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At least 721 records · Page 40Linked to original sources
PubMed1998

Acoustic field interaction with a boiling system under terrestrial gravity and microgravity.

Pool boiling experiments from a platinum wire heater in FC-72 liquid were conducted under terrestrial and microgravity conditions, both with and without the presence of a high-intensity acoustic standing wave within the fluid. The purpose of this research was to study the interaction between an acoustic field and a pool boiling system in normal gravity and microgravity. The absence of buoyancy in microgravity complicates the process of boiling. The acoustic force on a vapor bubble generated from a heated wire in a standing wave was shown to be able to play the role of buoyancy in microgravity. The microgravity environment was achieved with 0.6 and 2.1-s drop towers. The sound was transmitted through the fluid medium by means of a half wavelength sonic transducer driven at 10.18 kHz. At high enough acoustic pressure amplitudes cavitation and streaming began playing an important role in vapor bubble dynamics and heat transfer. Several different fixed heat fluxes were chosen for the microgravity experiment and the effects of acoustics on the surface temperature of the heater were recorded and the vapor bubble movement was filmed. Video images of the pool boiling processes and heat transfer data are presented.

Acoustics↗
PubMed1999

Acoustic correlates of talker sex and individual talker identity are present in a short vowel segment produced in running speech.

Although listeners routinely perceive both the sex and individual identity of talkers from their speech, explanations of these abilities are incomplete. Here, variation in vocal production-related anatomy was assumed to affect vowel acoustics thought to be critical for indexical cueing. Integrating this approach with source-filter theory, patterns of acoustic parameters that should represent sex and identity were identified. Due to sexual dimorphism, the combination of fundamental frequency (F0, reflecting larynx size) and vocal tract length cues (VTL, reflecting body size) was predicted to provide the strongest acoustic correlates of talker sex. Acoustic measures associated with presumed variations in supralaryngeal vocal tract-related anatomy occurring within sex were expected to be prominent in individual talker identity. These predictions were supported by results of analyses of 2500 tokens of the /epsilon/ phoneme, extracted from the naturally produced speech of 125 subjects. Classification by talker sex was virtually perfect when F0 and VTL were used together, whereas talker classification depended primarily on the various acoustic parameters associated with vocal-tract filtering.

Adolescent↗
PubMed2000

Calibration and comparison of the acoustic location methods used during the spring migration of the bowhead whale, Balaena mysticetus, off Pt. Barrow, Alaska, 1984-1993.

Between 1984 and 1993, visual and acoustic methods were combined to census the Bering-Chukchi-Beaufort bowhead whale, Balaena mysticetus, population. Passive acoustic location was based on arrival-time differences of transient bowhead sounds detected on sparse arrays of three to five hydrophones distributed over distances of 1.5-4.5 km along the ice edge. Arrival-time differences were calculated from either digital cross correlation of spectrograms (old method), or digital cross correlation of time waveforms (new method). Acoustic calibration was conducted in situ in 1985 at five sites with visual site position determined by triangulation using two theodolites. The discrepancy between visual and acoustic locations was <1%-5% of visual range and less than 0.7 degrees of visual bearing for either method. Comparison of calibration results indicates that the new method yielded slightly more precise and accurate positions than the old method. Comparison of 217 bowhead whale call locations from both acoustic methods showed that the new method was more precise, with location errors 3-4 times smaller than the old method. Overall, low-frequency bowhead transients were reliably located out to ranges of 3-4 times array size. At these ranges in shallow water, signal propagation appears to be dominated by the fundamental mode and is not corrupted by multipath.

Acoustics↗
PubMed2000

Acoustic scattering by benthic and planktonic shelled animals.

