bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of tubes for measurement of acoustical properties of materials
Authors: Anderson A. L. , Hampton L. D.
Published: October 2005

Tubes can be used in a variety of measurement techniques to determine the acoustical properties of materials. They are especially valuable for obtaining measurements at low frequencies in such materials as marine sediments. Several techniques for measuring compressional wave attenuation and dynamic shear modulus of sediments with tubes are described. The tube is used to establish standing waves in the measurement of low-frequency attenuation. In order to determine the dynamic shear modulus of the sediment, the resonance frequency of a gas bubble of known size is measured with the bubble submerged in the sediment inside an impedance tube. The resulting resonance frequency is shown to be related to the sediment dynamic shear modulus.
Interior noise considerations for powered-lift STOL aircraft
Authors: Barton C. Kearney
Published: October 2005

Several powered-lift configurations which are currently under development for future use on STOL aircraft involve impingement of the jet engine exhaust onto wing and flap surfaces. Previous studies have suggested that the impinging jet produces higher noise levels at lower frequencies than does the jet alone. These higher levels, together with the closer proximity of the engine and flap noise sources to the fuselage sidewall than for present-day jet aircraft, suggest that the noise levels in these aircraft may be high enough to interfere with passenger comfort. To investigate this possibility, interior noise levels were estimated for both “upper surface blown” (USB) and “externally blown flap” (EBF) configurations. The estimated levels were found to be very high, especially at low frequencies, compared with interior noise levels found on existing commercial jet aircraft. As a result of this finding, a research program has been initiated to develop better understanding of low-frequency noise transmission through aircraft fuselage structures and to develop prediction and control technology for application to power-lift STOL aircraft. This paper describes the interior noise estimation procedure, compares the estimated levels with levels on existing jets and other transportation modes, and describes the recently initiated research program.
Light vehicle sound dependence on size, operational mode, and monitoring sites
Authors: Coulter J. E.
Published: October 2005

In order to obtain a data base on light vehicle noise, 15 roadside locations were chosen to demonstrate a full range of operating conditions. Emphasis was made on the low-speed situations common to urban areas. Vehicles were subdivided into six categories ranging from sub-compact cars to light trucks. Data from each vehicle category and site were subjected to regression analysis for speed vs dBA after mean sample levels had been compared. Results of these analyses indicate significant differences in mean sound levels between seemingly similar test sites. Accelerating light vehicles are quite inconsistent from one site to the next but are only marginally louder than 30-mph vehicles. Small cars and light trucks give the highest acceleration sound levels but differ little from the standard “family car” at 30 mph. A significant difference was found between summer and winter monitoring at the same locations. Only vehicles in poor repair were noticeably affected by uphill grades. A hypothesis on the effect of operator driving psychology on noise levels at intersections is suggested.
Effects of wind and temperature gradients on the propagation of highway traffic noise
Authors: King F. D. , Oliver C. C.
Published: October 2005

Well-known experimental results permit the prediction of excess attenuations due to meteorological effects for the propagation of sound from point sources over open terrain. This study extends these methods by numerical means to examine the ease of a line source. In particular, line sources with the approximate characteristics of highways as noise sources are considered. Effects of wind and temperature gradients for such sources are predicted to be severe, even under mild weather conditions. These results are applied to an existing highway traffic noise prediction scheme, and examples are discussed.
Isochrony and disjuncture as aids to syntactic and phonological analysis
Authors: Lea Wayne A.
Published: October 2005

In read sentences and paragraphs, as well as simulated man-computer interactions, time intervals between onsets of stressed vowels (“disjunctures”) clustered near mean values around 0.4 to 0.5 sec, with standard deviations of about 0.15 sec. Contrary to published hypotheses, durations of disjunctures tended to increase about linearly with the number of intervening unstressed syllables. Mean disjuncture durations doubled when spanning clause boundaries, and tripled when spanning sentence boundaries. Mean pause durations. as measured by durations of unvoicing, tended to be equal to or twice the mean interstress interval, for clause and sentence boundaries, respectively. Syntactically dictated pauses thus appear to be one- or two-unit interruptions of rhythm. Long disjunctures also accompanied some perceived boundaries between syntactic phrases, and were found useful in determining which of several minimally contrastive syntactic structures had been spoken. Mean disjuncture durations, adjusted to take account of the number of unstressed syllables between stresses, appear to correlate well with differences between phonemic, phonetic, and computer-determined transcriptions of utterances, so that mean disjuncture durations, as acoustic measures of speech rate, might predict some phonological rules that apply to an utterance. [Research supported by the Advanced Research Projects Agency, Department of Defense.]
Vowel and sonorant lengthening as cues to phonological phrase boundaries
Authors: Kloker Dean
Published: October 2005

