplitude become minimized. Therefore, the vibrations of soft tissue are heavily damped. However, it has been hypothesized that the ability of muscle tuning decreases with fatigue. This study investigated the changes in vibration characteristics of soft tissue with fatigue. Vibrations of the gastrocnemius muscle of 8 runners during a prolonged run protocol on a treadmill at constant velocity (4ms−1) were measured using a tri-axial accelerometer. The vibration amplitude is calculated using the Fourier transform and a wavelet-based method was used to calculate the damping coefficient. The results showed that: (1) the vibration amplitude in longitudinal direction increased with fatigue, which may be interpreted as the decreased muscle function with fatigue. (2) The amplitude increase percent strongly depended on the vibration frequency. (3) The damping coefficient of the gastrocnemius increased with fatigue. A 1-DOF mass-spring-damper model was used in order to validate the wavelet based method and simulate the observed phenomena.

Acoustic correlates of velar flutter associated with nasal emission during /s/ in children with velopharyngeal dysfunction

Velar flutter can accompany obligatory nasal air emission in children with cleft palate. It usually occurs as a result of air passing through a partially closed velopharyngeal port that creates turbulence and tissue vibration due to aerodynamic-elastic forces. Nasal air emission can also occur without flutter. In this case, the velopharyngeal port is relatively large and turbulence is generated at the anterior nasal valve without flutter. In this study we applied auto-correlation to discriminate velar flutter from non-flutter nasal air emission. Three children with nasal turbulence and velar flutter and three children with nasal turbulence without flutter were recorded using the oral and nasal microphones of the Nasometer during production of /si/. Nasal emission of the /s/ sound captured by the nasal microphone was isolated and the auto-correlation functions of the signals were graphed using MATLAB. Results showed that nasal emissions with velar flutter have auto-correlation functions with periodic/quasi-periodic patterns. However, the auto-correlation functions of the non-flutter nasal emissions showed noisy fluctuations without periodic oscillations. Findings revealed that auto-correlation function can be used clinically as an acoustic technique to detect tissue vibration accompanied with nasal air emission.

A mathematical and numerical framework for magnetoacoustic tomography with magnetic induction

We provide a mathematical analysis and a numerical framework for magnetoacoustic tomography with magnetic induction. The imaging problem is to reconstruct the conductivity distribution of biological tissue from measurements of the Lorentz force induced tissue vibration. We begin with reconstructing from the acoustic measurements the divergence of the Lorentz force, which is acting as the source term in the acoustic wave equation. Then we recover the electric current density from the divergence of the Lorentz force. To solve the nonlinear inverse conductivity problem, we introduce an optimal control method for reconstructing the conductivity from the electric current density. We prove its convergence and stability. We also present a point fixed approach and prove its convergence to the true solution. A new direct reconstruction scheme involving a partial differential equation is then proposed based on viscosity-type regularization to a transport equation satisfied by the electric current density field. We prove that solving such an equation yields the true conductivity distribution as the regularization parameter approaches zero. Finally, we test the three schemes numerically in the presence of measurement noise, quantify their stability and resolution, and compare their performance.

The Nature of Nasal Fricatives: Articulatory-Perceptual Characteristics and Etiologic Considerations.

Nasal fricatives (NFs) are unusual, maladaptive articulations used by children both with and without palatal anomalies to replace oral fricatives. Nasal fricatives vary in articulatory, aerodynamic, and acoustic-perceptual characteristics with two generally distinct types recognized. One type is produced with velopharyngeal (VP) constriction that results in turbulent nasal airflow and, frequently, tissue vibration (flutter) at the VP port. Trost (1981) described these as posterior NFs that have a distinctive snorting quality. A second type of NF is produced without significant VP constriction resulting in turbulent airflow generated at the anterior liminal valve of the nose. Of importance, both types are "active" alternative articulations in that the speaker occludes the oral cavity to direct all airflow through the nose (Harding & Grunwell, 1998). It is this oral gesture that differentiates NFs from obligatory (or passive) nasal air escape that may sound similar due to incomplete VP closure. The purpose of this article is to (1) describe the articulatory, aerodynamic, and acoustic-perceptual nature of NFs, and (2) propose a theoretical framework for the acquisition of NFs by children both with and without cleft palate.