Acoustic backscattering measurements and associated scattering modeling were recently conducted on a type of benthic shelled animal that has a spiral form of shell (Littorina littorea). Benthic and planktonic shelled animals with this shape occur on the seafloor and in the water column, respectively, and can be a significant source of acoustic scattering in the ocean. Modeling of the scattering properties allows reverberation predictions to be made for sonar performance predictions as well as for detection and classification of animals for biological and ecological applications. The studies involved measurements over the frequency range 24 kHz to 1 MHz and all angles of orientation in as small as 1 degree increments. This substantial data set is quite revealing of the physics of the acoustic scattering by these complex shelled bodies and served as a basis for the modeling. Specifically, the resonance structure of the scattering was strongly dependent upon angle of orientation and could be traced to various types of rays (e.g., subsonic Lamb waves and rays entering the opercular opening). The data are analyzed in both the frequency and time domain (compressed pulse processing) so that dominant scattering mechanisms could be identified. Given the complexity of the animal body (irregular elastic shell with discontinuities), approximate scattering models are used with only the dominant scattering properties retained. Two models are applied to the data, both approximating the body as a deformed sphere: (1) an averaged form of the exact modal-series-based solution for the spherical shell, which is used to estimate the backscattering by a deformed shell averaged over all angles of orientation, and produces reasonably accurate predictions over all k1a(esr) (k1 is the acoustic wave number of the surrounding water and a(esr) is the equivalent spherical radius of the body), and (2) a ray-based formula which is used to estimate the scattering at fixed angle of orientation, but only for high k1a(esr). The ray-based model is an extension of a model recently developed for the shelled zooplankton Limacina retroversa that has a shape similar to that of the Littorina littorea but swims through the water [Stanton et al., J. Acoust. Soc. Am. 103, 236-253 (1998b)]. Applications of remote detection and classification of the seafloor and water column in the presence of shelled animals are discussed.

Acoustics↗
PubMed1998

Ultrasound-stimulated vibro-acoustic spectrography.

An ultrasound method based on radiation force is presented for imaging the acoustic response of a material to mechanical excitation. Acoustic energy was emitted from solids and tissues in response to an oscillatory radiation force produced by interfering focused beams of ultrasound. Frequency spectra of ultrasound-stimulated acoustic emission exhibited object resonances. Raster-scanning the radiation force over the object and recording the amplitude and phase of the emitted sound resulted in data from which images related to the elastic compositions of the acoustically emitting objects could be computed. Acoustic emission signals distinguished tuning-fork resonances, submillimeter glass spheres, and calcification in excised arteries and detected object motions on the order of nanometers.

Acoustic Stimulation↗
PubMed2005

Acoustics and psychosocial environment in intensive coronary care.

BACKGROUND: Stress, strain, and fatigue at the workplace have previously not been studied in relation to acoustic conditions. AIMS: To examine the influence of different acoustic conditions on the work environment and the staff in a coronary critical care unit (CCU). METHOD: Psychosocial work environment data from start and end of each individual shift were obtained from three shifts (morning, afternoon, and night) for a one-week baseline period and for two four-week periods during which either sound reflecting or sound absorbing tiles were installed. RESULTS: Reverberation times and speech intelligibility improved during the study period when the ceiling tiles were changed from sound reflecting tiles to sound absorbing ones of identical appearance. Improved acoustics positively affected the work environment; the afternoon shift staff experienced significantly lower work demands and reported less pressure and strain. CONCLUSIONS: Important gains in the psychosocial work environment of healthcare can be achieved by improving room acoustics. The study points to the importance of further research on possible effects of acoustics in healthcare on staff turnover, quality of patient care, and medical errors.

Acoustics↗
PubMed2006

Mobile phone use and acoustic neuroma risk in Japan.