Five sentences per speaker were selected from six individuals who participated in simulations of computer interactions. The utterances were distorted by spectral inversion and presented to five listeners who marked stressed syllables and the locations of phonological phrase boundaries, using only the prosodic cues remaining in the signal. Vowel and sonorant durations (with and without aspiration) were measured from spectrograms, and then declared stressed or unstressed based on the perceptions. Exploring the hypothesis that large increases in duration are syntactically determined [Klatt, Speech Communication Seminar Proceedings, Stockholm 277–289 (1974)], perceived boundary locations were compared with preceding segments which were 20%, 30%, and 40% above the median length for their categories. Of all the perceived phrase boundaries, those involving silences longer than 200 msec (pauses) were less reliably preceded by duration increases than perceived boundaries not at pauses. A possible reason is that the pause is enough of a cue to the boundary, and a duration increase is not needed. Of the lengthened segments not at perceived boundaries, some mark major syntactic boundaries, but most are at minor syntactic breaks, notably between modifiers and nouns, and after prepositions. The results suggest that speaker differences and style variations may be important. [Research supported by the Advanced Research Projects Agency, Department of Defense, and the Phonetics Laboratory, University of Michigan.]
The syllable and speech synthesis
Authors: Macchhi M. J. , Fujimura O.
Published: October 2005

Previous work [J. P. Olive and L. H. Nakatani, “Rule-Synthesis of Speech by Word Concatenation: A First Step,”J. Acoust. Soc. Am. 55, 660–666 (1974)] has shown that very natural speech can be synthesized by concatenation of linguistic units if the units are large enough, like words, and if prosodic parameters (particularly pitch and duration) are adjusted according to syntactic/phonological information. A similar approach is being tested by using the syllable, a purely phonological unit, for concatenation. Based on a reconsideration of the characteristics of English syllables [O. Fujimura, “Syllable as a Unit of Speech Recognition,” IEEE Trans. Acoust. Speech Signal Proc. (in press)], the syllable approach has been explored in several preliminary investigations: (1) concatenating waveforms corresponding to syllables; (2) concatenating formant-coded syllables and smoothing prosodic information only; (3) concatenating formant-coded syllables and smoothing both prosodic and phonetic features. The resulting speech was judged to be quite natural, even for (1), under certain conditions. These three forms of investigation will be discussed and tapes will be played.
Prediction of detection of sinusoids of different phases when masked by repeated waveforms of wide-band noise
Authors: Becker R. W. , Bell D. W.
Published: October 2005

In a previous paper (Bell and Schubert paper S8, this meeting), the detectability of sinusoids added to noise varied greatly with the phase with which the sinusoid was added to the noise. The S+N waveforms were created and filtered by two- and five-stage Butterworth filters of 50- and 110-Hz bandwidth centered at 500 Hz. Predictions of detectability were made using measurements made on the output of the filters, including maximum positive and negative peaks; integrated positive and negative amplitude; positive, negative, and total energy; and durations between zero crossings—all made every 10 msec for 150 msec. Other predictors included spectral sharpness and variance of the envelope amplitude in the filter output. None of the models fully explained the interphase detectability of the waveforms for a given noise, and the internoise detectability of the noises for a given phase; however, some models show promise for some parts of the data.
From tongue model data to sound
Authors: Miller Joan E. , Fujimura O.
Published: October 2005

A simulation of the tongue, described in the preceding paper, “Computational Model of the Tongue” by Kiritani, Fujimura, Miyawaki, and Miller, provides three-dimensional coordinates of the nodal points of tetrahedra, forming a geometric shape which represents the shape of the tongue according to the specified muscular contractions. A computational procedure is described in which these data points are first approximated by a smooth function representing the tongue's surface subject to constraints imposed by assumptions about the surrounding rigid structure. Secondly, vocal-tract cross-sectional areas are estimated as differences between the assumed outer walls of the tract and the computed tongue surface. Finally, the formant frequencies may be inferred from the estimated area functions so that the resulting tongue positions may be evaluated by synthesizing a corresponding sound. Graphic displays illustrating the results are presented.
Approach to vowel normalization
Authors: Wakita Hisashi
Published: October 2005

This study is to test the hypothesis that perceptually equivalent vowels which are produced by various speakers have a statistically unique vocal-tract area function. The test was made in the frequency domain. The vocal-tract area function was computed from a measured set of vocal-tract resonance frequencies along with the tract length. Then the area function was normalized to one having a certain reference length, from which normalized resonance frequencies were computed. The study was made with ten vowels in the context of “hVd” produced by seven male and six female speakers. Both unnormalized and normalized distributions of F1−F2, F1−F3, and F2−F3 were obtained. It was ascertained that the normalized distributions are substantially more compact than the unnormalized ones. This result is particularly useful for interspeaker normalization in automatic speech recognition. [This work was supported by the Office of Naval Research.]
Effect of panel curvature, internal pressurization, and external air flow on field-incidence transmission loss
Authors: Koval L. R.
Published: October 2005

