bluuebunny/crossref_metadata_2025 huggingface dataset:
An automated test battery for assessing the auditory fitness of aviators
Authors: Thomas Gerald B. , Williams Carl E. , McCardie Andrew H.
Published: October 2005

A microcomputer-based battery of tests has been developed to assess the performance of aviators on auditory tasks deemed important in the operation of aircraft. Included in the test battery are measures of hearing threshold levels, speech perception in cockpit noise, speeded response to auditory signals, auditory attention management, and auditory short-term memory. All auditory stimuli are computer synthesized or are digitized from analog sources, and all test administration and scoring procedures are automated; test duration is approximately 30 min. The test battery was administered to six aviator and nonaviator populations (N = 120) and showed significant (p<0.05) performance differences among the populations on one or more of the test battery elements. Test-retest reliabilities ranged from 0.71 to 0.88 (n = 64) within a restricted variance population (i.e., student naval aviators). Correlations between test battery scores and simulated “real world” performance are currently being determined.
Detection of silent temporal gaps in narrow-band noise stimuli having second-formantlike properties of voiceless stop/vowel combinations
Authors: Formby C. , Barker C. , Abbey H. , Raney J.
Published: October 2005

Delattre et al. [J. Acoust. Soc. Am. 27, 769–773 (1955)] reported that good-quality stop consonant/vowel pairs could be synthesized in two-formant representation by replacing the initial part of the second-formant (F2) transition with a silent temporal gap. The best silent gap for each stop varied with the timing and extent of the F2 transition, which we know is (1) dependent on coarticulation between the stop and vowel and (2) represented acoustically by the difference or change in frequency from the stop burst to F2 of the following vowel. Motivated by their report, temporal gap detection thresholds were measured in narrow-band noise-burst markers having acoustic characteristics that simulated isolated steady-state F2 properties of voiceless stop /p, t, k/ and vowel /i, æ, u, ɔ/ combinations. Gap detection thresholds increased systematically as a function of the difference between the simulated stop and vowel F2 frequencies, which accounted for 76% of the variance in the results. Differences in other stimulus features had little influence on detection. [Research supported by NIH.]
Far-field considerations in surface and bottom scattering
Authors: Jackson Darrell R. , Thorsos Eric I.
Published: October 2005

It is sometimes argued that the concept of scattering cross section is inapplicable for most surface and bottom scattering measurements, because the acoustic receiver is invariably in the near-field zone of the ensonified patch and scattering cross section is defined in the far-field limit. Winebrenner and Ishimaru [IEEE Trans. Antennas Propag.AP34, 847–849 (1986)] have shown that the correlation length of the surface field defines the relevant far-field region for stochastic scattering. This sets a less stringent constraint than the far-field criterion based on the ensonified patch size and greatly extends the domain of applicability of the scattering cross-section concept. Using a standard formalism that includes near-field phase terms, it is shown how the scattering cross section can be used even in the near field of the ensonified patch. The result is a proof of the method commonly used in reverberation calculations: One integrates over the ensonified patch with the appropriate propagation loss factors and bistatic scattering cross section as integration variables. This assumes that the far-field criterion based on the correlation length is satisfied. [Work supported by ONR.]
Sea surface scattering using 2-D perturbation theory
Authors: Thorsos Eric I.
Published: October 2005

Comparisons with exact integral equation results for 1-D surfaces have shown that perturbation theory, when carried to fourth order in kh for the scattering cross section, gives accurate predictions at low frequencies for low-grazing-angle backscattering from the “classical” sea surface. Here, k is the acoustic wave number, h is the rms surface height, and the classical sea surface assumes linear gravity waves with no bubbles. it will be shown that 1-D perturbation theory is accurate for frequencies up to 800 Hz for a Pierson-Moskowitz surface spectrum with a wind speed of 20 m/s (39 kn). For this example, kh = 7.1. Perturbation theory has now been extended to 2-D surfaces, in other words, to surfaces that vary in two horizontal directions. Similar accuracy for perturbation theory can be expected for 2-D and 1-D predictions. Examples of 2-D results for scattering strengths will be presented. [Work supported by ONR.]
Directional decomposition of the acoustic field scattered from rough ice
Authors: Fricke J. Robert , Baggeroer Arthur B.
Published: October 2005

At low frequency, ≃50 Hz, the acoustic field scattered from a single ice roughness element such as an ice keel or an ice edge contains plane-wave components in virtually all directions. The scatterer affects long-range propagation in two ways: It draws energy out of the coherent field, thus causing attenuation, and it injects incoherent energy into the environment, thus raising the noise level. In general, these two phenomena occur in different directions. The coherent energy deficit occurs in the specular direction and the incoherent scatter occurs over a wide band of angles. Using data generated with a finite-difference model, these phenomena are demonstrated. A plane-wave energy flux calculation reveals quantitatively how much energy is scattered in each direction. Every scattering element has a characteristic directional spectrum, thus implying a characteristic effect on long-range propagation. Results for an ice edge and several keels are compared. An ice edge acts primarily to attenuate the coherent field while the keels both attenuate the coherent field and scatter incoherent energy. In all cases, the energy deficit in the coherent field is greater than the incoherent scattered energy. The difference is converted to plate wave energy in the ice. For grazing angles around 7°, the coherent energy reflection coefficient R2 is about 0.97 for an ice edge. For keels, R2 varies from ≃0.95 down to ≃0.65, depending on keel size.
A computer controlled apparatus for measuring the angular scattering of ultrasound from a random medium
Authors: Leroux David R. , Korman Murray S.
Published: October 2005

