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PubMed1996

Some acoustical properties of the otic bones of a fin whale.

The otic bones in this report are the tympanic bulla, the periotic, and the three ossicles (malleus, incus, and stapes) of an adult fin whale (Balaenoptera physalus). The purpose was to determine if the periotic was denser than the other otic bones. It was found in one male adult fin whale that the density of all the otic bones is approximately the same, 2.50 kg/m3 with a maximum of 2.58. The lowest density was observed in the stapes (2.36). The sonic velocity seems to vary as the density but there also seems to be a structural effect. The maximum sonic velocity was 4.89 km/s in the malleus. The specific acoustic impedance was as high as 12.5 megarayles in the periotic. These values compare with those for human femur of 1.95 for the density, 3.73 for the sonic velocity, and 7.33 for the specific acoustic impedance. The ossicles weigh as much as 200 times as much as human ossicles. The density of whale ossicles are about ten percent greater than human ossicles. The mechanical natural frequency of the whale ossicles must be very low. The approximate uniformity of the properties of this whale's otic bones may be characteristic of the middle ear. The density of the otic bones of land mammals is less than for whales. The density of the horse petrosal (2.29 g/cc) is essentially the same as the density of adult human ossicles (2.23-2.27 g/cc). The high density of the otic bones for all mammals suggests it may be related to hearing acuity perhaps by increasing the specific acoustic impedance, which increases the acoustic contrast with the other body tissues.

Acoustics↗
PubMed1996

Acoustic radiation pressure in a three-dimensional lossy medium.

Acoustic radiation pressure exerted by an arbitrary acoustic wave in a three-dimensional lossy medium is calculated by extending an indirect approach developed by Chu and Apfel [B-T. Chu and R.E. Apfel, "Acoustic radiation pressure produced by a beam of sound," J. Acoust. Soc. Am. 72, 1673-1687 (1982)]. Without appealing to the detailed solutions of equations governing fluid motion, a general analytic expression for the radiation pressure in lossy media with arbitrary waves is obtained. When an infinite lossy medium is considered, the expression states that the radiation pressure, to the lowest order of approximation (i.e., second order), is equal to corresponding total energy density. For a special class of confined spaces, the expression leads to a rather general formula for the radiation pressure, in which the radiation pressure is given in terms of various energy densities in the field. Furthermore, a relationship among these energy densities is generalized to the case of lossy media, which enables one to compute the radiation pressure in the class of spaces with the knowledge of the first-order perturbation solution only.

Acoustics↗
PubMed1997

Inertial cavitation and associated acoustic emission produced during electrohydraulic shock wave lithotripsy.

The inertial cavitation and associated acoustic emission generated during electrohydraulic shock wave lithotripsy were studied using high-speed photography and acoustic pressure measurements. The dynamics of cavitation bubble clusters, induced in vitro by an experimental laboratory lithotripter, were recorded using a high-speed rotating drum camera at 20,000 frames/s. The acoustic emission, generated by the rapid initial expansion and subsequent violent collapse of the cavitation bubbles, was measured simultaneously using a 1-MHz focused hydrophone, The expansion duration of the cavitation bubble cluster was found to correlate closely with the time delay between the first two groups of pressure spikes in the acoustic emission signal. This correlation provides an essential physical basis to assess the inertial cavitation produced by a clinical Dornier HM-3 shock wave lithotripter, both in water and in renal parenchyma of a swine model. In the clinical output voltage range (16-24 kV), the expansion duration of the primary cavitation bubble cluster generated by the HM-3 lithotripter in water increases from 158 to 254 microseconds, whereas the corresponding values in renal parenchyma are much smaller and remain almost unchanged (from 71 to 72 microseconds). In contrast, subsequent oscillation of the bubble following its primary collapse is significantly prolonged (from 158-235 microseconds in water to 1364-1373 microseconds in renal parenchyma). These distinctive differences between lithotripsy-induced inertial cavitation in vitro and that in vivo are presumably due to the constraining effect of renal tissue on bubble expansion.

Acoustics↗
PubMed1997

Acoustic correlates of English and French nasalized vowels.

