bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of time-compressed speech in the assessment of central nervous system disorders
Authors: Baran Jane A. , Verkest Susan , Gollegly Karen , Kibbe-Michal Karen , Rintehlmann William F. , Musiek Frank E.
Published: October 2005

Twenty-seven subjects with surgically, radiologically, or neurologically confirmed lesions of the central nervous system were administered a 60% time-compressed version of the NU-6 word lists. Subjects ranged in age from 12 to 59 years. Twenty-four subjects had normal hearing (25 dB HL or better) bilaterally at 500 to 4000 Hz. Three subjects demonstrated a mild hearing loss at a single frequency in one ear. Test stimuli were presented at 40 dB SL re: speech reception thresholds. Percent correct scores were derived for each ear and compared to norms previously established [D. Beasley et al., J. Aud. Res. 12, 71–75 (1972)]. Results revealed that in 67% of the subjects tested, performance in at least one ear fell below established norms. For subjects with abnormal thresholds, performance was abnormal in the “better” ear, or in both ears, in all three cases. These results suggest that a time-compressed speech test may be moderately useful in the identification of CNS lesions. The implications of adding this test to a neuroaudiological test battery will be discussed.
Recognition of dichotically presented rhyme words in split-brain patients
Authors: Musiek F. E. , Gollegly K. , Kibbe-Michal K. , Verkest S.
Published: October 2005

A dichotic rhyme word task was administered to six young adult, right-handed, split-brain subjects with normal peripheral hearing. Two of these subjects were tested before and after surgical sectioning of the corpus callosum while the remaining four were tested post-operatively only. The dichotic task is composed of synthetic, well-aligned, rhyme words which were presented at 50 dB SL (re: spondee thresholds). The task is such that normal listeners repeat either the word presented to the right or left ear but seldom repeat both simultaneously presented stimuli. Therefore, normal performance is approximately 50% for each ear with a slight right-ear advantage. The split-brain subjects performed uniquely on the dichotic rhyme task. As expected, there was a severe left-ear deficit for verbal report of the stimuli. However, there also was a marked right-ear enhancement on this dichotic task. These trends were not present for the two subjects tested prior to surgery indicating that callosal sectioning was responsible for this phenomenon. The right-ear enhancement noted on this dichotic task may be an indication of “release from central auditory competition” for the left hemisphere.
Brainstem auditory evoked potentials (BAEPs) and audiograms after severe closed head injury (CHI)
Authors: Suffield J. Braxton , Campbell Ken B.
Published: October 2005

The use of the BAEP has largely been restricted to prognosticating from acute states, with few long-term studies after injury. We tested both ears of 20 survivors of severe CHI (X̄ coma duration = 28 days) on average 3.2 years after injury. Replicate averages of artifact-free BAEPs were recorded from Cz (passband 100–3000 Hz), with an ipsilateral low mastoid reference. A cutoff of 2.5 standard deviations from lab norms was used in discriminating normal from abnormal responses. In general, few patients had significantly abnormal BAEPs or audiograms. Although seven of the 22 patients had delays in the latency of peak I in one or both ears, all but one of these patients had bilaterally normal IPLs. Nonparametric correlations indicated left and right audiograms were correlated (p < 0.01), as were results from left and right BAEPs (p < 0.02). BAEPs and audiograms were also significantly correlated (p < 0.01). These results tend to validate the concept that lower structures, including those in the brainstem, suffer last and least, even in cases of very severe head injury.
Encoding voice pitch for profoundly hearing-impaired listeners
Authors: Grant Ken W.
Published: October 2005

The ability of five profoundly hearing-impaired subjects to “track” connected speech and to make judgments about the intonation and stress in spoken sentences, was evaluated under a variety of audiovisual conditions. These included speechreading alone, speechreading plus speech (low-pass filtered at 4 kHz), and speechreading plus a tone whose frequency, intensity, and temporal characteristics were matched to the speaker's fundamental frequency (F0). In addition, several frequency transfer functions were applied to the normal F0 range resulting in new ranges that were both transposed and expanded with respect to the original F0 range. Three of the five subjects were able to use any of the tonal representations of F0 nearly as well as speech to improve their speechreading rates and to make appropriate judgments concerning sentence intonation and stress. The remaining two subjects had difficulty integrating visual and auditory information despite intensive training periods lasting over a year, even though they were able to make appropriate judgments concerning intonation and stress with expanded F0 signals when not speechreading. [Work supported by a grant from NINCDS (NS 03856) to Central Institute for the Deaf, St. Louis, MO.]
Residual hearing in deafness
Authors: Hurteau Anne-Marie , Picard Michel
Published: October 2005