Measurements of the scattered sound intensity, I(θ), versus angle θ from submerged targets (such as a bubble cloud) require long tedious data runs. The task of generating a family of intensity curves (allowing for the adjustable parameters of a target) becomes insurmountable. An Apple IIe computer with an IEEE-488 instrument bus is programmed to control a digital oscilloscope (for data acquisition) and a stepper motor rotational unit (for angular positioning of the transmitting transducer). Typically, an average of 32 trials is used to measure the incoherent scattered energy from the received pulses at any particular angle. Scattering results from a cylindrical air bubble column are presented along with some theoretical predictions. [Work supported by the Naval Acad. Res. Council.]
Progress in noise control of mining equipment
Authors: Marraccini Leonard C.
Published: October 2005

With the advent of mechanization in the mining industry, one of the by-products has been the generation of excessive noise levels. In order to protect miners from these excessive noise levels, the Mine Safety and Health Administration has promulgated various noise regulations over the years, starting with the Coal Mine Safety and Health Act of 1969. One method used to reduce these excessive noise levels has been with the utilization of engineering noise controls. The progress in noise control of mining equipment has essentially followed three avenues of approach. These involve retrofit noise control, machine redesign, and advanced technology. One example of each of these approaches is (1) cut and fit application of acoustical materials to mobile equipment cabs, (2) redesign of cutting heads for underground continuous miners, and (3) electronic noise cancellation. This presentation will involve a general discussion of the progress made in noise control of mining equipment. In addition to the three examples previously mentioned, other examples of noise control will also be discussed.
Simulation of the radiated noise emitted by two coupled structures and application to the acoustic quietening of air conditioning equipment
Authors: Nicolas J.
Published: October 2005

The challenge of noise control for the nineties will be to leave trial and error methods that are efficient in specific well-known situations and to tackle the difficult and complex but inevitable problem of structural acoustics and vibration. In order to actually control the noise at the source at the design step, a mode of the radiation of a semicomplex structure has been developed. Based on an analytical approach using a variational method, this model allows prediction of the effects of the boundary conditions [J. Acoust. Soc. Am. (to be published)] as well as stiffeners and added masses with force or moment type of excitation. To go toward industrial applications, the calculus has been extended to the case of a mechanical source of vibration (electric motor, engine) which is attached to a large thin structure that acts as a noise radiator. A theoretical analysis of the problem is presented. The actual force input into the structure is determined as the resultant of both the output impedance of the source and the input impedance of the structure. A quadripole approach for the source assembly enables calculation of the force input, the kinetic energy, the radiation efficiency, and overall sound power. The key novelty of this method lies in its capacity of predicting a priori the radiated noise in various configurations, allowing the designer to choose rationally the best configuration in terms of noise control. This approach has been applied in order to decrease the unwanted noise emitted by air conditioning equipment. A new design has been proposed which led to a 10-dB improvement. In a general case, guidelines for the optimal suspension design will be presented.
Ray synthesis of backscattering by thin cylindrical shells
Authors: Sun N. H. , Marston P. L.
Published: October 2005

In previous research [P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)] the leaky Lamb wave contributions fl to the form function for backscattering from right circular cylindrical shells were expressed in terms of the phase velocity ratio cl/c, a radiation damping parameter βl in Np/rad, and a coupling coefficient Gl with |Gl| ≈ 8πβl/(πka)1/2. It was subsequently shown that the phase arg(Gl) ≈ π/4. The present research concerns the extension to contributions termed “creeping and trapped” waves from the far-field limit of an analysis (when corrected) by Felsen et al. [J. Acoust. Soc. Am. 87, 554–569 (1990)]. Such contributions are especially important for understanding scattering from thin shells. The extension of Marston's original equations requires that when cl < c, the effective angle of incidence θl for launching a guided wave becomes π/2 instead of the previous expression sin θl=c/cl also, arg(Gl) is revised when cl≲c. For example, for trapped waves arg(Gl) becomes ≈ −π/4. The expression for fl allows the caustic radius bl=ac/cl to be larger than the radius a of the shell. Comparisons with exact computations for 2.5% thick hollow steel cylinders support the approximations for the leaky and trapped wave contributions. The ka dependence of leaky, creeping, and trapped wave parameters are examined. [Work supported by ONR.]
Ray synthesis of the angular dependence and backscattering by thick cylindrical shells
Authors: Marston P. L. , Sun N. H.
Published: October 2005

