bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of increased spectral contrast on vowel intelligibility for hearing-impaired listeners
Authors: Dorman M. F. , Leek M. R.
Published: October 2005

At the previous meeting of the Society, we reported that hearing-impaired listeners required larger peak-to-valley differences in vowel spectra for correct identification than do normal-hearing listeners. This outcome suggests that errors in vowel identification might be reduced by increasing the contrast between spectral peaks and valleys of natural vowels. To test this hypothesis, we created three sets of four vowels: one set with normal peak-to-valley amplitudes, one set with valley amplitudes decreased by 5 dB, and one set with valley amplitudes decreased by 10 dB. Identification accuracy improved minimally with 5-dB enhancement but not at all with 10-dB enhancement. The failure to markedly improve identification accuracy suggests that the deficiency in vowel identification does not lie in locating the spectral peaks, but rather may be due to aberrant coding of frequency in the internal auditory representation.
Temporal processing and speech perception in reading disabilities
Authors: Reed Marjorie A.
Published: October 2005

This study examined the processing of speech and nonspeech sounds by 23 second and third grade reading disabled children and 23 age- and sex-matched controls. Tallal's [Brain and Lang. 9, 182–198 (1980)] finding that reading disabled children were found to be poor in discriminating 75-ms tones and in making temporal order judgments about the tones was replicated. The difficulty in process in brief stimuli was found to extend to stop consonant temporal order judgments but not to vowel stimuli. The stop consonant syllables were distinguished by brief formant transitions, while the vowels were differentiated by long, steady-state frequency differences. The present study also demonstrated that the deficit does not extend to the visual modality, nor does it reflect generally poor performance on all tasks. Reading disabled children were also impaired in discriminating words distinguished by initial stop consonants and showed less sharply defined boundaries between phonological categories on a place-of-articulation continuum, demonstrating that the deficit observed in the temporal order tasks influences the perception of speech in natural situations and the clarity of phonological representations.
Applications of SEAM to the noise analysis and design problems
Authors: DeJong Richard G.
Published: October 2005

A procedure for applying the principles of statistical energy analysis (SEA) to practical noise analysis and design problems has been developed and implemented in the computer program SEAM. Ths user models a system by specifying the geometric and material properties of subsystems. SEAM computes the necessary SEA parameters, such as modal density, impedance, and coupling loss factor, and then solves for the system response to a particular excitation. Examples are given of the application of SEAM to a variety of complex dynamic systems showing comparisons with measured results.
Response of a thin-wailed pipe section due to external excitation using energy accountancy I: Analytical study
Authors: Cuschieri J. M. , Sehapley R. F. , Dunn S. E.
Published: October 2005

The energy accountancy method has been shown by Richards et al. to be a very practical and useful tool to estimate the noise energy radiated by a machine structure in broad frequency bands. The radiated noise energy was estimated to within ±3 dB for structures with a high modal density. For structures with low modal density, the method was used to estimate the total radiated noise energy and the mean level of radiated noise. This method of use of the energy accountancy concept is very much similar to statistical energy analysis. However, unlike statistical energy methods which are mainly restricted either to high modal density structures, where one can use statistical averaging to model the behavior of the structure or to estimate the total level of radiated noise for low modal density structures, the energy accountancy method can be used to estimate the noise energy radiated by a structure in narrow frequency bands. In this paper, using an energy accountancy approach, an expression is developed for each of the different energy components based on a series solution of the response of the structure. Through this analysis it is shown that the energy accountancy approach can indeed be used to estimate the radiated noise energy from a structure in narrow frequency bands.
Response of a thin-walled pipe section due to external excitation using energy accountancy II: Experimental study
Authors: Schapley R. F. , Cuschieri J. M. , Dunn S. E.
Published: October 2005

The response of a thin-walled pipe section excited by an external force can be obtained using the energy accountancy method as described in the first part of this series of two papers. In order to verify this approach, an experimental study was conducted on a 2.88-m-long, thin-walled steel pipe section containing two different fluids, air and water. The pipe section, 0.06 m in diameter and 0.003 m thick, was simply suspended by wires with no other outside connections. The pipe was excited externally by a calibrated hammer with the response of the pipe measured by an accelerometer attached to the outer surface of the pipe. In these experiments the internal fluid was stationary. This did not impose any limitations on the understanding obtained from the experiments since, for water systems, the flow is at a very low Mach number and therefore the effects of the flow are negligible. The results obtained show good agreement between the measured energy input and the measured dissipated and radiated energy components, the energy levels being within 1 dB of each other. This verified the application of the energy accountancy concept in describing the response of a thin-walled pipe section. Furthermore, the results obtained can be simplified into a diagnostic tool which can be used for noise control purposes.
Prediction of helicopter cabin noise using statistical energy analysis (SEA)
Authors: Moore James A.
Published: October 2005

