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PubMed2006

Ocean acoustic hurricane classification.

Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques.

Journal Article↗
PubMed1985

On some issues in the pursuit of acoustic invariance in speech: a reply to Lisker.

This paper presents an alternative view of acoustic invariance in speech to that discussed by Lisker [J. Acoust. Soc. Am. 77, 1199-1202 (1985)]. Three points are considered--the minimal unit for acoustic invariance, the level of linguistic representation over which this unit operates, and the role that acoustic invariance plays in speech and language. Our position emphasizes the role of phonetic features in a theory of acoustic invariance, and we propose a series of working hypotheses to guide research in this area.

Humans↗
PubMed1985

Acoustic emissions from the ear: a summary of results from humans and animals.

As mentioned in Saunders et al. [J. Acoust. Soc. Am. 78, 299-311 (1985)] an understanding of the transduction of sound into the auditory neural code is a major goal of the hearing scientist. A variety of tools has been and is being used to achieve that goal. The recent discovery of physical acoustic emissions from the ear provides both new insight into possible transduction mechanisms and a useful new tool for research. The existence of narrow-band spontaneous acoustic emissions from the ear suggests the possibility of active cochlear processes that were not seriously considered a decade ago. Acoustic emissions, both spontaneous and evoked, also provide a simple and noninvasive means of monitoring a by-product of cochlear-mechanical activity. In the present paper, results of studies of acoustic emissions from human ears are briefly summarized and compared to results obtained with animals. Differences between human and animal emissions are noted and the implications of these differences and hypotheses to explain them are discussed.

Animals↗
PubMed1992

Inferring articulation and recognizing gestures from acoustics with a neural network trained on x-ray microbeam data.

This paper describes a method for inferring articulatory parameters from acoustics with a neural network trained on paired acoustic and articulatory data. An x-ray microbeam recorded the vertical movements of the lower lip, tongue tip, and tongue dorsum of three speakers saying the English stop consonants in repeated Ce syllables. A neural network was then trained to map from simultaneously recorded acoustic data to the articulatory data. To evaluate learning, acoustics from the training set were passed through the neural network. To evaluate generalization, acoustics from speakers or consonants excluded from the training set were passed through the network. The articulatory trajectories thus inferred were a good fit to the actual movements in both the learning and generalization conditions, as judged by root-mean-square error and correlation. Inferred trajectories were also matched to templates of lower lip, tongue tip, and tongue dorsum release gestures extracted from the original data. This technique correctly recognized from 94.4% to 98.9% of all gestures in the learning and cross-speaker generalization conditions, and 75% of gestures underlying consonants excluded from the training set. In addition, greater regularity was observed for movements of articulators that were critical in the formation of each consonant.

Adult↗
PubMed1995

A comparative acoustic study of English and Spanish vowels.

Languages differ widely in the size of their vowel inventories; however, cross-linguistic surveys indicate that certain vowels and vowel system configurations are preferred. A cross-linguistic comparison of the acoustic vowel categories of two languages that differ in vowel inventory size, namely, English and Spanish, was performed in order to reveal some of the language-specific and/or universal principles that determine the acoustic realization of the vowels of these two languages. This comparison shows that the precise location in the acoustic space of similar vowel categories across the two languages is determined, in part, by a language-specific base-of-articulation property. These data also suggest that the relatively crowded acoustic vowel space of English may be expanded with respect to the relatively uncrowded acoustic vowel space of Spanish; however, this effect is variable depending on the syllable context of the English vowels. Finally, the data indicate no difference in the tightness of within-category clustering for the large versus the small vowel inventory.

Humans↗
PubMed1999

Internal deformation of a uniform elastic solid by acoustic radiation force.

Tissue elasticity estimation is a growing area of ultrasound research. One proposed approach would apply acoustic radiation force to displace tissue and use ultrasonic motion tracking techniques to measure the resultant displacement. Such a technique might allow noninvasive imaging of tissue elastic properties. The potential of this method will be limited by the magnitude of displacements which can be generated at reasonable acoustic intensity levels. This paper presents methods for estimating the internal displacements induced in an elastic solid by acoustic radiation force. These methods predict displacements on the order of 400 microns in the human vitreous body, 0.008 micron in human breast, and 0.020 micron in human liver at an acoustic intensity of 1.0 W/cm2 (in water) and an operating frequency of 10 MHz. While the displacement generated in the vitreous should be readily detectable using ultrasonic methods, the displacements generated in the breast and liver will be much more difficult to detect. Methods are also developed for predicting the time dependent temperature increases associated with attenuated acoustic fields in the absence of perfusion. These results indicate promise for radiation force imaging in the vitreous, but potential difficulties in applying these techniques in other parts of the body.