The purpose of the investigation was to determine whether the nature of audiometric responses obtained from listeners with profound hearing loss are auditory or vibro-tactile. Two types of coupling systems were used to measure the sensitivity thresholds of seven adults with corner audiograms. One coupling system consisted of a standard TDH-39 earphone mounted on a MX41-AR cushion. In the other coupling system, a speculum was added to the earphone cushion in order to reduce the area of acoustical stimulation. Sensitivity thresholds and temporal integration functions were determined at 125, 250, and 500 Hz. The results obtained from individual subjects made it possible to clearly differentiate between auditory and vibro-tactile responses. The findings of the investigation will be discussed in terms of the potential perceptual abilities of listeners with profound sensorineural hearing loss.
Contralateral overmasking effects on Békésy audiometry
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Threshold and amplitude measurements of fixed frequency Békésy tracings were made both in the quiet and in the presence of contralateral white noise masking with 100 dB and 120 dB SPL for 28 subjects with unilateral sensorineural hearing impairment. Masking resulted in one of the following effects on the threshold and amplitude of the test ear: (1) no change in threshold and amplitude for both interrupted and continuous tones, (2) threshold shift for both interrupted and continuous tones by increased masking level with no change in amplitude, (3) threshold shift for both interrupted and continuous tones with increasing separation and reduction in amplitude of continuous tone by increased masking level. Factors affecting threshold and amplitude were discussed with relation to cross masking, central masking, adaptation and pathological conditions of hearing impairment, and were compared with effects of ipsilateral masking.
Acoustic wave propagation in a radial duct
Authors: Holger David K. , Wakumoto Mike
Published: October 2005

The results of an experimental investigation of acoustic wave propagation through a radial duct are reported. The investigation was limited to large wavenumbers in the absence of flow, and experimental results are compared to a correspondng analytical model. The apparatus consisted of an anechoic termination, one rigid duct wall, and one variable impedance duct wall. Preliminary experiments revealed that the measurement techniques were appropriate and that the apparatus was behaving as expected. Experimental plots of pressure versus radial position were found to be in agreement with analytical predictions for cases involving two rigid duct walls. A variable backing depth Helmholtz resonator array was substituted for one of the rigid duct walls, and measurements of pressure versus radial position were made for three backing depths. Values of radial attenuation were estimated from the pressure measurements using a large wavenumber approximation. Experimental radial attenuation estimates are in good qualitative agreement with analytical predictions.
Excitation of piping systems from fully turbulent internal flow
Authors: Cuschieri J. M.
Published: October 2005

A source of excitation in pipe systems is the internal, fully developed turbulent flow. This excitation is dependent on the roughness and speed of flow and the response of the pipe structure is very much controlled by the coupling between the structure and the internal medium. This coupling is very strong if the internal medium is a liquid such as water, while it is rather weak but not negligible if the internal fluid is very light such as air. In the past, the treatment of this excitation problem was through the use of joint acceptance functions. The excitation is random in nature and the pipe will accept vibrational energy preferably at its resonant modes. At high frequencies the modal density is high and thus the pipe accepts energy almost at any frequency. Using the joint acceptance function will not give the physical insight required, however, some assumption can be made regarding the joint acceptance function which will then allow the development of an expression which gives a physical understanding of the excitation mechanism. Using this approach, phenomena such as the decrease in the transmission loss of the pipe wall with increasing flow speed, the relation between the turbulent pressures and the excitation forces, and the structural response that can be used to determine the level of vibrational energy input into the pipe structure, can be deduced.
The development of a computerized noise generator for the study of the effects of impulse noise on hearing
Authors: Hétu R. , Laroche C. , Sawan M. , Nicolas J.
Published: October 2005

A computerized noise generator is being developed in order to conduct parametric studies of the effects of impulsive noise on hearing. The parameters considered are the rise and the decay time, the amplitude, the repetition rate, and more especially, the frequency content. Basically, the spectrum of the desired signal is divided by the frequency response of an acoustic driver coupled to a power amplifier; the inverse Fourier transform of the result determines the corrected signal which allows us to generate an amplified replica of the desired signal. A variety of controlled transient signals can be, at this stage, reliably generated within the following limits: frequency bandwidth between 300 and 5000 Hz, decay times up to 80 ms, peak amplitudes up to 140 dB SPL, and repetition rates between 0.1 to 10 p.p.s. Preliminary tests were conducted with a series of exposures to three impulsive noises of different frequency bandwidths: signal A extended from 300 to 1000 Hz, signal B from 300 to 3000 Hz, and signal C from 300 to 4000 Hz. Similar TTS growth curves were obtained when the peak SPLs of signals B and C were 10 to 12 dB lower than for signal A. The implications for damage risk criteria will be discussed considering that very slight variations in the time domain result in significant variations in the frequency content of impulse noise. [Work supported by I.R.S.S.T.]
NASA aeronautical noise research
Authors: Kayten Gerald G. , Wander Stephen M. , Stephens David
Published: October 2005