Previous research has confirmed ray models of leaky Lamb wave contributions fl are applicable to the forward and backward scattering from thick spherical shells [S. G. Kargl and P. L. Marston, J. Acoust. Soc. Am. 88, 1103–1113 (1990); and work in press]. The present research concerns the extension of the ray models to leaky Lamb waves that tend to dominate the elastic scattering contributions of thick cylindrical shells. The extension is important because the cylinder model should be generalizable to noncircular-shapes where solutions for the scattering may not be available. A previous analysis found that for cylinders, the coupling coefficient becomes |Gl| ≈ 8πβl/(πka)1/2 with the phase arg(Gl) ≈ π/4, where βl is the radiation damping parameter. The present computations show that for a 16.2% thick stainless-steel cylinder, a superposition of leaky and specular contributions synthesizes the exactly computed scattering for ka as small as 7. The scattering as a function of angle was synthesized at ka = 20 for the full 180° range. The synthesis combined leaky Lamb wave contributions with a background contribution of a rigid cylinder. The agreement with exact computations was good except near ray transition regions where paths changed abruptly with changes in the scattering angle. [Work supported by ONR.]
Differential scattering cross sections at arbitrary outgoing angles and their relation to target boundary conditions
Authors: George Jacob , Werby M. F.
Published: October 2005

It is usual to examine differential scattering cross sections in the backward direction as a function of frequency variation. When this is done in the asymptotic limit the resulting function is referred to as a form function. The form function proves to be sensitive to the boundary conditions of the target and may manifest resonances and circumferential diffraction effects typical of certain targets. However, such quantities at exit angles such as those in the forward direction prove to be somewhat less sensitive to the object's properties with increasing frequency. This characteristic is undesirable if one wishes to examine the material nature of the target. On the other hand, it can be valuable from the modeling point of view if one wishes to obtain forward scattering target strengths. In that case one may use the simplest target to obtain such a property. Forward and other exit angle target scattering strengths were examined over a frequency region to determine when the strengths begin to converge and thus when the simple approximations can be made.
Analysis of wind noise measurements
Authors: Morgan Scott , Raspet Richard
Published: October 2005

Wind noise in outdoor microphone measurements is composed of both the noise due to intrinsic turbulence in the flow and that due to the flow interacting with the microphone. This paper presents the analysis of wind noise and turbulence data taken in an outdoor environment in an effort to determine the primary source of the wind noise. Bare microphone data are compared with data taken during the same time period from microphones covered with a nose cone, a Brüel and Kjaer spherical windscreen, and a variety of experimental windscreens developed at the University of Mississippi. The theory behind these experimental screens is also presented and is compared to the experimental data. Conclusions concerning the dominant source of wind noise are drawn by examining microphone data and turbulence data and comparing them with published microphone data. The effectiveness of different windscreens is also examined. [Work supported by MIT Lincoln Laboratory.]
Magnitude estimation scaling of intelligibility by experienced and inexperienced listeners
Authors: Ellis Lee W. , Fucci Donald J.
Published: October 2005

Fifteen experienced listeners and 15 inexperienced listeners provided magnitude estimation scaling responses to indicate the intelligibility of two sets of nine audiotaped speech samples. These samples consisted of three utterances made up of 17 words and contained all of the consonant phonemes of English. These words were arranged to form a set of either meaningful or nonsense utterances. Nine separate versions of both the meaningful and nonsense utterances were created by systematically increasing the number of phonemes produced incorrectly on each of the nine recordings. Results indicated no significant difference between the magnitude estimation scaling responses of experienced and inexperienced listeners. Explanations for the results of this study and the advantages of magnitude estimation scaling as a measure of speaker intelligibility are discussed.
Intelligibility, phonetic distortion, and listener consensus in the speech of hearing-impaired talkers
Authors: Goldhor Richard
Published: October 2005

Recorded speech from 29 hearing-impaired and four normal-hearing speakers was reviewed by two trained phoneticians. Selected segments of the speech were judged according to 14 phonetic attributes such as consonant manner and place, vowel fronting, and breathiness. Magner intelligibility scores for the hearing-impaired speakers were also available. A feature-based perceptual distance measure was constructed and used to specify both the degree of phonetic accuracy of the speech and the level of consensus in listener judgments. Analysis of these data reveals strong direct relationships between phonetic accuracy, Magner intelligibility scores, and listener consensus. Analysis of the consensus data according to feature type indicates that listeners may perceive manner features most reliably, with stress, place, and voicing features perceived with successively less reliability (i.e., consensus). [Work supported by NIH.]
Frequency response of the swimbladders of fish
Authors: Lewis Thomas N. , Rogers Peter H. , Rogers David B. , Flanagan Steven N.
Published: October 2005

