bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate measurement of blood flow using ultrasound and time domain correlation
Authors: Hein Ilmar A. , O'Brien William D.
Published: October 2005

Using time domain correlation, the volume fluid flow in a vessel can be accurately and precisely estimated without any previous knowledge of the vessel size, flow velocity profile, or transducer measurement angle. This technique observes the change in arrival time (instead of change in frequency) of ultrasound reflected from moving scatterers. If a vessel with moving fluid is insonated by two ultrasonic pulses separated by time T, the scatterers within the ultrasonic beam will move some distance D between the first and second pulse. There will be a difference τ in the arrival times of the two pulses since the scatterers have moved. The scatterer velocity can then be calculated from the time difference τ. If the velocity is sampled at different positions within the vessel, the volume rate of flow can be calculated, along with the vessel dimensions and transducer measurement angle. The time domain correlation technique has been verified in a blood flow phantom system using both a blood mimicking substance and porcine blood. The transducer measurement angle has been determined within 5%, and pulsatile flow has been measured up to 150 beats/mix with accuracies better than 18%. Currently, this method is being experimentally investigated under in vivo conditions, with the eventual application being the diagnosis of venous thrombosis in humans. [Work supported by NSF/NHLBI Grant 1 ROI HL 37904.]
Wideband acoustic microscopy of tissue
Authors: Daft Christopher M. W. , Briggs G. A. D.
Published: October 2005

A scanning acoustic microscope (SAM) has been used to measure the elastic properties of tissue with a resolution of around 8 μm (C. M. W. Daft et al., Proc. 1986 IEEE Ultrasonics Symposium, 945—948). This is achieved by broadband excitation of the acoustic lens, and the recording of an undemodulated returning signal. This has the effect of separating the various contributions normally present in a SAM image of tissue. A method of analyzing this information to yield the sound velocity, acoustic impedance, section thickness, and acoustic attenuation is described. Results are presented from a sample of skin tissue, and sources of experimental error are discussed. The elastic properties of tissue appear to vary more substantially on this scale than in macroscopic investigations. High values of acoustic velocity and attenuation are observed in areas with high concentrations of structural protein and low water content. [Work supported by SERC and GEC Hirst Research Centre.]
Behavior of a dynamic mechanical model of a larynx
Authors: Brown Kevin , Bickley Corine
Published: October 2005

A dynamic mechanical model of an adult larynx was constructed. The components that represent the cartilages were machined out of metal. The sizes of the cartilages were taken from measurements reported in the literature [Maue (1970); Kahane (1982)]. A mechanism was designed to allow the arytenoid cartilages to be moved in a manner similar to the complex, natural movements. The vocal folds were simulated using natural rubber. The length of the vocal folds was based on measurements by Hirano and his colleagues [Hirano et al. (1981)]. The model exhibits the relative motions of the laryngeal cartilages and the vibration of the vocal folds. The vocal folds of the model vibrate in a manner similar to observed vibrations of human vocal folds. The fundamental frequency of vibration, or pitch, increases as tension is increased on the vocal folds. Measurements of the fundamental frequency of vibration, the pressures above and below the glottis, and the airflow through the glottis for various conditions of tension. mass, stiffness, glottal area, and profile of the vocal folds of the mechanical model will be reported. The behavior of the model is compared to measurements of pressure and airflow in previously reported static models and interpreted in light of current theories of vocal-fold vibration.
The crico-thyroid muscle in voicing control
Authors: Lofqvist Anders , Baer Thomas , McGarr Nancy S. , Story Robin Seider
Published: October 2005

Initiation and maintenance of vibrations of the vocal folds require suitable conditions of adduction, longitudinal tension, and transglottal airflow. This study explores the control of voicing and voicelessness in speech with particular reference to changes in the longitudinal tension of the vocal folds. Electromyographic recordings were made from the cricothyroid muscle in two speakers of American English and one speaker of Dutch. The linguistic material consisted of reiterant speech made up of CV syllables where the consonants were voiced and voiceless stops, fricatives, and affricates. The results indicate that the crico-thyroid activity increases substantially at the transition from a vowel to a voiceless consonant but not during the transition from a vowel to a voiced consonant. The activity level of the crico-thyroid is thus higher for a voiceless than for a voiced consonant. Measurements of the fundamental frequency at the beginning of a vowel following the consonant show the commonly observed pattern of higher F0 after voiceless consonants. It is thus suggested that the crico-thyroid muscle shows a different pattern of activation for voiced and voiceless consonants with higher activity for the latter. This finding most likely reflects a difference in the tension of the vocal folds associated with the voicing condition. The same mechanism also seems to contribute to the well-known difference between F0 at the beginning of vowel following voiced and voiceless consonants.
Wisconsin x-ray microbeam system: Subject variables and experimental procedures
Authors: DePaul Roxanne , Nadler Robert , Ishii Toyota , Johnson Carl
Published: October 2005