In the context of sound transmission through aircraft fuselage panels, equations for the field-incidence transmission loss of a single-walled panel are derived that include the effects of panel curvature, internal fuselage pressurization, and external air flow. These effects are incorporated into the classical equations for the TL of single panels, and the resulting double integral for field-incidence TL numerically is evaluated for a specific set of parameters. Curvature is found to stiffen the panel, thereby increasing the TL at low frequencies, but also to introduce a dip (analogous to the coincidence dip at the critical frequency) at the “ring frequency” of a full cylinder having the same radius as the panel. This effect, up to now qualitatively understood, can now be quantitatively estimated. Pressurization appears to produce a slight decrease in TL throughout the frequency range, and also slightly shifts the dips at the critical frequency and the ring frequency. Flow is shown to provide a modest increase in TL that is uniform with frequency up to the critical frequency. The increase is about 2 dB at M = Mach No. = 0.5, and about 3.5 dB at M = 1. Above the critical frequency where TL is damping controlled, the increase can be slightly larger at certain frequencies.
Binaural interaction in the macaque monkey
Authors: Flammino F. , Clopton B. M.
Published: October 2005

The effect of diotic and dichotic presentation on the loudness of tones partially masked by noise was studied in the macaque monkey. The animals were trained to perform a reaction-time task. Reaction time has been shown to be inversely related to intensity. The differences in reaction time between the diotic and dichotic modes of presentation were used as the measure of the masking level difference (MLD). The parameters which were varied were signal frequency, noise spectrum level, and interaural noise correlation. The general trends in the data were similar to the results obtained from experiments using human subjects. The size of the MLD decreased as the signal frequency was increased, but the frequency region for the largest MLD was shifted upward to 1 kHz. The MLD increased as a direct function of the masker level. As the interaural correlation approached zero, the MLD grew smaller, but at a faster rate than for humans. These discrepancies suggest that there are underlying differences in the ability of each species' auditory system to utilize temporal information. Monkeys can extract interaural phase information at higher frequencies than humans, but the time interval over which they can correlate events at the two ears is shorter.
Coordinated activity of the middle-ear and laryngeal muscles in echolocating bats
Authors: Jen P. H.-S. , Alster H. , Suga N.
Published: October 2005

The middle-ear muscles contract synchronously with the emission of orientation sounds and attenuate vocal self-stimulation. Apparently the vocalization center activates the middle-ear and laryngeal muscles in a coordinated manner for echolocation. With Myotis lucifugus, further experiments were performed on the coordinated activities of the crichothyroid (CTM) and stapedius muscles (SM) for vocalization and attenuation of vocal self-stimulation. We have also found that both the SM and CTM responded to acoustic stimuli. The CTM discharged action potentials to acoustic stimuli with a latency of 11 msec on the average. The shortest latency of the reflex was 8.0 msec, which was 4.6 msec longer than that of the acoustic SM reflex. Unlike SM fibers, tuning curves of CTM fibers were a simple triangle. The best frequencies ranged between 25 and 40 kHz and the Q−10-dB values ranged between 2 and 5. The lowest threshold measured was 50 dB SPL. [Supported by NSF Grant GB-40018.]
Electroelastic normal modes of ferroelectric cylindrical shells
Authors: Sabbagh Harold A. , Krile Thomas F.
Published: October 2005

A variational method, using finite elements as the basis functions, is used to calculate the short-circuit and open-circuit electroelastic normal modes of radially polarized and tangenttally polarized (segmented) ferroelectric cylindrical shells. One-dimensional finite elements of various orders are used for the radially polarized shell, whereas three-dimensional, first-order (i.e., linear) elements are used in the analysis of the tangentially polarized shell. The results for the radially polarized shell agree very well with those calculated using the “exact” differential equations of a thin shell. A discussion of the manner in which the finite elements are generated by means of higher-order convolutions of the unit pulse is also included.
Programmable electroacoustic test system
Authors: Henderson T. L.
Published: October 2005

A portable electroacoustic system has been assembled around a BASIC-programmable calculator for use in a variety of laboratory acoustical tests. The system contains a precision frequency synthesizer, a sample/hold, ac/dc volt meter, a coordinate-digitizing tablet, an x-y plotter, a frequency counter, and a programmable relay box for test control. The entire system is mounted on a mobile console. Principal considerations affecting the system design were that it be (1) as easy as possible to program and operate, (2) composed of off-of-the-shelf equipment, and (3) as flexible as possible in laboratory acoustical applications. The most successful application of the system has been the semiautomated processing of audiometric test results. Other automatic testing applications have included (1) anechoic chamber testing of sound-level meters, (2) dynamic response testing of occupational noise dosimeters, and (3) pure-tone audiometric testing. Additionally, the system has been connected to a third-octave-band analyzer for measurement of noise reduction characteristics of a sound-proof room. The ability of the system to perform statistical data processing as part of the test has been of great value.
Noise reduction analysis for a dispensary at a Naval Air Station
Authors: Rosenberg Carl J. , Paulhus Norman R.
Published: October 2005