The noise environment in the cabin of small 6–13 passenger commercial helicopters is dominated by mesh tones generated within the gearbox. Helicopter airframes are efficiently designed to support mechanical loads which results in their also being efficient transmitters of vibratory energy. Structural components of the airframe are characterized by many resonant vibratory modes at higher frequencies in the audio range. Statistical energy analysis (SEA) has proved to be a very useful tool in the development of a model of airframe vibration transmission and coupling to the acoustic environment in the cabin. Under contract support from NASA, Langley, an SEA model of the Sikorsky Aircraft S-76 helicopter was developed and implemented using the Cambridge Collaborative's general purpose SEAM computer code. Characterizations of the structural connections between frame members, and frame members and adjacent skin panels, were developed in implementing the model. Additional coupling loss factors between panels, frames, and acoustics spaces are needed in building the SEA model: Measurements on actual airframes with shaker excitation during flight operating conditions were performed with good agreement between measured and predicted vibration and cabin noise levels.
Rays aren't what they used to be
Authors: Felsen L. B.
Published: October 2005

Departing from the classical formulation of the propagation of light rays, modern ray theory has evolved by successive improvements and now provides one of the more effective methods for treating high-frequency wave propagation in general—in various environments and disciplines—in terms of field contributions localized around ray trajectories. By asymptotic analysis of canonical problems in the geometrical theory of diffraction (GTD), the category of incident, reflected, and refracted rays has been enlarged through inclusion of diffracted rays accounting for edge scattering, critical angle phenomena, and creeping waves in shadow regions on smooth convex surfaces. By asymptotic uniformization, failures of GTD in transition regions near shadow boundaries, caustics, or foci have been repaired; by collective treatment, multiple reflected ray fields in guiding regions have been converted into ray congruences that represent the normal modes; and from partial conversion of poorly converging ray clusters, there have emerged self-consistent and physically incisive hybrid ray-mode combinations. By extending the notion of a ray into complex coordinate space, it has been possible to incorporate evanescent fields and highly collimated beam fields within the ray format. Very recent studies have shown that the common foundation for all of these ray phenomena is a local plane-wave spectrum which is most severely shrunk around the ray paths when the ray fields are simple, but which must retain more “spectral flesh” in transitional and other critical domains. These concepts, which also extend to time-dependent propagation, are explored in the presentation, with emphasis on the motion of generalized ray fields as spectral objects. [Work supported by ONR.]
Chaotic phenomena in acoustic and elastic wave transmission lines
Authors: Moon Francis C.
Published: October 2005

A review of chaotic dynamics in nonlinear oscillators will be given. Evidence for chaotic phenomena in coupled nonlinear oscillators and wave propagation systems will be presented. In particular, large amplitude vibrations in flexible elastic and acoustic vibrations in a cylindrical cavity will be examined. In the latter problem, nonlinear boundary conditions at the end of the tube produce chaotic modulation of an acoustic carrier signal when excited by a deterministic harmonic signal. How higher-frequency acoustic waves can excite low-frequency chaotic vibrations of an elastic end plug of the tube will also be shown. New experimental methods for analyzing chaotic dynamics will be discussed, including Poincare maps and fractal dimensions. Speculation on the existence of chaotic waves in other wave systems will be posited. A demonstration of chaotic oscillations will also be presented.
Estimating the velocity vector of fast moving sound source exploiting the retardation effect
Authors: Schiller Joachim
Published: October 2005

The radiated noise of moving sound sources can be used to detect and localize these objects. Using microphone arrays with apertures comparing to the wavelength of the received signals, localization and velocity vector estimation will generally be done by means of triangulation. In this presentation it will be shown that, under certain conditions concerning the parameters of motion, the velocity vector itself (and not only the angular velocity) can be reconstructed using only the correlation measurements of one microphone array consisting of four microphones. The microphones of the array form three noncollinear bases with base lengths on the order of 0.5 m. The additional information needed results form the retardation effect. The retardation effect is a consequence of the finite signal velocity, and results in a mismatch between the indicated and the real target position if the target is moving. It becomes important at speeds of the sound source comparing to the signal propagation speed. On the basis of field measurements of low-flying aircraft, the reconstruction of the dynamic flight parameters (i.e., velocity vector, flight height, impact parameter) on the basis of the correlation measurements at one microphone array will be demonstrated and compared with simulation results.
An integrated approach to office acoustics in the computer age
Authors: Pei Hsien-Sheng (Jason)
Published: October 2005

The building environmental control system and computer/business equipment are two major noise sources in modern office buildings. This paper focuses on the technical challenges that must be addressed by the acoustical engineers in the design of office acoustics in the computer age. In several important areas (such as standards, design tools, technology development, etc.), integration is examined in some detail. The state-of-the-art of building environmental control systems and computer cooling systems will be reviewed. Technology integration potentials will be presented. A case study of integration is demonstrated. Current and future research needs are identified.
Effects of humidity on the characteristic impedance in air
Authors: Wong George S. K.
Published: October 2005