In this first year of operation of the x-ray microbeam laboratory for the study of speech movements, certain procedures and methods have been devised and/or have evolved from practical exprience. These include guidelines for the recruitment, screening, and selection of human subjects, along with acquisition of information regarding their anthropometric, linguistic, neurological, educational, dental, and auditory characteristics. Likewise, attempts have been made to devise consistent methods for placement of articulatory pellets as well as for across-subject standardization of those pellet placements. In addition, for pellets on each articulatory site, movement bandwidths and associated sampling rates have been empirically determined. In parallel, methods have been tested and refined for simultaneously sampling speech acoustic and other physiological signals as well as their postacquisition temporal alignment with pellet movement data. Other methods of experimental importance include techniques for cuing subjects and for presentation of utterance material. This presentation will cover these matters with the goal of providing society members with additional x-ray microbeam system familiarity as well as a forum for identification and discussion of yet other methodological issues. [Supported by NIH Grant NS-16373-8.]
Wisconsin x-ray microbeam system: Acquired articulatory data and some preliminary analyses
Authors: Abbs James H. , Nadler Robert D. , Nychis-Florence Caylee , Connor Nadine P.
Published: October 2005

To complement the two previous papers, it is useful to provide a more detailed description of data obtained on the new x-ray microbeam system. In the experiment to be described, two-dimensional movements were acquired for pellets placed on the mandible, tongue dorsum, tongue blade, and tongue tip as well as for two reference pellets on a vertical strut attached to an eye glass frame (for head movement corrections). Sampling rates reflected individual movement speeds: 180 samples/s (SPS) for the tongue tip, 90 SPS for the tongue blade, tongue dorsum, and mandible, and 45 SPS for the reference pellets. Four adult normal subjects each produced 50–75 repetitions of the utterances “hot apple,” “hat apple,” “haddock,” and “hassock.” Primary analyses focuesd on the contribution of these four movements to anterior lingual consonant productions, including 2-D pellet positions at palatal contact, and the velocity, amplitude, and direction of the trajectories in achieving those positions. Position and trajectory patterns, along with variability distributions, provide certain perspectives on the motor control of these gestures. [Work supported by NINCDS Grant 16373-8.]
Alterations in lip and jaw kinematics as a function of speech rate
Authors: Connor Nadine P. , Abbs James H. , Nychis-Florence Caylee , Caligiuri Michael P.
Published: October 2005

Manipulation of speech rate provides a means for examining variations in articulatory kinematics with natural alterations in speech motor timing. Such rate studies have been popular, based upon expected insights into underlying speech motor control processes. However, results from prior work on kinematic variations with speech rate have been equivocal. The divergent findings may be due to task differences, the few subjects studied in each experiment, and/or limitations in the number of task repetitions. In this context, each of ten normal subjects produced syllable repetition sequences and sentences with relatively large numbers of repetitions for each. Multiple measures of lip and jaw kinematics were applied, including some previously shown to be particularly revealing in studies of locomotion, arm, and hand movements. Findings indicated previously unreported speech rate-related variations in peak velocity-amplitude ratios, syllable-to-syllable magnitude and timing, vowel-consonant versus consonant-vowel movement durations, and peak velocity time-shifts. The results provide some new perspectives on speech kinematic control. [Work supported by NINCDS Grant 13274-12.]
Advanced turboprop aircraft flyover noise: Annoyance to counter-rotating-propeller configurations
Authors: McCurdy David A.
Published: October 2005

Two experiments were conducted to quantify the annoyance of people to the flyover noise of advanced turboprop aircraft with counter-rotating propellers (CRP). The objectives were: (1) determine the effects of tonal content on annoyance; and (2) compare annoyance to advanced turboprop aircraft with annoyance to conventional turboprop and jet aircraft. A computer system was used to synthesize realistic, time-varying simulations of advanced turboprop takeoff noise. For the first and second experiments, respectively, the system generated 27 noises representing CRP configurations with an equal number of blades on each rotor, and 35 noises representing CRP configurations with an unequal number of blades on each rotor. Included in each experiment were five conventional turboprop and five conventional jet takeoffs. Each noise was presented at three levels to subjects who judged the annoyance of each stimulus. Analyses of the judgments examine the effects on annoyance of blade passage frequency, tone-to-broadband noise ratio, and aircraft type. The annoyance prediction ability of current noise metrics is also examined.
Annoyance factors for common neighborhood noise
Authors: Alvord Lynn S.
Published: October 2005