In order to determine the noise reduction requirements of exterior construction for a proposed dispensary building at a Naval Air Station, measurements were made of peak noise levels and spectra of various aircraft operations flying near and over the site. The results of these measurements were significantly different from levels calculated using the CNR methodology. The differences appear to be related to the manner in which training missions are flown at military bases. Reliance on CNR data alone for noise reduction analysis at military bases can be misleading. To aid the architect in design and layout of the building, a series of guidelines was proposed. These guidelines related background noise criteria, speech communication distances within different spaces, and degree of acoustical privacy desired. Four allowable levels of intrusive noise were established, relating to these evaluations. The resulting allowable intrusive noise and the measured exterior noise exposure were then used to determine the noise reduction requirements of the exterior construction. The architect's visual and technical responses to this analysis are presented.
New approach to speech-reception testing
Authors: Miller James D. , Engebretson A. Maynard , Garfield Stanley A. , Scott Brian L.
Published: October 2005

Using a digital computer system, we have implemented a procedure that quickly locates those items of a large set that are unambiguous to the listener as well as those that are ambiguous. Items that have been correctly recognized by the listener have a low probability of occurrence. Items that have been incorrectly recognized, those with which they are confused, and those not yet presented have a high probability of occurrence. By the end of testing, high-probability items define the problem area, and since a trial-by-trial record is kept various analyses are possible. Preliminary studies with materials such as all initial-consonant clusters illustrate the procedure. This approach should help to specify successes and failures of speech communication systems including hearing-aid-patient combinations and also, more generally, those of pattern-recognition systems, human or artifical. [Supported by NIH Grants NS 03856 to CID and RR 00396 to BCL.]
Cyclic liquid-jet behavior in pulsating bubbles
Authors: Crum L. A. , Karangelin N. E. , Nordling D. A.
Published: October 2005

Motion pictures will be shown of liquid jets that develop in air bubbles pulsating at 60 Hz and redevelop in each cycle. The air bubbles grow by rectified diffusion from nuclei present in a glycerin-water mixture to sizes on the order of a few millimeters, and are then trapped on a platform situated within the resonator. The resonator consists of an aluminum cylinder, with heavy glass end windows, that is oscillated at 60 Hz by a vibration platform. The ambient pressure above the liquid is reduced to near that of the vapor pressure, which allows the resonator to generate large pulsation amplitudes in the air bubbles at low driving amplitudes. The pictures to be shown were made in two different ways. The first was made with a high-speed Fastax camera running at approximately 4000 frames/sec with bright field illumination. The second was made with bright field illumination from a high-intensity strobe that was driven near the oscillation frequency of the resonator. [Work supported by the Naval Academy Research Council and the Office of Naval Research.]
Effect of a dense gas equation of state on the expansion and contraction of an underwater gas bubble
Authors: Epstein David
Published: October 2005

At the high pressure believed to occur in underwater explosion gases, and in cavitation bubble collapse, deviations from an ideal gas much be considered. A theoretical investigation into the effect of a simplified dense gas equation of state on underwater gas bubble dynamics is presented. Our approach is to make a direct comparison between ideal and dense gas results. First, the lossless, incompressible liquid case is analyzed. The requirement of a realistic equation of state yields some startling results, placing severe bounds on some of the key parametrs: the peak bubble pressure, the maximum bubble wall velocity, and the minimum bubble radius. Next, nonviscous energy losses are discussed. A generalization of the Herring technique is used for approximate evaluation of the radiation loss integral derived from the Kirkwood-Bethe equation. These calculations appear to give physically reasonable loss estimates under both the ideal and dense gas assumptions. Also, an oft-quoted formula for the acoustic radiation loss has been found to be in error and has been corrected.
Rician distribution and the amplitude fluctuation of transmitted signals in the sea
Authors: Urick R. J.
Published: October 2005

In 1945, S.O. Rice, in a classic paper, derived the amplitude distribution of the sum of a sine wave and a narrow-band Gaussian random process. This function, called the Rician distribution, may be expected to apply to the fluctuation of transmitted sound in the sea whenever the received signal consists of a steady component plus a component resulting from scattering or multipath interference. In the limit when the steady component vanishes, the result is the well-known Rayleigh distribution. In the present context, it is physically meaningful for the Rician distribution to have as its parameter the ratio of the power in the random component to the total power. This quantity, which we may call the Rayleicity ratio, ranges from zero for a steady signal to unity for a signal consisting entirely of numerous scattered or multipath contributions. The validity of the Rician distribution is illustrated by examples from field-recorded data.
Auditory informational masking
Authors: Pollack Irwin
Published: October 2005

