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PubMed2004

Strategies for reliable automatic onset time picking of acoustic emissions and of ultrasound signals in concrete.

Determining the onset of transient signals like seismograms, acoustic emissions or ultrasound signals is very time consuming if the onset is picked manually. Therefore, different approaches exist, especially in seismology. The concepts of the most popular approaches are summarized. An own approach adapted to ultrasound signals and acoustic emissions, based on the Akaike Information Criterion (AIC), is presented. The AIC-picker is compared to an automatic onset detection algorithm based on the Hinkley criterion and also adapted to acoustic emissions. Manual picks performed by an analyst are used as reference values. Both automatic onset detection algorithms are applied to ultrasound signals which are used to monitor the setting and hardening of concrete. They are also applied to acoustic emissions recorded during a pull-out test. The AIC-picker produces sufficient reliable results for ultrasound signals where the deviation from the manual picks varies between 2% and 4%. Concerning acoustic emissions, only 10% of the events result in a mislocation vector greater than 5mm. It can be shown that our AIC-picker is a reliable tool for automatic onset detection for ultrasound signals and acoustic emissions of varying signal to noise ratio.

Journal Article↗

PubMed2006

Acoustic wave propagation in high-pressure system.

Recently, substantial attention is paid to the development of methods of generation of pulsations in high-pressure systems to produce pulsating high-speed water jets. The reason is that the introduction of pulsations into the water jets enables to increase their cutting efficiency due to the fact that the impact pressure (so-called water-hammer pressure) generated by an impact of slug of water on the target material is considerably higher than the stagnation pressure generated by corresponding continuous jet. Special method of pulsating jet generation was developed and tested extensively under the laboratory conditions at the Institute of Geonics in Ostrava. The method is based on the action of acoustic transducer on the pressure liquid and transmission of generated acoustic waves via pressure system to the nozzle. The purpose of the paper is to present results obtained during the research oriented at the determination of acoustic wave propagation in high-pressure system. The final objective of the research is to solve the problem of transmission of acoustic waves through high-pressure water to generate pulsating jet effectively even at larger distances from the acoustic source. In order to be able to simulate numerically acoustic wave propagation in the system, it is necessary among others to determine dependence of the sound speed and second kinematical viscosity on operating pressure. Method of determination of the second kinematical viscosity and speed of sound in liquid using modal analysis of response of the tube filled with liquid to the impact was developed. The response was measured by pressure sensors placed at both ends of the tube. Results obtained and presented in the paper indicate good agreement between experimental data and values of speed of sound calculated from so-called "UNESCO equation". They also show that the value of the second kinematical viscosity of water depends on the pressure.

Journal Article↗

PubMed1987

Acoustic signals from frog skeletal muscle.

Acoustic, force, and compound muscle action-potential signals were recorded simultaneously during maximal isometric twitches of frog gastrocnemius muscles. The onset of sound production occurred after the onset of muscle depolarization but before the onset of external force production. Acoustic waveforms consisted of oscillations that initially increased in amplitude, followed by decaying oscillations. The peak-to-peak acoustic amplitude increased with increasing temperature with a Q10 of 2.6 +/- 0.2 over a range of 7.0-25.0 degrees C. The acoustic amplitude increased with increasing muscle length up to approximately 90% of the optimal length for force generation. As length was increased further, the acoustic amplitude decreased. Microphones positioned on opposite sides of the muscle recorded acoustic signals that were 180 degrees out of phase. These results provided evidence that sound production is produced by lateral oscillations of muscle. The oscillation frequency may provide a measure of mechanical properties of muscle.

Action Potentials↗

PubMed2002

DC effects, sub-harmonics, stochasticity and "memory" for contact acoustic non-linearity.