Neighborhood noise is treated separately from aircraft or traffic noise in most local noise ordinances. Annoyance factors for common neighborhood noise were rated by 63 subjects in Salt Lake City, Utah. Subjects were asked to rate on a scale of 1 to 5, the degree to which each factor contributed to total annoyance. Most frequently mentioned annoying noise sources were dogs (38.1%), followed by sirens (12.7%). The following sources were also identified at higher than 3% incidence: garbage trucks, buses, children playing, doors slamming, noisy neighbors, helicopters, and metal stairways. Highest-rated annoyance factors were: loudness, time of occurrence, frequency of occurrence, sound quality, and interference with sleep. Relative importance of annoyance factors found in this study differ from those of previous studies, which dealt more with aircraft or traffic noise. Fear and interference with conversation and sleep are of less importance for “neighborhood” noise than aircraft and traffic noise [T. J. Schultz, J. Acoust. Soc. Am. 64, 377–405 (1978)]. For neighborhood noise “meaning” the sound portrays is an important factor in certain situations. The importance of “situational factors” found here emphasizes the need for increased use of specific prohibitions in local noise ordinances.
Altered susceptibility of the inner ear following repeated noise exposure
Authors: Franklin Daniel J. , Stagner Barden B. , Lonsbury-Martin Brenda L. , Martin Glen K.
Published: October 2005

The susceptibility of the inner ear to repeated noise exposure was investigated in the rabbit using tests of behavioral thresholds and distortion-product emissions (DPEs). Behavioral thresholds, measured by a classical-conditioning technique, were collected at 11 frequencies representative of the rabbit hearing range. Acoustic distortion products at the 2f1 − f2 frequency were measured as both DPE audiograms, generated by equilevel primaries at 45, 55, and 65 dB SPL, and input-output functions in 5-dB steps at nine frequencies. Following acquisition of control measures of DPEs and behavioral thresholds, DPEs were analyzed at regular intervals during both exposure and recovery periods and compared to corresponding behavioral measures. In four animals, following repeated episodes of exposure (octave band of noise centered at 1 kHz at 95 dB SPL) and recovery (3 weeks), both DPE amplitudes and behavioral audiograms revealed an increasing resistance to the effects of noise exposure. Comparison with the amount of amplitude reduction in a 4-kHz DP caused by a 5-min exposure during the preexposure periods to a 95-dB SPL tone at 4.215 kHz (1/2 octave below the geometric mean of the primaries) showed a poor correlation with the lessened susceptibility to repeated noise exposure. The concept describing a dynamic mechanism of repair of sensory elements proposed by a number of investigators to explain recovery from sound exposure may account for the increasing resistance to the effects of repeated noise exposure as detected by both DPEs and behavioral responses. [Work supported by NINCDS.]
Adaptation of a three-dimensional ray tracing code for use with gridded input oceanographic models
Authors: Dougherty J. , Newhall A. E. , Lynch J. F. , Chiu C. S.
Published: October 2005

In order to be able to adapt the Hamiltonian ray tracing program (HARPO) developed by NOAA's Wave Propagation Laboratory for use with gridded numerical oceanographic models, three different approaches have been employed. The first method employs using a 3-D Fourier decomposition of the sound-speed field, giving one the ability to use fast Fourier techniques and spatially filter input data but being limited to a constant grid with mesh determined by the highest spatial frequency along a given coordinate. The second technique employs an empirical orthogonal function analysis of the sound-speed field, the coefficients of which are splined to ensure the continuity requirements of the ray trace. This method allows one to: (1) simply filter the field by mode energy: (2) project easily on oceanographic modes; and (3) vary the sampling to meet the local ocean conditions, thus saving on computer memory requirements. The final technique employed is “feature hanging,” which combines using analytic forms for ocean features and gridded input for their positions. This is an extension of the existing HARPO feature to be consistent with current oceanographic models. Example calculations using each technique will be presented.
An integral equation approach to range-dependent boundary value problems in ocean acoustics
Authors: Dahl Peter H. , Frisk George V.
Published: October 2005

In ocean acoustics, the introduction of range discontinuities, for example, the water-to-ice canopy surface, creates a mixed boundary value problem. In this paper, an exact solution of certain mixed boundary value problems is discussed using the Wiener-Hopf method. A key attribute of this approach is that it is not fundamentally numerical in nature and allows additional insight into the mathematical and physical structure of the acoustic field due to range discontinuities. The problem discussed here is a canonical one: A plane wave is incident upon a planar surface where the boundary condition changes from Dirichlet (free surface) to Neumann (hard). The boundary conditions addressed in this problem are highly idealized renditions of what happens, when, say, a plane wave is incident upon a water-to-ice canopy surface; nevertheless, important features of the diffraction process are produced here, and the solution gives considerable insight into the process. The solution of the diffracted potential is partitioned into two components: a field consisting of cylindrical waves weighted by a polar gain function, resulting from the artificial source created by the discontinuity in the boundary; and a field containing a residue contribution which restores field continuity along the line corresponding to specular reflection. Contour plots of equal pressure amplitude show how the component fields superimpose such that the boundary conditions are maintained, and how energy is redistributed across the angular spectrum in the diffraction process. The latter is related to mode coupling due to boundary changes in waveguide problems. [Work supported by ONR.]
Gaussian beams and salt tables
Authors: Bucker H. P.
Published: October 2005