OBJECTIVES: The rapid increase of mobile phone use has increased public concern about its possible health effects in Japan, where the mobile phone system is unique in the characteristics of its signal transmission. To examine the relation between mobile phone use and acoustic neuroma, a case-control study was initiated. METHODS: The study followed the common, core protocol of the international collaborative study, INTERPHONE. A prospective case recruitment was done in Japan for 2000-04. One hundred and one acoustic neuroma cases, who were 30-69 years of age and resided in the Tokyo area, and 339 age, sex, and residency matched controls were interviewed using a common computer assisted personal interview system. Education and marital status adjusted odds ratio was calculated with a conditional logistic regression analysis. RESULTS: Fifty one cases (52.6%) and 192 controls (58.2%) were regular mobile phone users on the reference date, which was set as one year before the diagnosis, and no significant increase of acoustic neuroma risk was observed, with the odds ratio (OR) being 0.73 (95% CI 0.43 to 1.23). No exposure related increase in the risk of acoustic neuroma was observed when the cumulative length of use (<4 years, 4-8 years, >8 years) or cumulative call time (<300 hours, 300-900 hours, >900 hours) was used as an exposure index. The OR was 1.09 (95% CI 0.58 to 2.06) when the reference date was set as five years before the diagnosis. Further, laterality of mobile phone use was not associated with tumours. CONCLUSIONS: These results suggest that there is no significant increase in the risk of acoustic neuroma in association with mobile phone use in Japan.

Adult↗
PubMed1995

Efferent-mediated protection from acoustic overexposure: relation to slow effects of olivocochlear stimulation.

1. The present study attempts to resolve discrepancies in the reported role of olivocochlear (OC) efferent activation in protecting the inner ear from acoustic overstimulation: in previous studies, activating the OC system in guinea pigs reduced the threshold shift caused by 1 min monaural exposure to a 10-kHz tone; whereas unilateral OC activation in cats had no effect on threshold shifts following binaural exposure to a 10 min 6-kHz tone. 2. In this study, anesthetized and curarized guinea pigs were exposed either monaurally or binaurally to tones of different duration (1-5 min), frequency (6 to 10 kHz) and intensity (105-118 dB SPL). For each exposure condition, threshold shifts were compared among ears with different levels of OC activation: in some cases, the OC bundle (OCB) was electrically stimulated during (and/or before) the acoustic overexposure; in others, the OCB was cut before the exposure; in control cases, the OCB was neither cut nor electrically stimulated. 3. Electrical stimulation of the OCB delivered simultaneously with acoustic overstimulation produced significant reductions in threshold shift only for acoustic exposures at higher frequencies (8 and 10 kHz) and shorter durations (1 and 2 min). The protective effects on 1-min exposures could be extinguished by prior stimulation of the OCB, i.e., if the OC stimulation was turned on 4 min before the acoustic overexposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1999

Mauthner and reticulospinal responses to the onset of acoustic pressure and acceleration stimuli.

We determined how the Mauthner cell and other large, fast-conducting reticulospinal neurons of the goldfish responded to acoustic stimuli likely to be important in coordinating body movements underlying escape. The goal was to learn about the neurophysiological responses to these stimuli and the underlying processes of sensorimotor integration. We compared the intracellularly recorded postsynaptic responses (PSPs) of 9 Mauthner cells and a population of 12 other reticulospinal neurons to acoustic pressure and acceleration stimuli. All recorded cells received both pressure and acceleration inputs and responded to stimuli regardless of initial polarity. Thus these cells receive acoustic components necessary to determine source direction. We observed that the Mauthner cell was broadly tuned to acoustic pressure from 100 to 2,000 Hz, with a Q(10dB) of 0.5-1.1 over the best frequency range, 400-800 Hz. This broad tuning is probably due to input from S1 afferents and is similar to tuning of the behavioral audiogram. Our data suggest that cells have relatively more sustained responses to acceleration than to pressure stimuli, to which they rapidly adapted. For a given cell, PSP latencies and amplitudes varied inversely with stimulus intensity. For the entire population of cells studied, minimum onset latencies (i.e., those at the highest intensities) ranged from 0.7 to 7.6 ms for acoustic pressure and 0.7 to 9.8 ms for acceleration. This distribution in minimum onset latencies is consistent with earlier EMG and kinematic findings and supports our previous hypothesis that escape trajectory angle is controlled, in part, by varying the activation time of neurons in the escape network. While the Mauthner cell latency did not differ to both onset polarities of pressure and acceleration, this was not true of all cells. Also, the Mauthner cell responses to pressure were approximately 0.6 ms faster than to acceleration; for the other cells, this difference was 1.1 ms with some cells having differences </=3 ms. To both pressure and acceleration, the average, minimum Mauthner cell latency was approximately 1 ms faster than the average of the 12 other cells. These data are consistent with the hypothesis that the Mauthner cell fires first, followed by other reticulospinal neurons, which more finely regulate escape trajectory. Finally, analysis of our results suggests that while pressure is more important in depolarizing the cell near threshold, high levels of acceleration, perhaps from fluid flow, may be very important in activating the system in a directional manner.