This paper presents a broad historical overview of NASA's major aircraft noise research program, and the advances and contributions made to the understanding, prediction, and reduction of aeronautical noise. Major programs including Quiet Nacelle, Quiet Engine, Refan, and the Aircraft Noise Prediction Program (ANOPP) are described and their role in the technology transfer process is discussed. It outlines projected future activities and discusses prospects for further noise reduction on conventional turbofan transports. New directions and focus in aeroacoustics research and technology for advanced turboprops, rotorcraft, and supersonic transports are also discussed.
Cockpit noise in light aircraft
Authors: DeMetz Fred C.
Published: October 2005

Noise levels were measured in the cockpits of light civilian aircraft under various flight conditions and compared with OSHA noise standards. Dominant noise generation mechanisms are identified and the effectiveness of practical cockpit noise reduction techniques are explored.
Prediction of tissue composition from ultrasonic measurements and mixture rules
Authors: Apfel Robert E.
Published: October 2005

A methodology is presented for predicting the composition of tissues from measurements of the density, sound velocity, and acoustic nonlinear parameter, using mixture laws for the density, compressibility, and nonlinear parameter. It is shown that the mixture law for the nonlinear parameter plays an essential part in this methodology, which leads to the prediction of the volume fractions of water, protein, and fat in a given tissue. Data from the literature for solutions, blood, normal tissue, and cancerous tissue are investigated, and predicted fractions are consistent with tissue compositional information available in handbooks. More experimental work is needed with tissues of known composition in order to test more fully the proposed methodology. [Work supported by ONR.]
Angular equilibrium of an acoustically levitated sample
Authors: Barmatz M.
Published: October 2005

In a triple axis levitator, three orthogonal fields position a sample at the center of a square cross-sectioned rectangular chamber. There are two torque mechanisms associated with this system. One is the well-known “rotating” torque whose magnitude depends on the phase angle between the two degenerate fields. A model for a second retarding torque was developed using Rayleigh disk theory applied to orthogonal plane-wave fields. The sample angular equilibrium position for zero-phase shift depends on the sample shape asymmetry and the relative magnitude of the applied pressures. For small phase angles, the sample adjusts to an angular equilibrium position where the “Rayleigh” retarding torque balances the “rotating” torque. For typical experimental conditions, the sample begins to rotate at a critical phase angle where the “rotating” torque overcomes the maximum “Rayleigh” torque. The dependence of the angular equilibrium position on the applied pressures, sample shape, and phase angle will be presented. A video tape of the phenomenon will be shown. [Work supported by NASA.]
The effect of finite phonon and roton mean free paths on the attenuation of fourth sound in HeII filled porous solid
Authors: Baker Steven R. , Rudnick Isadore
Published: October 2005

Measurements of the attenuation of fourth sound in a HeII filled porous solid always show anomalously high values at low temperatures [M. A. Kriss, UCLA thesis (1969); H. J. Lauter and H. Wiechert, J. Low Temp. Phys. 36, 139 (1979); S. R. Baker, UCLA thesis (1985)]. It is shown that this anomaly can be attributed to a reduction in the apparent normal fluid shear viscosity due to the finite mean free paths of phonons and rotons. Results of a model calculation of the mean free path correction to the attenuation of fourth sound in a HeII filled porous solid, which separately treats the average drift of phonons and rotons as the flow of an ideal gas through a porous solid [A. E. Scheidegger, The Physics of Flow Through Porous Media, Third Edition, 1974, p. 173], compare very well with measurements made in 1-μ packed powder down to 1.1 K at SVP, where the observed anomaly amounts to more than an order of magnitude. [Work supported by ONR.]
Particle behavior in a rotating ultrasonic waveguide
Authors: Whitworth Glenn , Nyborg Wesley L.
Published: October 2005

An apparatus was designed to allow a suspension of biological cells to be subjected to a well-defined, 160-kHz standing ultrasonic field while being viewed through a stereo microscope. The chamber, which has a square cross section and pressure release walls, acts as a single mode acoustic waveguide. Aqueous metrizamide solution is used to fill the ultrasonic chamber because it has a unique combination of properties including low viscosity, low osmolarity, and high density. The chamber rotates about its axis (whose inclination can be varied) producing the centripetal force necessary to contain the buoyant cells in the axial region. Observations were made on stroboscopically illuminated suspensions both of latex microspheres and of red blood cells. The particles arranged themselves at half-wavelength intervals into axially symmetric formations that became complex and flowering when many particles were present. Some aspects of this behavior are explained by preliminary theory that considers gravitational, rotational, and acoustic radiation forces on the particles. [Work supported by NIH grants GM0729409 (University of Virginia) and GM08209 (University of Vermont).]
Sound amplification from controlled excitation reactions (SACER) in N2/H2 mixtures
Authors: Shields F. Douglas , Iskandar Dadang , Anderson Buford
Published: October 2005