Research on Subcutaneous Pulse Shape Measurement by Near-infrared Moiré Technique

A pulse is generated when the heart pumps blood into the arterial system. The heart pumps blood only when it contracts, not when it relaxes; therefore, blood enters the arterial system in a cyclical form. Artery beating is visible in some parts of the body surface, such as the radial artery of the wrist. This paper mainly uses the feature in which near-infrared spectroscopy penetrates skin to construct a non-invasive measurement system that can measure small vibration in the subcutaneous tissue of the human body, and then uses it for the pulse measurement. This measurement system uses the optical moir<TEX>$\acute{e}$</TEX> principle, together with the fringe displacement made by small vibration in the subcutaneous tissue, and an image analysis program to calculate the height variation from small vibrations in the subcutaneous tissue. It completes a measurement system that records height variation with time, and that together with a fast Fourier transform (FFT) program, they can convert the pulse waveform generated by vibration (time-amplitude) to heartbeat frequency (frequency-amplitude). This is a new and non-invasive medical assistance system for measuring the pulse of the human body, with the advantages of being simple, fast, safe and objective.

Damping and energy dissipation in soft tissue vibrations during running

It has been well accepted that the vibrations of soft tissue cannot be simulated by a single sinusoidal function. In fact, these vibrations are a combination of several vibration modes. In this study, these modes are extracted applying a recently developed method namely, partly ensemble empirical mode decomposition (PEEMD). Then, a methodology for estimating the damping properties and energy dissipation caused by damping for each mode is used. Applying this methodology on simulated signals demonstrates high accuracy. This methodology is applied to the acceleration signals of the gastrocnemius muscle during sprinting and the differences between the damping properties of different vibration modes were identified. The results were 1) the damping property of high-frequency mode was higher than that for low-frequency modes. 2) All identified modes were in under damped condition, therefore, the vibrations had an oscillatory nature. 3) The damping ratios of lower modes are about 100% increased compared to higher modes. 4) The energy dissipation occurred in lower modes were much more than that for higher mode; According to the power spectrum of the ground reaction force (GRF), which is the input force into the body, the recent finding supports the muscle tuning paradigm. It is suggested that the damping properties and energy dissipation can be used to distinguish between different running conditions (surface, fatigue, etc.)

Synchronized imaging and acoustic analysis of the upper airway in patients with sleep-disordered breathing

Progressive narrowing of the upper airway increases airflow resistance and can produce snoring sounds and apnea/hypopnea events associated with sleep-disordered breathing due to airway collapse. Recent studies have shown that acoustic properties during snoring can be altered with anatomic changes at the site of obstruction. To evaluate the instantaneous association between acoustic features of snoring and the anatomic sites of obstruction, a novel method was developed and applied in nine patients to extract the snoring sounds during sleep while performing dynamic magnetic resonance imaging (MRI). The degree of airway narrowing during the snoring events was then quantified by the collapse index (ratio of airway diameter preceding and during the events) and correlated with the synchronized acoustic features. A total of 201 snoring events (102 pure retropalatal and 99 combined retropalatal and retroglossal events) were recorded, and the collapse index as well as the soft tissue vibration time were significantly different between pure retropalatal (collapse index, 24 ± 11%; vibration time, 0.2 ± 0.3 s) and combined (retropalatal and retroglossal) snores (collapse index, 13 ± 7% [P ≤ 0.0001]; vibration time, 1.2 ± 0.7 s [P ≤ 0.0001]). The synchronized dynamic MRI and acoustic recordings successfully characterized the sites of obstruction and established the dynamic relationship between the anatomic site of obstruction and snoring acoustics.

Development of a time-dependent numerical model for the assessment of non-stationary pharyngoesophageal tissue vibrations after total laryngectomy.

Laryngeal cancer due to, e.g., extensive smoking and/or alcohol consumption can necessitate the excision of the entire larynx. After such a total laryngectomy, the voice generating structures are lost and with that the quality of life of the concerning patients is drastically reduced. However, the vibrations of the remaining tissue in the so called pharyngoesophageal (PE) segment can be applied as alternative sound generator. Tissue, scar, and geometric aspects of the PE-segment determine the postoperative substitute voice characteristic, being highly important for the future live of the patient. So far, PE-dynamics are simulated by a biomechanical model which is restricted to stationary vibrations, i.e., variations in pitch and amplitude cannot be handled. In order to investigate the dynamical range of PE-vibrations, knowledge about the temporal processes during substitute voice production is of crucial interest. Thus, time-dependent model parameters are suggested in order to quantify non-stationary PE-vibrations and drawing conclusions on the temporal characteristics of tissue stiffness, oscillating mass, pressure, and geometric distributions within the PE-segment. To adapt the numerical model to the PE-vibrations, an automatic, block-based optimization procedure is applied, comprising a combined global and local optimization approach. The suggested optimization procedure is validated with 75 synthetic data sets, simulating non-stationary oscillations of differently shaped PE-segments. The application to four high-speed recordings is shown and discussed. The correlation between model and PE-dynamics is ≥ 97%.