The gas-filled swimbladder of a fish resonates in the ambient noise field, scattering significant amounts of acoustic energy. This characteristic scattered field is thought to assist a fish's own hearing and also may allow for the detection and identification of other scatterers by the receiver [P. H. Rogers et al., J. Acoust. Soc. Am. Suppl. 1 85, S35 (1989)]. The frequency response of the swimbladder can be measured in vivo by a noninvasive vibration amplitude measurement system [M. Cox and P. H. Rogers, J. Vib. Acoust. Str. Rel. Des. 109, 55–59 (1987)]. The response for a variety of fish of the species Carassius auratus (common goldfish) and Astronotus ocellatus (oscar) was measured and correlated with respect to fish size. One aspect of the results further examined was the appearance of twin peaks in the response of some goldfish. X rays of the subjects indicated that differences in size of the anterior and posterior chambers of the swimbladder may be responsible. [Work supported by ONR.]
Surface roughness induced attenuation of ultrasonic waves transmitted through a liquid-solid interface at oblique incidence
Authors: Nagy Peter B.
Published: October 2005

Scattering of ultrasonic waves at a randomly rough liquid-solid interface has been studied for a long time and continues to be of considerable interest. Most previous efforts were directed at studying the diffuse reflection from rough surfaces while much less is known about the transmitted component that plays a very important role in ultrasonic nondestructive evaluation of material properties. A comprehensive experimental study has been conducted to measure the surface roughness induced attenuation of ultrasonic waves transmitted through liquid-solid interfaces at oblique incidence. Sand and shot-blasted aluminum samples with 5- to 50-μm rms roughness were used to determine the frequency spectrum of the transmitted beam between 2 and 20 MHz. A simple first-order phase perturbation technique [Nagy and Adler, J. Acoust. Soc. Am. 82, 193 (1987)] was extended for oblique incidence to derive approximate analytical formulas for the frequency and angular dependence of the surface roughness induced attenuation of the coherently transmitted field. Good agreement was found between these analytical predictions and the measured experimental data. Further improvements are expected from comparing the data to more sophisticated theoretical techniques adapted to the case under consideration. [Work supported by NSF under contract ECD-9008272.]
MacCAD and REP/ABRs: A new test battery for central auditory dysfunction
Authors: Lauter Judith L. , Lord-Maes Janiece
Published: October 2005

Traditionally, audiologists have specialized in the peripheral hearing system. However, recent advances in the diagnosis and treatment of peripheral problems, together with developments in brain imaging, suggest that the future of audiology is in the brain, focusing on dysfunctions resulting from CNS pathology. Financial realities dictate that the first steps toward this new future emphasize technologies which are already available and/or reasonably priced. Two components of a test battery based on these principles have been developed in our laboratories. A companion paper describes MacCAD, a Macintosh-based program for monaural/dichotic testing of speech and nonspeech sounds, which can be run on a Macintosh SE/30 with no additional hardware. Second, a simple repeated-measures modification of evoked-potential testing [repeated evoked potentials (REPs)] applied to auditory brainstem responses (ABRs) yields a dramatic increase in sensitivity to individual characteristics, based on standard EP equipment and procedures. Pilot testing with a combination of these two tests suggests that the two-part battery is not only sensitive to individual characteristics of central auditory function, but may also reveal striking correlations between the results on each test, such that details of an individual's performance on one may predict specific details observed with the other. Thus the combination of the two tests can provide complementary behavioral/physiological documentation of underlying dysfunction which may be invisible to conventional testing. In those cases where testing is available on more expensive brain-monitoring tools such as MRI, qEEG, and PET, this battery could also serve as a basis for hypothesis formulation, thus rendering their use more cost-effective.
Judgments of tactile texture gradient magnitude
Authors: Jansson Gunnar , Hughes Barry
Published: October 2005

A main problem in reading tactile pictures is the perception of depth. In visual pictures, texture gradients are very effective in providing 3-D information. The aim of this study was to investigate one aspect of this potential source of information in tactile pictures, namely, judgment of the magnitude of tactually presented texture gradients. The stimuli consisted of polar projections of regular plane patterns of points and lines at a slant from the frontal plane. Such projections were copied onto swell paper which, after heating, provided the texture gradient in imbossed form. The patterns were read with the tip of the index finger without any restrictions concerning kind of exploratory movements. The result was that the tactile texture gradients were judged well in accordance with the physical magnitude of the gradient. Other experiments, investigating hypotheses derived from analyses of recordings of the exploratory movements, with stimuli containing either the whole gradient, its central part, or its extremes demonstrated very similar results for the whole gradient and its extremes. The theoretical significance of these results is discussed.
Auditory factors in obscure auditory dysfunction
Authors: Mahanes Susan R. , Peters Robert
Published: October 2005