Acoustic analysis of nasalized vowels in the frequency domain indicates the presence of extra peaks: one between the first two formants with amplitude P1 and one at lower frequencies, often below the first formant, with amplitude P0. The first-formant amplitude A1 is also reduced relative to its amplitude for an oral vowel. These acoustic characteristics can be explained by speech production theory. The objective of this study was to determine the values for the acoustic correlates A1-P1 and A1-P0 (dB) for quantifying nasalization. They were tested as measures of nasalization by comparing vowels between nasal consonants and those between stop consonants for English speakers. Also, portions of nasal vowels following a stop consonant were compared for speakers of French, which makes a linguistic distinction between oral and nasal vowels. In the analysis of English, the mean difference of A1-P1 measured in oral vowels and nasalized vowels had a range of 10 dB-15 dB; the difference of A1-P0 had a range of 6 dB-8 dB. In the study of French, the difference of A1-P1 measured between the least-nasalized portion and the most-nasalized portion of the vowel had a range of 9 dB-12 dB; for A1-P0, the difference ranged between 3 dB and 9 dB. In order to obtain an absolute acoustic measure of nasalization that was independent of vowel type, normalized parameters were calculated by adjusting for the influence of the vowel formant frequencies.

Female↗
PubMed1999

Glottal characteristics of male speakers: acoustic correlates and comparison with female data.

Acoustic measurements believed to reflect glottal characteristics were made on recordings collected from 21 male speakers. The waveforms and spectra of three nonhigh vowels (/ae, lambda, epsilon/) were analyzed to obtain acoustic parameters related to first-formant bandwidth, open quotient, spectral tilt, and aspiration noise. Comparisons were made with previous results obtained for 22 female speakers [H. M. Hanson, J. Acoust. Soc. Am. 101, 466-481 (1997)]. While there is considerable overlap across gender, the male data show lower average values and less interspeaker variation for all measures. In particular, the amplitude of the first harmonic relative to that of the third formant is 9.6 dB lower for the male speakers than for the female speakers, suggesting that spectral tilt is an especially significant parameter for differentiating male and female speech. These findings are consistent with fiberscopic studies which have shown that males tend to have a more complete glottal closure, leading to less energy loss at the glottis and less spectral tilt. Observations of the speech waveforms and spectra suggest the presence of a second glottal excitation within a glottal period for some of the male speakers. Possible causes and acoustic consequences of these second excitations are discussed.

Adult↗
PubMed1999

Acoustical and perceptual study of gemination in Italian stops.

On the basis of theoretical considerations and results from acoustic and perceptual analyses, it is hypothesized that closure duration is the primary cue for gemination in Italian. Results of an acoustic analysis of a large number of single and geminate Italian utterances show two acoustic correlates of gemination: the length of the closure and the length of the vowel preceding the consonant. Other acoustic parameters were not systematically related to gemination. These results were validated perceptually. At the perceptual level, the above cues were used by the listeners in the geminate/nongeminate discrimination; however, closure duration played a major role. Moreover, it was found that the significant lengthening of consonant was only partially compensated by the shortening of the previous vowel and by a small lengthening of the geminate utterance with respect to the nongeminate one. This result suggests that speakers follow a sort of timing (rhythm) which is fixed in duration and depends on the number of syllables in the word: words with equal numbers of syllables do not change in utterance length, an elongated segment being partly compensated by the shortening of another. This process seems to be applied also perceptually suggesting that the timing (rhythm) of a language is also an auditory attitude.

Adult↗
PubMed2004

The immunohistochemical localisation of somatostatin receptors 1, 2, 3, and 5 in acoustic neuromas.

AIMS: Acoustic neuroma is a benign tumour, which develops through an overproliferation of Schwann cells along the vestibular nerve. Somatostatin is a naturally occurring peptide, which exerts antiproliferative and antiangiogenic effects via five membrane bound receptor subtypes. The aim of this study was to determine whether somatostatin receptor subtypes (SSTRs) 1, 2, 3, and 5 are present in acoustic neuromas. METHODS: The expression of SSTRs 1, 2, 3, and 5 was studied in both the Schwann cells and blood vessels of eight acoustic neuroma specimens, by means of immunohistochemistry using novel rabbit polyclonal antibodies raised against human SSTR 1, 2, and 5 subtype specific peptides, and a commercial anti-SSTR3 antibody. RESULTS: SSTR2 was the most prevalent subtype in Schwann cells (seven of eight), with intermediate expression of SSTR3 (six of eight), and lower expression of SSTRs 1 and 5 (four of eight and five of eight, respectively). There was ubiquitous vascular expression of SSTR2, with no evidence of SSTR 1, 3, or 5 expression in blood vessels. CONCLUSION: SSTRs 1, 2, 3, and 5 are differentially expressed in acoustic neuromas. Somatostatin analogues may have a therapeutic role in the management of this rare and challenging condition.

Adult↗
PubMed1975

Acoustical holography: physical parameters and potential clinical applications.

