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PubMed1983

Perception of static and dynamic acoustic cues to place of articulation in initial stop consonants.

Two recent accounts of the acoustic cues which specify place of articulation in syllable-initial stop consonants claim that they are located in the initial portions of the CV waveform and are context-free. Stevens and Blumstein [J. Acoust. Soc. Am. 64, 1358-1368 (1978)] have described the perceptually relevant spectral properties of these cues as static, while Kewley-Port [J. Acoust. Soc. Am. 73, 322-335 (1983)] describes these cues as dynamic. Three perceptual experiments were conducted to test predictions derived from these accounts. Experiment 1 confirmed that acoustic cues for place of articulation are located in the initial 20-40 ms of natural stop-vowel syllables. Next, short synthetic CV's modeled after natural syllables were generated using either a digital, parallel-resonance synthesizer in experiment 2 or linear prediction synthesis in experiment 3. One set of synthetic stimuli preserved the static spectral properties proposed by Stevens and Blumstein. Another set of synthetic stimuli preserved the dynamic properties suggested by Kewley-Port. Listeners in both experiments identified place of articulation significantly better from stimuli which preserved dynamic acoustic properties than from those based on static onset spectra. Evidently, the dynamic structure of the initial stop-vowel articulatory gesture can be preserved in context-free acoustic cues which listeners use to identify place of articulation.

Communication Devices for People with Disabilities↗

PubMed1990

Acoustic streaming in a rotating fluid.

Acoustic streaming theory is derived that is applicable to a fluid that is slow moving in a reference frame that rotates with a constant angular velocity omega. A simplified streaming equation is obtained for the special case in which the acoustic angular frequency omega is large relative to omega, and the change in fluid density due to rotation alone is negligible. For this special case it is shown that the "driving force" for the acoustic streaming is independent of omega. Thus, if no acoustic streaming is present in a fluid system that is stationary, then no steady-state acoustic streaming is predicted for a similar system that rotates with constant angular velocity. For a system in which acoustic streaming is present, the flow behavior depends on the relative magnitudes of the Coriolis forces and the viscous forces. If the Ekman number is large (that is, the viscous force dominates) then the predicted flow is identical to that which would exist in a stationary system. If, on the other hand, the Ekman number is small then the Coriolis force dominates and the component of flow in the direction of the axis of rotation can be much smaller in the rotating system than in a similar system at rest.

Acoustics↗

PubMed1996

Accurate recovery of articulator positions from acoustics: new conclusions based on human data.

Vocal tract models are often used to study the problem of mapping from the acoustic transfer function to the vocal tract area function (inverse mapping). Unfortunately, results based on vocal tract models are strongly affected by the assumptions underlying the models. In this study, the mapping from acoustics (digitized speech samples) to articulation (measurements of the positions of receiver coils placed on the tongue, jaw, and lips) is examined using human data from a single speaker: Simultaneous acoustic and articulator measurements made for vowel-to-vowel transitions, /g/ closures, and transitions into and out of /g/ closures. Articulator positions were measured using an EMMA system to track coils placed on the lips, jaw, and tongue. Using these data, look-up tables were created that allow articulator positions to be estimated from acoustic signals. On a data set not used for making look-up tables, correlations between estimated and actual coil positions of around 94% and root-mean-squared errors around 2 mm are common for coils on the tongue. An error source evaluation shows that estimating articulator positions from quantized acoustics gives root-mean-squared errors that are typically less than 1 mm greater than the errors that would be obtained from quantizing the articulator positions themselves. This study agrees with and extends previous studies of human data by showing that for the data studied, speech acoustics can be used to accurately recover articulator positions.

Humans↗

PubMed1997

The effects of surfactant additives on the acoustic and light emissions from a single stable sonoluminescing bubble.

The localized concentration of energy during a single bubble collapse is manifested in two forms, which are the emission of an acoustic pulse, and the emission of a light pulse. Through precise control of experimental parameters, one can levitate a single bubble in a standing wave field and measure the magnitude of the acoustic and light pulses resulting from the violent collapse of the cavity. The information acquired from such measurements provides better understanding of the mechanisms that are responsible for the emissions, which may lead to the practical application of controlled bubble implosions. An experimental apparatus was developed to measure the acoustic and light emissions from a single, stable sonoluminescing bubble. Two surfactant additives were studied to determine the effects on the bubble emissions. Triton X-100, which has previously been shown to provide free interfacial motion, reduced the magnitude of both the acoustic and light pulses from the bubble. The protein bovine serum albumin (BSA) which has been shown to hinder interfacial motion, allowed the bubble to be driven to higher acoustic pressures, and resulted in an increase in the magnitude of the light pulses from the bubble. Images of the sonoluminescing bubble indicate that the collapse remains spherical in the cases presented, and that bubble translation can be correlated with weak acoustic and light emissions.