Measurements of the resonant reverberation of sound in a closed tube have shown an increase in sound amplitude for 20 to 30 ms following the rapid excitation of the gas by an electrical discharge. The measurements have been corrected for sound absorption due to viscosity and thermal conductivity and the corrected amplification studied as a function of energy in the electrical discharge, vibrational frequency, gas pressure, and percentage of H2 in the mixture. The translational temperature during the relaxation process is monitored by measuring the sound speed in the tube. Amplification is attributed to the relaxation of the vibrational temperature which is left elevated to several thousand degrees following the electrical discharge. Experimentally measured gains have been compared to values previously predicted [F. D. Shields, J. Acoust. Soc. Am. 76, 1749–54 (1984)]. [Work supported by the Office of Naval Research.]
The effects of changes in correlation on the discriminability of noise samples
Authors: Fallon Susan M. , Robinson Donald E.
Published: October 2005

Hanna [Percept. Psychophys. 36, 409–417 (1984)] has shown that wideband samples of reproducible noise are highly discriminable over a large range of durations. The discriminability can be reduced by increasing the correlation between pairs of samples to be discriminated within a same-different paradigm. In the present experiments, the second sample of the pair was generated by repeating a temporal segment of the sample presented in the first interval and appending to it a new segment of noise. The inter-pair correlation is then determined by the duration of the new segment. The total burst duration, as well as the duration and position of the appended segment (beginning, middle, or end) were manipulated. For all burst durations studied, position had a large and consistent effect: segments placed at the end were more discriminable than those in the middle which were more discriminable than those at the beginning. The importance of the temporal position of changes in the spectral-temporal profile of these broadband, noise waveforms will be compared to similar results obtained using other waveforms. [Work supported by AFOSR and NMRDC.]
Amplitude-modulated noise detection by goldfish revisited
Authors: Coombs S. , Fay R. R.
Published: October 2005

Earlier studies on the ability of goldfish to detect amplitude-modulated (AM) noise signals [R. R. Fay, J. Neurophysiol. 44, 312–332 (1982)] suggested that goldfish were fundamentally different from other animals, including humans, in showing a flat modulation sensitivity function and no drop-off in sensitivity out to modulation rates of 400 Hz. To re-examine this anomaly, modulation sensitivity was measured in the goldfish at different sensation levels, using several experimental procedures and an improved technique for specifying the underwater acoustic stimulus at high modulation rates. Modulation sensitivity was found to be independent of sensation level at 10- and 100-Hz modulation. Sensitivity functions were relatively flat at modulation rates below 50–100 Hz with thresholds of AM detection occurring between 30% and 40% modulation. Greater than 60%–70% modulation was required for detection at 400 Hz. Randomly varying the overall intensity of unmodulated comparison noises and modulated noise signals produced little change in sensitivity or in the overall shape of the modulation function. These results show that the ability of goldfish to detect amplitude-modulated noise is not heavily dependent on intensity cues, nor fundamentally different from that of other species.
Capacity limitations for discrimination of isochronous and anisochronous tonal patterns
Authors: Watson C. S. , Foyle D. C.
Published: October 2005

In an earlier paper we reported that the discriminability of tonal patterns is strongly determined by the number of (sequential) components within the patterns. For patterns ranging in total duration from 62.5 ms to 2 s, accurate spectral-temporal resolution was possible only when patterns contained fewer than seven-nine tonal components [J. Acoust. Soc. Am. Suppl. 1 73, S44 (1983)]. Over this 32-fold range of total (and component) durations, patterns were nearly equal in discriminability when the frequency of a single component was varied by a fixed amount, or when randomly selected components were shifted from one sequential position to another. These results seem to demonstrate a limitation on the hearing of complex sounds that is based on total information content rather than on physical properties, specifically component duration. The previous experiments were conducted using an adaptive tracking procedure with n (the number of components in the patterns) as the dependent variable, and with the restriction that only isochronous patterns were presented. In two additional series of experiments it has now been shown that the same informational limits on pattern discrimination are obtained for anisochronous patterns and when the adaptive-tracking variable is the size of a frequency increment added to one of the pattern components. Possible meaning of this result for speech processing is considered. [Supported by NIH/NINCDS and by AFOSR.]
Factors affecting frequency discrimination in high- and low-pass noise backgrounds
Authors: Fantini Deborah A. , Emmerich David S.
Published: October 2005

Previously, we presented data which indicated that frequency discrimination performance was poorer for tones presented near the spectral edge of a low-pass noise than for tones presented either near the edge of a high-pass noise or in an unfiltered white noise background. [D. S. Emmerich, D. A. Fantini, and W. S. Brown, J. Acoust. Soc. Am. Suppl. 1 74, S34 (1983)]. The present study extends these findings in order to investigate how the steepness of the spectral edges of low- and high-pass maskers influences the discriminability of tones presented near these edges. Frequency separations corresponding to 75% correct responses were obtained in each of three low- and three high-pass noise backgrounds differing in the steepness of their filter skirts. The following results were obtained: (1) in the low-pass noise background, frequency discrimination performance improved as the filter skirt became more gradual, even though more noise power was added; (2) in the high-pass noise background, performance first improved and then became poorer as the filter skirt became shallower; (3) performance in low-pass noise was poorer than that in high-pass noise for the two steepest slopes employed (96 and 72 dB/oct) and better for the shallowest slope (36 dB/oct). Results are discussed in the context of a trade-off between possible edge effects and masking.
Identification of voicing contrast via the tactile mode
Authors: Collins M. J. , Hurtig R. R. , Besing J. , Schum D. J.
Published: October 2005