Elastic Tissue↗
PubMed2000

Calculation of acoustic radiation using equivalent-sphere methods

Among the methods generally used to solve a problem in the domain of acoustic radiation, the equivalent sources method offers an interesting alternative. It consists in replacing the vibrating surface with a distribution of acoustic sources placed inside the structure. The contribution of each source is determined in such a way that the acoustic field radiated by these sources verifies the same boundary conditions on the structure. The number of unknowns in the problem is no longer directly linked to the number of mesh points on the structure, as with boundary elements methods, but to the number of equivalent sources employed in the model. The equivalent source method is therefore of major interest if the acoustic radiation of the structure can be approximated with a sufficiently low number of sources. This paper proposes its application when the equivalent source is a sphere. In this case, the number of unknowns is equal to the number of modes. In contrast to the one-point multipole, the sphere has a surface surrounding a closed volume to express the boundary conditions. Although sphere/multipole equivalence has been demonstrated, the surface of the sphere allows normalization of the functions used, leading to stabilization of the system to be resolved. First, the main acoustic radiation characteristics of a sphere and of the linear system verified by the modal coefficients of an equivalent sphere are presented. The different parameters of the model are then studied: position and radius of the equivalent sphere, truncation of the series, and influence of the spatial sampling (mesh). In the same vein, a second approach is presented. It consists of making each point of the structure correspond to a point of the sphere, and the vibrating field at the surface of the sphere is deduced from that of the structure by simple geometric projection. Results can be obtained very quickly as no matrix inversion is required. The accuracy of the results depends on the distance between the sphere and the structure. Finally, an experimental validation that uses both methods is presented and shows interesting results when the structure is closed, and when its shape is not too far removed from a sphere.

Journal Article↗
PubMed2000

On reconstruction of acoustic pressure fields using the Helmholtz equation least squares method

This paper presents analyses and implementation of the reconstruction of acoustic pressure fields radiated from a general, three-dimensional complex vibrating structure using the Helmholtz equation least-squares (HELS) method. The structure under consideration emulates a full-size four-cylinder engine. To simulate sound radiation from a vibrating structure, harmonic excitations are assumed to act on arbitrarily selected surfaces. The resulting vibration responses are solved by the commercial FEM (finite element method) software I-DEAS. Once the normal component of the surface velocity distribution is determined, the surface acoustic pressures are calculated using standard boundary element method (BEM) codes. The radiated acoustic pressures over several planar surfaces at certain distances from the source are calculated by the Helmholtz integral formulation. These field pressures are taken as the input to the HELS formulation to reconstruct acoustic pressures on the entire source surface, as well as in the field. The reconstructed acoustic pressures thus obtained are then compared with benchmark values. Numerical results demonstrate that good agreements can be obtained with relatively few expansion functions. The HELS method is shown to be very effective in the low-to-mid frequency regime, and can potentially become a powerful noise diagnostic tool.

Journal Article↗
PubMed1996

Detection of abnormal aortic elastic properties in asymptomatic patients with Marfan syndrome by combined transoesophageal echocardiography and acoustic quantification.

OBJECTIVE: To evaluate the potential value of transoesophageal echocardiography combined with automated border detection and acoustic quantification for the assessment of elastic properties of the thoracic aorta in patients with Marfan syndrome. SUBJECTS: 16 patients with Marfan syndrome and 12 age matched normal controls. METHODS: Transoesophageal echocardiography was performed in all subjects. Minimum and maximum diameters of the descending thoracic aorta were obtained from M mode images and acoustic quantification was used for the on-line evaluation of cross sectional aortic area and peak positive area changes over time. Compliance, distensibility, and stiffness index were calculated using M mode data and non-invasively measured blood pressure and were compared with the indices derived from acoustic quantification. RESULTS: Aortic dimensions normalised for body surface area were not statistically different between patients and normal controls, but there were significant differences for all elasticity indices except compliance. Marfan patients had a lower distensibility [4.2 (SD 1.8) v 5.8 (2.1) cm2/dyn, P < 0.05] and a higher stiffness index [9.7 (3.0) v 7.1 (1.8), P < 0.05]. The dynamic indices derived from the acoustic quantification were significantly smaller in Marfan patients [peak positive area change: 5.1 (1.0) v 7.7 (1.7) cm2/s; P < 0.001; and normalised peak positive area change: 2.5 (1.2) v 4.0 (0.8) cm2/s respectively, P < 0.001] and were suitable to discriminate between normal and abnormal elastic properties. CONCLUSIONS: In Marfan syndrome elastic properties of the descending aorta are significantly different from normal controls, even in the absence of vessel dilatation. In addition to established static indices, indices derived from acoustic quantification reflect dynamic changes of the cross sectional area for the evaluation of regional vessel mechanics. The on-line assessment of peak positive area change allows differentiation from normal individuals and may be more accurate than standard M mode measurements.