In the study of many ocean acoustic systems it is desirable to perform very rapid calculations of the sound field. For most problems of practical interest, 2-D models provide accurate results. That is, the sound propagation is different along different radials but the interchange of energy between radials can be neglected. In this case, it is possible to use salt tables where sound angle level and time is tabulated as a function of range. This paper examines the compatibility of the Gaussian beam propagation model and salt tables. Special items covered are the partition of beams between tables, receivers on the surface and bottom boundaries, and the effect of beam displacement associated with boundary reflection. [Work partly supported by the NORDA NOP Program.]
A wide-angle initial field for parabolic equation models
Authors: Thomson David J. , Bohun C. Sean
Published: October 2005

Numerical predictions of underwater sound propagation are routinely carried out by applying marching algorithms to solve parabolic equations. These equations require initial field data to begin marching process. For many applications, a suitably normalized Gaussian or sinc function of depth (z) is used [E. R. Robinson and D. H. Wood, J. Acoust. Soc. Am. Suppl. 1 81, S10 (1987)]. These functions, however, do not model correctly the vertical-wavenumber (kz) spectrum associated with the farfield of a point source. In this paper, a new starting field is presented that matches the proper k, variation over the full spectral aperture needed by wide-angle parabolic equation models. The new field in the z domain is obtained numerically via a discrete Fourier transform of its bandlimited spectrum. Because of this efficient distribution of energy in the kz domain, a larger step-size (Δz) can be used than that required by the Gaussian initial field [H. M. Garon, J. S. Hanna, and P. V. Rost, J. Acoust. Soc. Am. Suppl. 1 61, S12 (1977)]. Numerical examples comparing the effects of different starting fields on wide-angle parabolic equation predictions are presented.
Phase space and path integral methods in computational acoustics
Authors: Fishman Louis
Published: October 2005

The development and application of microscopic phase space methods and global path integral constructions to both direct and inverse problems in acoustics are reviewed. The Helmholtz equation is considered for (1) one-way direct wave propagation, (2) two-way direct wave propagation, and (3) inverse formulations. The one-way theory concentrates on the construction of exact, numerical, and uniform perturbation solutions to the Weyl composition equation and their application to the further development and testing of the phase space marching algorithm. Specific comparisons will be made with the IFD codes for one-way wave equations derived from formal operator rational approximations. The two-way theory considers the evaluation of the Feynman/Garrod approximate path integral, the construction of an explicit path integral representation for the homogeneous Helmholtz equation, and the combination of transmutation and quantum field theoretic variable-dimensionality ideas to incorporate backscatter. The inverse analysis seeks to exploit the Fourier integral operator structure of both the finite and infinitesimal propagators and the semigroup property of the one-way Helmholtz equation to exactly solve the refractive index profile reconstruction problem for transversely inhomogeneous environments. [Work supported by NSF, AFOSR, ONR.]
In situ acoustic measurements for tactical ASW applications
Authors: Wiseman Charles H.
Published: October 2005

Temperature versus depth profiles provided by expendable bathy-thermograph (XBT), together with information from atlases of seasonal water conditions and ocean bottom mapping, constitute the inputs for predicting sound propagation conditions for operational ASW use. At sea, XBT inputs feed computer models and nomograms that furnish inference as to sound propagation conditions on which the ASW tactics can be based—for example, the routing of convoys or naval task units to minimize the likelihood of detection by enemy submarines; the selection of optimum modes for active and passive sonars; or the identification of targets for over-the-horizon long range weapons systems. While acoustic predictions based on XBT inputs are useful, they can he improved by supplementing them with in situ acoustic measurements at sea. The inferences as to sound propagation conditions based only on XBTs are limited by their number and placement considered against the backdrop of inhomogeneities of the ocean. On the other hand, the in situ measurement of sound is not an inference of sound propagation—in point of fact, it is the direct agent, sound itself. The ASW forces should steal a leaf from the Radio Communicator's notebook. While predictions of hf radio propagation are set forth in special atlases, in situ measurements of radio propagation conditions in the form of ionospheric soundings (ionograms) furnish the most accurate, real-time indications of usable frequencies with minimum multipath distortions. There are a variety of methods, overt and covert, which can be used by ships and aircraft to effect in situ acoustic measurement and these are discussed in the body of the paper.
Sound radiation and frequency response of classical and folk guitars
Authors: Watson Eric T. , Rossing Thomas D.
Published: October 2005

The sound radiation has been measured as a function of angle in an anechoic room when the guitar is driven with a sinusoidal force. Classical guitars radiate more strongly than folk guitars when the same force is applied to the bridge [J. Popp and T. D. Rossing, International Symposium on Musical Acoustics, Hartford, July 1986]. Radiation constants are large as 2.7 Pa/N are observed at guitar resonances. Near certain resonances, dipolar or quadrupolar radiation predominates. The radiated sound field is compared to the calculated and measured force on the bridge when the string is plucked.
An alternate fairy tale for brass instruments
Authors: Ayers R. Dean
Published: October 2005