Acoustics↗

PubMed1998

In vitro characterization of a novel, tissue-targeted ultrasonic contrast system with acoustic microscopy.

Targeted ultrasonic contrast systems are designed to enhance the reflectivity of selected tissues in vivo [Lanza et al., Circulation 94, 3334 (1996)]. In particular, these agents hold promise for the minimally invasive diagnosis and treatment of a wide array of pathologies, most notably tumors, thromboses, and inflamed tissues. In the present study, acoustic microscopy was used to assess the efficacy of a novel, perfluorocarbon based contrast agent to enhance the inherent acoustic reflectivity of biological and synthetic substrates. Data from these experiments were used to postulate a simple model describing the observed enhancements. Frequency averaged reflectivity (30-55 MHz) was shown to increase 7.0 +/- 1.1 dB for nitrocellulose membranes with targeted contrast. Enhancements of 36.0 +/- 2.3 dB and 8.5 +/- 0.9 dB for plasma and whole blood clots, respectively, were measured between 20 and 35 MHz. A proposed acoustic transmission line model predicted the targeted contrast system would increase the acoustic reflectivity of the nitrocellulose membrane, whole blood clot, and fibrin plasma clot by 2.6, 8.0, and 31.8 dB, respectively. These predictions were in reasonable agreement with the experimental results of this paper. In conclusion, acoustic microscopy provides a rapid and sensitive approach for in vitro chracterization, development, and testing of mathematical models of targeted contrast systems. Given the current demand for targeted contrast systems for medical diagnostic and therapeutic use, the use of acoustic microscopy may provide a useful tool in the development of these agents.

Acoustics↗

PubMed1999

Articulatory tradeoffs reduce acoustic variability during American English /r/ production.

The American English phoneme /r/ has long been associated with large amounts of articulatory variability during production. This paper investigates the hypothesis that the articulatory variations used by a speaker to produce /r/ in different contexts exhibit systematic tradeoffs, or articulatory trading relations, that act to maintain a relatively stable acoustic signal despite the large variations in vocal tract shape. Acoustic and articulatory recordings were collected from seven speakers producing /r/ in five phonetic contexts. For every speaker, the different articulator configurations used to produce /r/ in the different phonetic contexts showed systematic tradeoffs, as evidenced by significant correlations between the positions of transducers mounted on the tongue. Analysis of acoustic and articulatory variabilities revealed that these tradeoffs act to reduce acoustic variability, thus allowing relatively large contextual variations in vocal tract shape for /r/ without seriously degrading the primary acoustic cue. Furthermore, some subjects appeared to use completely different articulatory gestures to produce /r/ in different phonetic contexts. When viewed in light of current models of speech movement control, these results appear to favor models that utilize an acoustic or auditory target for each phoneme over models that utilize a vocal tract shape target for each phoneme.

Female↗

PubMed2000

Acoustic modeling of American English /r/.

Recent advances in physiological data collection methods have made it possible to test the accuracy of predictions against speaker-specific vocal tracts and acoustic patterns. Vocal tract dimensions for /r/ derived via magnetic-resonance imaging (MRI) for two speakers of American English [Alwan, Narayanan, and Haker, J. Acoust. Soc. Am. 101, 1078-1089 (1997)] were used to construct models of the acoustics of /r/. Because previous models have not sufficiently accounted for the very low F3 characteristic of /r/, the aim was to match formant frequencies predicted by the models to the full range of formant frequency values produced by the speakers in recordings of real words containing /r/. In one set of experiments, area functions derived from MRI data were used to argue that the Perturbation Theory of tube acoustics cannot adequately account for /r/, primarily because predicted locations did not match speakers' actual constriction locations. Different models of the acoustics of /r/ were tested using the Maeda computer simulation program [Maeda, Speech Commun. 1, 199-299 (1982)]; the supralingual vocal-tract dimensions reported in Alwan et al. were found to be adequate at predicting only the highest of attested F3 values. By using (1) a recently developed adaptation of the Maeda model that incorporates the sublingual space as a side branch from the front cavity, and by including (2) the sublingual space as an increment to the dimensions of the front cavity, the mid-to-low values of the speakers' F3 range were matched. Finally, a simple tube model with dimensions derived from MRI data was developed to account for cavity affiliations. This confirmed F3 as a front cavity resonance, and variations in F1, F2, and F4 as arising from mid- and back-cavity geometries. Possible trading relations for F3 lowering based on different acoustic mechanisms for extending the front cavity are also proposed.