Obscure auditory dysfunction (OAD), defined as a self-reported difficulty in understanding speech in noise by persons with normal audiograms and no other obvious causes, is commonly seen in clinical settings [G. H. Saunders and M. P. Haggard, Ear Hear. 10, 200–208]. In an attempt to characterize the hearing difficulties experienced by this population, measures of frequency selectivity, complex and pure-tone discrimination and gap detection were obtained, as well as speech, audiometric, and case history data. Results indicated impaired frequency selectivity at low frequencies, especially at 100 Hz and higher than normal thresholds for complex- and pure-tone pitch and gap detection also at the lower frequencies. Speech reception thresholds in noise were not consistently higher than for normal listeners. [Research supported by the American Speech-Language-Hearing Foundation, NC Regional Chapter of the Acoustical Society of America, and the Andrus Foundation.]
An acoustic-phonetic data base
Authors: Fisher William M. , Zue Victor , Bernstein Jared , Pallett David S.
Published: October 2005

DARPA has sponsored the design and collection of a large speech data base. Six hundred and thirty speakers read ten sentences each. Two sentences were constant for all speakers; the remaining eight sentences were selected from a set of 450 designed at MIT and 1890 selected at TI from text sources. The set of sentences is phonetically rich, balanced, and deep. Although all recordings were made in Dallas, we sampled as many varieties of American English as possible. Selection of volunteer speakers was based on their childhood locality to give a balanced representation of geographical origins. The subject population is adult; 70% male; young (63% in their twenties); well educated (78% with bachelor's degree); and predominantly white (96%). Recordings were made in a noise-reducing sound booth using a Sennheiser headset microphone and digitized at 20 kHz. A natural reading style was encouraged. The recordings are complete, and time-registered phonetic transcriptions are being added to the 6300 speech files at MIT. A version of the complete data base (16-kHz sample rate, with acoustic-phonetic transcriptions—approximately 50 megabytes of data) will be made available to researchers through the National Bureau of Standards. [Work supported by DARPA.]
Nonlinear distortion of ultrasonic waves in small crystalline samples
Authors: Blackburn Bruce D. , Breazeale M. A.
Published: October 2005

Harmonic generation of 30-MHz ultrasonic waves in small solid samples is analyzed to establish a technique for evaluating combinations of third-order elastic constants of samples which cannot be grown large enough to allow one to make the infinite plane-wave approximation. Results are reported for CsCdF3 and KZnF3.
Nonlinear generation of missing modes on a vibrating string
Authors: Legge K. A. , Fletcher N. H.
Published: October 2005

The nonlinear transfer of energy among modes of different frequencies on a vibrating string is investigated both theoretically and experimentally. The nonlinearity is associated with the well-known variation of string tension caused by the vibration modes, but it is essential that at least one of the end supports has finite mechanical admittance if there is to be any mode coupling. If the nonrigid bridge support has zero admittance in a direction parallel to the string, the coupling is of third order in the mode amplitudes. For a more realistic model in which the string changes direction as it passes over a bridge of finite admittance there are additional coupling terms of second order. The first mechanism gives driving terms of frequency 2ωn±ωm where ωn and ωm are, respectively, the angular frequencies of the nth and mth modes present on the string, while the second mechanism gives driving terms of angular frequencies 2ωn and 2ωm. Analysis shows that modes absent from the initial excitation of the string can be driven to appreciable amplitude by these mechanisms, reaching their maximum amplitude after a time typically of order 0.1 s. Modes that are in nearly harmonic frequency relationship behave simply but coupling of modes that are appreciably inharmonic may give rise to rapid amplitude fluctuations. A simple experiment with a wire deflected by a bridge of elastic cord and plucked so as to eliminate a particular mode from the initial excitation provided general semiquantitative confirmation of the theoretical predictions.
Partially coherent radiation from reverberant chambers
Authors: Parker Kevin J. , Maye Bonnie A.
Published: October 2005

Using a reverberant chamber, it is possible to radiate a partially coherent ultrasonic beam into a free field. This type of acoustic secondary source is shown to be analogous to the Lambertian source in optics. The features and potential uses of this type of field are in marked contrast to the case of fully coherent ultrasonic radiation produced by plane or focussed transducers. The partially coherent secondary sources are not difficult to construct in a laboratory setting, and provide a useful alternative in ultrasonic measurements of materials properties, and other applications such as imaging.
Ultrasonic velocity dispersion in liquids between 3.3 and 330 MHz using a high resolution phase measurement technique
Authors: Rogez D. , Bader M.
Published: October 2005

A description is given of a technique for measuring small ultrasound velocity differences between two liquids, based on a new high resolution phase comparison method. The technique uses a two-path acoustic system well suited for velocity dispersion measurements in the frequency range 3.3 to 330 MHz. The phase difference between two acoustic pulses traveling through the liquid is measured with a resolution of a few picoseconds. Velocity differences can be measured with an accuracy of ±1.5 cm/s. The unusually wide frequency capability and accuracy of the method are demonstrated with dispersion measurements on polystyrene samples dissolved in ethylbenzene.
Self-deactivation of water vapor: Role of the dimer
Authors: Zuckerwar Allan J.
Published: October 2005