Arthur Benade's well-known paperback Horns, Strings, and Harmony includes a didactic fairy tale about a bugler forced to play on a uniform pipe and stay in tune with ordinary bugles. With a bit of sawing and some impressive lipping, he manages to succeed. This story fits nicely with the prevailing view that the bell on a brass instrument causes a considerable variation in the effective length of a (singly) closed pipe, thus making the performer's job much easier. Another possible ending for this fairy tale is that the bugler solves his tuning problems with the hand-stopping technique of natural horn players, rather than with his embouchure. One day he accidentally closes the pipe completely and discovers that he now has a perfectly good harmonic series. A slight lengthening of the pipe puts him in tune with his colleagues. This ending is consistent with a view just emerging from time-domain studies that, in terms of reflection back to the driver, the bell of a brass instrument mimics the closed end of a uniform pipe. Demonstrations will be included.
Binaural modulation detection
Authors: Grantham D. Wesley , Bacon Sid P.
Published: October 2005

A sinusoidally amplitude-modulated (SAM) noise (modulation depth: 1.0) was used to mask another SAM noise, the signal, in a two-interval forced-choice experiment. Signal and masker modulation frequency were both either 4 or 32 Hz, and were added in quadrature. The same wideband noise carrier was used for both masker and signal (spectrum level: 15 dB SPL). The whole stimulus was filtered after modulation (either 4-kHz low pass or 4-kHz high pass). Modulation depth (m) of the signal was varied adaptively to track threshold. In the case of diotic presentation (Mo-So), threshold m was about 0.30 for both modulation frequencies and both filtering conditions. In a binaural condition Mo-Sm (masker presented to both ears and signal to only one ear) some subjects. showed a release from masking of up to 10 dB (m = 0.10), while others. showed none. The release from masking occurred for both filtering conditions, but only for the lower (4-Hz) modulation rate. The results will be, discussed in relation to current models of binaural processing and the sluggish nature of the binaural system. [Work supported by NIH.]
Lateralization on the basis of interaural envelope delays: The effect of component starting phase
Authors: Dye R. H. , Niemiec A. J. , Stellmack M. A.
Published: October 2005

Threshold interaural envelope delays were measured with a 2 AFC paradigm as a function of modulation frequency (fm = 25, 50, 100, 200, 300, 400, and 500 Hz) for three- and five-component complexes whose center frequencies (fc) were equal to 4000 Hz. Comparisons were made between thresholds obtained when the starting phases were randomized and when they were all set to zero. The level of each component was approximately 50 dB SPL, and the signal duration was 200 ms with 10-ms linear rise/decay times. While reductions in depth of modulation elevate threshold envelope delays [G. B. Henning, J. Acoust. Soc. Am. 55, 84–90 (1974)], no such effects were found for phase randomization even when modulation rates were low and all components fell within a critical band. This seems surprising in light of the fact that both reduce depth of modulation and phase randomization reduce the peak factors of the waveforms, which is commonly believed to interfere with entrainment by the peripheral auditory system. Efforts to reconcile the absence of phase effects with the deleterious effects of reduced depth of modulation will be presented. [Work supported by NIH/NINCDS and AFOSR.]
Accruing binaural cues across frequency
Authors: Buell Thomas N. , Hafter Ervin R.
Published: October 2005

Localizing a complex sound requires in part an analysis of the interaural difference of time (IDT) of the component frequencies. Above about 500 Hz, the IDT is constant across the frequency spectrum. This commonality may be used to group components that arise from a single source as well as segregating such components from those which arise from competing sources. Interactions across components can be shown by measuring changes in IDT thresholds when a target is lateralized in the presence of other simultaneous sounds. When the nontarget sound has a dissimilar IDT, thresholds may actually increase. This effect has been aptly termed “interference” [D. McFadden and E.G. Pasanen, J. Acoust. Soc. Am. 59, 634–639 (1976)]. In the present experiment, listeners detected an IDT in a 600-Hz target tone both with and without the presence of a nontarget tone. Of special interest was the harmonic relation between target and nontarget. Among other factors, the results show that a simple relation such as 400 Hz can produce more interference than one that is nonharmonic, even when the interfering tone is closer to the target, e.g., 531 Hz. [Research supported by NIH.]
Discrimination of direction in the free field
Authors: Hafter Ervin R. , Buell Thomas N. , Basiji David A. , Shriberg Elizabeth E.
Published: October 2005

The psychophysics of direct comparison (two-alternative, forced choice) was applied to the study of localization. For complex signals, the interaural parameters presented by stimuli in the free field are more “natural” than those heard through earphones though more difficult to control. In this study, digital preprocessing was used to reverse the spectral characteristics of each loudspeaker to make its response uniform and indiscriminable. The listener sat in an anechoic chamber with his or her head optically fixed at the center of a semicircular array of speakers. The stimuli were trains of n filtered clicks (n = 1, 9, or 18) whose center frequencies were either 2050, 4050, or 6050 Hz. Interclick intervals (ICIs) were either 4 or 12 ms and levels were set so that a single click was 10 dB SL. Minimum audible angles (MAAs) were found to increase as the azimuth increased from 0 to 60 deg; performance was best at 2050 Hz. Studies of lateralization with earphones have led to speculations about “binaural adaptation,” a process whereby improvements in threshold with increased n depend on the click rate (1/ICI). Similar analyses show this also to be true for free-field listening. [Research supported by the NIH.]
Sound localization without interaural time or intensity differences
Authors: Wightman Frederic , Kistler Doris , Arruda Marianne , Schwister Linda
Published: October 2005