Recent investigations into the effects of humidity and temperature on the specific heat ratio γ air have led to the prediction of the above effects on sound speed [G. S. K. Wong and T. F. W. Embleton, J. Acoust. Soc. Am. 76, 555–559 (1984); 77, 402–407 (1985); 77, 1710–1712 (1985)]. With an approach which is similar to the above prediction, one is able to ascertain the variation of the characteristic impedance ρc in air with humidity and temperature. In standard atmospheric air, the numerical value of ρc decreases with the increase in humidity and temperature. An approximate equation will be presented for the calculation of ρc over the range of relative humidity from 0 to 1.0, temperature from 0° to 30°C, and at 1 atm.
Resonances in the impedance curves for outdoor ground covers
Authors: Sabatier James M. , Bass Henry E.
Published: October 2005

Measurements of the outdoor ground surface impedance for frequencies below 200 Hz are sparse. Recent experimental measurements at low frequencies show “glitches” or resonances in the measured impedance values [for example G. A. Daigle and M. R. Stinson, J. Acoust. Soc. Am. Suppl. I 78, S86 (1985)]. Using a modified version of the Biot-Stoll model for wave propagation in poroelastic media (J. Acoust. Soc. Am., submitted) the impedance of these outdoor ground surfaces is predicted. The glitches are theoretically predicted and explained as p- and s-wave interferences within the weathered porous layer of the ground.
The acoustic role of the noseleaf in a bat emitting frequency-modulated signals
Authors: Hartley David I. , Suthers Roderick A.
Published: October 2005

Carollia perspicillata is a New World frugivorous bat which emits low-intensity, broadband, frequency-modulated sonar pulses through the nostrils, which are embedded in a noseleaf structure. The emission pattern of this bat is of interest because the relationship between the nostril spacing and emitted wavelength should vary during the pulse, potentially causing complex interference patterns in the horizontal dimension. Sound pressures were measured around the bat using a moveable microphone and were referenced to a stationary microphone positioned directly in front of the animal. It was found that the emission pattern differed markedly from those of bats previously studied in that there were prominent sidelobes in the horizontal dimension. The pattern suggests an effective nostril spacing of around 0.75 λ. at the frequency of maximal pulse energy (between 90 and 100 kHz). Interference between the nostrils was confirmed by blocking one nostril which eliminated the sidelobes. Displacement and manipulation of the dorsal lancet of the nineleaf showed that this structure serves to direct the sound in the vertical dimension. [Work supported by NSF.]
Correlations between auditory capabilities and measures of phoneme perception
Authors: Espinoza-Varas B. , Watson C. S. , Geddes D. A.
Published: October 2005

Performance of 32 normal-hearing listeners on the test of basic auditory capabilities [Watson et al., J. Acoust. Soc. Am. Suppl. I 71, S73 (1982)] was correlated with each of the following measures of phoneme perception (obtained with the CUNY Nonsense Syllable Test): (l) hit probability for the overall test, and for each individual phoneme; (2) P(C)max for identification of each individual phoneme; and (3) P(C)max for discrimination of each possible phoneme pair within a set of phonemes. Relative to the total number of correlations that can be calculated, the percentage of significant correlations (p < 0.05, n = 32) were 0% for overall hit probability, 10% for phoneme-specific hit probability, 17% for identification P(C)max and 10% for pairwise discrimination P(C)max. These results support the hypothesis [Espinoza-Varas and Watson, J. Acoust. Son. Am. Suppl. 1 78, S47 (1985)] that auditory capabilities may be correlated more strongly with the ability to process specific phonemes than with overall measures of speech processing (e.g., whole-test speech discrimination scores). It was also found that a number of phonemes yielding either near-chance or near-perfect performance contribute little or nothing to the correlations or, presumably, to the information provided by the overall speech score. [Work supported by NIH and AFOSR.]
Auditory presentation of fundamental frequency as an aid to lipreading
Authors: Hanin Laurie , Boothroyd Arthur , Hnath Terry
Published: October 2005

The probability of work recognition, in sentence context, was measured in eight normal subjects under two conditions: lipreading alone, and lipreading supplemented by fundamental voice frequency (F0). Test materials were 48 sets of sentences, each set containing 12 sentences varying in length from 3 through 14 words. Sentences were video recorded by a female talker, one audiochannel containing the acoustic speech waveform, and the other channel containing the output of an electroglottograph. This second channel, low-pass filtered at 360 Hz, provided the F0 supplementation. Subjects were informed of the topic of each sentence, but were not given feedback on performance. Some learning was observed during the initial stages of testing, mostly in the supplemented condition. After the scores stabilized, mean scores were 32% words correct for lipreading alone and 76% words correct for supplemented lipreading. Application of probability theory shows that the addition of F0 is equivalent to multiplying, by 3.7, the sources of statistically independent information in the lipreading stimulus. These data illustrate the high potential for auditory, tactile, visual, or electrocochlear presentation of F0 as an aid to lipreading in the postlingually deaf. [Research funded by NIH grant ♯ 17764.]
Comprehension of natural and synthetic speech using a sentence verification task
Authors: Manous Laura M. , Pisoni David B. , Dedina Michael J. , Nusbaum Howard C.
Published: October 2005