Acceleration↗
PubMedDate not supplied

Diverse acoustic cues at consonantal landmarks.

The consonantal segments that underlie an utterance are manifested in the acoustic signal by abrupt discontinuities or dislocations in the spectral pattern. There are potentially two such discontinuities for each consonant, corresponding to the formation and release of a constriction in the oral cavity by the lips, the tongue blade, or the tongue body. Acoustic cues for the various consonant features of place, voicing and nasality reside in the signal in quite different forms on the two sides of each acoustic discontinuity. Examples of these diverse cues and their origin in acoustic theory are reviewed, with special attention to place features and features related to the laryngeal state and to nasalization. A listener appears to have the ability to integrate these diverse, brief acoustic cues for the features of consonants, although the mechanism for this integration process is unclear.

Cues↗
PubMedDate not supplied

Acoustic properties of vocally disruptive behaviors in the nursing home.

BACKGROUND: Disruptive vocalizations are among the most common behavior problems in the nursing home. However, their acoustic properties have not been previously investigated. OBJECTIVE: This paper examines the acoustic properties of disruptive vocalizations and attempts to link them to resident and verbalization characteristics. METHODS: This study characterizes the sounds emitted by 26 nursing home residents who manifested disruptive vocalizations. Verbalizations were audiotaped and then used in a sonographic evaluation and an acoustic analysis. RESULTS: Vocalizations of verbally agitated nursing home residents were characterized by their relatively short duration. Consistent positive correlations were found between seemingly disturbing types of vocalizations, such as yelling and howling, and higher levels of several parameters of the fundamental frequency. A similar positive correlation was also found between acoustic parameters and medical disease indicators. With the exception of the length of stream of utterances, the indicators did not differentiate between types of dementia. CONCLUSIONS: Because of the large number of comparisons undertaken, it is difficult to conclude which associations between acoustic properties and resident or vocalization characteristics are attributable to real underlying trends and which are due to chance and error. Consistencies that deserve further research pertain to the perceptions of the types of vocalizations the person tends to emit and to the physical health of the person.

Aged↗
PubMedDate not supplied

Suitability of acoustic perturbation measures in analysing periodic and nearly periodic voice signals.

In recent years, acoustic perturbation measurement has gained clinical and research popularity due to the ease of availability of commercial acoustic analysing software packages in the market. However, because the measurement itself depends critically on the accuracy of frequency tracking from the voice signal, researchers argue that perturbation measures are not suitable for analysing dysphonic voice samples, which are aperiodic in nature. This study compares the fundamental frequency, relative amplitude perturbation, shimmer percent and noise-to-harmonic ratio between a group of dysphonic and non-dysphonic subjects. One hundred and twelve dysphonic subjects (93 females and 19 males) and 41 non-dysphonic subjects (35 females and 6 males) participated in the study. All the 153 voice samples were categorized into type I (periodic or nearly periodic), type II (signals with subharmonic frequencies that approach the fundamental frequency) and type III (aperiodic) signals. Only the type I (periodic and nearly periodic) voice signals were acoustically analysed for perturbation measures. Results revealed that the dysphonic female group presented significantly lower fundamental frequency, significantly higher relative amplitude perturbation and shimmer percent values than the non-dysphonic female group. However, none of these three perturbation measures were able to differentiate between male dysphonic and male non-dysphonic subjects. The noise-to-harmonic ratio failed to differentiate between the dysphonic and non-dysphonic voices for both gender groups. These results question the sensitivity of acoustic perturbation measures in detecting dysphonia and suggest that contemporary acoustic perturbation measures are not suitable for analysing dysphonic voice signals, which are even nearly periodic.

