bluuebunny/crossref_metadata_2025 huggingface dataset:
Quieting of axial flow fans through blade design
Authors: Gray Leslie M.
Published: October 2005

The noise of an axial fan can be significantly reduced by carefully designing the blade shape for the local fan environment. Reduction in both the broadband spectrum of fan noise and of fan tones by >8 dBA are achievable, with no loss in fan efficiency. This paper presents some of the acoustic and aerodynamic design factors that must be correctly accounted for in the fan design. Results are shown for three successful low noise fan designs, where careful attention was paid to three-dimensional flow effects. Some of the pitfalls of low noise fan design are outlined.
Determination of sound power levels of large fans in power plants
Authors: Nuspl Steve P. , Hickman Charles E. , Fearing Harold A.
Published: October 2005

In an attempt to comply with noise regulations, the electric power industry is developing methods to predict noise levels in and around generating facilities. Predictive techniques require data on sound power levels of plant equipment. An extended two-surface method has recently been used to determine sound power levels of large fans in a power plant environment. The method has been used extensively and successfully for similar measurements around coal pulverizers. The measurement method is summarized and problems encountered with the method as it applies to large fans are discussed. The results of the two-surface method measurements are presented. The possibilities of the method and areas in need of future work are noted.
Compared ototoxicities of gentamicin, tobramycin, and dibekacin: A functional and morphological study in guinea pigs. Part I: Cochlear study. Part II: Vestibular study
Authors: Aran Jean-Marie , Erre Jean-Paul , Guilhaume Anne , Aurousseau Catherine , Casals Yves
Published: October 2005

Pigmented guinea pigs were treated with daily subcutaneous injections of gentamicin, tobramycin, and dibekacin, respectively, at the dose of 90 mg/kg/day for 20 consecutive days. The cochlear function (thresholds of click evoked potentials at the auditory cortex) and the vestibular function (number of electronystagmographic saccedes during damped sinusoidal rotatory oscillations) were monitored before, during, and after the treatment in some guinea pigs chronically implanted with temporal cortex and periocular electrodes. Other simultaneously treated guinea pigs were similarly implanted and tested but only at the end of the experiment, just before sacrifice (from 30 to 100 days post Rx). The structure of the cochlear receptor (surface preparations) and of the vestibular receptors (serial sectioning) of one ear were evaluated quantitatively while the other ear was observed in scanning electron microscopy. These functional and morphological observations, which correlate very precisely, indicate that, in such experimental conditions, gentamicin has been highly cochleo- and vestibulotoxic, dibekacin on the contrary has been only, and to a lesser degree, vestibulotoxic while tobramycin appeared cochleotoxic rather like gentamicin and vestibulotoxic more like dibekacin. [Work supported by Inserm grant 8-ASR-6 Oreille interne.]
Effect of iodoacetic acid upon cochlear potentials
Authors: Kobayashi T. , Ise I. , Marcus D. C. , Thalmann R.
Published: October 2005

Lotz et al. [Inner Ear Biology, INSERM, 233 (1977)] reported that perilymphatic application of 5 × 10−3 M iodoacetic acid (IAA) does not influence the first-order cochlear microphonics (CM1). However, in ischemia the rate of decline of CM11 was significantly increased by IAA. The authors concluded that glycolysis plays no role in the maintenance of the CM1, but that it is responsible for supporting the CM11. In carefully controlled experiments we were unable to reproduce these findings. Both the endolymphatic potential (EP) and the CM declined drastically due to perfusion with 5 × 10−3 M IAA (within 10 min the EP dropped to −58 ± 4.5 mV (SD), and the CM declined to about 6% of the control). The CM was abolished after 45 min of perfusion with 5 × 10−3 M IAA, while it persisted for periods exceeding 120 rain in total anoxia. We cannot account for the discrepancy between our findings on CM1 and those of Lotz et al. Nevertheless, our experiments confirm the hypothesis that the CM11 is supported by anaerobic glycolysis. In addition, we observed an anoxia sensitive negative component of the EP in severe intoxication with IAA, a phenomenon hitherto considered peculiar to intoxication with “loop” diuretics. [Supported by NIH grant NS06575.]
Transient residue pitch changes by adaptation
Authors: Hall Joseph W. , Soderquist David R.
Published: October 2005