A verification task was used to study sentence comprehension using two natural voices and five different synthetic voices generated by automatic text-to-speech conversion. Subjects listened to true and false, three- and six-word sentence produced by one of these voices. Sentence verification accuracy and speed, and sentence transcription accuracy were measured. A significant effect of voice type was obtained for true and false sentences for all three measures. In addition, for false sentences, subjects were less accurate in transcribing six-word sentences and they were slower in verifying these sentences. Furthermore, there were significant interactions of voice type with sentence length for all three dependent measures. Verification speed revealed a clustering of the seven voices into three basic categories corresponding to: (1) natural speech, (2) high-quality synthetic speech, and (3) moderate- to low-quality synthetic speech. Results from a second sentence verification task used to investigate effects of sentence predictability will also be discussed. [Work supported by AFOSR and NIH.]
Segmental intelligibility of synthetic speech produced by eight text-to-speech systems
Authors: Greene Beth G. , Logan John S.
Published: October 2005

Several studies measuring the segmental intelligibility of eight text-to-speech systems and a natural speech control using the modified rhyme test (MRT) have been conducted in the Speech Research Laboratory. Results indicated that the voices tested could be grouped into four categories: natural speech, high-quality synthetic speech, moderate-quality synthetic speech, and low-quality synthetic speech. The overall performance of the best system, DECtalk-Paul, was equivalent to natural speech only in terms of performance on initial consonants. The findings from these laboratory studies will be discussed in terms of recent work investigating the perception of synthetic speech under more severe conditions. Additional results obtained using a variation of the standard MRT will be presented. Suggestions for future research on improving the quality of synthetic speech will be discussed. [Work supported, in part, by NIH and AFOSR.]
Diagnostic evaluation of a synthesizer's acoustic inventory
Authors: Wright C. E. , Altom M. J. , Olive J. P.
Published: October 2005

In speech synthesis, utterances are created by concatenating elements from an acoustic inventory made up of phonemes, dyads, syllables, or other convenient units. For further development of the AT&T text-to-speech system [J. P. Olive and M. Y. Liberman, J. Acoust. Soc. Am. Suppl. 1 78, S6 (1985)] we need a fast, simple method to identify problems with elements in the acoustic inventory. Phonetic transcription is one method that has been used in the past for this type of synthetic-speech evaluation. However, transcription experiments are difficult to run and require specially trained listeners. Other methods that have been used, e.g., the diagnostic rhyme test, are better suited to provide comparative information about several synthesizers than the diagnostic information needed for this evaluation. To fill this gap, we have developed a procedure that we call verification. It is an interactive, computer-based procedure that can be used with listeners who have little training. In this talk we describe the procedure and its early application.
German text-to-phoneme software driven any speech synthesizer
Authors: Kulas W. , Blauert J.
Published: October 2005

The SYRUB system is a software system that converts any German text into phonemes. In addition to its high-quality conversion on word level, SYRUB automatically generates a German sentence intonation and controls its speech timing to obtain partial isochrony for more naturalness. Its universal synthesizer interface enables it to drive any speech synthesizer, thus allowing for an integration of the phoneme representations of seven European languages. Furthermore, special attention has been paid to the design of the system's user interface. The system distinguishes between trained and untrained users, and, subsequently supplies them with different sets of error and help messages, either acoustically or via screen. We will present the nonlanguage-specific aspects of our system: the user interface, the universal synthesizer interface, and the generation of speech rhythm.
Intelligibility of synthetic CVC stimuli over the telephone
Authors: Malsheen Bathsheba J. , Wright James T. , Yue Melanie , Peet Margot
Published: October 2005

Intelligibility tests of initial and final English consonants were made over a simulated long-distance telephone line for two leading text-to-speech converters descended from MITalk. CVC stimuli were presented to subjects in open-response listening tests to determine how vulnerable the intelligibility of synthetic speech would be to the effects of telephone bandwidth limitations. Subjects were also tested under nontelephone conditions for comparison. It was hypothesized that telephone bandpassing would produce a systematic breakdown in consonant intelligibility, and that certain phonemes, e.g., alveolar fricatives and alveolar stops before front vowels, would suffer the greatest loss due to their reliance on cues normally present at the higher frequencies. Our results show that overall intelligibility of high-quality synthetic speech is significantly reduced over the telephone. As expected, alveolar fricatives produced a large number of errors. Alveolar stops, on the other hand, remained robust and generated few perceptual errors. Velar stops, contrary to expectation, produced a large number of place and manner confusions. Intelligibility scores for initial and final consonants will be presented, and grouped by manner class.
Synthesizing British English intonation using a nondownstep model
Authors: Williams Briony J. , Alderson Peter R.
Published: October 2005