It has been shown that tactile perception of speech can be categorical along a voice onset time (VOT) continuum and that the boundary between /ga/ and /ka/ occurs at a longer VOT value for tactile than for auditory perception [M. J. Collins and R. R. Hurtig, J. Acoust. Soc. Am. Suppl. 1 75, S33 (1984)]. In that study, a hearing aid with a bone conduction receiver had been used for tactile delivery of speech signals, and the question arose as to the uniqueness of the findings to the velar stop consonant and the specific device employed. The present investigation was designed to determine the consistency of the effect across place for stop consonants and across signal processing and transducer characteristics. An identification paradigm was used to determine the VOT boundary for three processor-transducer combinations along /ka-ga/, /ta-da/, and pa-ba/ continua. Boundaries fell at similar VOT values for each processor-transducer condition for velar and alveolar stimuli; complex interactions occurred for bilabials. It was concluded that both tactile system limitations and device characteristics were determinants of VOT boundaries. [Work supported in part by the Spelman Rockefeller Foundation.]
Inelastic response of deeply submerged stiffened shells subjected to transient loads from explosions
Authors: Daddazio R. , Atkatsh R. , Baron M. L.
Published: October 2005

The large deflection elastoplastic response of stiffened cylindrical shells subjected to transient loadings from explosions is considered. Because the cylinders are located at deep submergence, the effects of initial stress distributions due to hydrostatic pressure are included in the analysis. A large deflection elastoplastic shell theory is utilized in the analysis. This shell theory defines a yield surface at each cross section of the shell in terms of the moment and direct force components at the section. An associated flow rule is utilized to define the plastic-strain rate. The EPSA (elastoplastic shell analysis) code is utilized in the analysis of the shell response to the dynamic loadings. Results obtained from the analysis have compared well with the results of experiments.
Numerical analyses of the linear interaction of pressure pulses with submerged structures
Authors: Huang H.
Published: October 2005

This paper discusses the linear and nonlinear dynamic response of submerged structures to the impingement of pressure pulses, the strengths of which are such that their governing equations can he linearized. The range of validity of this linearization is assessed by comparing the linear and nonlinear solutions to a classical problem. The numerical analysis technique for cases where the structure is surrounded by a noncavitating fluid utilizes the boundary element representation of the surrounding wave fields in conjunction with finite element analysis of the structure response. The boundary element formulation is based on the exact Kirchoff retarded potential integral solution to the linear wave equation. Therefrom a hierarchy of approximate boundary element formulations can also be obtained. The effectiveness of these formulations are examined by comparison of results to available classical solutions. The solution technique for cases of cavitating surrounding fluid requires the use of finite element representation of the exterior pressure field. Some effects of cavitation on the structural response are scanned.
A study of ambient and amplitude correction in isolated utterance recognition
Authors: Das Subrata K.
Published: October 2005

Experiments demonstrating the importance of ambient and amplitude correction in an isolated word speech recognition system are reported. Whenever a speaker produces the speech input in a nonanechoic environment, such as in in ordinary office, the method of ambient correction helps to neutralize the effect of any change in ambient which would otherwise adversely influence the performance of the recognizer. On the other hand, the goal of amplitude correction is to compensate for amplitude level fluctuations encountered in any normal speech input. The experiments compare the performances with and without the corrections in the context of an experimental speech recognition system developed at IBM. A database consisting of the speech collected from three male and one female speaker is used for this study. Performance is measured by examining both the error rate and the time taken by the decoder. Significant improvement in performance is observed on both counts when the corrections are applied.
Adaptive length normalized DP matching method for connected word recognition
Authors: Matsuda Yasuhiro , Kaneko Toyohisa
Published: October 2005

From a man-machine interface viewpoint, connected or continuous mode is much more preferred to isolated mode, but the former is much more difficult technically. A two-level DP [H. Sakoe, IEEE Trans. Acoust. Speech, Signal Process. ASSP-27, 588–595 (1979)] is a most widely used method for this problem. When we experimented with the two-level DP, we observed high error rates primarily due to the fact that the speaking speed often differs substantially between the training phase and recognition phase. To deal with this problem, our proposed method uses normalization of word length. Our method has two steps. The first step is to apply the conventional two-level DP. Then we normalize the length of each word and apply a two-level DP around the word boundaries obtained at the first step. We obtained the following improvement compared to a two-level DP with the following test data: 35 sequences of four-digit words by three male speakers with a single template for each digit. The average recognition rate in terms of digits, four-digit sequences, and the number of digits was improved by 1.9% {from 93.6% to 95.5%), by 6.7% (from 76.2% to 82.9%) and by 9.5% (from 88.6% to 98.1%), respectively. The computation time increased only about 10%.
A practical implementation of speaker verification
Authors: Hicks James W.
Published: October 2005