Masking is typically defined in terms of the threshold change in signal level resulting from the presence of a neighboring noise. By contrast with “energetic” masking, informational masking is defined in terms of the threshold change in statistical structure resulting from the presence of a neighboring signal of the same amplitude. Forward masking, backward masking, combined masking, etc., may be defined in terms of the temporal relations of the neighboring to the informational sequences. Forward informational masking is shown to be appreciably smaller than backward or combined informational masking. The threshold change in statistical structure tends to be proportional to the ratio of the durations of the neighboring to the informational sequences.
Studies of sound transmission in the ocean mixed layers
Authors: Hall Marshall
Published: October 2005

Several experiments on sound propagation in the ocean mixed layer have been conducted. These experiments have been designed to encompass a wide range of oceanographic conditions. The thickness of the mixed layer, for example, ranged from 30 to 100 m; the thermocline sound-speed gradient varied from −0.06 to −0.29 sec−1 and the sea surface roughness ranged between 0.3 and 2.4 m. An acoustic wavelength of 0.4 m was employed. Results for propagation loss at depths both within and below the mixed layer have been obtained in each experiment, for horizontal ranges between 1 and 6 km. When the mixed layer is thick (50 to 100 m), or when the surface roughness is small (less than 1 m), then the energy below the layer is 10 to 20 dB weaker than the energy within the layer. The results obtained in these cases are in reasonable agreement with normal-mode theory. When the mixed layer is less than about 50 m thick, and the surface roughness is greater than 1 m, the acoustic energy fluctuates considerably but the average levels are independent of depth. In this case, the energies are approximately consistent with “spherical spreading” and there is no evidence of trapped propagation in the mixed layer.
Implications of detailed truck noise survey results on noise regulations
Authors: Coulter J. E.
Published: October 2005

Fourteen roadside locations were chosen to give a full range of truck operating conditions to include: low steady speed; low-speed acceleration; high steady speed; and grades with low speed. Data from similar locations were compared for various registered vehicle weight categories and multiple regression analysis was performed of dBA vs speed, registered weight, and grade. Results showed that for vehicles with more than three axles, registered weight capacity is of little significance, and speed is not important when less than 40 mph. Mean noise levels on grades were found to be significantly higher than those on level read but all grades above 2% gave comparable levels. Alternate methods are suggested for categorizing trucks for noise regulation purposes. Pros and cons of each method are considered. Similarly, methods for choosing regulatory maximum sound levels are put forward with comments on the implications of each.
Study of the space-frequency relationship in the scattered fields of simple target arrays
Authors: Diercks K. J. , Goldsberry T. G. , Ryan W. W.
Published: October 2005

The scattered field of an array of reflectors insonified by a broad bandwidth signal is frequency (or time) structured. The relationship of space and frequency, or space and time, in the fields of single- (linelike) and multidimensional (nonlinelike) configurations of simple reflectors is described and specified. Limitations upon the ability to observe and measure the relationship are identified. The phenomenon is examined using both frequency modulated chirps and broad-band impulsive bursts. It is revealed that the space-frequency (or time) relationship at a fixed target orientation is not unique to any specific target configuration. However, the relationship for a linear array is a well-behaved function of the array's orientation, whereas that for a nonlinear array is not, as revealed by sequential measurements performed upon turning targets. Quantification of the measurement limitations is provided.
Observation of oceanic density structure with a large-aperture acoustic array
Authors: Anderson V. C. , Kaye G. T.
Published: October 2005

A large-aperture planar array has been constructed for an indirect sensing of the vertical oceanic density fine structure distribution. The array is approximately 14 m square and consists of 128 hydrophones arranged in a horizontal plane around an 8-kW sound source. Operating frequencies are from 2 to 20 kHz; pulse durations are from 12 to 1 msec. The array is towed to sea, submerged to a depth of 20 m, and suspended from R/P ORB (Oceanographic Research Buoy). A spring compression system decouples array motion from the motion of the surface support vessel for vertical excursions of up to 3 m. The back-scattered energy from each transmission is clipped and digitized in 1024 depth intervals, covering approximately the upper 400 m of the water colume. Beamforming of the information at each depth interval allows discrimination between specular reflectors and point scatterers. [This research is supported by the Advanced Research Projects Agency.]
Whole-nerve action potential runing curves
Authors: Dallos Peter , Cheatham Mary Ann
Published: October 2005

A great deal of recent evidence indicates that, contrary to earlier notions, the compound action potentials (AP) of the auditory nerve are strongly frequency dependent. One of the most convincing means of demonstrating this frequency dependence can be obtained by tone-on-tone masking techniques. In these experiments, the AP is elicited by brief tone bursts and a second tone (variable frequency and level) is used to suppress the AP to a desired degree. The resulting masking functions strongly resemble single unit and psychophysical tuning curves. The dependence of various features of such AP tuning curves upon stimulus level, simultaneous versus forward-masking paradigm, and features of the masker are detailed in the present work. [Supported by Grants from the NINCDS.]
Comparison of auditory thresholds determined behaviorally and electrocochleographically in normal and kanamycin-treated gerbils
Authors: Özdamar Ö. , Dallos P. , Ryan A. , Harris D.
Published: October 2005