A method will be described for synthesizing British English intonation patterns from an initial representation in terms of tonetic stress marks. The resultant synthesized patterns compare favorably with those of the resynthesized originals. The data comprises fluently spoken whole sentences of natural speech, rather than unrealistically short utterances produced under artificial conditions. The tonetic stress mark system used is a modification of those used by O'Connor and Arnold (1961) and Crystal (1969). It is being used for large-scale prosodic transcription of a corpus of spoken English. Rules have been formulated for converting the tonetic stress marks to “target values” on a scale of one to ten, as in Pierrehumbert (1981). A declining topline and level baseline are then superimposed, yielding a frequency value for each syllable. The resultant F0 contour is compared with the original, for objective evaluation. The close match obtained suggests that tonetic stress marks are a valid starting point for intonation synthesis from annotated text. Since these units also carry functional weight, they may well be more satisfactory than an abstract tonal representation, for the purposes of speech synthesis from text.
Assimilatory versus nonassimilatory neutralization processes in Catalan
Authors: Charles-Luce Jan
Published: October 2005

In general, phonologists claim that neutralization results in the acoustic-phonetic obliteration of an underlying phonemic contrast in favor of one the members of the contrast. For Catalan, two possible processes are involved in the neutralization of underlying voicing in word-final stops: (1) word-final devoicing, and (2) regressive voice assimilation. In the latter case, word-final stops are realized as either voiced or voiceless depending upon the voicing of the following phonetic segment. However, in the former case, word-final stops are always realized as voiceless in those environments that do not overlap with regressive voice assimilation. In the present investigation, native Catalan speakers produced monosyllabic minimal pairs differing in the underlying voicing of the final stop in two nonassimilatory environments and in two assimilatory environments. Vowel duration preceding the final stop, voicing during closure, and closure duration of the final stop were measured as acoustic correlates of voicing. The results bear on the question of whether complete neutralization may best be defined as an assimilatory or a nonassimilatory process in speech production. [Supported by NIH Training Grant NS-07134.]
Cross-language switching in Dutch-English bilinguals
Authors: Eefting W. , Flege James Emil
Published: October 2005

A major issue in L2 research is whether bilinguals develop separate or merged phonetic systems. This study tested whether native speakers of Dutch, a language in which /p,t,k/ are realized with short-lag VOT values, would label the members of a VOT continuum ranging from /da/ to /ta/ differently when listening in a Dutch as opposed to English set. High-, mid-, and low-proficiency subgroups (ten each) were formed from a group of 50 Dutch university students on the basis of (a) global accent judgments by native British English listeners, (b) self-rating of ability to pronounce English, and (c) the VOT measured in their production of English /t/. A language specific set was established by having the subject produce and process Dutch or English speech prior to, or during, each half of the experiment. The mean location of the phoneme boundaries was only slightly longer in the English (35.6 ms) than Dutch set (33.5 ms). The effect of the language set was significant, but not the effect of proficiency or set x proficiency, indicating that the extent to which L2 learners adopt different, language-specific criteria in making phonetic judgments does not depend on language proficiency. However, the Dutch subjects showed a considerably larger shift in producing /t/ in English (60.3 ms) versus Dutch (22.8). English VOT was positively correlated with the global accent ratings, and subjects judged to have the least authentic English accent failed to distinguish /t/ in English and Dutch. [Work supported by NIH grant NS20963.]
Perception of coarticulatory variation in Shona
Authors: Manuel Sharon Y.
Published: October 2005

In Shona, a Bantu language, anticipatory vowel-to-vowel coarticulation is very strong in some VCV sequences, such as /api/. Two experiments were conducted to test whether native listeners are sensitive to these coarticulatory effects. The stimuli were versions of /api/, /apa/, /upi/, /upa/ in which the first vowel had been cross spliced from original /_pi/, /_pa/, or /_pu/ environments. In experiment 1, the task was to press a button whenever the second vowel was /i/. Subjects' responses were fastest when the first vowel carded the appropriate coarticulatory information (i.e., when it derived from the original /_pi/ environment). In experiment 2, subjects responded whenever the first vowel was /a/; they were slowest when the /a/ came from original /api/. Thus coarticulatory shifts in vowel quality facilitate the processing of later occurring information while, at the same time, they make the vowel itself less prototypical. These results, together with similar ones obtained by others for English, illustrate listeners' perceptual sensitivity to subphonemic phonetic variation. [Work supported by NICHD.]
Are F0 differences after stops accidental or deliberate?
Authors: Kingston John
Published: October 2005