This paper describes a pilot study in the implementation of a speaker verification system. Ten individual (seven males and three females) from the voice group at SCI served as enrollees for the verification system. In addition, four other group members acted as impostors/infiltrators in order to try to circumvent the system. The system employed was a Votan VPC-2000 in an IBM-PC. The enrollees to the system trained it with their name, employee number, and a password. The training was conducted on day 1 of the experiment and subsequently on days 14, 28, and 42. Each subject tested the system every working day for 2 months against each of their four training templates. Two of the four impostors were provided with the name, employee number, and password for each of the “authorized” subjects, while the other two impostors were not given this information. Each of the impostors attempted to access the system during the 2-month experimental period. Data analysis is currently underway. Specific aspects of the instructions were effective and how future instructions data and results will be discussed.
Classification of impulse noise: Comparison of crest factor and kurtosis as metrics
Authors: Erdreich John
Published: October 2005

In this session honoring Jim Botsford, I will address one aspect of a problem with which he was concerned, whether impulsive noise should be (or could be) considered separately from continuous noise exposures. Recently, I presented a method for classifying noise as impulsive based on a statistical distribution measure of “peakedness,” the kurtosis (b2). This is the first step in addressing the “separability” of noise types. It is likely that Botsford and others of a practical demeanor would ask what advantage, if any, this has over familiar measures such as crest factor (cf). By defining a ratio, a, such that a = b2/cf2, we show that the measures are related such that for a given impulse form, a is constant for any duration signal. Only the form of the impulse changes the value of a. Thus, for a rectangular impulse, a = 1 and for an exponentially decaying sinusoid, a = 3/2. The crest factor may, therefore, have some utility for classifying impulsive environments. This utility is diminished, however, for cases at the border between impulsive and continuous noise. For signals with 3 < b2 < 6, the crest factor is unreliable for classifying the environment because of its dependence on a single peak. Examples of the relative efficiency of the metrics for classification will be drawn from actual samples of industrial noise.
Noise dosimeter transient response characteristics
Authors: Earshen John J.
Published: October 2005

Noise dosimeters used to monitor worker exposures to noise must have prescribed transient response characteristics to satisfy the requirements of the U.S. Department of Labor, Occupational Safety and Health Administration. In addition, computation of noise dose or average sound level must be based on a 5 dB per time doubled trading ratio. Various individuals have concluded that there is an apparent discrepancy between measured and computed doses when industrial noise contains impulsive components. The discrepancy results when computation neglects the effects of the prescribed transient response characteristics. In particular, “slow” response has a critical effect when trading ratios of 4 or 5 dB are used. A dosimeter is required to produce measurement results which correspond to results that can be computed from SLM readings. This paper shows the relationship between transient response and measured dose resulting from noise containing impulses. Furthermore, experimental results are presented which show that dosimeter and SLM derived results are consistent and correct. Reported results purporting to show that dosimeters give incorrect measurements of impulsive noise are shown to be incorrectly evaluated because theoretically computed reference values fail to account for U.S.D.O.L. OSHA prescribed transient response. The effect of Substituting “fast” response is also presented.
The effects of instructions and feedback on speaker consistency in a speech recognition framework
Authors: Roberts Linda A. , Wilpon Jay G. , Egan Dennis E. , Bakk Jean
Published: October 2005

Past research has demonstrated that a major problem in automatic speech recognition is speaker consistency. Instructions (suggestions of specific behaviors for consistent speech) and feedback (a visual display indicating the distance between each utterance and its template) were evaluated in a speaker-dependent recognition system as means of helping people speak more consistently. Utterances of 60 subjects were recorded using a 2 × 2 design. Dependent measures included the difficulty of forming templates, distances between utterances and templates, and recognition accuracy. For every dependent measure, instructions had a positive effect on speaker consistency but feedback had no reliable effect. When subjects were retested 2 weeks after initial training, their speech was less similar to the templates than on the day the templates were formed, but the instructional effect was still reliable. An extensive analysis of speech errors was carried out. Judges subjectively classified each utterance according to different error categories. These subjective ratings were then compared to recognition accuracies. The error analyses suggested which aspects of the instructions were effective and how future instructions might be improved.
A simple second-order toroid microphone
Authors: West J. E. , Sessler G. M.
Published: October 2005