The measurements of two electrical responses of the auditory periphery have been proposed for the objective assessment of the auditory sensitivity. The first is the classical method of measuring cochlear microphonic (CM) isopotential curves. The second is obtaining thresholds of whole-nerve action potentials (AP) by using shaped tone bursts. To determine the validity and shortcomings of both methods, measurements have been conducted on normal and kanamycin-treated gerbils and they are compared with behavioral audiometry. The study shows that between 500 and 24 000 Hz, AP threshold curves compare favorably with behavioral thresholds whereas CM isopotential curves generally do not. At very high frequencies, both responses fail to approximate the behavioral response pattern. Studies with kanamycin also support the idea that the whole-nerve action potentials can be objectively used for the measurement of audiometric patterns. Such a proposal is also consistent with the observations that AP generated by low-intensity tone bursts is produced by a relatively small number of primary auditory fibers whose characteristic frequencies correspond to the frequency of the stimulus. [Supported by Grants from the NINCDS.]
Speaker sex identification utilizing a constant laryngeal source
Authors: Brown W. S. , Feinstein S. H.
Published: October 2005

It has been demonstrated that the sex of speakers can be reliably and accurately identified in the absence of idiosyncratic glottal wave forms. This finding led to the hypothesis that there are other sex-related differences in the supraglottal vocal tract which produce discriminable acoustic differences in speech. As a test of this hypothesis, ten males and ten females counted to ten and read the second sentence of the “Rainbow Passage” using an electronic artificial larynx (F0=120 Hz) with a closed glottis. Tho vocalizations were tape recorded, randomized, and played to 30 listeners who then determined the speakers' sex. Later, the vocalizations were subjected to a sound spectrum analysis. Results indicated that male voices with energy concentrations shifted toward the lower frequencies were identified above chance as were females with energy concenctrations shifted toward the higher frequencies. Speakers whose energy concentrations were centralized were most often confused. These results confirm the hypothesis that sex-related supraglottal vocal tract characteristics play a major role in the identification of speaker sex.
Joint microbarograph and radar observations of a meteor
Authors: ReVelle D. O. , McIntosh B. A. , Watson M. D.
Published: October 2005

On the night of 13–14 December 1974, joint observations were made at Springhill Meteor Observatory using both meteor radar and a specifically designed array of microbarographs. At about 5 a.m. local time (near the peak of the Geminid meteor shower), a relatively large meteor was recorded on two radars followed about 14 min later by the arrival of infrasonic pressure waves at all four sensors. The signal is not a simple N wave, but contains at least three well-defined cycles (with an overall dominant frequency ∼2 Hz, a peak-to-peak amplitude of ∼6 μ and a total duration of ∼9 sec). Not only is the time delay appropriate (corresponding to an acoustic signal velocity of ∼300 m/sec), but estimates of meteor mass (∼1 kg) made using the radar echo theory of McIntosh and the line source blast wave theory of ReVelle are in good agreement. Unfortunately, due to overcast conditions at the time, photographic data were not available for this event. Additional recordings are currently being made with the Springhill system and a second microbarograph array is being installed on the Canadian Prairies to be operated in conjunction with the camera network of the Meteorite Observation and Recovery Project.
Atmospheric acoustic gravity modes at frequencies near and below low frequency cutoff imposed by upper boundary conditions
Authors: Kinney W. A. , Pierce A. D. , Kapper C. Y.
Published: October 2005

Perturbation techniques are described for the computation of the imaginary part of the horizontal wavenumber (k1) for modes of propagation. Numerical studies were carried out for a model atmosphere terminated by a constant sound-speed (478 m/sec) half space above an altitude of 125 km. The GR0 and GR1 modes have lower-frequency cutoffs. It was found that for frequencies less than 0.0125 rad/sec, the GR1 mode has complex phase velocity; k1 varying from near zero up to a maximum of 3×10−4 km−1 with analogous results for the GR0 mode. There is an extremely small frequency gap for each mode for which no poles in the complex k plane corresponding to that mode exist. These mark the transition from undamped propagation to damped propagation. In the complete Fourier synthesis, branch line contributions compensate for the absence of poles in these gaps. Computational procedures are described which facilitate the inclusion of the low-frequency portions of these modes in the waveform sysnthesis. [Work supported by Air Force Cambridge Research Laboratory.]
Ray paths in an inversion for small source height
Authors: Embleton T. F. W. , Thiessen G. J. , Piercy J. E.
Published: October 2005