Acoustical holography achieves real-time imaging of bodily structures through ultrasound. The fundamentals of acoustical holography and a description of a prototype unit undergoing trials at the authors' institution are presented. Physical parameters and means of calibrating the acoustic beam are discussed, and results of preliminary experimental and clinical studies reviewed. Acoustical holography has the potential for providing complementary diagnostic information which, after further technical developments, may furnish clinically useful information.

Accident Prevention↗
PubMed1988

Comparison of glottic areas measured by acoustic reflections vs. computerized tomography.

We compared measurements of glottic area obtained by acoustic reflection technique with anatomically equivalent area measured from computerized tomographic (CT) scans of the neck in 11 subjects with glottic pathology. Both measurements were performed in the supine position during tidal breathing at functional residual capacity. We found excellent agreement in glottic areas obtained by both methods: the mean (+/- SD) values were 1.8 +/- 0.8 cm2 for the acoustic method and 1.7 +/- 0.9 cm2 for the CT method. Linear regression analysis revealed the following relationship between the area measured by acoustic technique (AAC) and that measured by CT (ACT): AAC = 0.81.ACT + 0.36. There was a significant correlation between the two measurements of glottic area (r = 0.95, P less than 0.0001). We conclude that the acoustic reflection technique may be used reliably in clinical and physiological studies concerned with glottic geometry.

Acoustics↗
PubMed1994

Artifacts associated with acoustic rhinometric assessment of infants and young children: a model study.

The present study was undertaken to determine in model studies whether currently available acoustic rhinometry instrumentation might be used to analyze the nasal cavity configuration of infants and children. A simple nasal cavity model was constructed using eight Lucite inserts that were placed between standard nosepieces provided by the manufacturer and a 35-cm-long polyvinyl chloride pipe closed at its distal end. To simulate the nasal valve, the inserts were 12 mm in length and had apertures ranging in diameter from 2 to 9 mm. A series of experiments was conducted to evaluate the accuracy with which the acoustic rhinometer measured the size of each insert aperture and the configuration of the model system distal to that aperture. Transmission losses caused errors in the area measurement of the insert aperture and the tube distal to the insert. When the insert aperture was < 6 mm in diameter (0.28 cm2), the aperture area was overestimated by > 10%, whereas the area of the distal tube was underestimated by > 10%. As a result of response lags, the acoustic rhinometer also failed to provide an accurate indication of insert length. Finally, oscillation artifacts caused estimates of the distal pipe area to fluctuate. These three systematic errors are described, and their potential impact on acoustic rhinometry in children is discussed.

Acoustics↗
PubMed2000

A new nasal acoustic reflection technique to estimate pharyngeal cross-sectional area during sleep.

The conventional acoustic reflection technique in which acoustic waves are launched through the mouth cannot be applied during sleep, nor can it be applied to the nasopharynx, which is the major site of occlusion in patients with obstructive sleep apnea syndrome. We propose a new technique of nasal acoustic reflection to measure pharyngeal cross-sectional areas including the nasopharynx. The acoustic waves are introduced simultaneously to both nostrils during spontaneous nasal breathing. A new algorithm takes into account the nasal septum with asymmetric nasal cavities on both sides and assumes prior knowledge of the cross-sectional area of the nasal cavities and the position of the nasal septum. This method was tested on an airway model with a septum and on healthy human subjects. The conventional technique gave inaccurate measurements for pharyngeal cross-sectional areas for an airway model with asymmetric branching, whereas the new technique measured them almost perfectly. The oro- and hypopharyngeal cross-sectional area measurements acquired by the new method were not different from those obtained by the conventional method in normal subjects. This new method can be used as a monitor of upper airway dimensions in nocturnal polysomnography.

Acoustics↗
PubMed2003

Information content of auditory cortical responses to time-varying acoustic stimuli.

The present study explores the issue of cortical coding by spike count and timing using statistical and information theoretic methods. We have shown in previous studies that neurons in the auditory cortex of awake primates have an abundance of sustained discharges that could represent time-varying signals by temporal discharge patterns or mean firing rates. In particular, we found that a subpopulation of neurons can encode rapidly occurring sounds, such as a click train, with discharges that are not synchronized to individual stimulus events, suggesting a temporal-to-rate transformation. We investigated whether there were stimulus-specific temporal patterns embedded in these seemingly random spike times. Furthermore, we quantitatively analyzed the precision of spike timing at stimulus onset and during ongoing acoustic stimulation. The main findings are the following. 1) Temporal and rate codes may operate at separate stimulus domains or encode the same stimulus domain in parallel via different neuronal populations. 2) Spike timing was crucial to encode stimulus periodicity in "synchronized" neurons. 3) "Nonsynchronized" neurons showed little stimulus-specific spike timing information in their responses to time-varying signals. Such responses therefore represent processed (instead of preserved) information in the auditory cortex. And 4) spike timing on the occurrence of acoustic events was more precise at the first event than at successive ones and more precise with sparsely distributed events (longer time intervals between events) than with densely packed events. These results indicate that auditory cortical neurons mark sparse acoustic events (or onsets) with precise spike timing and transform rapidly occurring acoustic events into firing rate-based representations.