Adult↗
PubMedDate not supplied

Detection of the acoustic reflex below 80 dB HL.

A new method for detecting the acoustic reflex that utilizes standard otoacoustic emissions recording techniques is introduced and discussed. Two successive identical tone bursts of 100 ms duration and 10 ms interstimulus interval are presented in the occluded ear canal at a repetition rate of one per second. If the acoustic reflex is elicited, the contraction of the stapedius muscle is delayed with respect to the onset of the first stimulus. Hence, the acoustic compliance in the ear canal decreases primarily during the second stimulus. The difference of the microphone signals produced by the two stimuli is computed and averaged across a certain number of repetitions of the sequence. The presentation level is increased until this difference is larger than -40 dB (with respect to the stimulus level) and if its signal-to-noise ratio exceeds 20 dB. For normal-hearing subjects, the acoustic reflex threshold measured with this method is on average 8 dB lower than in a standard clinical setup. In 5 out of the 10 tested hearing-impaired subjects, the new method could detect an acoustic reflex at one or more frequencies where no reflex was detected in the clinical setup.

Adult↗
PubMed1994

The influence of language on the acoustic properties of phonetic features: a study of the feature [strident] in Ewe and English.

This study explored the extent to which the acoustic manifestation of a phonetic feature is influenced by the linguistic role that the feature plays in the sound inventory of the particular language. To this end, we investigated the acoustic property associated with the feature [strident] in the production of bilabial and labiodental fricatives in Ewe, and labiodental and alveolar fricatives in English, and explored whether the acoustic manifestation of the feature [strident] varied in the instantiation of [f] in Ewe and English. In Ewe, the feature [strident] plays a contrastive role distinguishing labiodental from bilabial fricatives, whereas in English the feature [strident] does not play a contrastive role. Results showed that a measure of turbulence noise was able to distinguish bilabial and labiodental fricatives in Ewe and labiodental and alveolar fricatives in English. Moreover, the range of values associated with defining the amplitude characteristics for [f] was similar in the two languages. Nevertheless, differences emerged in the acoustic fine structure of the noise amplitude for [f v] in the two languages, with the frequency distribution for the labiodental fricative in Ewe being skewed towards the high amplitude range relative to English. These results suggest that while the fundamental manifestation of the acoustic property is the same across languages, its instantiation may be influenced by the functional role that its associated feature plays in the language.

Adult↗
PubMedDate not supplied

Decreased expression of the c-Fos, but not Jun B, transcription factor in the auditory pathway of the rat after repetitive acoustic stimulation.

Between the 21st and 34th postnatal days, male rats received an acoustic stimulus every second day, and the expression of c-Fos and Jun B proteins was compared with rats that received only a single acoustic stimulus at postnatal day 34. For acoustic stimulation, 8-kHz pure-tone bursts (100 ms duration at a rate of 6.3 Hz) were applied for 5 min. The numbers of neurons immunoreactive to c-Fos and Jun B were studied 2 h after the last or acute stimulus, respectively, in the ventral cochlear nucleus (VCN), dorsal cochlear nucleus (DCN) and inferior colliculus (IC). Compared with the single stimulus, repetitive stimulation significantly reduced the number of c-Fos labeled neurons in the VCN by 51%, in the DCN by 75% and in the IC by 48%. In contrast to c-Fos, repetitive stimulation did not significantly lower the number of Jun-B-expressing neurons. These findings indicate that independent intraneuronal pathways terminate on the induction of c-Fos- and Jun-B-expressing genes during the juvenile maturation of the acoustic pathway and that chronic exposure of acoustic events alters the program of intraneuronal gene expression by reducing transcriptional activities with subsequent stabilization at the genetic level.