Magnetoacoustic tomography with magnetic induction for high‐resolution bioimepedance imaging through vector source reconstruction under the static field of MRI magnet

Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ∼ 1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction.

Magnetic resonance imaging study of peripharyngeal mucosal intensity in obstructive sleep apnea patients

Introduction Obstructive sleep apnea (OSA) is a common sleep disorder characterized by repetitive episodes of airway closure which usually occur in the retro-palatal region of the oropharynx. It has been known that upper airway mucosa in OSA patients is described as edematous. Recurrent injuries owing to vibration of the upper airway tissues or repetitive negative pressure may contribute to this phenomenon. On the other hand, fluid redistribution from the lower to the upper body during nocturnal recumbency could shift the fluid into neck and tissue around airway. The combination of these might contribute the occurrence or worsening of OSA by compressing the airway. Therefore, this study aims to investigate and establish simple magnetic resonance imaging (MRI) parameters, namely T2 mucous-to- masseter intensity ratio (T2MMIR), to assess the degree of tissue water content at the retro-palatal level and its relationship with sleep parameters in OSA patients. Materials and methods Twenty-seven subjects with OSA underwent polysomnography and cervical MRI with 1.5-tesla during wakefulness (age 55.0 ± 16.5 y, 77.8% male, with apnea-hypopnea index (AHI) 54.1 ± 27.6 and a body mass index (BMI) 29.4 ± 5.5) were included. On the axial T2-weighted images from the epipharynx to the oropharynx, the signal intensities for masseter muscle and peripharyngeal mucosa were measured. T2 mucous-to-masseter intensity ratio was calculated, and was used as an estimate of water content in the retro-palatal region. Pearson correlation analysis was performed to examine the correlation between peripharyngeal T2MMIR and polysomnography parameters. Results T2 mucous-to-masseter intensity ratio had moderate, positive correlation with supine AHI ( r = 0.388, P r = 0.408, P r = 0.411, P r = 0.419, P r = 0.645, P r = −0.401, P Conclusion This is the first report to establish peripharyngeal T2MMIR as one simple parameter representing peripharyngeal mucosal water contents due to inflammatory edema and/or fluid redistribution during recumbency, related to severity of OSA. This finding suggested its potential usefulness in reevaluation of change of peripharyngeal mucosa after OSA treatment to confirm its success.

Ultrasound vibrometry using orthogonal- frequency-based vibration pulses

New vibration pulses are developed for shear wave generation in a tissue region with preferred spectral distributions for ultrasound vibrometry applications. The primary objective of this work is to increase the frequency range of detectable harmonics of the shear wave. The secondary objective is to reduce the required peak intensity of transmitted pulses that induce the vibrations and shear waves. Unlike the periodic binary vibration pulses, the new vibration pulses have multiple pulses in one fundamental period of the vibration. The pulses are generated from an orthogonal-frequency wave composed of several sinusoidal signals, the amplitudes of which increase with frequency to compensate for higher loss at higher frequency in tissues. The new method has been evaluated by studying the shear wave propagation in in vitro chicken and swine liver. The experimental results show that the new vibration pulses significantly increase tissue vibration with a reduced peak ultrasound intensity, compared with the binary vibration pulses.

Complex vibratory patterns in an elephant larynx

Elephants' low-frequency vocalizations are produced by flow-induced self-sustaining oscillations of laryngeal tissue. To date, little is known in detail about the vibratory phenomena in the elephant larynx. Here, we provide a first descriptive report of the complex oscillatory features found in the excised larynx of a 25 year old female African elephant (Loxodonta africana), the largest animal sound generator ever studied experimentally. Sound production was documented with high-speed video, acoustic measurements, air flow and sound pressure level recordings. The anatomy of the larynx was studied with computed tomography (CT) and dissections. Elephant CT vocal anatomy data were further compared with the anatomy of an adult human male. We observed numerous unusual phenomena, not typically reported in human vocal fold vibrations. Phase delays along both the inferior-superior and anterior-posterior (A-P) dimension were commonly observed, as well as transverse travelling wave patterns along the A-P dimension, previously not documented in the literature. Acoustic energy was mainly created during the instant of glottal opening. The vestibular folds, when adducted, participated in tissue vibration, effectively increasing the generated sound pressure level by 12 dB. The complexity of the observed phenomena is partly attributed to the distinct laryngeal anatomy of the elephant larynx, which is not simply a large-scale version of its human counterpart. Travelling waves may be facilitated by low fundamental frequencies and increased vocal fold tension. A travelling wave model is proposed, to account for three types of phenomena: A-P travelling waves, 'conventional' standing wave patterns, and irregular vocal fold vibration.