Acoustic wave interaction with non-bonded contacts was found to be inherently non-linear due to asymmetrical stiffness distribution across the interface. A diode-type non-linearity results in local static elastic fields inside the contact, which are shown to be a source of transient longitudinal and shear DC-acoustic pulses polarized oppositely to a biasing contact stress. A parametric modulation of contact stiffness leads to acoustic instability effects, multiple sub-harmonics, and amplitude "self-modulation", and provides chaotic noise-like non-linear acoustic excitations in solids. For realistic cracked flaws, contact acoustic non-linearity exhibits amplitude hysteresis and storage caused by acoustic wave impact on the defect. Maximum storage time observed comes to several hours for read-in time less than half a minute. A long-term non-linear memory is believed to be due to a slow relaxation of thermally induced micro-strain within the crack area.

Journal Article↗

PubMed1999

Is there a critical developmental 'window' for isolation rearing-induced changes in prepulse inhibition of the acoustic startle response?

In a previous study, rats reared in isolation from weaning exhibited normal prepulse inhibition (PPI) before puberty, whilst after puberty (6-8 weeks post weaning) isolation reared rats exhibited deficits in PPI. The developmental timing of the onset of this isolation effect appears to be critical because similar isolation of adult rats has no effect on PPI. The present study examined the time and duration of the period or 'window' of isolation necessary to induce these behavioral changes. Male Sprague-Dawley rats were isolated for either only the first 2 weeks from weaning, only the first 4 weeks from weaning, only weeks 3 and 4, or continuously from weaning (ISO group), and compared with rats reared in normal social conditions (SOC group). Eight weeks after weaning, we compared acoustic and airpuff startle reactivity, acoustic and light PPI, and acoustic and airpuff startle habituation across the groups. There were no significant changes in any of the measures in the groups exposed to 2- or 4-week periods of isolation. In the ISO and SOC groups, acoustic or airpuff startle reactivity was similar, while acoustic PPI was reduced significantly in the ISO group. Airpuff startle habituation was increased significantly in the ISO group compared to SOC controls and there was a similar trend with acoustic startle habituation. These results indicate that only animals isolated for more than 4 weeks after weaning display deficits in PPI, and provide evidence that there is no critical pre-pubertal developmental window for inducing PPI deficits, rather, continuous post-weaning isolation is needed to induce the PPI deficit effect.

Age Factors↗

PubMed2003

Neural mechanisms and behaviors for acoustic communication in teleost fish.

Sound communication is not unique to humans but rather is a trait shared with most non-mammalian vertebrates. A practical way to address questions of vocal signal encoding has been to identify mechanisms in non-mammalian model systems that use acoustic communication signals in their social behavior. Teleost fishes, the largest group of living vertebrates, include both vocal and non-vocal species that exploit a wide range of acoustic niches. Here, we focus on those vocal species where combined behavioral and neurobiological studies have recently begun to elucidate a suite of adaptations for both the production and the perception of acoustic signals essential to their reproductive success and survival. Studies of these model systems show that teleost fish have the vocal-acoustic behaviors and neural systems both necessary and sufficient to solve acoustic problems common to all vertebrates. In particular, behavioral studies demonstrate that temporal features within a call, including pulse duration, rate and number, can all be important to a call's communicative value. Neurobiological studies have begun to show how these features are produced by a vocal motor system extending from forebrain to hindbrain levels and are encoded by peripheral and central auditory neurons. The abundance and variety of vocal fish present unique opportunities for parallel investigations of neural encoding, perception, and communication across a diversity of natural, acoustic habitats. As such, investigations in teleosts contribute to our delineating the evolution of the vocal and auditory systems of both non-mammalian and mammalian species, including humans.

Animal Communication↗

PubMed2000

Grey-scale contrast enhancement in rabbit liver with DMP115 at different acoustic power levels.

