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At least 91 records · Page 5Linked to original sources
PubMed1976

Acoustic reflex test in neuro-otologic diagnosis. A review of 24 cases of acoustic tumors.

Acoustic and other tumors of the cerebellopontine angle are not uncommon, and they usually have otologic symptoms or findings. Early diagnosis depends on a high index of suspicion and a thorough evaluation of patients with suspected tumors. This is a report of 24 cases selected from a group of 184 surgically confirmed tumors. Had the cases been evaluated only on the basis of pure tone or speech audiometry or on the basis of plain roentgenograms, the diagnosis might not have been made. Audiological examination should include the acoustic reflex test. The results of this test indicated a retrocochlear problem (absence or decay of the reflex) in 19 of 24 cases (80%). The test was positive in 11 of 12 patients with normal or near normal hearing and in seven of eight patients with normal x-ray films.

Adolescent↗
PubMed1991

Identifying acoustic scattering sources in normal renal parenchyma from the anisotropy in acoustic properties.

Acoustical and histological properties of dog kidney parenchyma are examined in vitro to determine sources of acoustic scattering in the normal kidney. The speed of sound, attenuation, backscatter, effective scatterer size and scattering strength were measured within the frequency range 1-15 MHz and at eight angles of incidence with respect to the predominant nephron orientation. Significant angular dependence, or anisotropy, was observed in backscatter coefficient and scattering strength estimates; attenuation was found to be weakly anisotropic. All three parameters, each measured at 19 degrees C, exhibited values that were maximum for perpendicular incidence and minimum for parallel incidence. Speed of sound and scatterer size estimates were observed to be independent of scanning angle. Comparisons between these data for renal cortex and histological observations suggest that the glomerulus is the principal scatterer at low frequencies, and renal tubules and blood vessels at high frequencies.

Animals↗
PubMed2004

High-frequency acoustic emissions generated by a 20 kHz sonochemical horn processor detected using a novel broadband acoustic sensor: a preliminary study.

This paper describes the application of a novel broadband acoustic sensor to evaluating the acoustic emissions from cavitation produced by a typical commercial 20 kHz sonochemical horn processor. Investigations of the reproducibility of the processor, and of the variation in cavitation emissions as a function of output setting and sensor location are described, and resulting trends discussed in terms of the broadband integrated power in the megahertz frequency range. Companion studies with a conventional membrane hydrophone have illustrated for the first time that cavitation emissions produced by a sonochemical horn processor can extend to frequencies beyond 20 MHz, and the sensor shows that significant nonlinearity can be seen in measured cavitation activity with increasing nominal output power.

Journal Article↗
PubMed1989

An addendum to "Effects of Noise on Speech Production: Acoustic and Perceptual Analyses" [J. Acoust. Soc. Am. 84, 917-928 (1988)].

The authors respond to Fitch's comments [H. Fitch, J. Acoust. Soc. Am. 86, 2017-2019 (1989)] on an earlier paper. New analyses are presented to address the question of whether F1 differences observed in the original report are an artifact of linear predictive coding (LPC) analysis techniques. Contrary to Fitch's claims, the results suggest that the F1 differences originally reported are, in fact, due to changes in vocal tract resonance characteristics. It is concluded that there are important acoustic-phonetic differences in speech when talkers speak in noise. These differences reflect changes in both glottal and supraglottal events that are designed to maintain speech intelligibility under adverse conditions.

Humans↗
PubMed2000

Acoustic radiation from an elastic baffled rectangular plate covered by a decoupling coating and immersed in a heavy acoustic fluid

The vibroacoustic behavior of an elastic, simply supported rectangular plate covered by a locally reacting decoupling layer supporting thickness deformation is presented. The model simulates the vibration and acoustic response of the system immersed in water and subjected to a point force disturbance. A simplified version of the theory is derived in the limiting case of a large decoupling (low mechanical impedance of the layer/high frequency). An appropriate vibratory indicator, representative of the acoustic attenuation provided by the decoupling treatment, and independent of the structure dimensions, is also investigated from the perspective of small-scale laboratory characterization.

Journal Article↗
PubMed1984

[Limits between normal and pathologic auditory fatigue following acoustic stress with high peak pressures in its significance for acoustically-induced hearing loss].

The extent of hearing fatigue as a consequence of acoustic impacts is an important factor in predicting an anticipated hearing impairment. It is essential to know whether hearing fatigue is due to physiological or pathological conditions. Mass screenings of thousands of soldiers suffering from hearing fatigue due to acoustic impact, showed that hearing fatigue is subject to considerable individual fluctuation. The time of recovery, or rather the time required by the auditory reception to return to the preimpact threshold, is of paramount importance. Recovery from an audiometrically traceable TTS within 10 minutes can be considered unobjectionable. Recovery time of up to half an hour can be found in 10--20% of the screened personnel, depending on the impact. This is within physiological variation range and can be considered unobjectionable. Recovery times of a TTS of up to 3 hours constitute a limit beyond which pathological effects in the cochlea can be expected. Recovery times of 24 hours and more signify a definite impairment if impacts continue.