Humans↗

PubMed2000

On acoustic scattering by a shell-covered seafloor.

Acoustic scattering by the seafloor is sometimes influenced, if not dominated, by the presence of discrete volumetric objects such as shells. A series of measurements of target strength of a type of benthic shelled animal and associated scattering modeling have recently been completed (Stanton et al., "Acoustic scattering by benthic and planktonic shelled animals," J. Acoust. Soc. Am., this issue). The results of that study are used herein to estimate the scattering by the seafloor with a covering of shells at high acoustic frequencies. A simple formulation is derived that expresses the area scattering strength of the seafloor in terms of the average reduced target strength or material properties of the discrete scatterers and their packing factor (where the reduced target strength is the target strength normalized by the geometric cross section of the scatterers and the averaging is done over orientation and/or a narrow range of size or frequency). The formula shows that, to first order, the backscattering at high acoustic frequencies by a layer of shells (or other discrete bodies such as rocks) depends principally upon material properties of the objects and packing factor and is independent of size and acoustic frequency. Estimates of area scattering strength using this formula and measured values of the target strength of shelled bodies from Stanton et al. (this issue) are close to or consistent with observed area scattering strengths due to shell-covered seafloors published in other papers.

Acoustics↗

PubMed1980

Comparison of direct and acoustical area measurements in physical models of human central airways.

Total cross-sectional areas were computed from direct measurements made on two human central airway casts. Acoustic pulse-response measurements were obtained on rigid-walled positive replicas of these casts. From the acoustic response data of each cast, we computed the area-distance function of the acoustically equivalent structure (i.e., the structure with regular branching and negligible viscous losses, but with similar acoustic properties). The acoustic data predicted equivalent areas that compared favorably to the total cross-sectional areas in the casts at all points from the beginning of the trachea to distances about 6 cm beyond the carina corresponding to airways of the third, fourth, or fifth generation. These results indicate that, at least in the central airways, branching asymmetry and internal energy losses introduced negligible errors in estimates of cross-sectional areas derived from acoustic pulse-response measurements. This rapid noninvasive technique thus shows promise as a method of detecting upper and central airway obstruction.

Acoustics↗

PubMed1979

Acoustic input to single neurons in pulvinar-posterior complex of cat thalamus.

1. Extracellular microelectrode recordings have been made of 429 single neurons in the pulvinar-posterior (Pul-PO) complex and adjacent regions of the thalamus of cats anesthetized with either sodium pentobarbital or alpha-chloralose. Controlled acoustic stimuli were presented by sealed systems incorporating probe microphone assemblies. 2. Neurons in pulvinar, lateralis posterior, and nucleus posterior were unresponsive to acoustic stimulation. Few cells in medial PO were observed to receive acoustic input, while sensitivity to tonal stimuli was a general feature of driven cells in other PO divisions. 3. Cells in lateral PO were generally sharply tuned to stimulus frequency, while the majority of cells in magnocellular medial geniculate and intermediate division of PO were broadly tuned. 4. Neurons in lateral PO and magnocellular medial geniculate had short response latencies to acoustic stimulation. Cells in intermediate division of PO were more often long latency. 5. Divisions of PO could not be differentiated on the basis of their binaural properties. Cells receiving excitatory input from solely the contralateral ear (E/O) or fros with onset discharge patterns showed occlusive binaural interaction properties. For cells with multiple-component discharge patterns, individual response components frequently had different patterns of binaural input and/or interaction. 6. On the basis of their discharge patterns, short latency, and frequency-tuning properties, it is suggested that lateral PO and magnocellular medial geniculate might derive their acoustic input from different divisions of the inferior colliculus. In contrast, the long latencies of units in PO intermediate division suggests a corticofugal input. 7. These data support anatomical parcelations of the Pul-PO complex, and the suggestion that this complex might provide acoustic input to the association cortices is evaluated.

Acoustic Stimulation↗

PubMed1988

Role of the acoustic striae in hearing: contribution of dorsal and intermediate striae to detection of noises and tones.