Acoustic Stimulation↗
PubMed1991

The olivocochlear efferent bundle and susceptibility of the inner ear to acoustic injury.

1. The role of the efferent olivocochlear bundle (OCB) in protecting the inner ear from acoustic injury was studied in the anesthetized cat. Middle-ear muscles (MEM) were cut to eliminate possible effects of this feedback system on the auditory periphery. In each of a series of animals, the OCB was unilaterally transected. The animal was then exposed binaurally to an intense pure tone, and the resultant damage to the two sides compared by measuring threshold shifts in the compound action potential from each ear. Data from each animal provide one control measurement (threshold shift with an intact OCB) and one experimental measurement (threshold shift without a functional OCB). 2. Two experimental series were analyzed. In one the OCB was electrically stimulated, providing maximal firing rates in the efferents projecting to the control ear. In another series the OCB was not electrically stimulated: thus any OCB activity to the control ear was only that evoked by the acoustic stimulation itself. 3. In neither experimental series was there evidence that activity in the OCB provides protection from acoustic injury. These results are in disagreement with conclusions drawn from experiments with acoustic overstimulation of guinea pigs. 4. Interpretations for the discrepancy between the present study and those on guinea pigs include interspecies differences and the possible contribution of the MEM reflex or cochlear blood-flow changes to previously observed effects.

Acoustic Stimulation↗
PubMed1997

Conditioning-related protection from acoustic injury: effects of chronic deefferentation and sham surgery.

The inner ear can be made less vulnerable to acoustic injury by a "conditioning" treatment involving exposure to a moderate-level acoustic stimulus before the acoustic overexposure. The present study was designed to explore the role of the olivocochlear (OC) system in this "protection." Guinea pigs were divided into a number of groups: some (trauma-only) were exposed to a traumatic noise for 4 h at 109 dB SPL; others (condition/trauma) were conditioned by daily exposure to the same noise at 85 dB SPL before the traumatic exposure. In OC-intact animals, the condition/trauma group showed significantly less permanent threshold shift (PTS) than the trauma-only group as measured via compound action potentials and distortion-product otoacoustic emissions (DPOAEs). Other animals with identical noise-exposure regimens underwent deefferentation surgery before the start of conditioning: the OC bundle (OCB) was cut in the brain stem, either at the midline (cutting the crossed OCB to both ears) or at the sulcus limitans (cutting all OC fibers to 1 side). Lesion success was quantified by measuring OC fascicles to the outer hair cell region in each ear. The results from the surgical groups showed that total loss of the OCB significantly increased the noise-induced PTS, whereas loss of the COCB only did not; that the conditioning exposure in deefferented animals increased, rather than decreased, the PTS from the traumatic exposure; and that animals undergoing sham surgery (brain stem cuts that failed to transect the OCB) appeared protected whether or not they received the conditioning noise exposure. The latter result suggests that conditioning-related protection may arise from a generalized stress response, which can be elicited by noise exposure, brain surgery, or a variety of other means. The former results make an OC role in the conditioning process, per se, difficult to assess, given the large effects of OC activity on general acoustic vulnerability.

Acoustic Stimulation↗
PubMed1999

Acoustic and current-pulse responses of identified neurons in the dorsal cochlear nucleus of unanesthetized, decerebrate gerbils.

