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At least 307 records · Page 17Linked to original sources
PubMed2002

Acoustic reflex thresholds at varying click rates in children.

OBJECTIVE: Previous studies conducted with young adults have shown that ipsilateral acoustic reflex thresholds improve with an increase in the click-rate. Older adults also show an improvement in acoustic reflex thresholds with an increase in the click-rate. However, the click-rate induced facilitation (RIF) of acoustic reflex thresholds is significantly reduced in older adults. These results suggest that slower temporal processing in older adults can be documented by measuring the click-RIF of acoustic reflex thresholds. Thus, the click-RIF of acoustic reflex thresholds may prove to be a valuable tool for the assessment of temporal processing disorders in young children. However, click-RIF of ipsilateral acoustic reflex thresholds has not been studied in young normal children. The purpose of this study was to evaluate and document the click-RIF in young normal children to provide normative data for this age-group. METHODS: The study included a total of 30 participants (12 male and 18 female) with normal hearing between the ages of 6 and 10 years. Children with outer, middle ear, or neurological disorders were excluded from the study. Ipsilateral acoustic reflex thresholds were determined in the left and right ears with clicks presented at the rate of 50 and 100 per s. The frequency of the probe tone was 226 Hz and intensity was 85 dB SPL. A statistical analysis using a three factor mixed MANOVA was planned to explore differences between ears, click rates and gender. RESULTS: The MANOVA revealed a significant effect (P=0.0000) for the click-rate. There were no differences between ears or gender and no interactions. The mean click-RIF with an increase in the rate from 50 to 100 per s was 10.50 dB. CONCLUSION: Comparison of these results with previous results obtained from young adults suggests that young normal children show click-RIF that is similar to that apparent in young adults.

Acoustic Stimulation↗
PubMed1979

Static acoustic-immittance measurements.

The basic principles of deriving static acoustic-immittance measurements in human ears are presented. Problems caused by differences in instrumentation, computations, and measurement technique are discussed in terms of the utility and comparisons of static acoustic-immittance measurements. Data are provided regarding the short- and long-term variabilities inherent to static measurements. Although our subject pool was relatively small, certain patterns were apparent in the short- and long-term variability inherent to static acoustic-impedance measurements. The intra-event variability about the mean static acoustic impedance was small and varied inversely with probe-tone frequency. Standard deviations were less than 50 acoustic ohms for a 220-Hz probe tone and less than 25 acoustic ohms for a 660-Hz probe tone. Session-to-session variability in static measurements varied little within subjects but varied greatly across subjects. There was little correlation between the mean and standard deviation for within-subject measurements. Standard deviations across subjects approximate a relatively constant proportion (30-40%) of the mean static value. The need for large population studies of static acoustic-immittance measurements is noted.

Acoustic Impedance Tests↗
PubMed1985

Tympanometric and acoustic-reflex studies in neonates.

Tympanograms and acoustic reflexes for a broadband noise and for a 1000-Hz tone were measured in normal neonates. Notched tympanograms were typical of neonatal ears for a 220-Hz probe tone. A single-peaked tympanogram was most characteristic for a probe frequency of 660 Hz. Ipsilateral and contralateral acoustic reflexes were present more frequently for a 660-Hz probe tone compared to a 220-Hz probe tone, but acoustic-reflex thresholds were not significantly different between probe tones. As with adults, acoustic-reflex thresholds for the noise were significantly lower than for the tone, and ipsilateral reflex thresholds were lower than contralateral reflex thresholds. Reliability of acoustic-reflex and tympanometric measures was high. Age change from 2 to 4 days had no significant effect on tympanometric or acoustic-reflex characteristics. There was no apparent relation between tympanometric pattern and acoustic-reflex characteristics.

Acoustic Impedance Tests↗
PubMed2002

Rating, ranking, and understanding acoustical quality in university classrooms.