A second-order gradient microphone with a toroidal directional characteristic is described. The microphone consists of four commercially available, inexpensive first-order-gradient electret microphones which are arranged in the wall of a hollow cylinder at 90° angular spacings and whose outputs are added. The toroidal microphone shows a directional characteristic which is relatively frequency independent. It is characterized by rotational symmetry around the cylinder axis and by a cosine-squared dependence in the plane containing the rotational axis. In the direction of the axis, the sensitivity at midfrequencies is typically 20 dB lower than in the equatorial plane. The equalized frequency response in this plane is within ± 3 dB from 0.3–3 kHz, with a 1-kHz sensitivity of about − 60 dBV/Pa. The noise level of the microphone, measured in the frequency band 0.3–10 kHz, is − 120 dB re: 1 V, corresponding to an equivalent sound-pressure level of 34 dB.
Experience with the two-microphone method for measuring the terminating impedance of a ducted burner during operation
Authors: Howard R. E. , Mahan J. R.
Published: October 2005

Previous papers on the two-microphone method establish its superiority over the classical impedance tube method for measuring the terminating impedance of a duct. The technique has been adapted here to measure the terminating impedance of a ducted burner with combustion noise acting as the sound source. The measurement system encounters a large dynamic range (30 dB) and high temperatures (900 K). Flow effects are negligible since Mach numbers remain below about 0.03. Results are compared to similar data from the literature, obtained using the classical impedance tube method, for duct terminating impedance in the presence of a hot flow. The method permits in situ measurement of the terminating impedance of a ducted burner during operation in spite of the hostile environment within the duct.
Comparison of the thermoacoustic efficiency of premixed and diffusion hydrogen-flame ducted burners
Authors: Mattan J. R. , Howard R. E.
Published: October 2005

It has long been known that confining a flame within a duct has an influence on the efficiency with which it converts chemical energy to acoustic energy. The present paper describes an experimental program aimed at explaining and quantifying this influence. Results are presented for premixed and diffusion hydrogen-flame ducted burners of otherwise similar design operating in the 5- to 10-kW range. The results show that the premixed flame yields the higher thermoacoustic efficiency at a given thermal power level, and that its efficiency is sensitive to the power level. The thermoacoustic efficiency of the diffusion flame is lower and relatively insensitive to the power level. The results are explained in terms of Rayleigh's criterion and current combustion noise generation theories.
The electroacoustic description of an underwater magnetohydrodynamic transducer
Authors: Schreppler Stephen C. , Busch-Vishniac Ilene J.
Published: October 2005

The Lorentz law, electromagnetic force in a conducting-dielectric, compressible, fluid medium, is investigated as a source of underwater acoustic radiation. The transducer system investigated consists of a duct which confines a conducting-dielectric fluid medium. A time-steady magnetic field and mutually orthogonal time-varying current density are established across the transverse dimensions of the duct. The system radiates from the longitudinal ends of the duct in a dipole, two-point array mariner. The electroacoustic system equations in two port form, theoretical and experimental projector sensitivity, and pressure field directivity patterns will be discussed. [Work supported by ONR.]
Derivation of the equations of motion of a piezoelectric accelerometer using the Lagrangian and modified piezoelectric stress equations
Authors: Jameson Paul W.
Published: October 2005

The equations of motion of a piezoelectric accelerometer are determined by using the piezoelectric strain equations in inverse form to calculate the electromechanical stored energy in the system. In this form, the electric field and the stress are expressed as functions of the displacement vector D and the strain S. These latter quantifies are used as the general coordinates for calculating the Lagrangian equation in a very straightforward manner. The mechanical and electrical impedance of the accelerometer is then computed and compared with experimental measurements of the sensor.
Nearfield calibration array utilizing piezoelectric polymer
Authors: Luker L. Dwight , Petrie S. , Van Buren A. L.
Published: October 2005

The Trott nearfield calibration array (NFCA) concept allows the farfield acoustic properties of underwater transducers to be determined in measurement facilities that are too small for direct farfield measurements. As a projector, the NFCA produces a nearly uniform plane wave throughout a large adjacent volume. The farfield sensitivity of a receiver can then be measured directly by placing it in the “plane-wave” volume. As a receiver, the NFCA measures only a single plane-wave component of the sound radiated by a projector located in the “plane-wave” volume. Existing NFCA's are primarily used as receivers and utilize small piezoceramic hydrophone elements arranged in planar or cylindrical configurations. The spacing between elements limits the upper frequency of operation of the NFCA; e.g., a 1-in. spacing allows operation up to about 50 kHz. This paper describes the design and construction of a planar NFCA utilizing a mosaic of nonelectroded sheets of the piezoelectric polymer PVDF attached to full area electrodes that subdivide the array into independently controlled annular elements. The PVDF NFCA was tested successfully as both a projector and a receiver by calibration of a high-frequency transducer. Although the available electronics limited the upper frequency of the test to 150 kHz, the PVDF NFCA should be useable, with suitable electronics, up to megahertz frequencies. [Work partially supported by ONR Code 220.]
Reciprocity calibration in a compliant cylindrical tube
Authors: Johnson Michael B. , Garrett Steven L.
Published: October 2005