1. Behavioral thresholds were obtained from cats, first with only their right ear and right dorsal, intermediate, and ventral acoustic striae (DAS, IAS, and VAS, respectively) intact, and then again with only their right ventral acoustic stria intact. 2. Using usual definitions of "threshold" the loss of the dorsal and intermediate acoustic striae results in no measurable deficit in the detection of noises or tones on a silent background. 3. In sharp contrast, even partial damage of the ventral acoustic stria (i.e., trapezoid body section) results in marked deficits in sound detection. 4. Therefore, the ventral acoustic stria is both necessary and sufficient to maintain normal acoustical sensitivity. 5. However, loss of the dorsal and intermediate striae seems to result in a degradation of reliability in the detection of suprathreshold sounds--perhaps akin to a deficit in listening.

Acoustic Stimulation↗

PubMedDate not supplied

Acoustic and intelligibility characteristics of sentence production in neurogenic speech disorders.

The purpose of this study was to examine the relationship between scaled speech intelligibility and selected acoustic variables in persons with dysarthria. Control speakers and speakers with amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) produced sentences which were analyzed acoustically and perceptually. The acoustic variables included total utterance durations, segment durations, estimates of the acoustic vowel space, and slopes of formant transitions; the perceptual variables included scaled speech intelligibility and severity of speech involvement. Results indicated that the temporal variables typically differentiated the ALS group, but not the PD group, from the controls, and that vowel spaces were smaller for both neurogenic groups as compared to controls, but only significantly so for the ALS speakers. The relation of these acoustic measures to scaled speech intelligibility is shown to be complex, and the composite results are discussed in terms of sentence vs. single-word intelligibility estimates and their underlying acoustic bases.

Aged↗

PubMed1994

Acoustic method to estimate the longitudinal area profile of endotracheal tubes.

A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. Acoustic results were compared with the results obtained by an hydraulic reference method, which was the only method available to measure ETT obstruction in mechanically ventilated patients. In vivo acoustic results showed that area reductions were maximal near the tracheal extremity of the ETT, with a range from 2 to 36% (mean value 13 +/- 10%), when estimated relative to the area measured in an unused ETT of the same inner diameter (7 to 9 mm). Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.

Acoustics↗

PubMed1987

Airway area by acoustic response measurements and computerized tomography.

In order to determine more precisely the accuracy with which the acoustic reflection technique (ART) can infer airway area during spontaneous breathing, we compared acoustic measurements of airway area with equivalent areas measured from computerized tomographic (CT) scans of the neck and chest in 7 patients (mean age, 54 yr; range, 33 to 69 yr) with a history of upper airway abnormalities. At the time of the study, all patients were clinically stable and had no recurrent nerve palsy. Measurements of airway area by ART and CT were performed in the supine posture while patients breathed quietly at FRC. We found that there was considerable intersubject variability in area-distance functions determined by acoustic reflections. None of the subjects had a flat tracheal plateau. Once the acoustic and CT data were aligned, we compared cross-sectional areas at various distances from the glottis. Comparison points were separated by 1 cm, and as many as 13 different CT sections were used in some subjects. Mean values for all data points (n = 83) were 2.45 +/- SD = 0.69 cm2 and 2.56 +/- SD = 0.82 cm2 for the acoustic and CT methods, respectively, Z = 0.93; p greater than 0.05. Linear regression analysis revealed a correlation coefficient (r) of 0.92; p less than 0.0001. On the basis of these findings, we conclude that the acoustic reflection technique may be used reliably for clinical and physiologic studies of the upper airways in humans.

Acoustics↗

PubMed1996

Acoustic measurement of subglottic stenosis.

A device that determines cross-sectional area (CSA) of the airway by acoustic reflections (Hood, Inc) was used to measure subglottic area. Airway models were made from Plexiglas rings with known internal dimensions similar to clinically encountered stenoses of various lengths and diameters. Acoustic measurements of airway area were made and compared to actual CSA. There is a strong correlation between CSA measured acoustically and the actual area of simulated stenoses. However, when the CSA of the stenosis was < 0.64 cm2, the signal was impaired, resulting in overestimation of the stenotic CSA. In simulated stenoses with a CSA of < 0.38 cm2, acoustic measurement of the CSA beyond the stenotic segment was unreliable. Determination of the origin of stenosis was accurate with this method. The CSA of cadaver airways was also measured acoustically. The CSA 2.0 cm below the glottis of normal airways in males ranged from 1.28 to 2.74 cm2 and in females 0.87 to 1.43 cm2, with means of 2.16 and 1.09 cm2. It appears that acoustic measurement of CSA of subglottic stenosis is a feasible clinical technique that yields dimensions of the airway in situations in which direct measurements are impossible. It was suggested that this technique be used for assessment of subglottic stenosis and evaluation of the efficacy of treatment of subglottic stenosis.