Adult↗
PubMed1994

Influence of stimulus level on acoustic motion-direction sensitivity in barn owl midbrain neurons.

1. Many neurons in the owl's midbrain are able to discriminate by their responses the motion of an acoustic source in one direction, the preferred direction, from the motion of the source in the opposite direction, the null direction. This differential response can be understood by the action of an acoustic motion detector. However, the motion detector would work in an effective way only if the motion direction-sensitive responses of a cell were largely independent of stimulus level. 2. We investigated the level dependence of acoustic motion sensitivity in midbrain neurons with standard extracellular recording techniques. We used an apparent motion paradigm with sounds moving clockwise or counterclockwise in the horizontal plane or stationary sounds for stimulation from free-field speakers. In most cases we added a constant level of background noise to the stimuli having a variable level. Thus we could analyze the responses as a function of the signal-to-noise ratio. 3. Moving and stationary sounds yielded similar response thresholds and similar dynamic ranges. 4. When the background level was changed the response threshold changed accordingly, so that the response threshold always occurred at a constant signal-to-noise ratio independent of background level. 5. The preferred direction of all cells was independent of stimulus level and some 22 percent of the cells showed a directional bias of their response at threshold. In no cell was a change in the preferred direction observed when stimulus level was varied. Typically, however, the motion direction sensitivity, measured by a signed directionality index, was not maximal at threshold. However, the dynamic range, i.e., the range of stimulus levels over which motion direction sensitivity changed, was < or = 20 dB in most cases. Therefore these cells are indeed able to encode motion direction largely independently of stimulus level. 6. We discuss the data within the framework of the acoustic motion detector mentioned above and with respect to earlier reports on acoustic motion sensitivity in the owl and other animals.

Animals↗
PubMed2006

Steering by hearing: a bat's acoustic gaze is linked to its flight motor output by a delayed, adaptive linear law.

Adaptive behaviors require sensorimotor computations that convert information represented initially in sensory coordinates to commands for action in motor coordinates. Fundamental to these computations is the relationship between the region of the environment sensed by the animal (gaze) and the animal's locomotor plan. Studies of visually guided animals have revealed an anticipatory relationship between gaze direction and the locomotor plan during target-directed locomotion. Here, we study an acoustically guided animal, an echolocating bat, and relate acoustic gaze (direction of the sonar beam) to flight planning as the bat searches for and intercepts insect prey. We show differences in the relationship between gaze and locomotion as the bat progresses through different phases of insect pursuit. We define acoustic gaze angle, theta(gaze), to be the angle between the sonar beam axis and the bat's flight path. We show that there is a strong linear linkage between acoustic gaze angle at time t [theta(gaze)(t)] and flight turn rate at time t + tau into the future [theta(flight) (t + tau)], which can be expressed by the formula theta(flight) (t + tau) = ktheta(gaze)(t). The gain, k, of this linkage depends on the bat's behavioral state, which is indexed by its sonar pulse rate. For high pulse rates, associated with insect attacking behavior, k is twice as high compared with low pulse rates, associated with searching behavior. We suggest that this adjustable linkage between acoustic gaze and motor output in a flying echolocating bat simplifies the transformation of auditory information to flight motor commands.

Animals↗
PubMed2000

[The possibility for the early diagnosis of suppurative-inflammatory wound complications of the maxillofacial area and neck by using an acoustic skin analyzer].