In an effort to establish relationships between cell physiology and morphology in the dorsal cochlear nucleus (DCN), intracellular single-unit recording and marking experiments were conducted on decerebrate gerbils using horseradish peroxidase (HRP)- or neurobiotin-filled micropipettes. Intracellular responses to acoustic (tone and broadband noise bursts) and electric current-pulse stimuli were recorded and associated with cell morphology. Units were classified according to the response map scheme (type I to type V). Results from 19 identified neurons, including 13 fusiform cells, 2 giant cells, and 4 cartwheel cells, reveal correlations between cell morphology of these neurons and their acoustic responses. Most fusiform cells (8/13) are associated with type III unit response properties. A subset of fusiform cells was type I/III units (2), type III-i units (2), and a type IV-T unit. The giant cells were associated with type IV-i unit response properties. Cartwheel cells all had weak acoustic responses that were difficult to classify. Some measures of membrane properties also were correlated with cell morphology but to a lesser degree. Giant cells and all but one fusiform cell fired only simple action potentials (APs), whereas all cartwheel cells discharged complex APs. Giant and fusiform cells all had monotonic rate versus current level curves, whereas cartwheel cells had nonmonotonic curves. This implies that inhibitory acoustic responses, resulting in nonmonotonic rate versus sound level curves, are due to local inhibitory interactions rather than strictly to membrane properties. A complex-spiking fusiform cell with type III unit properties suggests that cartwheel cells are not the only complex-spiking cells in DCN. The diverse response properties of the DCN's fusiform cells suggests that they are very sensitive to the specific complement of excitatory and inhibitory inputs they receive.

Acoustic Stimulation↗
PubMedDate not supplied

Ultrasound-mediated biophotonic imaging: a review of acousto-optical tomography and photo-acoustic tomography.

This article reviews two types of ultrasound-mediated biophotonic imaging-acousto-optical tomography (AOT, also called ultrasound-modulated optical tomography) and photo-acoustic tomography (PAT, also called opto-acoustic or thermo-acoustic tomography)-both of which are based on non-ionizing optical and ultrasonic waves. The goal of these technologies is to combine the contrast advantage of the optical properties and the resolution advantage of ultrasound. In these two technologies, the imaging contrast is based primarily on the optical properties of biological tissues, and the imaging resolution is based primarily on the ultrasonic waves that either are provided externally or produced internally, within the biological tissues. In fact, ultrasonic mediation overcomes both the resolution disadvantage of pure optical imaging in thick tissues and the contrast and speckle disadvantages of pure ultrasonic imaging. In our discussion of AOT, the relationship between modulation depth and acoustic amplitude is clarified. Potential clinical applications of ultrasound-mediated biophotonic imaging include early cancer detection, functional imaging, and molecular imaging.

Acoustics↗
PubMed1999

Fractionated stereotactic radiosurgery for treatment of acoustic neuromas.

BACKGROUND: Microsurgery and single-fraction radiosurgery for acoustic neuromas are associated with high rates of control, but can result in facial palsy and trigeminal neuropathy. To reduce the morbidity of treatment for acoustic neuromas while maintaining efficacy, we explored fractionated stereotactic radiosurgery (FSR). METHODS: We reviewed data for 31 acoustic neuromas in 30 patients treated with 25 Gy (linear accelerator) given in 5 consecutive daily fractions. The minimum follow-up was 6 months (6-44 months). The mean tumor volume was 1.1 cm(3) (0.1-8.74 cm(3)). RESULTS: All tumors remain controlled (9 smaller, 22 unchanged). No patient has experienced post-radiosurgery facial motor dysfunction. Two patients developed new trigeminal neuropathy; 2 patients with preexisting trigeminal nerve symptoms had improvement after FSR. Balance improved in 3 patients, was unchanged in 20 and worsened in 7 patients. Of the 12 patients with useful hearing (PTA < or = 50 dB) prior to treatment, 9 patients retained useful hearing following FSR. Subjectively, of 25 patients with any hearing prior to treatment, 2 had improvement, 10 remained unchanged and 13 had worsening. CONCLUSIONS: Short course FSR for acoustic neuromas results in acceptable toxicity and may provide high control of tumors. Longer follow-up is needed to assess outcomes.

Adult↗
PubMedDate not supplied

Resolution of single deviant intervals in periodic stimuli by auditory cortex neurons: comparison of intracochlear electric pulse and acoustic click stimulation.

Responses of neurons in the primary auditory cortex were compared in gerbils receiving intracochlear electric or acoustic stimulation. Stimuli were trains of periodic electric pulses or of acoustic clicks. Interspersed between intervals of equal length were single intervals which were longer, by some Delta t. The Delta t and the repetition rate of these prolonged intervals were varied. The degree of synchronization of spikes to the regular occurrences of prolonged intervals was quantified. While thresholds for synchronized responses to Delta t (at Delta t repetition rates of 4--6 Hz) were about a hundredfold higher for electric (about 5--10 ms) than for acoustic stimulation (about 30 s), Delta t repetition rate response functions were similar for both types of stimulation. The results suggest the feasibility of coding brief acoustic transients by prolonged intervals in electric pulse trains with high pulse repetition rates, which could be another useful strategy for cochlear implants.

Acoustic Stimulation↗