The effect of pitch adaptation by a complex stimulus was examined in two experiments. In experiment 1 a monaural residue pitch change was measured after ipsilateral or contralateral complex stimulus adaptation. While ipsilateral adaptation resulted in pitch changes away from the residue pitch of the adapting stimulus, no pitch change occurred for contralateral adaptation. The precision of pitch matching was reduced by both ipsilateral and contralateral adaptation. Experiment 2 examined whether the residue pitch changes in experiment 1 could be accounted for by pitch changes induced in the pure-tone components. Results indicated that changes induced in pure-tone components were too small to account for the residue shift magnitudes found in experiment 1. These results support an independence of residue pitch from the pitches of the pure-tone components. Results also supported pitch extractor specialization for a particular ear of stimulus presentation.
Low-frequency acoustics in shallow water: Experimental and theoretical propagation and noise studies
Authors: Schmalfeldt Bernd , Rauch Dieter
Published: October 2005

Digital three-component ocean-bottom seismometers (OBS) with radio link have been developed to study extremely low-frequency sound propagation (about 1–15 cps) in coastal waters (mainly below the cutoff of the shallow-water duct). They have been deployed successfully in conjunction with variable depth hydrophones during several sea trials in the Mediterranean. By recording the hydroacoustic and seismic signals from small underwater explosions and by the power and cross spectra of ambient and ship-induced noise, it has been demonstrated that the infrasonic energy is mainly transmitted via a seismic interface wave. In general this propagation mode may be termed a modified Scholte wave as it is guided by the acoustically most significant interface between water column (including liquid-type sediments) and solid basement. The very particular features of this wave type are investigated in detail with the help of different software packages, and a theoretical study has been made using a seismic fast field program to model the geoacoustic waveguide.
Aspect-independent cylinder discrimination by human observers using broadband sonar pulses
Authors: Martin Douglas W. , Au Whitlow W. L.
Published: October 2005

An experiment was conducted to determine the capabilities of four human subjects to discriminate broadband sonar echoes from cylindrical targets independent of target aspect. Digital recording of target echoes were obtained using dolphinlike echolocation signals, and played back to the subjects at 150 of the original sample rate. The targets, which were 17.8 cm long and 7.62 cm in diameter, included cylinders of solid aluminum and rock, hollow water-filled steel, and hollow aluminum filled with water, air or powder. The subjects were first trained to discriminate between a pair of targets at 0°, 45°, and 90° until performance reached 100% correct at each aspect. Next the subjects were trained until they achieved near perfect performance with the three target aspects occurring randomly during a session. The subjects' abilities to generalize discrimination cues from the three previously learned aspects were measured by randomly presenting target echoes from seven aspects during a session, four of which were new aspects. For target pairs involving hollow aluminum versus rock, hollow versus solid aluminum, and solid aluminum versus rock, the subjects' scores for the new signals were between 75% and 85% correct on their first sessions. This performance improved to approximately 95% for all subjects, after seven sessions. The results indicate that the subjects could generalize discrimination cues independent of the target aspect. With a few exceptions, the verbal cues for each target pair were similar across subjects.
Velocity discrimination by the echolocating bat Noctilio leporinus
Authors: Wenstrup Jeffrey J. , Suthers Roderick A.
Published: October 2005

Two echolocating, fish-catching bats (Noctilio leporinus) performed a discrimination between sequentially-presented targets moving parallel to the bats' flight path and differing in the velocity of movement. The target, a small hemisphere placed on a wire, was moved by means of a submerged track in an artificial pond. The bats learned to dip their hind claws at the target if it moved at the lesser of two velocities (25 cm/s), and to avoid the target if it moved at a greater velocity. Both animals were able to perform the discrimination above the chance level (p < 0.001, binomial test) until the faster target was reduced to within 35–45 cm/s of the slow target. The bats continued to perform the discrimination in darkness, and when possible cues related to the size of the wake, motor sounds, or target position were eliminated. Both bats used sonar pulses which included a constant-frequency component and are consistent with the hypothesis that these bats employ Doppler-shift information to discriminate velocity, although the use of successive range determinations for velocity discrimination cannot be excluded. [Supported by NSF grant BNS 79-05606.]
Determination of behavioral refractory period in anuran amphibians
Authors: Narins Peter M.
Published: October 2005