Past efforts to interpret experimental data on the self-deactivation rate of the ν2 (1→0) vibrational mode of water vapor have been thwarted because of the attempt to fit the data to a single relaxation time. In a phenomenological theory proposed here the deactivation takes place by means of three parallel processes: (1) collisional de-excitation of the excited monomer, (2) a two-step reaction involving association and spontaneous redissociation of an H2O collision complex, and (3) spontaneous dissociation of the stably bound H2O dimer. In pure H2O and in mixtures without O2, the reaction rate for association of the collision complex is found to be very slow, and the remaining relaxation modes (1) and (3) are effectively decoupled. In mixtures of H2O–air and H2O–O2 the association rate of the complex increases strongly, suggesting that O2 serves as an effective ‘‘chaperon’’ for this reaction, and the relaxation modes of the monomer (1) and complex (2) become strongly coupled. Fourteen sets of past data, representing a wide variety of test conditions and experimental methods, both acoustical and nonacoustical, are organized into three groups—each corresponding to a relaxation mode predicted by the theory. An analysis of an ultrasonic absorption peak, based on process (3), yields values for the standard entropy and enthalpy of dissociation of the stably bound H2O dimer.
A numerical method for ocean-acoustic normal modes
Authors: Porter Michael , Reiss Edward L.
Published: October 2005

The method of normal modes is frequently used to solve acoustic propagation problems in stratified oceans. The propagation numbers for the modes are the eigenvalues of the boundary value problem to determine the depth dependent normal modes. Errors in the numerical determination of these eigenvalues appear as phase shifts in the range dependence of the acoustic field. Such errors can severely degrade the accuracy of the normal mode representation, particularly at long ranges. In this paper we present a fast finite difference method to accurately determine these propagation numbers and the corresponding normal modes. It consists of a combination of well-known numerical procedures such as Sturm sequences, the bisection method, Newton’s and Brent’s methods, Richardson extrapolation, and inverse iteration. We also introduce a modified Richardson extrapolation procedure that substantially increases the speed and accuracy of the computation.
Dispersion and ranging of transient signals in the Arctic Ocean
Authors: Yang T. C.
Published: October 2005

A method of estimating the source to receiver range of wideband underwater acoustic pulses is critically examined in this paper. The method is based on the time–frequency dispersion of broadband signals received at a single hydrophone. Shot data recorded at field locations in the Arctic are analyzed by this technique. The resulting range predictions are compared with the observed ranges. Good agreement is found for those cases in which the bottom depth along the propagation path is greater than 1 km. At these depths, the upward refraction feature of Arctic sound propagation minimizes the effects of bottom topography. As long as the signal is above the noise level, the method is insensitive to the type of background noise and to the source spectrum shape. The frequency dispersion for an N2 bilinear sound-speed profile is investigated analytically. This profile yields a very close and useful approximation to the Arctic underwater sound field. The results are used to interpret the experimental data and to identify the factors which may influence the range estimation method.
Phase relationship between bone and air conducted impulse signals in the human head
Authors: Boezeman E. H. J. F. , Bronkhorst A. W. , Kapteyn T. S. , Houffelaar A. , Snel A. M.
Published: October 2005

Using the cancellation method we investigated the phase relationship as well as the amplitude ratio between impulse signals transmitted simultaneously via both bone and air conduction channels. The psychophysical findings indicated a phase difference corresponding to a time delay of about 0.9 ms by which the air input led the bone input in the case of frontal bone stimulation. Changing the polarity of the bone conduction signal a maximum in the loudness sensation was found just in the same phase difference. The psychophysical findings, predicted mathematically, were verified with brainstem evoked potentials elicited to similar signals. Preliminary results showed that the time lag observed relied on the location of the bone vibrator on the head and furthermore on the frequency used. This suggests different transmissions of vibratory energy reaching the inner ear along the skull.
Performance of a postbeamformer interference canceller in the presence of broadband directional signals
Authors: Cantoni A. , Godara Lal C.
Published: October 2005

A Postbeamformer Interference Canceller, PIC, is essentially a single-channel noise canceller. Two beams are formed; one in the target direction and another in the interference direction. The interference direction beam is processed with a tapped delay filter before being subtracted from the target beam to yield the system output. A detailed analysis of PIC is presented in the paper. The performance which can be achieved with PIC is shown to depend critically on the input signal to interference ratio and the tapped delay line length.
Infants’ discrimination of intensity variation in multisyllabic stimuli
Authors: Bull Dale , Eilers Rebecca E. , Oller D. Kimbrough
Published: October 2005

Two groups of 5- to 11-month-old infants were tested for their ability to discriminate within-utterance intensity variations similar to those associated with linguistic stress. A visually reinforced discrimination procedure was used to determine sensitivity to increments in peak intensity for a final position, synthetic CVC syllable within either a bisyllabic (CVCVC) or a trisyllablic (CVCVCVC) context. Discrimination performance was above chance for a 2-dB increment, and improved for 4- and 6-dB increments. In addition, infants were more sensitive to intensity increments in the bisyllablic as compared to the trisyllabic context. Infant sensitivity for within-utterance intensity variations is sufficient for the detection of some linguistic stress contrasts.
Reduction of discrete frequency noise in small, subsonic axial-flow fans
Authors: Fitzgerald James M. , Lauchle G. C.
Published: October 2005