Differences in F0 after stops are generally thought to be unavoidable perturbations of the rate of vocal fold vibration brought about by changes in the tension of the folds during the stop [Hombert, Ohala, and Ewan, Language 55, 37–58 (1979)]. For example, F0 is depressed after voiced stops because the folds are slackened during the closure, but elevated after voiceless stops because the folds are tensed. Recent work has shown, however, that all the mechanisms proposed to account for differences in F0 after stops are seriously flawed [Kingston, MS thesis (1985)] and, furthermore, that stops of the same phonetic type, e.g., voiceless unaspirated, can elevate F0 in one language but depress it in another [Caisse, MS thesis (1982)]. The F0 differences may therefore be introduced deliberately. to enhance the phonological contrast, rather than arising as accidental byproducts of other articulations. This possibility was tested with data from Tamil, a language which contrasts long and short stops where the long stops are predictably voiceless and the short ones are predictably voiced. Since voicing is allophonic rather than distinctive in this language, F0 differences need not appear after stops if they are deliberate. On the other hand, if the F0 differences are simply an accidental byproduct of having the folds vibrating or not, then they should appear regardless of the phonological role of vocal fold vibration. Measurements of F0 after stops in Tamil show no significant difference at the onset of vowels following the two kinds of stops, supporting the contention that F0 differences are deliberate in other languages.
English word and sentences stress patterns as spoken by non-native speakers
Authors: Fokes Joann , Bond Zinny S.
Published: October 2005

Non-native speakers from six different language backgrounds and native American English speakers produced tokens of three-syllable word, such as confession and four syllable words, such as confirmation in isolation and in sentences. The acoustic-phonetic correlates of stress—amplitude, fundamental frequency, and durations—were measured for the first two syllables of each word. Both groups of speakers were highly variable. The Americans consistently produced stress syllables with longer durations than unstressed, but varied considerably in their use of fundamental frequency and amplitude. Syllables of words in sentences were shorter than the words in citation form. In contrast, non-native speakers' fundamental frequency and amplitude variability was even greater, and they did not differentiate between stressed and unstressed syllables by means of not differentiate between stressed syllables were too short and the unstressed too long. Lengthening unstressed syllables in sentence context was a characteristic pattern of these non-native speakers.
Time series simulation in shallow water using eigenrays with beam displacement
Authors: Westwood Evan K. , Tindle C. T.
Published: October 2005

A ray model for time series simulation in a multilayered, stratified environment has been extended to include the effects of beam displacement. Beam displacement is important in shallow water and occurs when the phase shift of the plane-wave reflection coefficient at an interface is a function of angle of incidence. The ray paths become frequency dependent, but the dependence is smooth so that a small number of frequency components (three or six) is sufficient to accurately estimate the transfer function of an eigenray with beam displacement. The caustics and shadow zones caused by beam displacement are also included. Simulated time series are compared with time series measured in a tank experiment having shallow water over a sand bottom. The significant ray paths have up to 14 bottom interactions, and agreement of the waveforms is good. The usual normal mode features of shallow water propagation arc accurately reproduced. [Work supported by Independent Research and Development Program at Applied Research Laboratories, The University of Texas at Austin.]
A range-dependent normal mode model with full mode coupling
Authors: Robinson E. Richard , Wood David H.
Published: October 2005

A preliminary version of a range-dependent transmission loss model is presented. It assumes that the ocean is piecewise constant in range. Full mode matching at the interfaces is used to compute the acoustic field. Our approach is similar to that used by Evans and Gilbert [Comput. Math. Appl. 11, 795–805 (1985)] in that we also expand the desired normal modes as a weighted sum of depth-dependent basis functions. As is well known, this “Galerkin method” leads to a linear algebraic problem for the unknown weights. However, our approach is different because we insist on using other basis functions that lead to structured algebraic problems, where fast techniques are available. The future development of a fast version of this model will exploit this special algebraic structure. Implementation within the generic sonar model is used because this allows for considerable flexibility in updating developments and the choice of supporting submodels.
Comparisons between A-weighted sound-pressure levels in the field and those measured on people or manikins
Authors: Kuhn George F.
Published: October 2005

The A-weighted sound-pressure levels for 75 different industrial noise spectra were determined. Previously published sound-pressure level transformations by Kuhn and Guernsey [J. Acoust. Soc. Am. 73, 95–105 (1983)] from the field, either progressive or diffuse, to the body or head surface were applied to these noise spectra and the resulting A-weighted sound-pressure levels were calculated. For the most part, a microphone at the torso or head measures a larger A-weighted sound-pressure level than a microphone in the unobstructed sound field. The range of the resulting measurement error, due to the presence of the body or the head, is approximately − 1 dB(A) to + 5 dB(A). The magnitude of the error is sensitive to the type of sound field, the subject's orientation relative to the angle of incidence of the sound, the noise spectrum, and the microphone location. Other factors, for example, the microphone size and directivity, the distance between the microphone and the body, and the absorption of the sound by different types of clothing will also affect the measurement errors. Although these factors are implicit in some of the reported transformations, their individual, explicit effect on the measurement errors remains to be determined.
The use of personal computers in the calibration of noise dosimeters
Authors: Crivaro Michael A.
Published: October 2005