Some species of calling frogs respond to particular acoustic stimuli by changing the temporal pattern of their vocalizations. One form of temporal alteration is the production of a call note quickly following and synchronized to another frog's vocalization. Synchronization of one frog's call to another frog's vocalization (trigger) may be viewed as an adaptation for acoustic avoidance in highly noisy environments. This simple strategy ensures that the call will (1) not be interfered with and (2) be detected by the frog initializing the interaction. It was hypothesized that the ability of a frog to synchronize should be a function of the elapsed time since his previous call. To test this, a series of behavioral experiments were carried out with the treefrogs Eleutherodactylus coqui and Hyla ebraccata in their natural habitats. Pure tone stimuli (3 kHz) triggered by the frog's own call were presented with a digitally controlled delay which could be varied from 1 to 5000 ms. E. coqui was incapable of synchronizing to stimuli occurring less than 800 ms after its previous call, whereas H. ebraccata could typically synchronize to stimuli presented less than 400 ms after its previous call. These times, referred to as behavioral refractory periods, are correlated with the density of calling males for each species.
Perception of CV syllables, words, and sentences by listeners with speech/language disorders
Authors: Elliott Lois L. , Clifton Lu Ann B.
Published: October 2005

Developmental differences in the performance of normal 6- and 10-year-old children and young adults, for a group of tasks that includes detection, identification, and labeling of synthesized CV syllables [ba, da, ga] have recently been reported [L. L. Elliott et al., “Developmental differences in identifying and discriminating CV syllables,” J. Acoust. Soc. Am. 70, 669 (1981); L. L. Elliott et al., “Detection and identification thresholds for consonant-vowel syllables,” Percept. Psychophys. (in press)]. We now describe performance on these tasks, the NU-CHIPS Test, and the SPIN Test for a group of children and adults with speech and/or language disorders. Results showed that: (1) all subjects performed more poorly than normals on one or more of the tasks; (2) they performed poorly on different tasks; (3) poor performance on the experimental tasks could be related to subjects' individual speech/language problems; and (4) aberrant performance on these tasks was not predictable from performance on standard clinical tests.
A hierarchy of cues to intervoealic /S/
Authors: McCasland George P.
Published: October 2005

Twelve tokens each of /SiSi, SiSa, fifi, fifa/ were recorded by one male speaker and manipulated in a PCM system. Duration and intensity of each segment were measured. A matched pair of /SiSi, SiSa/ tokens was edited to produce additional tokens in which the intensity of /S2/ noise was reduced in 3-dB steps. Control variables were: /S2/ noise duration; /S1/ noise present or absent; final vowel. A very strong relationship between /S2/ noise intensity and % /S2/ percepts was apparent in the data from 10 subjects who listened to the stimuli. From 100% /S2/ at natural levels, an 18 dB reduction in intensity shifted the percepts to 2% /S2/, 95% /θ, f/, 3% /p, t/. There was a nonoverlapping intensity differential between /S2/ and /f2/ noise in the measurements from the 48 original tokens. A trade-off between /S2/ noise duration and intensity was apparent in the perceptual data, but not in the measurements from the original /SiSi, SiSa/ tokens. /S1/ present/absent had a consistent but even smaller trading value. Final vowels had no effect. See the pilot study [J. Acoust. Soc. Am. Suppl. 1 67, S39 (1980)]. [Haskins Laboratories provided valuable assistance in processing the speech samples on NICHD Contract No. NIH-71-2420.]
The role of silence in the perception of initial FM-glides
Authors: Pastore Richard E.
Published: October 2005

Recent research with speech stimuli has demonstrated that varying the silent interval between two phonemes can alter the perception of the later phoneme. We synthesized a series of stimuli to investigate the possibility that some of the apparent phonetic role of silence might be explained in terms of the simple interaction of basic acoustic stimuli. We used an adaptive psychophysical procedure to measure the threshold for detecting an FM-glide initial to a steady state time as a function of the glide duration, the intensity of an initial burst of noise, and the silent interval between the voice and the glide onset. The results will be discussed in terms of explanation of the perceptual role of silence for initial position auditory stimuli. [Work supported by Grant BNS 80-03704 from NSF.]
The role of friction and formant transitions in the perception of the English voiced fricatives [v] and [ð]
Authors: Pollack Suzi
Published: October 2005

Using the SYNTH serial software synthesizer [Mattingly, Pollock, Levas, Scully and Levitt, J. Acoust. Soc. Am. Suppl. 1, 69, S83 (1981)], the voiced fricatives [v] and [ð] were produced in initial position before the vowels [iy], [a], and [uw]. Frequencies of both a consonant pole and formant transition onsets (F2 and F3) were varied along continua in order to examine their effect on the perception of the voiced fricatives [v] and [ð]. The range of the formant transition onsets differed for each vowel but the consonant pole varied from 2400 to 4400 Hz in every case. The stimuli were presented in forced choice labelling tests. Preliminary testing indicates that the boundary shift from [v] to [ð] in each vocalic context depends significantly more on the change in formant transition than on the position of the consonantal pole. That is, with rising or relatively straight formant transitions, subjects reported hearing [v] whereas they heard [ð] with falling transitions regardless of the pole position. These results support the findings of previous studies with natural and synthetic speech that formant transitions are indeed important cues for distinguishing between labiodental and dental fricatives. [Work supported by NSF Grant PFR 8006144.]
The contribution of extended CV transitions and aperiodic formant structure to the perception of duration
Authors: Raphael L. J. , Dorman M. F.
Published: October 2005