The propagation of sound between a source and a receiver, each a small but finite height above the ground, is considered for an atmosphere in which the sound velocity increases linearly with height. For source and receiver separation large compared with their heights above the ground, there are in general four possible ray paths (given by the roots of a quartic equation) having a given number of ground reflections, n > 1. For n = 0, i.e., no reflections, there is one ray path; and for n = 1 there are three possible ray paths. By suitable regrouping of the ray paths, it is possible to evaluate the effects of reflection at a ground of known, finite impedance (in practical cases, especially near the source) assuming coherence between adjacent ray paths, and also to evaluate the net sound intensity of waves traveling via more widely separated paths in the atmosphere assuming incoherence.
Adaptive array processing for directional uncertainties
Authors: Hodgkiss W. S. , Nolte L. W.
Published: October 2005

This paper illustrates the Bayes approach to an optimum array detection problem. A specific example presented is the detection of a known plane-wave signal in independent Gaussian noise plus an interfering plane-wave noise source of uncertain arrival angle. Computer simulations of the a posteriori probability densities of the interference arrival angle conditioned on the received data illustrates the manner in which the Bayes optimum array adapts to the unknown interference angle. ROCs are presented which characterize the detection performance of the array. [Supported by Office of Naval Research, Code 222.]
Effects of beamformer output signal characteristics on the detection performance of passive sonar receivers
Authors: Nitsche Jude R. , Piersel Allan G. , O'Connor James C.
Published: October 2005

When one builds a mathematical model of the passive sonar equation, it is neither sufficient nor appropriate to represent the sonar receiver (processor-display-operator) by a single, constant value of the recognition differential. The detectability index d′ is presented as the most appropriate performance metric for realistic sonar receivers, and it is shown to be a primary function of the working environment and the character of real beamformer output signal and noise. It is shown that the characteristics that are of significance include the probability density distributions and the autocorrelation functions of the signal and the noise. Having motivated the need to consider these characteristics, two sets of operational beamformer output data were analyzed, This paper summarizes the analyses of the three basic constituents of the data, namely, signal, broadband noise, and signal-like noise (due to surface shipping). It was found that both the signal and the noise were subject to large fluctuations over time periods that were comparable to typical processor integration times. In addition, the signal-like noise components were found to have rather unique probability distributions. They did not in fact exhibit the probability structure of stable sinusoids in white Gaussian noise. The probability density distributions of the data at the input and the output of the receiver are fundamentally important. Consequently, the paper closes with the description of a methodology for determining the parameters of the receiver operator characteristic (ROC) curve for a particular receiver in situ. [Work supported by the Naval Undersea Center.]
Noise propagation over a surface of variable impedance
Authors: Hadden W. James , Vidimos Robin A. , Sencil Philip M. , Pierce Allan D.
Published: October 2005

Previous analyses of sound propagation over uniform plane surfaces suggest that, for fixed source and receiver locations, only a limited portion of the surface makes an important contribution to the character of the received signal. Experiments in an anechoic chamber are reported which examine this hypothesis and which give insight into the magnitudes of critical scale sizes for surfaces of variable ground impedance. An estimate of the minimum size of the ground region most strongly affecting the received sound is obtained from data taken with finite sized surfaces of finite impedance centered at the probable reflection point. The data is interpreted using a theoretical model using concepts similar to those in Kirchhoff's theory of diffraction. [Work supported by NASA Langley Research Center.]
Propagation of noise from multiple sources over level ground
Authors: Hixson E. L. , Little T. M.
Published: October 2005

Multiple noise sources on vehicles were simulated by two omnidirectional loudspeakers. They were used singly or in pairs to form monopoles, dipoles, or two correlated or uncorrelated sources. Pure tones, or 1/3-octave and octave-band noise at 1 KHz, were used. With fixed source height of 1.65 m and spacing from 0.5 to 3 m, noise levels were measured versus distance and azimuth over hard level ground with sparce vegetation. Noise Source Level was measured for pass-by at 50 ft. For microphone heights of 1.5-m fluctuations due to phase interference were observed for distance and angle measurements. However, for zero microphone height fluctuations versus distance were eliminated. Due to nonideal reflection from the ground spherical spreading was not observed out to the 100-ft limit of the measurements. A successful propagation model was derived using spherical spreading from each source and its image, and a reflection coefficient of one with a phase shift dependent on angle of incidence. [Work sponsored by U.S. Department of Transportation.]
Vibration of the vocal cords in some pathological conditions
Authors: Matsushita H. , Hirano M. , Kawasaki H.
Published: October 2005

Vibratory mede of some pathological vocal cords was investigated with a use of ultrahigh-speed photography. The most frequent abnormalities in vibration in the cases of unilateral recurrent laryngeal nerve paralysis are an incomplete glottic closure, asymmetric movements of the two cords, and a decrease in or absence of mucosal wave on the affected cord. In the cases of vocal cord polyp, a relatively soft mass, the vibrating abnormal mass causes an incomplete glottic closure, a decrease in amplitude of vibration, and phase differences between movements of the affected portion and those of the nonaffected. A cancerous lesion, which always has a great stiffness, results in absence of vibration of the affected area and a hindrance to the movements of the nonaffected cord.
Nature of compensatory speech patterns: Mechanisms responsible for vowel changes
Authors: Hamlet S. , Stone M.
Published: October 2005