In a series of localization experiments, blindfolded listeners were asked to give the apparent azimuth and elevation coordinates of 250-ms broadband noise bursts. The noise bursts were spectrally shaped so that the spectrum level in each critical band was set randomly (from trial to trial) within a 20-dB range. In a reference condition, the sounds were transduced by miniature loudspeakers placed at 36 locations in an anechoic chamber. Performance in this free-field condition agreed with previous results in the literature except for an increased frequency of frontback reversals, which is felt to be the result of the lack of a visual frame of reference. In a control condition, digital techniques were used to synthesize headphone-presented stimuli that were nearly identical, as measured in listeners' ear canals, to the free-field stimuli. Localization performance with these stimuli was virtually the same as in free field, thus verifying the adequacy of the simulation. The digital filters used to synthesize the stimuli were then modified such that in one condition the interaural time differences were removed from all 36 stimuli, and in another condition the interaural amplitude differences were removed. In both of these conditions, localization performance was degraded. However, preliminary results suggest that the degradation caused by removal of interaural time differences is considerably greater than that caused by removal of interaural intensity differences. [Work supported by NIH, NSF, and NASA.]
Advanced acoustic test methods used in aircraft interior acoustic design
Authors: Lang Mark A.
Published: October 2005

Advanced measurement techniques, particularly sound intensity measurement, are becoming an important design and diagnostic tool in aircraft design. The utilization of these tools in aircraft measurement presents unique challenges that must be overcome to obtain meaningful data. Once the data are obtained, careful analysis must be utilized in order to interpret the measurement results. A working group under SAE Committee A-21 is currently drafting a document intended to provide guidelines on sound intensity measurement under flight conditions. This document will be discussed in the light of some recent sound intensity measurements made in the Douglas Aircraft Fuselage Acoustic Research Facility as well as under flight conditions to highlight some of the measurement challenges involved in this type of measurement.
Test procedure for improved data quality in aircraft interior noise measurements
Authors: Holmer Curtis I.
Published: October 2005

Vehicle interior noise measurements, and especially aircraft measurements, present a test environment that is inimical to considered data gathering due to the expense of operating time and the fact that the vehicle characteristics change during the measurement. A method for dealing with this is to construct a measurement procedure that provides for independent evaluation of data quality after the measurement is complete. One such method relies on the use of the relationship between the integral of intensity on a closed surface and the power produced or consumed within. Performing the measurement to permit estimation of this integral and an independent estimate of the power provides the opportunity to check data validity. This paper explores the approach in detail and examines the resulting data for a series of in-flight measurements. The measurements were performed on the Gulfstream IV aircraft as part of a program to define noise source areas. Value of the technique is explored as a function of several parameters including amount of absorption within the closed surface, reactivity of the measurement volume, and other significant parameters. [Work supported in part by Gulfstream Aerospace Corporation, Savannah, GA.]
Perceptual evidence for anticipatory assimilation of adjacent stops
Authors: Chan Jeffrey W. , Dolcourt-McElroy Amy
Published: October 2005

Prior work showed that /akta/, created by splicing together appropriate parts of /aka/ and /ata/, are perceived as /ata/ when the stop closure duration approximates that of a single medial stop; at long stop durations, both stops are heard. Apparently listeners need to integrate the multiple acoustic events into a single percept that makes sense for their language. At short closure duration, production constraints dictate that there is only time for one stop, hence the weaker cues for the first stop are disregarded. The present study reinforces this interpretation by showing that voiceless consonant-spliced clusters, e.g., /akta/, require a longer closure interval to be heard as two segments than do voiced ones, e.g., /agda/, because in natural speech voiceless stop closures are longer than voiced stop closures. Perception, then, is guided by listeners' expectations that are further based on naturally occuring speech events.
Effects of varying chord progressions on P3 event-related potentials in musicians and nonmusicians
Authors: Chuang Sarah W. , Frisina Robert D. , Crummer Gary C. , Walton Joseph P.
Published: October 2005

