SEARCH · Search PubMed

Results for “ACOUSTICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources

PubMed2002

CAN: an example of nonclassical acoustic nonlinearity in solids.

A new class of nonlinear acoustic phenomena has been observed for acoustic wave interaction with simulated and realistic nonbonded contact interfaces (cracked defects) in solids. "Nonclassical" effects are due to substantially asymmetric stiffness characteristics of the interface for normal stress that results in specific contact acoustic nonlinearity (CAN). The asymmetry in the contact restoring forces causes the stiffness parametric modulation and instability of oscillations, which results in acoustic wave fractional subharmonic generation. The CAN subharmonics and higher harmonics reveal threshold dynamic behaviour, evident hysteresis, and instability effects.

Journal Article↗

PubMed2000

Measurement of ultrasonic power and electro-acoustic efficiency of high power transducers.

In this paper, an improved method for the measurement of acoustic power and electro-acoustic efficiency of high power ultrasonic transducers is presented. The measuring principle is described, the experimental results are given. In comparison with traditional methods, the method presented in this paper has the advantages of simplicity, economy and practicality. The most important is that it can measure the output acoustic power and the electro-acoustic efficiency of the transducer under the condition of high power and practical applications, such as ultrasonic cleaning and soldering.

Electricity↗

PubMed2000

Design of a self-calibrating simulated acoustic emission source.

The use of conical piezoelectric transducers as point acoustic sources has been investigated. It has been shown that transducers based on a design originally developed at the National Institute for Standards and Technology in the USA can be used as point transmitters over the frequency range of interest in acoustic emission measurements (100 kHz to around 1 MHz). They should, therefore, be suitable for use in experiments to calibrate structures so that acoustic emission source strengths can be determined. It has also been shown that measurements of the response of the transmitting transducer backing can be used to assess the coupling efficiency, and hence to remove concerns about inconsistent coupling affecting the calibration measurements. The results indicate that the variation of the backing response with coupling is due to a shift in the resonance frequencies of the transducer with the mechanical load impedance. If other transducers can be shown to behave in a similar fashion this effect could be used to measure coupling in standard acoustic emission and ultrasonic transducers.

Calibration↗

PubMed2000

Angular spectrum approach for the computation of group and phase velocity surfaces of acoustic waves in anisotropic materials

The decomposition of an acoustic wave into its angular spectrum representation creates an effective base for the calculation of wave propagation effects in anisotropic media. In this method, the distribution of acoustic fields is calculated in arbitrary planes from the superposition of the planar components with proper phase shifts. These phase shifts depend on the ratio of the distance between the planes to the normal component of the phase slowness vector. In anisotropic media, the phase shifts depend additionally on the changes of the slowness with respect to the direction of the propagation vector and the polarization. Those relations are obtained from the Christoffel equation. The method employing the fast Fourier transformation algorithm is especially suited for volume imaging in anisotropic media, based on holographic detection in transmission of acoustic waves generated by a point source. This technique is compared with measurements on crystals performed by phase-sensitive scanning acoustic microscopy.

Journal Article↗

PubMed1991

Acoustic startle induced ultrasonic vocalization in the rat: a novel animal model of anxiety?

Ultrasonic vocalization was induced by either high intensity acoustic stimuli or by electric footshock in the rat. High intensity acoustic stimuli elicit a startle response, while electric footshocks provoke an immediate withdrawal of the feet often accompanied by a pain reaction. Flunitrazepam (0.5 mg/kg), diazepam (5 mg/kg), and ipsapirone (5 mg/kg) reduced the vocalization induced by both averse stimuli. Maprotiline (10-25 mg/kg) enhanced the vocalization. FG 7142 (10 mg/kg) had no effect. The acoustic startle-induced vocalization paradigm like the electric footshock-induced vocalization paradigm may provide a simple and reliable tool in the study of anxiety. The advantage of an acoustic pulse as the averse stimulus is discussed.

Animals↗

PubMed2006

[Ocular coloboma associated with cervico-oculo-acoustic syndrome].

INTRODUCTION: Cervico-oculo-acoustic syndrome is an uncommon syndrome consisting of Klippel Feil syndrome, deafness, and Duane syndrome. We relate a new case of cervico-oculo-acoustic syndrome. CASE REPORT: We report the case of 15-month-old girl referred for esotropia of the right eye. Ocular examination revealed type 1 Stilling Duane syndrome in the right eye, in which we also noted microcornea, iris coloboma, and papillary and inferior chorioretinal coloboma sparing the macular area. The left eye was normal. The physical examination revealed Klippel Feil syndrome characterized by an extremely short neck with limited movement, a low posterior head line and fusion of the cervical vertebrae on radiography. The association of hearing loss (due to agenesis of the external ear) with Klippel Feil syndrome and Stilling Duane syndrome confirmed the diagnosis of cervico-oculo-acoustic syndrome. CONCLUSION: This case is unique because of the association of cervico-oculo-acoustic syndrome with ocular coloboma of the right eye. This association has not been reported previously in the literature.