Attempts to compensate for an alteration in palatal configuration produced by wearing dental prosthesis may cause a change in vowel formants. Three prostheses, each with a different configuration, were worn by subjects over a period of a week for each prosthesis. Formant shifts, when present, cannot be predicted from the type of prothesis being worn. Measurements of jaw and larynx position reveal individually distinctive adjustments to the presence of a prosthesis, which can be related to the acoustical characteristics of vowels spoken while wearing the prosthesis. Lowering of the larynx and either a restriction or exaggeration of jaw movements may be seen in the initial stages of speech compensation.
Analysis of recognition scores of hearing-impaired subjects using Fairbanks Rhyme Test
Authors: Franklin B.
Published: October 2005

The five lists of the Fairbanks Rhyme Test were presented to the better ear of 12 teenagers with bilateral, congenital, moderate to profound sensorineural hearing losses at 20 dB above their speech reception thresholds. Analysis of the recognition scores for each consonant for all subjects revealed that the /s/ score of 69% was the highest. The average score for alveolars /d/ and /t/ of 49% was almost double the average score for labials /b/ and /p/ of 25%. The relatively high scores for /s/, /d/, and /t/, and low scores for /b/ and /p/ are different from what one would expect on basis of subjects' audiograms in relation to acoustic energy in these consonants. There was an unexpected variation in the number of times the same consonant was correctly identified on different lists, for example, /b/—eight times for list V and 21 times for list I. There were also unexpected discrepancies in the number of correct responses for certain words, for example, “fame,” “vain,” “fed,” and “buck” were missed by all 12 subjects; whereas &“look” and “saw” were correctly identified by 11 subjects.
Studies of the soprano voice
Authors: Sundberg J.
Published: October 2005

The paper is meant to overview various aspects of the soprano voice. The two lowest formant frequencies in different vowels sung at different pitches are measured; the results seem to explain why, for a given vowel, increases in pitch end to be accompanied by increases in the jaw opening. The amplitude of the higher formants in different types of soprano voices is analyzed and the importance of these formants to the personal timbre is discussed. Measurements of the glottal source spectrum in vowels are presented; the result seems to shed some light on certain acoustic differences between the “chest” and the “head” registers. The role of nasal resonance is discussed. Experiments with vowels identification in vowels with varied fundamental frequencies are reported.
Development of a community noise prediction model
Authors: Judd S. H. , Dryden S. L. , Tornheim L.
Published: October 2005

A new computer model includes features and flexibility which allow the simulation of noise propagation between multiple sources and remote observers through complex environments. Features include three-dimensional geometry; computation of the position of the position of obstructions relative to the wave path; computation of attenuation by solid barriers, prominent topographical features, semi-transparent arrays of equipment and forests; and computation of air absorption as a function of temperature and relative humidity. Flexibility includes the ability to represent sources as points, lines, or planes, to break complex sources down into separate components, and to designate “efficiency” factors for obstructions to account for flanking or reduced acoustic opacity. Input includes temperature and relative humidity; location coordinates and names for sources, obstructions, and observers; source octave band power levels; and various options. Output includes the predicted composite octave band, overall and A-weighted sound pressure level plus a list of major sources showing their octave band and dBA contributions, ranked in order of dBA, for each observer.
Evolution of hearing and acoustic communication in vertebrates
Authors: Beecher M. D.
Published: October 2005

Selective pressures on acoustic communication fall into several general categories. (1) Reproductive isolation. The pressure for species recognition has favored both species-specific calls and sensitivity to them. In some instances, this sensitivity is accomplished by narrow tuning of the peripheral auditory system, in others apparently by higher neural mechanisms (e,g., “auditory templates”). (2) Predator avoidance. Alarm calls, for example, are often narrow-band signals which are difficult to localize. Some species may produce sounds that are inaudible to their predators; the ultrasonic vocal and hearing systems of mammals may have evolved in this context. (3) Long-distance communication between conspecifics. Animals characteristically produce calls for this purpose that are attenuated minimally over distance, and their hearing is best at frequencies near those of these calls. (4) Intraspecific contact maintainance. Contact calls, for example, are typically wide-band signals which are easily localized. (5) Complex social organization. Highly social animals have developed acoustic communication systems which require sophisticated vocal and processing mechanisms to produce and discriminate a variety of sound elements. These species show enhanced acuity for the relevant acoustic signal parameters. Some species, in addition, have increased the potential information in their vocal repertoire by using graded rather than discrete signals. There is some evidence that increases in the complexity of the vocal repertoire are accompanied by specializations of the processing mechanism, as may be true in categorical perception.