Audiometry↗
PubMed1983

Mechanical and acoustical influences on spontaneous oto-acoustic emissions.

Spontaneous, tone-like emissions produced by normal ears and measured in the closed outer ear canal can be affected by mechanical and acoustical events. Such effects can be measured in steady-state conditions as well as for transient stimulation, and are seen in response to the stapedius reflex, to ear canal air pressure changes, and to the presentation of external tones. Frequency and level of the emissions follow certain characteristics which are described and discussed. The emissions seem to react with 2 ms delay and with an exponential rise and decay, the time constant of which is about 13 ms.

Acoustic Impedance Tests↗
PubMed1985

Fetal acoustic stimulation testing: a retrospective experience with the fetal acoustic stimulation test.

The nonstress test is of accepted value in the surveillance of high-risk pregnancies. In order to improve the efficiency of testing, the authors retrospectively evaluated the adjunctive use of acoustic stimulation testing (FAS-TEST) in 1241 patients who underwent 3464 antepartum fetal heart rate tests. The results were compared to those in the previous 6 months during which time 1307 patients underwent 3573 nonstress tests. The frequency of nonreactive tests was 12.6% in the nonstress test group and 6.1% in those patients who underwent the FAS-TEST. The antepartum fetal death rates were not significantly different when the two groups were compared. The FAS-TEST decreases the percentage of nonreactive tests in a high-risk population and, as a consequence, may reduce the testing time.

Acoustic Stimulation↗
PubMed1990

Non-contact acoustic method for the simultaneous measurement of thickness and acoustic properties of biological tissues.

The frequency dependence of the magnitude and phase shift of reflected waves from a thin tissue specimen has been found to yield characteristic patterns as a function of the specimen thickness. By analysis of those characteristic patterns, the specimen thickness can be determined so that the attenuation constant and the sound speed can be obtained by a non-contact procedure. The method is demonstrated in the frequency range 100 MHz to 200 MHz, using a scanning acoustic microscope and approximately 10 microns thick myocardial tissue samples of human origin, one paraffin embedded.

Acoustics↗
PubMed1995

Acoustic features and acoustic changes are represented by different central pathways.

The central processing of acoustic stimulus changes can be observed neurophysiologically in the mismatch negativity auditory evoked potential (MMN). Stimuli differing in interaural phase were used to investigate the contributions of the primary and non-primary auditory pathways to the encoding of binaural stimuli and to investigate passively elicited measures of binaural processing in experimental animals. In guinea pigs, the MMN was obtained in response to 1000 Hz tones embedded in white noise (S:N = 2 dB). Using a modified oddball paradigm (that is, two stimuli presented in a series, each with a different probability of occurrence), stimuli were presented binaurally with both the tone and noise in-phase to the two ears (S0N0) as the standard stimulus ans the tone 180 degrees out-of-phase (S(PI)N0) as the deviant stimulus. The MMN, by definition, should occur only in response to a change, or 'mismatch,' between the standard and deviant stimuli. The response to the deviant stimulus in the oddball paradigm was compared to the response to the same stimulus when presented in a series alone. The responses to S0N0 and S(PI)N0 collected in a series alone, termed the intrinsic responses, were also compared. Responses were recorded from two surface epidural electrodes - one at the posterior midline and one over the left temporal lobe. AEPs from these locations have been shown to reflect the activity of primary and non-primary thalamo-cortical pathways respectively. A significant MMN was observed at the midline electrode, but no MMN was observed over the temporal lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed2002

Acoustic inhomogeneity of carotid arterial plaques determined by GHz frequency range acoustic microscopy.

Characterization of the structure and composition of carotid arterial plaques is important to predict the risk of embolic and thrombotic events. In clinical echography, echolucent lesions seem to be more associated with stroke than echogenic lesions, and a low grey-scale median is associated with a fivefold increase in the incidence of silent infarcts. In the present study, five fixed human carotid atherosclerotic lesions were observed by GHz-range scanning acoustic microscopy (SAM). The atherosclerotic lesions were characterized by either thickened fibrosis with dense collagen fibers or lipid accumulation with sparse collagen network by optical microscopy. SAM revealed that the fibrosis was classified into type I and III collagen by attenuation of ultrasound (US) and that the sound field of lipid accumulation lesions became inhomogeneous. The results would provide the scientific basis for the images of vulnerable plaques being produced in diagnostic US.