A new method for absolute calibration of electroacoustic transducers is described which permits low-frequency reciprocity calibration in a test apparatus of small dimensions. The method takes advantage of the reduced wave speed in a cylindrical water column bounded by a compliant PVC tube to reduce the length of the standing wave to dimensions which can be easily handled in the laboratory. Results of a limited series of experiments show a mean reproducibility of ± 0.8 dB in a 1-m-long tube at frequencies between 750 and 1100 Hz and sound speeds from 330–365 m/s. The hydrophone voltage sensitivities obtained by the method, however, systematically differ by 1.5 dB from those measured by comparison with a standard hydrophone. Additional research will be required to resolve this discrepancy. [Work supported by ONR.]
Improvement to the transfer function method for determining the complex dynamic modulus of polymer composites
Authors: Semple Arthur E. , Thompson William
Published: October 2005

The Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802 Measurements of loss factor and storage modulus of diphasic transducer composites of polymers and piezoceramic were made using the transfer function method. This method consists of exciting a mass-loaded rod into longitudinal vibrations. The complex acceleration ratio between its ends is related to the complex modulus by two coupled, transcendental equations derived from the solution of the longitudinal wave equation with appropriate boundary conditions. In theory, these equations can be solved at any frequency by an iterative procedure. In practice, convergence problems reduce the valid solutions to those just at the longitudinal resonance frequencies. Improvements made during this study enable the equations to be solved at any frequency, except where the phase of the acceleration ratio is zero. Plots of loss factor and storage modulus are presented for a number of these new composites and other high-damping polymeric materials. A comparison between present results and those quoted in other studies indicates that this method produces reliable results. The improvements enable results to be obtained more quickly and with much less effort than previously required. [Work supported by ONR.]
Rule-controlled data base search
Authors: Carlson Rolf , Granström Björn
Published: October 2005

In current acoustic-phonetic research, there is a need for huge speech data bases. There are considerable problems in administering such data bases, both to transcribe and segment the speech and to easily access stored material. We have created a speech analysis system to attempt to alleviate these problems. Speech data are stored in sentence-sized files. These files are segmented and transcribed semiautomatically [M. Blomberg and K. Elenius, STL/QPSR 1/(1985)] given a phonetic transcription of the utterance. This transcription is generated by the text-to-phonetic component of our synthesis by rule system [R. Carlson and B. Granström, IEEE-ICASSP (1976)]. The same rule structure, similar to the notation used in generative phonology, is used for accessing the data. By a brief rule statement, speech segments meeting the specified contextual conditions can be identified. Durational data can be collected directly during the data base search. Spectral analysis programs, operating with a variety of spectral representations [R. Carlson and B. Granström, Eds., The Representation of Speech in the Peripheral Auditory System (Elsevier/North Holland)] have also been created that display the result, typically as a mean/ s.d. spectrum or contour histogram spectrum.
Frequency of acoustical patterns in Spanish syllables
Authors: Guirao Miguelina , Jurado María García
Published: October 2005

This work aims at a better understanding of the internal acoustical structure of Spanish speech sounds. A sample of 43 000 words was used to analyze the frequency of occurrence of the main spectral patterns of 68 141 syllable-sized segments. Acoustical syllabic components (ASC) were classed in periodic nonvocalic (P) and vocalic (V) sounds, bursts (B), and noise sounds (N). The first computer-aided count gave the frequency of syllabic types in conjunction with their acoustical classes. Within type CV (55.8%) combinations of ASC were B + V 26.8%, P + V 18.6%, and N + V 10.4%. Within type CVC (15.8%) predominant combinations were B + V + P 5.5%, P + V + N, and B + V + N each one 2.7%. A second count gave the incidence of ASC in the first 3996 words. Combinations were P + V 29% and B + V 24%. Vowels sounds were 14%. The most frequent ASC in initial and final word position were registered. Starting words B + V are 40% and vowels 25%; terminating words B + V are 45% and P + V 30%. Relative occurrences of B + V in both positions indicate their high functional load at setting acoustical boundaries between Spanish words.
An acoustic and Perceptual study of the voiceless portion of unvoiced stop consonants in American English
Authors: Ringo Carol Chapin
Published: October 2005

An investigation of the acoustic properties of the voiceless portion of unvoiced stops was undertaken. Three male native speakers of American English were recorded reading a list of “CVd” words, in which the consonants /p,t,k/ appeared before the vowels /i,ɪ,e,E, ae,u,ᴜ,ʌ,o,a/. For each speech token, formant frequencies and amplitudes at 10-ms intervals were estimated visually from hard copies of computer-implemented DFT displays. It was found that for certain CV combinations the ratio of the average amplitude of F3 to that of F2 during the aspiration interval is considerably greater than the same ratio computed during the vowel. This finding could be explained either by greater losses through the open glottis for the second formant, or by the different excitation of the formants as a consequence of the source location and spectrum. In some cases, the presence of substantial energy in the region of F4 and F5 favors the latter explanation. These results raise questions concerning the perceptual importance of F2 in identifying place of articulation in voiceless stop consonants. Preliminary perceptual experiments are described in which this issue is explored. [Work supported by a grant from NINCDS.]