Coloboma↗

PubMed1997

A novel method to measure acoustic speed of bone tissue.

Acoustic speed is an important parameter that can be used to characterize bone tissue for evaluation of osteoporosis. Traditional approaches for measuring acoustic speed require knowledge of either the specimen thickness, which is sometimes difficult to obtain from biological tissues, or the reference fluid velocity that, moreover, is an unknown parameter for internal tissue in in vivo measurement. In this paper, a new method is proposed to measure acoustic speed from dual reflected ultrasound signals. This technique utilizes two transducers placed on the same side of the test object; one for transmitter and receiver, and the other one for receiver only. The acoustic speed of the test object is based on the information of time-of-flight from the signals received by both transducers and the separation distance between the transducer pair. The technique developed here not only eliminates the requirement of knowledge of specimen thickness, but also shows a feasibility for clinical applications. The results of different porcine and bovine bone samples measured in vitro by this technique are in good agreement with those measured by other published methods. In vivo measurement results of 10 healthy young volunteers' tibias are also reported.

Adult↗

PubMed1998

Acoustic modeling of shell-encapsulated gas bubbles.

Existing theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents Quantison and Myomap. An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and validated for these agents and Albunex. The acoustic transmission and scattering are measured in the frequency band from 1-10 MHz. The measured transmission is used to estimate two parameters, the effective bulk modulus, Keff, describing the elasticity, and the friction parameter, SF, describing the viscosity of the shell. For the scattering, the difference between measurements and calculations is < 3 dB. For Quantison, the effective bulk modulus is independent of the bubble diameter. For Albunex, it increases for decreasing bubble diameter. The nonlinear response of Quantison is minimal for acoustic pressures up to 200 kPa. For acoustic pressures above 200 kPa, the measured scattering abruptly increases. This increase reaches a level of 20 dB for an acoustic pressure of 1.8 MPa. This response cannot be predicted by the theoretical model developed in this article.

Albumins↗

PubMed2003

Heat shock transcription factor HSF1 is required for survival of sensory hair cells against acoustic overexposure.

To analyze the role of heat shock response in the cochleae, we induced major heat shock proteins, Hsp70, Hsp90, and Hsp27 by perfusion of hot saline into the middle ear cavity (called 'local heat shock') in guinea pigs. Hsps were induced in almost all of the cochlear cells including the sensory hair cells in the organ of Corti. We showed that loss of both the sensory hair cells and the auditory function induced by acoustic overexposure was inhibited by pretreatment of the inner ear with local heat shock. To examine the role of heat shock transcription factor 1(HSF), which activates heat shock genes in response to heat shock, in the protection of sensory hair cells, we analyzed acoustic injury in HSF1-null mice. We found that the loss of sensory hair cells was more significant in HSF1-null mice compared with that of wild-type mice when mice were subjected to acoustic overexposure. These results indicate that HSF1 is required for survival of the sensory hair cells against acoustic overexposure.

Animals↗

PubMed1998

Nasal passage patency in patients with allergic rhinitis measured by acoustic rhinometry: nasal responses after allergen and histamine provocation.

We investigated nasal passage patency after allergen and histamine provocation in patients with allergic rhinitis by acoustic rhinometry. In total, 75 outpatients with allergic rhinitis were studied. The threshold of nasal hypersensitivity to histamine was measured by the 10 microliters instillation of serial 10-fold dilution in the ipsilateral nasal cavity. Nasal provocation testing to specific antigen was applied to the anterior part of inferior turbinate in bilateral sides in sitting position. Measurement of nasal patency by acoustic rhinometry was repeated three times in each nasal cavity. The minimal cross-sectional area and total volume of nasal cavity were measured in an individual subject. The minimal cross-sectional area and total volume in the histamine challenged-side significantly decreased on the 10(-2), 10(-1), 10(-0) of end point, and up to 30 min after challenge with the threshold dose, but not in the unchallenged side. This means acoustic reflection technique is sensitive at least 100-fold in comparison with classical method like findings by anterior rhinoscopy and symptom scores. Nasal passage patency after bilateral allergen provocation showed predominant in the unilateral side, suggesting the cross over-reflex effects. It was concluded that acoustic rhinometry is one of the highly quantitative and sensitive method which can observe the change of nasal congestion.

Adolescent↗

PubMedDate not supplied

Beat-to-beat variability of left ventricular indexes measured by acoustic quantification: influence of heart rate and respiration--correlation with M-mode echocardiography.