The discrete frequency noise radiated from representative tyes of axial-flow fans used in electronic equipment is studied in detail. Narow-band analysis of the discrete frequency noise radiated by these types of fans has been conducted in an anechoic environment. The farfield sound pressure level and radiated directivity of the discrete frequency noise are presented. The influence of operating condition on the radiated sound is determined. The discrete frequency noise dominates the characteristic acoustic spectra at high flow coefficients. The radiated directivity of the discrete frequency noise is generally uniform. Based on the data collected and on the theoretical aspects presented, the principal source of the discrete frequency noise is identified for each of the fans as the interaction of the fan rotor with a circumferentially distorted, nonuniform flow. A collection of prototype design modifications is developed for each representative fan to reduce the radiated discrete frequency noise by improving the uniformity of the local flow field. A modified prototype configuration is developed for each representative fan which is evaluated acoustically and compared to the original baseline data.
The accuracy of hair cell counts in determining distance and position along the organ of Corti
Authors: Thorne Peter R. , Gavin John B.
Published: October 2005

The relationship between the density of hair cells (cells/mm) and measured distance along the guinea pig organ of Corti was determined using light microscopy and the surface specimen technique. It was demonstrated that the density of inner hair cells (IHC; mean 92.0±2.4) and 1st row of outer hair cells (OHC1; mean 118.7±2.3) did not show significant variation along the organ of Corti except within 0.5–1.0 mm of the apex and base where there was considerable variation between animals in the density of cells. There was a close relationship between the accumulated number of either IHC or OHC1 and distance from the base along the organ of Corti. Distances estimated by hair cell counts were similar to those determined by direct measurement. It is concluded that hair cell counts can be used to reliably estimate distances along the organ of Corti where accurate direct measurement is not possible, such as in scanning electron microscopy.
A systems model of the thickness mode piezoelectric transducer
Authors: Hayward G. , MacLeod C. J. , Durrani T. S.
Published: October 2005

A new model for piezoelectric ultrasonic transducers is proposed. Using a systems engineering approach, the concept of feedback is used to explain secondary piezoelectric effects and to clearly describe electromechanical interaction. The model is derived from the fundamental piezoelectric equations and it embraces the relevant practical situations where the transducer is subject to arbitrary electrical and mechanical loading. Block diagram representations of the piezoelectric transducer acting as a generator and receiver of ultrasound are developed. The physical significance of each element in the block diagrams are explained to provide a clear and distinct relationship between electrical and mechanical quantities. This permits the factors which control secondary piezoelectric action to be readily defined, along with the importance of this effect on the overall transfer function. It is considered that no other transducer model illustrates these concepts with the same degree of clarity and the technique offers significant advantages over existing transducer analogies. A number of computer simulations and experimental water tank measurements of acoustic wave profiles are presented. Close substantiation of the theoretical analysis is shown.
Architectural acoustic measurements using periodic pseudorandom sequences and FFT
Authors: Chu W. T.
Published: October 2005

The generation and some relevant properties of a class of periodic pseudorandom sequences called the maximum-length sequence is described briefly. A simple and practical method is proposed to resolve a technical difficulty in using these sequences with FFT processing. The potential advantage of using a maximum-length sequence as a test signal for architectural acoustic measurements is discussed and illustrated by an example.
On the short wave acoustic radiation from planar panels or beams of rectangular shape
Authors: Levine Harold
Published: October 2005

An exact representation which involves single (as opposed to double) integrals is established for the time-average power output generated by individual modes of normal surface velocity on a simply supported and baffled rectangular panel; fluid loading is not taken into account. The representation enables analytical estimates to be found in the short wavelength range and provides details hitherto unresolved by numerical analysis.
The influence of beam type on the back reflection of ultrasonic beams from a liquid–solid interface
Authors: Norris Andrew N.
Published: October 2005

We consider the phenomenon of back reflection of a beam of ultrasound from a liquid–solid interface. We show that the magnitude of the back reflection depends critically upon the profile of the incident beam. The beam profile is first related to the excitation field at the plane of the transducer. Different beams are considered by changing the field at the transducer. We show that a purely Gaussian profile gives no back reflection. Other beam profiles with less severe decay away from the beam center can produce an effect of the same order as observed experimentally. We present an example of such a beam.
Description of a color spectrogram
Authors: Kuhn G. M.
Published: October 2005

We define a color spectrogram which retains all the information of the standard spectrogram, and which encodes information about the shape of each short-time spectrum into the chromaticity with which that spectrum is illuminated. The chromaticity for each spectrum is derived by interpreting each spectrum as an energy distribution in the visible light frequencies.
Measurement of speed and attenuation of ultrasound in egg white and egg yolk
Authors: Javanaud C. , Rahalkar R. R. , Richmond P.
Published: October 2005