Acoustic Stimulation↗
PubMed2000

Airway flow dynamics and voice acoustics after autologous fascia augmentation of paralyzed vocal fold.

The aim of this study was to assess the effect of vocal fold medialization, accomplished by injection of autologous fascia, on airflow dynamics and voice acoustics. Ten patients with unilateral vocal fold paralysis were included. Flow-volume spirometry, body plethysmography, and acoustic analysis of voice were performed within 1 week before injection of autologous fascia and 4 to 14 months after operation. Medialization of the paralyzed vocal fold decreased the mean peak inspiratory flow (PIF) from 4.63 L to 4.10 L (p = .012). The acoustic characteristics of the voice improved: the values of jitter, shimmer, and mean noise-to-harmonics ratio decreased significantly (p = .006, p = .017, and p = .047, respectively), and the mean maximal phonation time almost doubled (p = .002). Changes in PIF and shimmer showed a negative correlation (r = -.857, p = .007). In conclusion, injection of autologous fascia improves voice acoustics, but induces a slight abnormal limitation on PIF. The results also suggest that improvement in voice acoustics is most prominent in subjects with the least deterioration in inspiratory airflow.

Aged↗
PubMed2003

Histopathology of the inner ear in unoperated acoustic neuroma.

Although hearing loss is the most common presenting symptom in patients with acoustic neuroma, the pathophysiology of hearing loss associated with acoustic neuroma is unknown. Although primary dysfunction of the auditory nerve is intuitively logical, available histopathologic and clinical data suggest that although neural degeneration is common, it alone does not adequately account for hearing loss in many cases. The purpose of this study was to evaluate 11 cases of unoperated unilateral acoustic neuromas. Temporal bones were identified by means of a search mechanism provided by the National Temporal Bone, Hearing, and Balance Pathology Resource Registry and were prepared for light microscopy by standard techniques. Quantification of spiral ganglion cells, hair cells, stria vascularis, and spiral ligament was accomplished for each specimen. In addition, the maximum diameter and volume of each tumor were calculated from histopathologic sections. Increasing tumor size did predict a reduced spiral ganglion count. However, although there was a tendency for decreasing spiral ganglion cell count and for increasing tumor size to predict a higher pure tone average and lower speech discrimination score, these correlations did not reach statistical significance. In tumor ears in which the speech discrimination score was 50% or less, there was always significant degeneration of other structures of the inner ear in addition to neurons, including hair cells, the stria vascularis, and the spiral ligament. Endolymphatic hydrops and eosinophilic precipitate in the perilymphatic spaces were found in 2 of 3 such cases. It is concluded that acoustic neuromas appear to cause hearing loss, not only by causing degeneration of the auditory nerve, but also by inducing degenerative changes in the inner ear. It is hypothesized that the proteinaceous material seen histologically may represent the products of up-regulated genes in acoustic neuroma, some of which may interfere with normal cochlear function.

Aged↗
PubMedDate not supplied

The price of preservation of hearing in acoustic neuroma surgery.

Translabyrinthine surgery for acoustic neuroma was introduced in Denmark in 1976, and the results of the first 100 operations are presented. Two deaths occurred, unrelated to the translabyrinthine surgery. Postoperatively, 75% of the patients had normal facial function, while function was reduced in 15% and abolished in 10%. The series represents 85% of all acoustic neuromas operated in Denmark, with 30 new neuromas being diagnosed each year, derived from a population of 5.1 million. The overall postoperative results are compared with the available results from suboccipital removals of acoustic neuromas, and are clearly in favor of the translabyrinthine approach. It is concluded that centralization of acoustic neuroma surgery is necessary, that all acoustic neuromas regardless of size can be removed by the translabyrinthine approach and that the discussion about the hypothetical preservation of hearing by applying the suboccipital approach is being made without solid grounds. To adduce the theoretical chance of preserving hearing in a very small percentage of patients as an argument in favor of the suboccipital approach appears quite irrelevant, and the price of attempting this with the suboccipital approach is too high.

Adult↗