Event-related potentials were recorded from the scalps of both musicians and nonmusicians while actively engaging in an auditory discrimination task. Using a classical “oddball” paradigm [Donchin, Psychophysiology 18, 493 (1981)], subjects (N = 19) listened to one series of pure tones and four series of musical chord progressions in which the second of four chords differed for the target stimuli. The level of discriminability for the progressions relied upon the degree of change of the target chord in terms of melodic interval, sonority, and voicing alteration in the alto and soprano lines. The P3 waveforms displayed greater latencies and widths for chord progressions relative to the pure tones. For the chord progressions, musicians had a higher percentage of hits compared to nonmusicians, with the former group showing a significant inverse correlation between number of hits and P3 latency. Additional observations were that the P1 potential for the first chord of the progressions was considerably greater in amplitude than the P1 for the three later chords. Also, P1 amplitudes were greater for musical sounds compared to pure tones, and the negative wave immediately following P1 showed a larger amplitude for the pure tones relative to the chords. The results suggest that melodic interval and voicing cues differentially affect neural potentials generated from central auditory and memory systems. Different cognitive strategies related to musical training may underlie these observations. [Work supported by Eastman School of Music, Program in Biology and Medicine, Audiology Division, University of Rochester.]
Vibrational modes of a baritone guitar
Authors: Lozano Juan , Watson Eric T. , Rossing Thomas D.
Published: October 2005

This work studied the principal modes of vibration of a baritone guitar with steel strings tuned to A1, D2, G2, C3, E3, and A3, a fifth below those of the usual folk guitar. Likewise, the corresponding resonances are designed to be a fifth below those of a steel-string folk guitar [R. E. Ross and T. D. Rossing, J. Acoust. Soc. Am. 65, S72 (1979)]. The modal shapes have been determined by scanning the plates with an accelerometer and also by scanning the nearfield sound with a probe microphone. Sound radiation fields in an anechoic room for several of the modes are also shown.
An automated portable transducer test system
Authors: Rehn Karl W. , Cannon Gregory L.
Published: October 2005

A set of computer programs was developed to control an automated portable transducer test system. The system hardware, consisting of commercial test equipment and a custom-designed amplifier/attenuator unit, was controlled by a Hewlett-Packard integral personal computer. Pulsed measurements were used for all tests to decrease the effects of self-resonances and reflections, which can corrupt continuous-wave (cw) measurements. This computer-automated transducer test system offers the user a wide selection of tests, such as immittance loops, impedance and phase plots, dc resistance (megohm) measurements, discrete frequency measurements, and FFT analysis. Besides being able to perform each type of test singly, the user can combine test types and setup parameters into “canned” routines in which the system executes a user-defined test sequence. The structure and content of the overall test system are discussed, and a qualitative discussion of the sytem's efficiency, accuracy, and flexibility is given. The limitations of the system and sample test configurations and output are also presented [Work supported by NAVSEA.]
Nonlinear sound scattering of crossed focused beams in the presence of turbulence
Authors: Rife Stephen C. , Korman Murray S.
Published: October 2005

Experiments are performed involving the interaction of mutually perpendicular crossed ultrasonic beams overlapping and interacting in the presence of turbulence in water. The turbulence is created by a d = 0.64-cm-diam submerged water jet with nozzle exit velocity 13.3 m/s. A profile of sum frequency pressure p+ versus distance, with characteristics of turbulent velocity, is detemined by scanning across the width of the jet with the two cw acoustic beams (of frequencies f1 = 1.9 MHz, f2 = 2.1 MHz) focused on a point in the jet. The focal lengths are 15.2 cm for both sending units. In scanning, the receiving transducer unit (unfocused and located 15.2 cm from the interaction region) moves along with the senders so that propagation distances never change. The receiver axis is perpendicular to the jet. Scattered sum frequency pressure profile scans (at distances of 16d and 34d from the nozzle) compare well with known values of the radial turbulent rms velocity profile. Statistical properties of skewness s and kurtosis k from fluctuations in p+ are measured as a function of radial distance. [Work supported by the Naval Academy Research Council.]
Interaction of acoustic and thermally induced instabilities
Authors: West Stacey , Thompson Charles
Published: October 2005

Thermal convection in a low Prandtl number fluid can exhibit both steady and unsteady flow states. The state to which the fluid is attracted is dependent on the ratio of the body forces to the viscous forces. This ratio is called the Rayleigh number. Above a critical value of the Rayleigh number it has been shown that unsteady thermal modes cut on and cut off in discrete ranges of temperature with increasing value of the Rayleigh number. In this paper, results of an experimental investigation into how high-frequency acoustics waves interact with these unsteady thermal modes are presented.
An Algorithm for obtaining immittance or impedance loops
Authors: Cannon Gregory L. , Rehn Karl W.
Published: October 2005

An immittance loop algorithm has been developed for automated sonar transducer testing. This algorithm produces an excellent loop given only two frequencies separated by a resonance. Measurements of impedance and phase are made at increasing frequencies until the difference between the last recorded phase value and the current phase value approaches a calculated phase increment. At this point the new data are recorded and a new phase increment is calculated. Measurements continue for increasing frequencies until the specified upper frequency is reached. When plotted as a loop, the recorded data can be used to determine resonance frequencies, bandwidth, and other properties of resonant circuits. The algorithm has been implemented on two computer-controlled measurement systems with excellent results. Benefits of this algorithm include measurement of devices that have multiple resonances, measurement of high-Q devices, wide frequency range of operation, very efficient use of data space, and ease of implementation. The algorithm and its limitations are discussed, and sample programs and output are presented. [Work supported by NAVSEA.]
Scattering of a focused sound beam by turbulence
Authors: Jackson Mary M. , Korman Murray S.
Published: October 2005