The acoustic method was used for early diagnosis of pyo-inflammatory complications of wounds of the maxillofacial area and neck. Acoustic skin analyzer was used. The velocities of acoustic wave propagation (Vx, Vy) were notably increased in the pyo-inflammatory focus in comparison with perifocal tissues and with the symmetrical contralateral side. The difference in the absolute values of velocities was about 45-65 m/s. No acoustic anisotropy was observed in the focus of inflammation. Hence, the acoustic method can be used as a method for early diagnosis of pyo-inflammatory complications and for monitoring the wound status in the course of wound process.

Abscess↗
PubMed2003

Communication in noise with acoustic and electronic hearing protection devices.

The purpose of the present study was to evaluate communication ability in noise at two signal presentation levels when using acoustic and electronic hearing protection devices (HPDs). Fourteen normal hearing subjects were fitted binaurally with custom acoustic HPDs (ER-15) and custom electronic HPDs (Starkey SA T9). Probe microphone measurements were obtained on 28 ears for three experimental conditions (open ear, acoustic HPD, electronic HPD) at four input signal levels (60, 70, 80, 90 dB SPL). Also, communication in noise was evaluated for three conditions (open ear, acoustic HPD, electronic HPD) at two input signal levels (75 and 90 dB SPL) using the Hearing In Noise Test. Results indicated significantly greater attenuation as well as significantly better communication in noise for the acoustic HPD. Results also indicated that the electronic HPD failed to attenuate any input signal utilized. Although results of behavioral testing indicated that communication ability in noise was not significantly impacted by varying the signal presentation level when utilizing either HPD, a more salient finding may be that utilization of the electronic HPD may place listeners at risk for temporary or permanent sensorineural hearing loss.

Adult↗
PubMedDate not supplied

[Subjective acoustic analysis of dysphonia caused by tumor using the RBH (roughness, breathiness, hoarseness) scale].

The goal of psycho acoustic or subjective voice analysis, in a phoniater's everyday work, is to describe a subjective experience based on the physical parameters created in the process of phonation. The work was a clinical prospective study and the sample consisted of 80 people of both sexes, 40 people with benign and pseudo tumors of vocal cords and 40 people with malign tumors of vocal cords. All the patients were otorinolaringologically and phoniatrically examined. The subjective acoustic analysis was done with the patients pronouncing numbers from 1 to 10 in the comfortable zone. Afterwards, the quality of the voices was estimated in RBH scale. The subjective acoustic analysis found roughness in the voices of 87.50% patients in the first group and the most frequent value was Mod = 3 (intense roughness), 62.50% patients. Hoarseness was present in 90.00% cases, with largest value Mod = 2 (moderate hoarseness), 55.00% patients. In the second group, roughness existed in the voices of 70.00% patients, most often intense one (Mod = 3), 30.00% patients. Hoarseness existed in 95.00% cases, 45.00% with moderate (Mod = 2) and 35.00% with intense one. T test showed that there is a statistically significant difference between the strength of the roughness determined by the subjective acoustic analysis in the first and the second group, with p < 0.01. The difference between the strength of the hoarseness in the first and the second group is also statistically significant, with p < 0.01. All the growths on vocal cords irrespective of their nature change the characteristics of the voice, most of all its clearness. In cases of vocal cords tumors, by the subjective acoustic analysis, i.e. the perception of the psycho physiological characteristics of voice, a human ear can register pathological phenomena of the voice but cannot determine the character of the growth on the vocal cords.

Adult↗
PubMed1991

Clinical and animal experiment studies to optimise the therapy for acute acoustic trauma.

Despite extensive educational measures and improved ear protection, acute acoustic trauma still represents a major problem for the young soldier in the Federal Armed Forces. The aim of the investigation was thus to establish the optimum therapeutic scheme that could be applied by the generally young and still inexperienced unit medical officer to patients who had suffered acute acoustic trauma and to demonstrate the therapeutic scheme in animal experiments. In the clinical section, ten studies conducted on 500 patients who had suffered acute acoustic trauma made it possible to show that the combination of low-molecular dextran, or low-molecular hydroxyethyl starch, and hyperbaric oxygenation produced the best therapeutic results in terms of hearing gain and tinnitus elimination by a statistically significant margin. The studies only included patients who showed no tendency towards spontaneous recovery, with strict exclusion criteria being applied. Through animal experiments, it was seen that hyperbaric oxygenation, in the manner in which we conducted it (100% oxygen at 2.5 bar), leads to an increase in the oxygen partial pressure in the perilymph of the guinea pig cochlea. This is due partly to diffusion and partly to the blood flow. In a further experimental approach using animals, it proved possible to show that 60 hours after damage by acoustic trauma and hyperbaric oxygenation, the number of inner ear sensory cells that had suffered morphological damage in the animal was lower than without the hyperbaric oxygenation by a statistically significant margin. At the same time, valuable information was gained on the epidemiology of acute acoustic trauma.