Nonoptimal classroom acoustical conditions directly affect speech perception and, thus, learning by students. Moreover, they may lead to voice problems for the instructor, who is forced to raise his/her voice when lecturing to compensate for poor acoustical conditions. The project applied previously developed simplified methods to predict speech intelligibility in occupied classrooms from measurements in unoccupied and occupied university classrooms. The methods were used to predict the speech intelligibility at various positions in 279 University of British Columbia (UBC) classrooms, when 70% occupied, and for four instructor voice levels. Classrooms were classified and rank ordered by acoustical quality, as determined by the room-average speech intelligibility. This information was used by UBC to prioritize classrooms for renovation. Here, the statistical results are reported to illustrate the range of acoustical qualities found at a typical university. Moreover, the variations of quality with relevant classroom acoustical parameters were studied to better understand the results. In particular, the factors leading to the best and worst conditions were studied. It was found that 81% of the 279 classrooms have "good," "very good," or "excellent" acoustical quality with a "typical" (average-male) instructor. However, 50 (18%) of the classrooms had "fair" or "poor" quality, and two had "bad" quality, due to high ventilation-noise levels. Most rooms were "very good" or "excellent" at the front, and "good" or "very good" at the back. Speech quality varied strongly with the instructor voice level. In the worst case considered, with a quiet female instructor, most of the classrooms were "bad" or "poor." Quality also varies with occupancy, with decreased occupancy resulting in decreased quality. The research showed that a new classroom acoustical design and renovation should focus on limiting background noise. They should promote high instructor speech levels at the back of the classrooms. This involves, in part, limiting the amount of sound absorption that is introduced into classrooms to control reverberation. Speech quality is not very sensitive to changes in reverberation, so controlling it for its own sake should not be a design priority.

Acoustics↗
PubMedDate not supplied

[Synthetic sentence identification (SSI) and contralateral acoustic stapedius reflex].

BACKGROUND: The study of the relationship of the contralateral acoustic reflex with the auditory skill of closure. AIM: To analyze the identification of a speech signal in the presence of competitive sounds in subjects with absence of contralateral acoustic reflex. METHOD: Application of the synthetic sentence identification (SSI) test under the conditions of competitive contralateral message (SSI-CCM), with the signal-to-noise ratio of 0 and -40dB, and ipsilateral competitive message (SSI-ICM), with the signal-to-noise ratio of 0, -10, -15 and -20dB, in 43 young adults (group A = 21 subjects with contralateral acoustic reflex present in all of the investigated frequencies, and group B = 22 subjects with contralateral reflex absent at the frequency of 500Hz, or in all of the investigated frequencies, or still in some of the investigated frequencies necessarily including 500Hz), of both gender, with no hearing, otologic or learning disabilities. RESULTS: The acoustic reflex threshold was above 100dB NA in 59% of the individuals in group B and in 14% of the individuals in group A. All subjects performed according to the normal pattern suggested in the specialized literature for the SSI test. The performance of group B in the SSI-ICM test was inferior to that of group A for all the signal-to-noise ratios used, although the difference was not statistically significant. Group B, which presented an acoustic reflex threshold higher than 100dB NA or the absence of the acoustic reflex, was also the group that presented the worse performance in the SSI test. CONCLUSION: The absence of the contralateral acoustic reflex seems to interfere in the identification of the speech signal in the presence of competitive noises.

Acoustic Impedance Tests↗
PubMedDate not supplied

Click-rate induced facilitation of the acoustic reflex using constant number of pulses.

This investigation was designed to evaluate acoustic reflex thresholds at various repetition rates using a constant number of clicks (constant acoustic energy). Ipsilateral acoustic reflex thresholds were obtained from 19 left ears by presenting 300 clicks at the repetition rates of 50, 100, 150, 200 and 300/s. The results showed an improvement in the acoustic reflex thresholds with an increase in the repetition rates (rate integration). Thus for the test conditions used in the study, rate-induced facilitation of the acoustic reflex thresholds can be demonstrated even if the acoustic energy in the stimuli at various rates is held constant. Greater acoustic energy at higher repetition rates is unnecessary for such facilitation.

Acoustic Stimulation↗
PubMed2006

Acoustic methods of detection in gas chromatography.

A brief review of the use of acoustic detection methods in GC is presented. While a number of methods (some quite similar) have been developed for use as gas-phase sensors in various applications, this article focuses specifically on those techniques that have been used to detect analytes following their separation by GC. Overall, a number of "active" acoustic methods (which measure analytes through their interaction with a controlled external acoustic wave source) were reportedly used as GC detectors. These include ultrasonic, thickness shear mode, surface acoustic wave (SAW), and flexural plate wave methods. Conversely, "passive" acoustic methods (those that produce an acoustic signal through some chemical reaction with the analyte) have also been used as GC detectors. These include photoacoustic and acoustic flame methods of detection. Of the two major classifications, reports of active methods are far more prevalent. In particular, the usage of SAW techniques with GC is an area of research that has seen accelerated growth in recent years.

Acoustics↗
PubMed1982

The current state of the radiological diagnosis of acoustic neuroma.