Influence of heart rate and respiration on beat-to-beat variability of left ventricular indexes measured by acoustic quantification was examined. These indexes were correlated with their counterparts measured by M-mode echocardiography. Parameters of left ventricular performance were recorded for 1 full minute in 43 children with a mean age of 5.9 +/- 3.9 years. Beat-to-beat variability was documented. The effect of respiration on such variability was examined in another 10 subjects. A wide range of heart rates and respiration did not show significant influence on the degree of variance among these parameters. The indexes measured correlated well with their counterparts measured by M-mode echocardiography. Acoustic quantification separated those with normal from those with abnormal left ventricular function with the same statistical significance as did M-mode echocardiography. A moderate degree of beat-to-beat variability occurs in acoustic quantification-derived left ventricular indexes. Heart rate variability and respiration do not influence the beat-to-beat variance of parameters of left ventricular performance measured with the acoustic quantification. Excellent correlation was documented between this technique and M-mode echocardiography.

Adolescent↗

PubMed2005

The influence of acoustic power on multibubble sonoluminescence in aqueous solution containing organic solutes.

The effect of varying the applied acoustic power on the extent to which the addition of water-soluble solutes affect the intensity of aqueous multibubble sonoluminescence (MBSL) has been investigated. Under most of the experimental conditions used, the addition of aliphatic alcohols to aqueous solutions was found to suppress the MBSL intensity, although an enhancement of the MBSL intensity was also observed under certain conditions. In contrast, the presence of an anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solutions generally enhanced the observed MBSL intensity. For a series of aliphatic alcohols and SDS, a strong dependence of the MBSL intensity on the applied acoustic power (in the range of 0.78-1.61 W/cm(2)) at 358 kHz was observed. The relative SL quenching was significantly higher at higher acoustic powers for the alcohol solutions, whereas the relative SL enhancement was lower at higher acoustic powers in SDS solutions. These observations have been interpreted in terms of a combination of material evaporation into the bubble, rectified diffusion, bubble clustering and bubble-bubble coalescence.

Journal Article↗

PubMed2004

Use of visual, acoustic, and olfactory information during embedded invertebrate foraging in brown capuchins (Cebus apella).

Experiments were conducted to investigate which sensory cues are used by brown capuchins (Cebus apella) in embedded invertebrate foraging. The importance of visual, olfactory, and acoustic cues in such foraging was determined by presenting subjects with a stimulus log modified to block out given sensory cues. Experiment 1 was designed to investigate whether subjects could locate an invertebrate embedded in wood when only visual, acoustic, or olfactory information was available. Experiments 2 and 3 were designed to investigate extractive foraging behavior when two sensory cues were provided. It was hypothesized that the combination of visual and acoustic information would be necessary for subjects to successfully locate embedded invertebrates. Results indicated that subjects' performance was most successful when both visual and acoustic information was available.

Animals↗

PubMed2002

Bubble-induced acoustic micromixing.

A mixing technique based on the principle of bubble-induced acoustic microstreaming was developed. The mixer consists of a piezoelectric disk that is attached to a reaction chamber, which is designed in such a way that a set of air bubbles with desirable size is trapped in the solution. Fluidic experiments showed that air bubbles resting on a solid surface and set into vibration by the sound field generated steady circulatory flows, resulting in global convection flows and thus rapid mixing. The time to fully mix a 22 microL chamber is significantly reduced from hours (for a pure diffusion-based mixing) to tens of seconds. Numerical simulations showed that the induced flowfield and thus degree of mixing strongly depend on bubble positions. Optimal simulated mixing results were obtained for staggered bubble distribution that minimizes the number of internal flow stagnation regions. Immunomagnetic cell capture experiments showed that acoustic microstreaming provided efficient mixing of bacterial cell (Esherichia coli K12) matrix suspended in blood with magnetic capture beads, resulting in highly effective immunomagnetic cell capture. Bacterial viability assay experiments showed that acoustic microstreaming has a relatively low shear strain field since the blood cells and bacteria remained intact after mixing. Acoustic microstreaming has many advantages over most existing chamber micromixing techniques, including simple apparatus, ease of implementation, low power consumption (2 mW), and low cost.

Journal Article↗

PubMed2002

Acoustic coupling of transverse waves as a mechanism for the label-free detection of protein-small molecule interactions.

An on-line acoustic transverse wave device has been used to study the binding interactions of human serum albumin with the small molecule drug, warfarin. Four linking systems for the covalent attachment of the protein to the surface of the gold electrode of the sensor were employed, namely thioctic acid, cysteamine, an N-hydroxysuccinimide ester and 11-mercaptoundecanoic acid. All the attachment protocols involve the ability of thiols to form gold-sulfur bonds at the metal surface. The functional group present at the distal end of each thiol was chemically activated in order to facilitate covalent attachment of the protein. On-line sensor measurements of acoustic parameters show that the binding of warfarin to the protein can be detected, and depending on the linking monolayer used three of four possible combinations of changes in series resonance frequency and motional resistance are observed. Calculations of possible mass and thickness viscoelastic effects demonstrate that these conventional notions are invalid in terms of an explanation of the acoustic signals observed for the warfarin-protein interaction. The responses are ascribed to acoustic coupling phenomena.