Evaluation of Upper Airway in Obstructive Sleep Apnea: Synchronized Imaging and Acoustic Analyses

Objectives: Snore signals are produced by soft tissue vibration in the upper airway (UA). To date, there is no gold standard to localize UA narrowing sites in patients with obstructive sleep apnea syndrome (OSAS). In this study, we use a “vocal tract model” to investigate the association between snore acoustic characteristics and UA collapse. Dynamic magnetic resonance imaging (dMRI) was used to provide UA anatomy information. Methods: We report data from 44 polysomnography (PSG)-confirmed snoring episodes. Dynamics of UA and acoustic manifestations of snore events during natural sleep were recorded with synchronized dMRI and fiber-optic microphone recording. After the deletion of background dMRI noises, the spectrum envelope was reconstructed by applying a vocal tract model to characterize the snoring patterns. The temporal change of spectrum envelope was analyzed using Gabor transformation to correlate with UA dynamics. Results: The snore events were categorized into 28 none, 7 typical (velopharyngeal), and 9 mixed (velopharyngeal and hypopharyngeal) obstructions. The snore’s dominant frequency of envelop spectrum can differentiate none from typical UA obstructions (82.3±16.4Hz vs 101.9±9.1 Hz, p&lt;0.01); and can differentiate mixed from typical obstructions (131.9±19.8 Hz vs.101.9±9.1 Hz, p &lt; 0.05) Conclusions: The dynamics of acoustic patterns derived from the envelope of Gabor spectrogram are unique and characteristics in different types of obstruction with the advantage of low-cost and easy availability. Therefore, the dynamics of acoustic patterns warrants further investigation to identify the structural changes of the obstruction sites in OSAS patients.

Phase-sensitive imaging of tissue acoustic vibrations using spectrally encoded interferometry

Acoustic vibrations in tissue are often difficult to image, requiring high-speed scanning, high sensitivity and nanometer-scale axial resolution. Here we use spectrally encoded interferometry to measure the vibration pattern of two-dimensional surfaces, including the skin of a volunteer, at nanometric resolution, without the need for rapid lateral scanning and with no prior knowledge of the driving acoustic waveform. Our results demonstrate the feasibility of this technique for measuring tissue biomechanics using simple and compact imaging probes.

Effect on Auditory Threshold of Air and Water Pockets Bordering the Pathway between Soft Tissue Stimulation Sites and the Cochlea

Auditory sensation can be elicited by applying a bone conduction vibrator to skin sites on the head, neck, and thorax over soft tissues. This is called soft tissue conduction (STC). We hypothesized that introducing substances with acoustic impedances that sharply deviate from those of soft tissues, such as air pockets, into the soft tissues beneath soft tissue stimulation sites would have an effect on the auditory threshold to stimulation at skin sites over soft tissue. In human subjects, we assessed the auditory threshold with a bone vibrator applied to several STC sites, especially the cheek, and to several bone conduction sites on the skull. The subjects were equipped with bilateral earplugs. The subject then filled his or her cheek with either air or water, and the auditory threshold was again determined. We also recorded the auditory brain stem response to STC stimulation under the chin in fat sand rats in the absence and presence of subcutaneous air or saline solution pockets (0.4 mL) under the chin. In humans, the threshold to stimulation on the cheek was elevated (13 to 18 dB) in the presence of an air-inflated cheek, but not with a water-filled cheek. In animals, in the presence of an air pocket, the auditory brain stem response threshold was elevated by 10 to 20 dB; no threshold change occurred with a saline solution pocket. The introduction of air (but not water) into the soft tissues beneath the soft tissue stimulation sites led to a threshold elevation in both humans and animals. This was not the case when an identical volume of water was introduced, which would also have interrupted a possible parallel bone conduction pathway. These results provide evidence that soft tissue stimulation at low intensities induces tissue vibrations that are transmitted to the cochlea along a series of soft tissues with similar acoustic impedances.