Experiments are performed involving the scattering of a cw beam of focused ultrasonic waves by turbulence in water. The turbulence is created by a d = 0.64-cm-diam submerged waterjet with a nozzle exit velocity of 13.3 m/s. A mechanical apparatus positions a focused beam of sound (of frequency 1.9 MHz) to scan across the width of the turbulent waterjet plume. The sending transducer unit has a focal length of 15.2 cm and is always directed at an angle of 45° to the jet axis and aimed “downstream.” A transducer receiving unit (fixed relative to the sender) is directed perpendicular to the jet axis. This unit is unfocused and is located 15.2 cm from the focal point. The scattering angle between sender and receiver is 45° in the “upstream” direction. Profiles of scattered pressure ps as a function of the radial scanning distance r are compared to known turbulent rms velocity profiles at distances of 16d and 34d from the nozzle exit. Measurements of the spectral broadening and Doppler shift of the scattered pressure taken at points across the width of the jet will be used to predict the local values of the rms turbulent velocity and the mean jet velocity, respectively, across the width of the jet. [Work supported by the Naval Academy Research Council.]
Acoustic remote sensing of the upper ocean
Authors: Shorey J. , Chotiros N. P.
Published: October 2005

There are particles suspended in the ocean, such as bubbles and biological debris, which can backscatter acoustic waves. It is postulated that the backscatter from a collection of particles produces a unique acoustic signature. Since these particles are passive riders, it would be feasible to track the movement of the water by using a sonar and a cross-correlation method. The volume scatterers and the operation of an acoustic tracker were simulated on a computer in FORTRAN. Then a signal simulator was used to generate a set of backscattered signals for a multibeam sonar system. The scatterers were ensonified as their positions were changed in a way that simulated flows and eddies in the water. The signals from successive pings were cross correlated, and the resulting peaks in the correlation matrices were used to estimate movement. A reasonably accurate portrayal of the water motion has been demonstrated.
Passive damping with differential density fluid damper
Authors: Bart J. , Morris C. , Gormley M.
Published: October 2005

This project presents a new class of passive fluid dampers that uses the differential density between floating spheres and a damping fluid to provide high damping characteristics over a wide frequency band. The developed damper is not only light in weight but also effective in damping multidirectional vibrations. These features make it superior to the fully filled or the partially filled fluid loop dampers that are routinely used to damp out the vibration of spinning spacecrafts and satellites. The effect of varying the design parameters of the damper on its dynamic characteristics is investigated in an attempt to determine the optimum values of these parameters. The considered design parameters are, namely, the viscosity of the damping fluid and the concentration of the floating spheres. The performance of the damper alone is determined when subjected to step and sinusoidal vibrations as well as when it is integrated in a large space structure.
Some research “toys”
Authors: Killion Mead C.
Published: October 2005

An unbridled curiosity and a certain lack of self-discipline have resulted in a series of products whose research usefulness sometimes exceeds their immediate economic value to the author's company. On display will be low-noise, low-vibration-sensitivity microphones for measuring spontaneous and stimulated cochlear emissions; a 12-in in. microphone with switchable diffuse-field-inverse filter for simplified KEMAR' measurements; insert earphones with 70–100 dB of interaural isolation, 30–50 dB of noise exclusion, and various frequency responses (flat pressure response at the eardrum to beyond 12 kHz, flat diffuse-field-referenced response, and TDH-39-1ike response); and a 1-mm-o.d. probe microphone with flat frequency response beyond 10 kHz and two types of precision tubing (soft silicone rubber with approximately 35-dB wall attenuation and semirigid polyethylene with approximately 50-dB wall attenuation).
Instrumentation for dolphin echolocation experiments
Authors: Au Whitlow W. L.
Published: October 2005

The use of personal computers has contributed significantly in dolphin echolocation research by providing an inexpensive instrument to measure echolocation signals, monitor and control experimental devices, and to store data. Dolphins typically emit short duration (50–100 μs), broadband click signals with repetition rates that can vary from tens of clicks per second to several hundred clicks per second. In this paper, three electronic measurement devices used with Apple II computers in dolphin echolocation experiments will be discussed. The first device measures the number of clicks emitted, the intervals between clicks, the peak-to-peak amplitude of each click, and the time of activation of various switches. The second device measures the frequency spectrum (between 30 and 135 kHz) of each emitted click signal in real time, with a resolution of 15 kHz. The third device is a phantom electronic target simulator that digitizes each emitted click and then retransmits the click signal under control of the computer. The development of these three devices has been a process of evolution in sophistication over a period of several years of dolphin echolocation research conducted at the Naval Ocean Systems Center.