Electrochemistry↗

PubMed1975

Static and dynamic acoustic impedance measurements in infant ears.

Tympanometry and acoustic reflex threshold data are reported for a series of presumable normal infants ranging in age from 55 to 132 days. In general, tympanograms displayed single peaks between +/- 50 mm H2O. Susceptance tympanograms with a 660-Hz probe frequency were sometimes characterized by monotonically increasing susceptance as ear canal pressure was changed from -200 to +200 mm H2O. Static values of acoustic conductance, susceptance, admittance, resistance, reactance, impedance, and phase angle were computed from tympanograms using the values of ambient and +200 mm H2O (0/+200 procedure) and maximum and minimum tympanometric values (MAX/MIN procedure). Comparison of the data from the two computational procedures suggested that the MAX/MIN procedure produces means and standard deviations of static values which are more manageable for establishing confidence limits with which to evaluate potentially pathological subjects. The MAX/MIN procedure resulted in lower mean values of conductance and susceptance for infant subjects relative to previously reported adult data using a similar computational procedure. Acoustic reflex thresholds were clearly present in all testable infants at coupler sound pressure levels similar to adult data, suggesting that the relations between reflex thresholds and hearing sensitivity demonstrated in adult subjects are similarly applicable to infant subjects. Mild sedation to induce sleep without altering the reflex would make acoustic reflex threshold measurement a useful procedure for screening large numbers of infants.

Adult↗

PubMed1978

Effects of stimulus duration and stimulus off time on the auditory and acoustic reflex thresholds.

The effects of stimulus duration and stimulus off time on the thresholds of hearing and the acoustic reflex were investigated in 10 normal-hearing subjects and 10 subjects with sensorineural hearing loss. A 1000-Hz stimulus with on-off times of 500-500 msec and 30-30 msec was used to obtain hearing sensitivity and acoustic reflex thresholds via a tracking method. Auditory threshold was poorer for the 30-30 msec tone than the 500-500 msec stimulus in both groups. Using the different stimuli, no significant difference in acoustic reflex threshold was observed in either group. These results suggest that the addition of a short off time modifies the previously observed effects of both duration and off time on the acoustic reflex and auditory threshold.

Adult↗

PubMedDate not supplied

Chronic paroxysmal hemicrania presenting as otalgia with a sensation of external acoustic meatus obstruction: two cases and a pathophysiologic hypothesis.

OBJECTIVE: To describe two cases of chronic paroxysmal hemicrania manifested by otalgia with a sensation of external acoustic meatus obstruction and to suggest that the trigeminal-autonomic reflex is a mechanism for the sensation of ear blockage. BACKGROUND: Maximum pain in chronic paroxysmal hemicrania is most often in the ocular, temporal, maxillary, and frontal regions. It is less often located in the nuchal, occipital, and retro-orbital areas. Review of the literature on chronic paroxysmal hemicrania found no reports of pain primarily localized to the ear and associated with a sensation of external acoustic meatus obstruction. METHODS: The history, physical examination, imaging studies, and successful treatment plan in two patients with otalgia and ear fullness and a subsequent diagnosis of chronic paroxysmal hemicrania are summarized. RESULTS: The first patient was a 42-year-old woman with a 10-year history of unilateral, severe, paroxysmal otalgia occurring five times a day with a duration of 2 to 60 minutes. During an attack, the ear became erythematous and the external acoustic meatus felt obstructed. There were no other associated autonomic signs. The second patient was a 49-year-old woman with a 3-year history of unilateral, severe, paroxysmal otalgia occurring 4 to 15 times a day with a duration of 3 to 10 minutes. During an attack, her ear felt obstructed, and she noted ipsilateral eyelid edema and ptosis. Both patients quickly became pain-free after taking indomethacin and required its continued use to prevent headache recurrence. CONCLUSIONS: Chronic paroxysmal hemicrania may be manifested by otalgia with a sensation of external ear obstruction. When the otalgia is paroxysmal, unilateral, severe, frequent, and associated with autonomic signs, one should consider the diagnosis of chronic paroxysmal hemicrania, especially because of the prompt response to indomethacin. The most important feature to consider when making the diagnosis of chronic paroxysmal hemicrania is the frequent periodicity of discrete, brief attacks of unilateral cephalgia separated by pain-free intervals. It is hypothesized that the sensation of ear obstruction in these patients is due to swelling of the external acoustic meatus mediated through increased blood flow by the trigeminal-autonomic reflex.

Adult↗