Personal and handheld computers are used in the acoustical calibration laboratory of the Mine Safety and Health Administration (MSHA), Pittsburgh Health Technology Center. The laboratory was established to calibrate noise dosimeters used by MSHA coal and metal/nonmetal mine inspectors. Equipment was selected to set up new systems and to make existing systems more efficient. Analog signals from some dosimeters are measured by the computer systems and converted to useful information, while other dosimeters come equipped with standard computer interfaces. Programming of the systems was done in-house. This has two advantages. First, the programmer has constant communication with the eventual end users of the system, which results in better planning. Second, the system can be adapted immediately by anyone familiar with the program, when changes in operating procedures become desirable or necessary. In general, the systems are accurate, prevent time-consuming mistakes, and can be made to guide the user through the calibration procedure. The installation of computer controlled calibration systems has proven to be successful.
Acoustic propagation under lapse conditions using fast Fourier transforms
Authors: Lloyd S. R. , Van Moorhem W. K.
Published: October 2005

In this paper the propagation of acoustic waves from a point source above a finite impedance ground under a temperature lapse condition is analyzed. The temperature profile chosen is a model of a fully developed lapse condition that fits the available data. This profile has a large temperature gradient near the ground and asymptotically approaches a finite value high above the ground. An analytical solution of the wave equation with variable sound speed is obtained using Hankel transform techniques. The present study implements a fast Fourier transform technique to invert the analytical solution to real space. Sound pressure level results to horizontal distances of 1000 m have been computed. The results show the expected interference pattern within the insonified region. At distances of a few 100 m from the source a rapid sound pressure decline, indicative of the shadow boundary, is observed. The sound pressure level behavior predicted is in agreement with the limited data available. [Work supported by NASA.]
Acoustic field of a finite array of out-of-phase simple sources
Authors: Akay Adnan
Published: October 2005

Radiation field of a finite array of out-of-phase simple sources is obtained. The results are generalized for monopole, dipole, and axial quadrupole source arrays. Closed-form solutions are obtained for the sound power and radiation efficiency of the array. It is shown that the maximum acoustic intensity of an array of n sources occurs at the coincidence frequency and is proportional to n2. Results for the radiation patterns and efficiencies are given for different array characteristics. [Work supported by NSF.]
Acoustic radiation from bending waves of a plate
Authors: Akay Adnan , Ingard K. Uno
Published: October 2005

Acoustic radiation from bending waves of a plate is reexamined by considering radiation loading of a plate driven by a traveling harmonic force. The results show that the plate displacement vanishes at the coincidence frequency and the coincidence frequency depends on the phase velocity of the forcing function with respect to the speed of sound in the fluid. Viscothermal losses in the boundary layer are also considered in the derivations to examine the effects of these losses on the radiated sound pressure and conversion of mechanical energy into heat below the coincidence frequency. [Work supported in part by NSF.]
Barrier insertion loss with a directional sound source
Authors: Moreland J. B.
Published: October 2005

The purpose of the work described in this presentation is to investigate the effect of source directivity on the sound attenuation of an acoustical barrier. The approach consisted of forming the coherent summation of the sound pressures produced by the source and its image to calculate the sound pressure arriving at the barrier edge, and from that summation, calculate the mean-squared sound pressure arriving at the receiver. This approach accounts for interference phenomena observed when a barrier rests on a reflecting plane. The source directivity can have a considerable effect on the sound field. At a given distance from the source, differences as much as 10 dB were calculated and measured by orientating the major lobe of the source radiation pattern in directions which were between 0 and 90 deg with respect to the reflecting plane. Also, the interference due to ground reflections results in negative insertion loss at distances determined by the source, barrier, and receiver geometry, and the frequency. Finally, the orientation at which maximum insertion loss occurs depends on the distances between the source, barrier, receiver, and ground plane. These results are significant because they show that serious errors (as much as 20 dB) in predicting the insertion loss of a barrier in an otherwise reflection-free environment can result from neglecting the ground reflections.
Sound transmission through foam-lined double panel constructions
Authors: Bolton J. Stuart , Green Edward R.
Published: October 2005

This paper describes the sound transmission performance of foam-lined double panel constructions, in particular, the acoustical effect of two foam mounting arrangements. The foam considered is relatively stiff and partially reticulated, the type most often used in noise control. A recent theory is used to model the foam [J.S. Bolton and E. Gold, J. Acoust. Soc. Am. Suppl. 1 77, S59 (1985)]; the theory allows for both a frame wave and an airborne wave. The applicability of the theory is demonstrated by comparing theoretical and measured transmission coefficients and impulse responses for freely suspended foam layers. The extension of the theory to allow for bonded or unbonded facing panels is then described. It is shown that when the foam lining is bonded directly to the facing panels sound transmission through the foam occurs largely via the high impedance frame wave. As a consequence, the transmission loss of foam-lined double panels is improved, particularly at low frequencies, when the lining and panels are separated by a small air gap; in this case a larger fraction of the energy is carried by the more heavily damped airborne wave.
Glazing sound transmission loss studies
Authors: Tocci Gregory C. , Foulkes Timothy J. , Wright Randolph E.
Published: October 2005