Acute Disease↗
PubMed1990

Diagnostic value of acoustic rhinometry: patients with allergic and vasomotor rhinitis compared with normal controls.

By means of the acoustic reflection technique, termed acoustic rhinometry, cross-sectional areas along the whole upper airway can be measured by an acoustic click. This paper describes the normal values obtained from 134 probands. The normal curve shows the minimal cross-sectional area (I-notch) to be located at the isthmus nasi. The second narrowest segment of the nasal cavity is located at the head of the inferior concha (C-notch). In patients with turbinate hypertrophy due to allergic or vasomotor rhinitis the minimal cross-sectional area is sited at the head of the inferior turbinate. Furthermore, acoustic rhinometry allows exact measurements of size and location of the congested mucosa following challenge with allergens in patients affected with allergic rhinitis. After anterior turbinoplasty of patients with turbinate hypertrophy improved nasal breathing was associated with an enlargement of the cross-sectional areas at the head of the anterior inferior turbinate. Acoustic rhinometry not only enables to distinguish the various deviations of the nasal structures from normal (valve stenosis, septal deviation, turbinate hypertrophy, tumour masses) concerning their location and size, but also allows to demonstrate exactly the efficacy of rhinosurgical techniques.

Adult↗
PubMed1995

[Acoustic microscope and its medical applications].

There are two kinds of the acoustic microscope, the one is the Scanning Laser Acoustic Microscope, SLAM and the other the Mechanical Scanned Acoustic Microscope, SAM. In the acoustic microscope, high frequency ultrasound of 100 MHZ to 500 MHZ was used and the resolving power was in the range of 5 to 10 microns. The propagating speed and attenuation of ultrasound from the C-mode image which was obtained by mechanically scan with laser or ultrasound. From the results of the experiments by using the SAM to analyze acoustic characteristics of the tissue specimens which were taken from the patients with cardiac sarcoidosis, HCM, DCM, gastric and kidney cancer, clinical significances and usefulness of the evaluation for physical characteristics of the tissue were discussed in this paper.

Cardiomyopathies↗
PubMed1994

Influence of efferent stimulation on acoustically responsive vestibular afferents in the cat.

In the preceding article (McCue and Guinan, 1994) we described a class of vestibular primary afferent fibers in the cat that responds vigorously to sounds at moderately high sound levels. Like their cochlear homologs, vestibular afferents and their associated hair cells receive efferent projections from brainstem neurons. In this report, we explore efferent influences on the background activity and tone-burst responses of the acoustically responsive vestibular afferents. Shock-burst stimulation of efferents excited acoustically responsive vestibular afferents; no inhibition was seen. A fast excitatory component built up within 100-200 msec of shock-burst onset and decayed with a similar time course at the end of each shock burst. During repeated 400 msec shock bursts at 1.5 sec intervals, a slow excitatory component grew over 20-40 sec and then decayed, even though the shock bursts continued. Efferent stimulation excited acoustically responsive vestibular afferents without appreciably changing an afferent's sound threshold or its average sound-evoked response. This evidence supports the hypothesis that excitation is due to efferent synapses on afferent fibers rather than on hair cells. Efferent stimulation enhanced the within-cycle modulation of afferent discharges evoked by a tone; that is, it increased the "AC gain." No appreciable change was noted in the degree of phase locking to low-frequency tones as measured by the synchronization index. Little or no improvement in the bidirectionality (linearity) of transduction was seen. Vestibular afferent responses to tones normally had one peak per cycle; however, during efferent stimulation, two peaks per cycle were sometimes seen. We hypothesize that this is caused by two driving components acting at different sound phases with the components differentially affected by efferent activity. We discuss the relationship of our findings to efferent influences on acoustic responses in cochlear afferent fibers. The acoustically responsive vestibular afferents provide a mammalian model for studying purely excitatory efferent effects in a hair cell system.

Animals↗