Acoustics↗
PubMed2002

Provisional mapping of quantitative trait loci modulating the acoustic startle response and prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) of the acoustic startle response (ASR) is a form of sensorimotor gating, defined as an inhibition of the startle response when a low intensity stimulus, the prepulse, precedes the startling stimulus. Deficits in PPI have been reported in schizophrenia and other psychiatric/neurological disorders, and correlate with symptom severity in schizophrenia, suggesting that deficient PPI per se or abnormalities in neural circuits regulating PPI may cause some symptoms of schizophrenia. If so, then genes conferring reduced PPI may contribute toward genetic vulnerability to schizophrenia. Studies with selectively bred rodent strains indicate that PPI is under genetic control; however, the identity of the relevant genes is unknown. The current study used recombinant congenic mouse strains derived from C57BL/6J and A/J parents to assess genetic variability in PPI and in ASR and to identify provisional quantitative trait loci (QTLs) modulating these phenotypes. Significant between-strain differences in ASR and in PPI at each of several prepulse intensities (75, 80, 85, 90, 95 dB) were found. Correlations between PPI at the various prepulse intensities were highly significant, suggesting appreciable overlap in genetic regulation of PPI across prepulse intensities. Five QTLs (chromosomes 3, 5, 7, 16) associated with PPI across all prepulse intensities, but not with ASR, were identified. Two additional QTLs (chromosomes 2, 11) associated with both PPI and ASR were found. Fifteen QTLs were associated with ASR alone. Data on genotypes of informative congenic strains were used to support probable involvement of loci modulating PPI and to narrow the probable chromosomal location of QTLs. If confirmed, these QTLs may suggest candidate genes directing novel mechanisms for regulation of PPI

Acoustic Stimulation↗
PubMed2003

Similar effects of attention directed to acoustic and tactile stimuli on prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) is assumed to index automatic and controlled processing. In three experiments (n= 32, 22, and 30) participants were asked to judge the duration of a prepulse in comparison with a stimulus presented 4000 ms before the prepulse. A distracter was presented simultaneously with the prepulse to increase the cognitive demands of the task. PPI was assessed at stimulus onset asynchronies (SOAs) of 30-150 ms, and 420 ms. The prepulse was either a tone (60 dB) or a tactile stimulus (21 kPa), and startle was elicited by 95 dB white noise. Directing attention to the prepulse increased PPI at SOAs of 60 ms and longer in all experiments, but the sensory modality to which attention was directed played only a minor role. We conclude that directing attention to both acoustic and tactile prepulses increased PPI.

Acoustic Stimulation↗
PubMed2002

Acoustic competition in the gulf toadfish Opsanus beta: acoustic tagging.

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male-male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound-pressure levels and frequency spectra that correspond with those of recognized neighbors, suggesting that one fish is grunting during another's call, a phenomenon here termed acoustic tagging. Snaps of nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally produced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with increased trigger amplitude. Tagging is distinct from increased calling in response to natural calls or stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally reciprocal between fish, suggesting parallels to dominance displays.

Acoustics↗
PubMed2003

Acoustic tumors: operation versus radiation--making sense of opposing viewpoints. Part II. Acoustic neuromas: sorting out management options.

Patients with acoustic neuromas have several options available to them. Large tumors with significant brain stem compression usually require surgical resection. For patients with small or medium-sized tumors, radiosurgery has become a common treatment, with excellent long-term results being reported. Patients must be comfortable with the concept of tumor control rather than tumor removal. Most seem to be satisfied with this concept if it allows them to avoid brain surgery. Surgeons should strive to educate their patients with information from the peer-reviewed literature. Confusion exists among patients, because the information from Internet sources, newsletters, support groups, and physicians has not always been validated and supported by outcomes data. Although we are asked to provide our opinions, our comments should not be based on myth, conjecture, training bias, or socioeconomic concerns.

Decision Making↗
PubMed2003

Numerical investigation and electro-acoustic modeling of measurement methods for the in-duct acoustical source parameters.

It is known that the direct method yields different results from the indirect (or load) method in measuring the in-duct acoustic source parameters of fluid machines. The load method usually comes up with a negative source resistance, although a fairly accurate prediction of radiated noise can be obtained from any method. This study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated by using the method of characteristics. The equivalent circuits for such simulations are also analyzed by considering the system as having a linear time-varying source. It is found that the results from the load method are quite sensitive to the change of cylinder pressure or valve profile, in contrast to those from the direct method. In the load method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance.

Journal Article↗
PubMed1990

Potentiation of the acoustic startle response by a conditioned stimulus paired with acoustic startle stimulus in rats.

The hypothesis that the standard acoustic startle habituation paradigm contains the elements of Pavlovian fear conditioning was tested. In a potentiated startle response paradigm, a startle stimulus and a light conditioned stimulus (CS) were paired. A startle stimulus then was tested alone or following the CS. Freezing behavior was measured to index conditioned fear. The startle response was potentiated on CS trials, and rats froze more in CS than in non-CS periods. In Experiment 1, response to a previously habituated, weak startle stimulus was potentiated. In Experiment 2, response to the same stimulus used as the unconditioned stimulus (US) in training was potentiated. This CS-potentiated response retarded the course of response decrements over training sessions as compared with an explictly unpaired control group. Conditioned fear is a standard feature of this habituation paradigm, serves to potentiate the startle response, and provides an associative dimension lacking in the habituation process per se.

Animals↗