Measurements of the speed and absorption of ultrasound in egg white and yolk at 2.10, 4.12, and 6.79 MHz over the approximate temperature range 20°–25 °C have enabled distinct trends to be detected. Further measurements using a different piece of apparatus enabled values for the absorption, every 10 MHz, over the frequency range up to 124 MHz, (from 5 MHz for the yolk and from 15 MHz for the white) to be found. These results tie in well with the more accurate lower frequency data. Egg yolk and egg white have very different ultrasonic characteristics. The temperature coefficient of the speed of sound in the former could not be detected, whereas that of the latter is very close to that of water. On the other hand, the negative temperature coefficient of absorption in the yolk shows up quite clearly, whereas that of the white is small and possibly changes sign near 4 MHz. The frequency dependence of absorption (up to 124 MHz) is close to linear in the white (exponent ∼1.2) and slightly greater in the yolk (exponent ∼1.5). Dispersion in velocity could not be detected over the frequency range of 2.1–6.8 MHz.
Waves of an arbitrary frequency in random fibrous composites
Authors: Beltzer Abraham I. , Brauner Neima
Published: October 2005

It is shown that the K–K relations method can be applied to wave propagation in random fibrous composites at an arbitrary frequency. The results indicate strong dispersion attributed to scattering by inclusions.
Farfield directivity pattern of a piston in a nonrigid baffle
Authors: Holly Arthur C. , Lucas Bernard F.
Published: October 2005

This letter gives the experimental results of beam pattern measurements on a piston mounted in a nonrigid baffle. The results indicate good agreement between experiment and a simple theoretical form representing the radiation pattern of a piston in a rigid baffle, but modified by a corrective factor.
Behavioral vocal response thresholds to mating calls in the bullfrog, R
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Authors: Megela-Simmons Andrea
Published: October 2005

Male bullfrogs will vocalize in response to playbacks of the mating (advertisement) calls of conspecifics. This behavior was studied in response to playbacks of bullfrog mating calls presented at six different sound intensity levels. The lowest sound intensity level tested (50 dB SPL) was insufficient to evoke calling from any of the animals. Calling was evoked by playback levels of 60 dB SPL and higher. The data suggest that behavioral evoked calling thresholds lie between 50-60 dB SPL for these animals. Playback intensity levels of 80 dB SPL were more effective in evoking responses than were intensity levels up to 20 dB higher or lower. This was true both in terms of the total number of evoked responses and the trial number at which responding ceased. Moreover, significantly less habituation of evoked calling occurred at levels of 80 dB SPL than at higher or lower levels. The data suggest that a sound pressure level of 80 dB represents a behaviorally preferred intensity level for evoked calling in the bullfrog. Field recordings of bullfrog choruses show that the intensity produced by an individual calling male reaches a level of 80 dB SPL at a distance of 1 m. This intensity level is identical to that producing maximal evoked calling in the laboratory.
The detection of French accent by American listeners
Authors: Flege James Emil
Published: October 2005

The five experiments presented here examine the ability of listeners to detect a foreign accent. Computer editing techniques were used to isolate progressively shorter excerpts of the English spoken by native speakers of American English and French. Native English-speaking listeners judged the speech samples in one- and two-interval forced-choiced tests. They were able to detect foreign accent equally well when presented with speech edited from phrases read in isolation and produced in a spontaneous story. The listeners accurately identified the French talkers (63%–95% of the time) no matter how short were the speech samples presented: entire phrases (e.g., ‘‘two little dogs’’), syllables (/tu/ or /ti/), portions of syllables corresponding to the phonetic segments /t/, /i/, /u/, and even just the first 30 ms of ‘‘two’’ (roughly, the release burst of /t/). Both phonetically trained listeners familiar with French-accented English and unsophisticated listeners were able to accurately detect accent. These results suggest that listeners develop very detailed phonetic category prototypes against which to evaluate speech sounds occurring in their native language.
Intelligibility ratings of continuous discourse: Application to hearing aid selection
Authors: Cox Robyn M. , McDaniel D. Michael
Published: October 2005

Twelve normal-hearing subjects rated the intelligibility of 35-s, hearing-aid-processed continuous discourse (CD) passages. Three talkers (two male, one female), four hearing aids, and two signal-to-babble (S/B) ratios were used in a completely crossed design. Research questions concerned: (1) ability of listeners to rate intelligibility, (2) sensitivity of hearing aid rankings when rankings were based on intelligibility ratings for three CD passages per instrument, and (3) dependence of hearing aid rankings on (a) S/B ratio, and (b) talker characteristics. Results were: (1) listeners were able to rate intelligibility, (2) rankings based on intelligibility ratings of three CD passages per hearing aid were capable of identifying two superior instruments within a group of four hearing aids that were similar in frequency/gain function, (3) listening in a more difficult S/B ratio substantially decreased the sensitivity of the hearing aid rankings for the female talker but had only minor effects on the rankings for the male talkers, and (4) hearing aid intelligibility rankings were found to be different for different talkers. Applications to hearing aid selection are discussed.