Thin, overlapping section, contrast-enhanced, axial and coronal CT, with additional high-resolution (HR) treatment of the sections through the internal auditory canal, was performed on 31 patients clinically suspected of acoustic neuroma. With this technique 13 acoustic neuromas protruding more than 10 mm and eight acoustic neuromas protruding between 2 and 10 mm outside the internal auditory canal were unequivocally diagnosed. O2CT cisternography was performed on ten patients. An intracanalicular neuroma was diagnosed in three cases with this technique, also a small extracanalicular neuroma in one case, and an acoustic neuroma was definitely excluded in six cases. It is concluded that O2CT cisternograhy is the diagnostic procedure of choice for the detection of purely intracanalicular neuromas and the definite exclusion of acoustic neuroma. HR CT proved superior to polytomography for the evaluation of the internal auditory canal and should be performed in every case suspected of acoustic neuroma. A protocol for the radiological investigation of patients suspected of acoustic neuroma is given.

Contrast Media↗
PubMed1997

[Acoustic reflection position monitoring of tracheal cannulae. A contribution to quality assurance?].

Non-invasive acoustic airway monitoring was evaluated in an experimental study. Recording amplitude and travel time of acoustic pulse response, an area-distance function of the cross sectional dimensions of the endotracheal tube and the adjacent airway was calculated to obtain an acoustic pattern of the airway. Measurements on models and excised human cadaver lungs were performed to discover whether displacement or obstruction of the artificial airway can be detected in the acoustic equivalent. Regression analysis revealed a close correlation between displacement of tracheostomy tubes and the shifting of the acoustic area-distance function (corr. coeff. 0.97-1). Dispersion analysis confirmed reasonable reliability (coeff. of variation 0.6-2.1%). Location and amount of obstruction could likewise be identified. Thus acoustic mapping provides an adequate approximation of the true geometry of tracheostomy and endotracheal tubes. We conclude that acoustic monitoring may provide a powerful tool to achieve primary prevention of airway disturbances in intubated and mechanically ventilated patients, as geometrical changes of airway configuration can be detected even before they cause substantial effects on respiratory metabolism.

Acoustics↗
PubMed2006

Acoustic rhinometry in nasal provocation test in perennial allergic rhinitis.

Acoustic rhinometry is one method to evaluate nasal geometry by an acoustic reflection technique. The aim of this study was to investigate the changes in acoustic rhinometry after nasal provocation in patients with exclusively perennial allergic rhinitis. In 19 patients, acoustic rhinometry and active anterior rhinomanometry were performed before and after nasal provocation test. There was a statistically significant nasal flow reduction measured by active anterior rhinomanometry after nasal provocation (p < 0.05) and a median symptom score of four points, both indicating a positive response to nasal provocation. On the other hand, there was no statistically significant change in the values of acoustic rhinometry after nasal provocation (p > 0.05). In patients with exclusively perennial allergic rhinitis, acoustic rhinometry does not seem to significantly change after nasal provocation. In contrast, active anterior rhinomanometry values decreased significantly after nasal provocation. The presented results indicate that acoustic rhinometry does not seem to be a diagnostic method superior to active anterior rhinomanometry in this context.

Adolescent↗
PubMed1988

Interactive periodontal and acoustic influences on the masseteric post-stimulus electromyographic complex in man.

Post-stimulus electromyogram (EMG) complexes (PSECs) were studied in the full-wave rectified and averaged EMGs of the masseter muscles in 15 subjects, who clenched at a controlled level. The PSECs, a series of downward- and upward-going waves reflecting inhibitory and excitatory influences upon the masseteric motoneurones, were elicited by mechanical stimulation of a tooth. The stimuli selectively activated mechanoreceptors in the periodontium and, by bone-conduction, acoustic receptors. Application of acoustic masking during the periods of stimulation revealed a series of inhibitory and excitatory acoustic influences in the PSEC, which were absent after local electrical stimulation of receptors in the periodontium or their afferents. By applying local anaesthesia to the periodontium of a mechanically stimulated tooth, the durations of the acoustic influences were on the average reduced by 76%. In subjects whose PSECs consistently included a second inhibitory period, the duration of the acoustic influences with respect to that of the PSEC (30%) was larger than otherwise (13%), suggesting a central gating of periodontal pathways which can block both periodontal and acoustic influences. The acoustic influences, of which the appearance in the PSEC largely depends upon activated periodontal pathways, represent a new finding of audio-motor reflexes.

Acoustic Stimulation↗
PubMed1993

Collision-like interactions between acoustic and electrical signals that produce startle reflexes in reticular formation sites.