Monsanto has recently commissioned sound transmission loss tests at Riverbank Laboratories on various glazing configurations, including single thickness, air spaced, and laminated glass. Comparisons of various parameters such as STC, glass thickness, total glazing thickness, and noise reduction performance for various noise sources are made. These data have also been used to assemble glazing cost versus STC relationships that are useful for the building design prefessions. The presentation will also include a comparison of laboratory test data versus field performance for some of the glazing systems. [Work supported in part by Monsanto.]
Nonsymmetric effect in finite amplitude sound beams radiating from a baffled circular transducer
Authors: Miao H. C. , Ginsberg J. H.
Published: October 2005

Prior investigations of nonlinear effects in sound beams have treated cases where the transducer oscillates axisymmetrically. Here, an analysis of a situation where the harmonic spatial vibration of the transducer has a cos θ dependence on the azimuth angle, as would be the case for a piston that rocks about its diameter, shall be presented. The method of investigation parallels that employed earlier [H. C. Miao and J. H. Ginsberg, J. Acoust. Soc. Am. Suppl. 1 78, S39 (1985)], which used the King integral to generate nonlinear source terms. A dual asymptotic description based on assumptions appropriate to the regions very close to, and far from, the beam axis is obtained, and then reconciled to obtain a uniformly accurate description. An intermediate form of the solution featuring coordinate straining transformations is converted to a Fourier time series. The linearized signal shows nodal lines in the azimuthal direction that match those of the transducer vibration, and it shall be shown that the higher harmonics exhibit similar behavior. [Work supported by ONR, Code 425-UA.]
The nonpropagating hydrodynamic soliton in annular geometries
Authors: Everbach Erich Carr , Apfel Robert E.
Published: October 2005

The nonpropagating hydrodynamic soliton discovered by Wu et al. [Phys. Rev. Lett. 52, 16 (1984)] exists as a localized finite amplitude disturbance in a parametrically excited rectangular channel. The behavior of the nonpropagating soliton in annular resonators of various radii of curvature is investigated. The distortion of the soliton profile, which increases with decreasing radius of curvature, suggests that as energy is moved from lower to higher wavenumbers, the dispersion must increase to balance the increasing nonlinearity. At a critical radius of curvature, the soliton changes form. As the inner annular radius decreases further, the soliton merges with a nonlinear mode of the circular tank. This mode resembles the (1,2) normal mode in that it consists of a localized maximum-minimum pair, but occurs at a frequency slightly below that of the (0,2) normal mode. The behavior and properties of this nonlinear “sub-(0,2)" mode are compared to that of the one-dimensional nonpropagating soliton. [Work supported by ONR.]
Numerical solution of Burgers' diffusion equation for arbitrary waveforms
Authors: Mellen R. H.
Published: October 2005

By transformation of the functional argument, Burgers' nonlinear equation for plane waves in dissipative fluids reduces to the diffusion equation. An “exact” solution for an initially sinusoidal wave has been obtained [D. T. Blackstock, J. Acoust. Soc. Am. 36, 534–542 (1964)]. The advantage is that the waveform can be calculated for any range without iteration. Solutions are also possible for initial waveforms of arbitrary shape by using computer methods to determine the Fourier coefficients. Effects of phase reversal of sawtooth waves at a pressure-release surface are estimated. No simple solutions have been found for nonplane waves; however, effects of phase quadrature in refractive media can also be approximated by neglecting divergence and the local details of the caustic region. Waveform distortion, “N-wave” formation, migration of the spectral energy, and chaotic properties of random noise are illustrated.
Observation of focal shift of a convergent beam: Another Rayleigh angle phenomenon
Authors: Nagy Peter B. , Cho Kangra , Adler Laszlo , Chimenti Dale E.
Published: October 2005

The nonspecular reflection of acoustic beams at critical angles, especially at the Rayleigh angle, has been widely studied. An interesting detail, the focal shift of convergent ultrasonic beams, was recently predicted by Bertoni et al. [Trait. Sign. 2, 201–205 (1985)]. Their analysis shows that the axial displacement could be much higher than that of the better known lateral Schoch displacement. However, because the acoustic fields of well-collimated beams change much slower along the axis of the beam than in the laterial direction, this effect is less pronounced. It is shown that by carefully choosing the acoustical and geometrical parameters of a convergent beam, this otherwise rather weak effect is readily detectable. The cylindrically focused beam of a 10-MHz transducer of φ10-mm diameter and 100-mm focal length was reflected from a water-aluminum interface. It is shown by Schlieren photography, that much below, exactly at, and much above the Rayleigh angle there is no focal shift, while slightly below and above the Rayleigh angle the focal shift was found to be a few centimeters in negative and positive directions, respectively, which is in good qualitative agreement with theoretical predictions.