The contrast enhancement effect of ultrasound (US) contrast agent DMP-115 (YM454, Definity) in rabbit liver at two acoustic transmit power levels was studied. A total of 12 rabbits with healthy livers and 7 rabbits with VX-2 tumors were used. Grey-scale ultrasonograms in both fundamental (3.75 MHz) and harmonic (2.5/5.0 MHz) imaging modes were performed at a frame rate of 26 Hz under baseline acoustic power (MI = 0.6) or lower acoustic power (MI = 0.2). The contrast enhancement depended on the contrast agent dose and the acoustic power. The video intensity change was higher in the portal vein under the baseline acoustic power and higher in the liver parenchyma under the lower acoustic power. The contrast-enhanced US observation of the VX-2 tumor in the arterial phase correlated well with the angiographic and histopathological appearance of the tumor. In the parenchymal phase, the borderline of the tumor could be clearly delineated from the surrounding liver parenchyma. Continuous fundamental and harmonic grey-scale imaging with DMP115 has the capability of making peripheral circulation images of liver parenchyma and tumors.

Angiography↗

PubMed1996

Detection of acoustic emission from cavitation in tissue during clinical extracorporeal lithotripsy.

A 1-MHz focused hydrophone has been used to search for acoustic emission expected to arise from cavitation occurring in tissue during clinical extracorporeal shock-wave lithotripsy (ESWL). The hydrophone is acoustically coupled to the patient's skin and the focus directed at depth in tissue under ultrasound guidance. The measured amplitude-time variation of the acoustic emission from tissue near the shock-wave focus of the Storz Modulith SL20 lithotripter has been examined in four patients. There is evidence of increased amplitude acoustic emission at 1 MHz from regions within tissue that also appear hyperechoic in simultaneously acquired ultrasound images. The acoustic emission from these regions decays from an initial peak to the noise level in about 500 microseconds following each shock-wave pulse. Within this period, a second peak, often of higher amplitude than the first, is typically observed about 100 microseconds after the shockwave. The time between the initial and second peaks is found to increase with increasing shock-wave amplitude. The results are similar to those previously observed from cavitation induced by shock-wave exposure in water and indicate that the 1-MHz acoustic emission arises from inertial cavitation in tissue during clinical ESWL.

Humans↗

PubMed1996

Influence of tissue preparation on the high-frequency acoustic properties of normal kidney tissue.

The influence of various tissue preparations on the acoustic properties of normal kidney tissue at high frequencies was investigated. Eight surgically excised normal kidney tissue specimens were classified into three groups: (i) fresh, frozen section, (ii) formalin-fixed, frozen section and (iii) formalin-fixed, paraffin section. Scanning acoustic microscopy operating in the frequency range of 100-200 MHz was used to display the two-dimensional distribution of attenuation constant and sound speed. Our results indicate that (i) there is no significant variation in both acoustic parameters between the three tissue groups, (ii) fixation by 10% formalin produces no significant change in the acoustic parameters, (iii) in fat-free tissue regions, the acoustic parameters are independent of preparation method and (iv) frozen sections must be used to assess the acoustic parameters in fat-rich tissues.

Histocytological Preparation Techniques↗

PubMed1999

Experimental investigation of the acoustic nonlinearity parameter tomography for excised pathological biological tissues.

The acoustic nonlinearity parameter B/A tomography is proposed as a novel imaging method in this paper. By using this method, the B/A tomography for various kinds of normal and pathological porcine tissues in vitro, including eight kinds of diseased livers, four kinds of diseased kidney and one kind of diseased spleen, are studied. Results indicate that all diseased tissues with changes in tissue composition and structural features exhibit higher grey-scale (higher B/A values) than corresponding normal tissues. In addition, the acoustic nonlinearity parameter is more sensitive to pathological states than acoustic linear parameters. To make a comparison with the acoustic nonlinearity parameter tomography, the acoustic linear parameter images, including two B-scan images for two kinds of diseased specimens, are also presented. Results of this paper show that the acoustic nonlinearity parameter tomography may be a novel method for tissue characterization in ultrasonic medical diagnosis.