A startle-like response can be evoked at low currents by one-pulse electrical stimulation of reticular formation sites from the rostrolateral pons to the caudomedial medulla. To test whether this response is mediated by the same reticular formation neurons as those that mediate the acoustic startle, we delivered a brief, subthreshold acoustic stimulus followed by an 0.1-ms electrical pulse to one side of the reticular formation of rats. The current thresholds for electrical startle were usually powerfully reduced (50-80%) whenever the acoustic stimulation was presented within 5 ms of the electrical pulse. This summation was, however, interrupted by brief (0.2-1.0 ms) spike-like increases in threshold when the electrical pulse was delivered 4.0-4.6 ms after the offset of the acoustic stimulus. The timing of the spike-like increase in threshold shifted to longer intervals in more caudal sites, consistent with the conduction of action potentials in the startle pathway. For example, the increase occurred at an interval of 4.1 ms near the ventral lateral lemniscus (VLL) and at intervals of 4.4-4.6 ms for sites in the pontine or medullary reticular formation. The increases in startle threshold are attributed to collisions between antidromic action potentials evoked by the electrical pulses and orthodromic action potentials evoked by the acoustic stimuli. These results suggest that the neurons in reticular formation that produce the acoustic startle reflex overlap greatly with the neurons that mediate electrically evoked startle-like responses. Also, the acoustic signals mediating the startle reflex must be, in large part, a synchronous volley of action potentials conducted by longitudinal bundles of reticular formation axons.

Acoustic Stimulation↗
PubMed2005

Acoustic signal typing for evaluation of voice quality in tracheoesophageal speech.

SUMMARY: Because of the aperiodicity of many tracheoesophageal voices, acoustic analysis of the tracheoesophageal voice is less straightforward than that of the normal voice. This study presents the development and testing of an acoustic signal typing system based on visual inspection of a narrow-band spectrogram that can be used by researchers for classification of voice quality in tracheoesophageal speech. In addition to this classification system, a selection of acoustic measures [median fundamental frequency, standard deviation of fundamental frequency, jitter, percentage of voiced (%Voiced), harmonics-to-noise ratio (HNR), glottal-to-noise excitation (GNE) ratio, and band energy difference (BED)] was computed to provide more insight into the acoustic components of tracheoesophageal voice quality. For clinical relevance, relationships between the acoustic signal types and an overall judgment of the voice were investigated as well. Results showed that the four acoustic signal types form a good basis for performing more acoustic analyses and give a good impression of the overall quality of the voice.

Aged↗
PubMed2006

Acoustic power measurement of high intensity focused ultrasound in medicine based on radiation force.

How to measure the acoustic power of HIFU is one of the most important tasks in its medical application. In the paper a whole series of formula for calculating the radiation force related to the acoustic power radiated by a single element focusing transducer and by the focusing transducer array were given. Various system of radiation force balance (RFB) to measure the acoustic power of HIFU in medicine were designed and applied in China. In high power experiments, the dependence of radiation force acting the absorbing target on the target position at the beam axis of focusing transducer was fined. There is a peak value of "radiation force" acting the absorbing target in the focal region when the acoustic power through the focal plane exceeds some threshold. In order to avoid this big measurement error caused by the 'peak effect' in focal region, the distance between the absorbing target of RFB and the focusing transducer or transducer array was defined to be equal to or less than 0.7 times of the focal length in the National Standard of China for the measurements of acoustic power and field characteristics of HIFU. More than six different therapeutic equipments of HIFU have been examined by RFB for measuring the acoustic power since 1998. These results show that RFB with the absorbing target is valid in the acoustic power range up to 500W with good linearity for the drive voltage squared of focusing transducer or array. The uncertainty of measurement is within +/-15%.

Acoustics↗
PubMed2002

Acoustic startle, prepulse inhibition, and fear-potentiated startle measured in rhesus monkeys.