Culture Techniques↗

PubMed1983

Specific cellular immunity in acoustic neuroma patients.

An indirect leukocyte migration agarose technique to detect cell-mediated immunity was modified to obtain a specific assay for release of human leukocyte migration inhibitory factor. Acoustic neuroma patients exhibited a significant cellular immune response against acoustic neuroma extract (P less than .01) as well as perilymph from acoustic neuroma patients (P less than .01) when compared to healthy control persons. All 19 patients tested reacted to acoustic neuroma extract. Seven of 21 perilymph samples did not elicit migration inhibition. Crossover determination of antigenicity of two negative and four positive perilymph samples against three patients revealed highly reproducible results, uncorrelated to perilymph concentration of potassium and protein. Flow cytofluorometry did not reveal malignant DNA patterns in 10 acoustic neuromas examined. Immunofluorescence studies did not reveal autoantibodies against acoustic neuromas in sera from 11 patients. The responsible antigen(s), the mechanism of immunization, and the diagnostic implications remain to be determined.

Adult↗

PubMed1994

Presentation and diagnosis of small acoustic tumors.

With the recent advent of magnetic resonance imaging and auditory brain stem response, it is now possible to diagnose acoustic tumors while they are still quite small. As a result, it is becoming obvious that the clinical presentation of these smaller lesions can be somewhat variant to what is considered typical for an acoustic neuroma. Likewise, although the sensitivity of auditory brain stem response for larger tumors is believed to be quite good, the sensitivity for smaller tumors has recently been questioned, particularly when the patient is first seen early in the course of the disease with only mild otologic complications. To assess auditory brain stem response results as well as clinical and audiologic presentations, we conducted a retrospective study of patients treated for small acoustic tumors (less than 1 cm). Of the 70 patients included in the study, auditory brain stem response was abnormal in 65 (93%), on the basis of wave V latency prolongation and interaural latency differences. This would indicate that auditory brain stem response is a valid screening test for acoustic tumors, even in early stages of development. The clinical presentation of patients with small acoustic tumors was similar to that reported for acoustic tumors in general, but with vertigo occurring more frequently in patients with smaller tumors. Several atypical patterns of hearing loss were also noted.

Adult↗

PubMed2003

Sounds of emotion: production and perception of affect-related vocal acoustics.

In his writing Darwin emphasized direct veridical links between vocal acoustics and vocalizer emotional state. Yet he also recognized that acoustics influence the emotional state of listeners. This duality-that particular vocal expressions are likely linked to particular internal states, yet may specifically function to influence others-lies at the heart of contemporary efforts aimed at understanding affect-related vocal acoustics. That work has focused most on speech acoustics and laughter, where the most common approach has been to argue that these signals reflect the occurrence of discrete emotional states in the vocalizer. An alternative view is that the underlying states can be better characterized using a small number of continuous dimensions such as arousal (or activation) and a valenced dimension such as pleasantness. A brief review of the evidence suggests, however, that neither approach is correct. Data from speech-related research provides little support for a discrete-emotions view, with emotion-related aspects of the acoustics seeming more to reflect to vocalizer arousal. However, links to a corresponding emotional valence dimension have also been difficult to demonstrate, suggesting a need for interpretations outside this traditional dichotomy. We therefore suggest a different perspective in which the primary function of signaling is not to express signaler emotion, but rather to impact listener affect and thereby influence the behavior of these individuals. In this view, it is not expected that nuances of signaler states will be highly correlated with particular features of the sounds produced, but rather that vocalizers will be using acoustics that readily affect listener arousal and emotion. Attributions concerning signaler states thus become a secondary outcome, reflecting inferences that listeners base on their own affective responses to the sounds, their past experience with such signals, and the context in which signaling is occurring. This approach has found recent support in laughter research, with the bigger picture being that the sounds of emotion-be they carried in speech, laughter, or other species-typical signals--are not informative, veridical beacons on vocalizer states so much as tools of social influence used to capitalize on listener sensitivities.

Affect↗