Animals↗

PubMed1999

Intercomparison of acoustic output measurements of a diagnostic ultrasound device.

An intercomparison of acoustic output measurements with 9 participants from four countries was performed. A commercial diagnostic ultrasound device including a 3.5-MHz M-mode transducer was circulated for that purpose. The acoustic output of the device was measured and the temporal-average power output, peak-negative acoustic pressure, output beam intensity, spatial-peak temporal average derived intensity and arithmetic-mean acoustic-working frequency were determined. Although the majority of results were in good agreement with one another, there were also some significant deviations from the corresponding grand mean values, and the overall ranges of the participants' reported measurement results were as follows. Temporal-average power output: 3.8 mW to 9.0 mW; peak-negative acoustic pressure: 1.50 MPa to 2.86 MPa; output beam intensity: 7.3 mW/cm2 to 13.2 mW/cm2; spatial-peak temporal-average derived intensity: 72 mW/cm2 to 176 mW/cm2; arithmetic-mean acoustic-working frequency: 3.27 MHz to 3.33 MHz. The reasons for the occurrence of significantly low or high values could be identified by the participants concerned. The results show that correct ultrasonic measurements are not easy to conduct and strongly advise periodically checking the measurement tools and procedures.

Humans↗

PubMed2000

Acoustic analysis after radiotherapy in T1 vocal cord carcinoma: a new approach to the analysis of voice quality.

PURPOSE: The study of acoustic voice parameters (fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio) in extended vowel production, oral reading of a standard paragraph, spontaneous speech and a song in irradiated patients for Tis-T1 vocal cord carcinoma. METHODS AND MATERIALS: Eighteen male patients irradiated for Tis-T1 vocal cord carcinoma and a control group of 31 nonirradiated subjects of the same age were included in a study of acoustic voice analysis. The control group had been rigorously selected for voice quality and the irradiated group had previous history of smoking in two-thirds of the cases and a vocal cord biopsy. Radiotherapy patients were treated with a 6MV Linac receiving a total dose of 66 Gy, 2 Gy/day, with median treatment areas of 28 cm(2). Acoustic voice analysis was performed 1 year after radiotherapy, the voice of patients in extended vowel production, oral reading of a standard paragraph, spontaneous speech, and in a song was tape registered and analyzed by a Kay Elemetric's Computerized Speech Lab (model CSL# 4300). Fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio were obtained in each case. Mann Whitney analysis was used for statistical tests. RESULTS: The irradiated group presented higher values of fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio. Mann-Whitney analysis showed significant differences for fundamental frequency and jitter in vowel production, oral reading, spontaneous speech, and song. Shimmer only showed differences in vowel production and harmonics-to-noise ratio in oral reading and song. CONCLUSIONS: In our study only fundamental frequency and jitter showed significant increased values to the control group in all the acoustic situations. Sustained vowel production showed the worst values of the acoustic parameters in comparison with the other acoustic situations. This study seems to suggest that more work should be done in this field.

Aged↗

PubMed1999

In vivo targeting of acoustically reflective liposomes for intravascular and transvascular ultrasonic enhancement.

OBJECTIVES: The purpose of this study was to target acoustically reflective liposomes to atherosclerotic plaques in vivo for ultrasound image enhancement. BACKGROUND: We have previously demonstrated the development of acoustically reflective liposomes that can be conjugated for site-specific acoustic enhancement. This study evaluates the ability of liposomes coupled to antibodies specific for different components of atherosclerotic plaques and thrombi to target and enhance ultrasonic images in vivo. METHODS: Liposomes were prepared with phospholipids and cholesterol using a dehydration/ rehydration method. Antibodies were thiolated for liposome conjugation with N-succinimidyl 3-(2-pyridyldithio) propionate resulting in a thioether linkage between the protein and the phospholipid. Liposomes were conjugated to antifibrinogen or anti-intercellular adhesion molecule-1 (anti-ICAM-1). In a Yucatan miniswine model, atherosclerosis was developed by crush injury of one carotid and one femoral artery and ingestion of a hypercholesterolemic diet. After full plaque development the arteries were imaged (20-MHz intravascular ultrasound catheter and 7.5-MHz transvascular linear probe) after injection of saline, unconjugated liposomes and antibody conjugated liposomes. RESULTS: Conjugated liposomes retained their acoustically reflective properties and provided ultrasonic image enhancement of their targeted structures. Liposomes conjugated to antifibrinogen attached to thrombi and fibrous portions of the atheroma, whereas liposomes conjugated to anti-ICAM-1 attached to early atheroma. CONCLUSIONS: Our data demonstrate that this novel acoustic agent can provide varying targeting with different antibodies with retention of intravascular and transvascular acoustic properties.