BACKGROUND: Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely valuable for analysis of neural systems associated with fear and anxiety. Until recently, there have been few efforts to develop acoustic startle measurement in nonhuman primates. We report here development of a whole-body acoustic startle protocol in rhesus monkeys. METHODS: Eight juvenile rhesus monkeys were tested in a new whole-body (somatic) acoustic startle protocol. Startle responses were assessed in three paradigms: 1) stimulus intensity-response amplitude, 2) prepulse inhibition (PPI), and 3) fear-potentiated startle. RESULTS: Initial studies revealed that the amplitude of whole-body startle in monkeys, as in rodents and humans, is directly proportional to acoustic stimulus intensity and gradually habituates with repeated exposures. Presentation of a weak acoustic stimulus 45-2020 msec before a startle stimulus reduces startle amplitude by 40%-50%, depending on interstimulus interval length (PPI). We have also measured significant potentiated startle amplitude in the presence of a visual stimulus after pairing it with an inescapable pulse of pressurized air (fear-potentiated startle). CONCLUSIONS: Our data demonstrate that acoustic startle in nonhuman primates successfully bridges rodent and human research in two broad areas: stimulus-response relationships and behavioral plasticity represented by habituation, PPI, and fear potentiation. The opportunity now emerges to link concepts developed in rodents to the more complex neuroanatomical and cognitive processes common to monkeys and humans.

Acoustic Stimulation↗
PubMed1999

Effects of bilateral electrical stimulation of the ventral pallidum on acoustic startle.

The ventral pallidum (VP) is believed to occupy a critical position between the limbic and the motor systems, for transferring motive information into motor commands. To estimate the time course of signaling from the VP to motor outputs, in the present study we examined the effects of bilateral electrical stimulation of the VP on the acoustic startle reflex in awake rats. When the interstimulus interval (ISI) between VP stimulation and acoustic stimulation was shorter than 5 ms, VP stimulation potentiated acoustic startle. When the ISI was longer than 5 ms, VP stimulation inhibited acoustic startle over a large range of ISIs with the maximum inhibition at ISIs between 15 and 25 ms. In contrast, bilateral electrical stimulation of the amygdala did not have a significant inhibitory effect on acoustic startle, but strongly augmented acoustic startle at shorter ISIs (0-10 ms). Compared to unilateral electrical stimulation of the inferior colliculus (IC), bilateral stimulation of the VP gave rise to a rightward shift of the ISI curve, indicating that the neural pathways conveying the inhibitory influence from the VP to the acoustic startle circuit are longer than those from the IC.

Acoustic Stimulation↗
PubMed1989

Acoustic and plasma guided lasertripsy (APGL) of urinary calculi.

The feasibility of using pulsed laser generated acoustic and plasma optical emission signals to monitor laser fragmentation of urinary stones was studied in vitro. A flashlamp pumped tunable dye laser operating at a wavelength of 504 nm. (coumarin green) was used as the laser source. Acoustic signals were recorded with a hydrophone which has a useful frequency response of up to 350 KHz. Plasma optical emissions were transmitted retrograde along the laser fiber and reflected through a beam splitter to an optical detection system consisting of a series of spectral filters (to transmit plasma radiation from 380 nm.-440 nm. and block any 504 nm. laser light) and a photomultiplier tube. Measurements of acoustic and plasma signals were taken from different urinary calculi, guidewires, catheters, blood, blood clots, bruised soft tissue and normal ureter. Signals were also obtained from stones placed in ureter of an ex vivo bovine urinary tract specimen. Results of monitoring both plasma and acoustic signals show that it is possible to determine, without direct vision, whether the laser is hitting stone, ureteral wall or lumen. Strong plasma and strong acoustic signals are produced by calculi; strong acoustic but no plasma signals suggest that the laser is hitting blood clot or bruised ureteral wall. Absent plasma and acoustic response indicate that the laser is discharging on normal ureter or in the lumen. These distinctions may allow clinical stone fragmentation without direct ureteroscopic vision.

Acoustics↗
PubMed2000

Visualization of human umbilical vein endothelial cells by acoustic microscopy.

The morphology and acoustic properties of the human umbilical vein endothelial cells (HUVECs) were evaluated using a scanning acoustic microscope system. HUVECs were cultured for 4 days and exposed to the endotoxin for 4 h. The frequency of the scanning acoustic microscope was variable between 100 and 210 MHz. By changing the measuring frequency, ultrasonic amplitude and phase were measured and the quantitative value of attenuation was calculated. Before and after endotoxin stimuli, HUVECs were observed by scanning acoustic microscopy and the attenuation was measured. The acoustic images were successfully obtained to identify the outer shape of the HUVEC and the location of the nucleus in the cell. The attenuation of the nucleus is higher than that of the cytoplasm. The attenuation of the cytoplasm was increased and became inhomogeneous after endotoxin exposure. This finding would be related to the change of F-actin filaments, which is the main component of the cytoskeleton. Scanning acoustic microscopy is useful for assessing the cellular viscoelastic properties since it can detect both the morphological and acoustic changes without contacting the cellular surface.

Acoustics↗