Animals↗

PubMed1998

Age dependency of left atrial and left ventricular acoustic quantification waveforms for the evaluation of diastolic performance in left ventricular hypertrophy.

We evaluated diastolic performance in 50 normal subjects and 50 patients with concentric left ventricular (LV) hypertrophy. Age-dependent normal values were determined for LV and left atrial (LA) acoustic quantification parameters. Pulsed wave Doppler echocardiography was also performed on all subjects. Patients with LV hypertrophy had higher peak velocities of atrial contraction and atrial contributions to filling. The acoustic quantification waveforms revealed lower rapid filling percentage of total filling and lower peak rapid filling rates. The LA acoustic quantification analysis confirmed the dependence on active atrial emptying in the patients with LV hypertrophy. There were significant correlations with age for most of the LV and LA acoustic quantification parameters. Acoustic quantification provided confirmatory results in subjects with an abnormal relaxation or restrictive Doppler pattern. In subjects with a normal Doppler pattern, the acoustic quantification was of added diagnostic value, identifying abnormalities in 77% to 80% of the patients.

Adult↗

PubMed1995

Elastic properties of osteoporotic bone measured by scanning acoustic microscopy.

A combination of low bone mass and decreased bone quality underlies osteoporotic fracture. We used scanning acoustic microscopy, a nondestructive method for assessing bone elasticity at a resolution of about 60 microns, to estimate the quality of biopsied iliac bones. We compared the acoustic velocities and bone volumes among premenopausal normal (n = 10), osteoporotic (n = 20), and postmenopausal normal (n = 10) subjects, the latter age-matched to the osteoporotic subjects. The acoustic measurements were highly reproducible (coefficient of variation = 0.32%). Bone volume of osteoporotic subjects (BV/TV = 13.3%) was lower than that of premenopausal and age-matched normals (BV/TV = 22.8%, p = 0.0007; BV/TV = 24.8%, p = 0.0004, respectively). Acoustic velocity of osteoporotic bone was 6.2% lower than that of age-matched normal bone (p < 0.02), but 3.4% higher than that of bone from premenopausal normal women. The lower acoustic velocity of osteoporotic bone than that of age-matched normal subjects implies that osteoporosis involves altered tissue elasticity. However, the lowest acoustic velocities were measured in premenopausal normal subjects. This unexpected result may indicate a complex relationship between tissue level properties and fragility in bone.

Aged↗

PubMed2005

Effect of surfactants on inertial cavitation activity in a pulsed acoustic field.

It has previously been reported that the addition of low concentrations of ionic surfactants enhances the steady-state sonoluminescence (SL) intensity relative to water (Ashokkumar; et al. J. Phys. Chem. B 1997, 101, 10845). In the current study, both sonoluminescence and passive cavitation detection (PCD) were used to examine the acoustic cavitation field generated at different acoustic pulse lengths in the presence of an anionic surfactant, sodium dodecyl sulfate (SDS). A decrease in the SL intensity was observed in the presence of low concentrations of SDS and short acoustic pulse lengths. Under these conditions, the inhibition of bubble coalescence by SDS leads to a population of smaller bubbles, which dissolve during the pulse "off time". As the concentration of surfactant was increased at this pulse length, an increase in the acoustic cavitation activity was observed. This increase is partly attributed to enhanced growth rate of the bubbles by rectified diffusion. Conversely, at long pulse lengths acoustic cavitation activity was enhanced at low SDS concentrations as a larger number of the smaller bubbles could survive the pulse "off time". The effect of reduced acoustic shielding and an increase in the "active" bubble population due to electrostatic repulsion between bubbles are also significant in this case. Finally, as the surfactant concentration was increased further, the effect of electrostatic induced impedance shielding or reclustering dominates, resulting in a decrease in the SL intensity.

Journal Article↗

PubMed2000

Dynamic assessment of imbalance in acoustic neuroma patients by sway magnetometry

INTRODUCTION: Imbalance may be a significant problem for patients with acoustic neuromas. Prospective data on patients with acoustic neuromas to establish how the vestibular system performs dynamically, in the perioperative phases, is not available. Posturography is an established method of measuring balance and sway magnetometry has been developed as a reliable technique in this field. AIMS: Prospectively to assess pre- and postoperative dynamic vestibular function in patients with acoustic neuromas using sway magnetometry. METHODS: Sway patterns were recorded on 12 patients with acoustic neuromas tested under two sets of conditions: first, a baseline test for 120 s, repeated after 120 s of vestibular stimulation. After each test a validated questionnaire to assess balance subjectively was compeleted: before operation and 1, 3 and 6 months after operation. RESULTS: (1) Patients with acoustic neuromas demonstrate 'overswing' on baseline testing: most exaggerated 1 month postoperatively. After vestibular stimulation the 'recovery' time was prolonged to 50 s postoperatively, 62 s postoperatively (1/12), 43 s (3/12), and 47 s (6/12) postoperatively. (2) Mean path length (normal range, 163-287 mm) was increased in all groups: preoperative = 332 mm, 1 month postoperatively = 358 mm, 3 months postoperatively = 308 and 6 months postoperatively = 343 mm (3) The Dizziness Handicap Inventory scores were elevated at all times of testing and significantly correlated with baseline path length (rs = 0.6, P = 0. 03) and vestibular stimulation path length (rs = 0.7, P = 0.01) preoperatively. CONCLUSIONS: This is the first dynamic, prospective study of balance in patients with acoustic neuromas. Abnormal sway patterns and prolonged recovery times pre- and postoperatively, most marked at 1 month, were demonstrated. A subjective assessment of balance disturbance reflected these abnormal sway measurements confirming its clinical usefulness.

Journal Article↗

PubMed1990

[How can hyperreactive rhinopathy be modified surgically? II: Acoustic rhinometry and anterior turbinoplasty].

By means of the acoustic reflection technique, or acoustic rhinometry, all cross-sectional areas of the upper airway can be measured by an acoustic signal. In this paper, the normal mean curve of 134 normal probands is determined. This normal curve shows the minimum cross-sectional area (I-notch) to be located at the Isthmus nasi. The second narrowest segment of the nasal cavity is located at the head of the inferior concha (C-notch). In patients with turbinate hypertrophy due to allergic or vasomotor rhinitis the minimum cross-sectional area is sited at the head of the inferior turbinate. Furthermore, acoustic rhinometry allows the exact size and location of the congested mucosa to be determined following provocation with allergens in patients with allergic rhinitis. Acoustic rhinometry could further demonstrate why nasal breathing in patients with turbinate hypertrophy improves in the long term after anterior turbinoplasty: in this operation the narrow cross-sectional areas at the head of the inferior turbinate are enlarged. Acoustic rhinometry not only allows the location and size of the various deviations of the nasal structures to be distinguished from normal (valve stenosis, septal deviation, turbinate hypertrophy, tumor masses), but also allows an exact demonstration of the efficacy of rhinosurgical techniques.

Adult↗