The results of research previously reported [Raphael and Dorman, J. Acoust. Soc. Am. Suppl 1, 67, S51 (1980)] indicated that CV transitions contribute equally with steady-state formants to the perception of that vowel duration which can cue consonant voicing in natural speech. The experiments reported here extend the earlier work by considering the contributions of /r/ + /V/ transitions and of formants in noise (/h/) to the perception of duration. Under computer control, a single speaker's utterances of /rεd/, /hεd/, and /tεd/ were edited to form /rεd/-/rεt/, /hεd/-/hεt/, /tεd/-/tεt/, and (three) /εd/-/εt/ continua by varying the duration of the quasi-steady-state portion of the vowel /ε/. Listeners were asked to identify the final consonant in the stimuli of each continuum as /t/ or /d/. The locations of the /t/-/d/ boundaries suggest that both extensive periodic transitions and robust aperiodic formant structure contribute equally with periodic steady-state formants to the perception of duration. Implications for measuring vowel duration in stop-initiated syllables will be discussed. [Work supported by NICHD.]
Initial stop voicing perception for cue-adjusted syllables for impaired- and normal-hearing listeners
Authors: Revoile S. , Pickett J. M. , Holden Lisa D. , Talkin David
Published: October 2005

Further work will be presented on voicing cues, specifically for initial stops, used by the hearing-impaired. The set of test syllables /pæd, kæd, tæd, bæd, gæd, dæd/ was randomized 10 times on a list recorded by a male. Based on acoustical analyses, the potential sources of voicing cues in the syllables were: release-burst duration, transition-pattern of vowel onset, and vowel pitch. Among different conditions these cues in the syllables were modified cumulatively, so as to eliminate the contribution to voicing of each cue. The modifications were made through LPC resynthesis and/or waveform deletions. The conditions were administered monaurally at comfortable levels to six normal- and 21 impaired-hearing adults. The syllables of each condition were presented in single-interval identification trials without feedback. Generally, a similar pattern of results was seen between the impaired and the normal groups, although the impaired group performed somewhat poorer. Perception of initial stop voicing was unaffected by equalized vowel pitch. For voiceless stops deletion of the release burst reduced voicing perception for most listeners. However, for voiced stops the burst deletion worsened performance for less than half of the listeners. When the voiced burst and vowel-onset-transitions were removed, voicing perception was reduced for most listeners.
Combining sources of evidence in speech perception
Authors: Massaro Dominic W.
Published: October 2005

A central issue in speech perception research is how the listener evaluates and integrates the multiple sources of evidence in the message. Bottom-up theories stress the contribution of acoustic featural information specifying the identity of small segments of the speech signal. Top-down theories stress the contribution of higher-order linguistic and semantic constraints in the disambiguation of the message. An alternative model is proposed to account for both bottom-up and top-down contributions to speech perception. The critical assumption of the model is that acoustic featural information and higher-order constraints provide independent sources of information. These sources are evaluated and integrated together by the listener. Evidence from experiments varying acoustic featural information, phonological constraints, lexical context, and sentential constraints will be discussed in the framework of the model. [Work supported by NIMH.]
Subjective response to whole-body vibration
Authors: Shoenberger Richard W.
Published: October 2005

Pioneer studies of subjective response to whole-body vibration were mainly directed toward construction of equal intensity contours, described by such subjective labels as “intolerable,” “alarming,” or “annoying.” In a series of more recent investigations, carried out at AFAMRL, psychophysical measurement and scaling techniques have been adapted for use in whole-body vibration experiments, primarily to evaluate the intensive dimension of various types of vibration environments. A program of research is described in which the methods of magnitude estimation and intensity matching (a variation of cross-modality matching) have been used to construct a family of Z-axis equal intensity curves in the whole-body resonance frequency range; investigate subjective response for frequencies below 1 Hz; evaluate alternative methods for assessing the severity of multifrequency and random vibrations; and compare the subjective intensity of vibrations in various translational and angular modes. Results from these experiments have contributed to the expansion and improvement of whole-body vibration exposure criteria. [The voluntary informed consent of the subjects used in this research was obtained as required by Air Force Regulation 169-3.]
Sound transmission as a probe of ocean internal waves and microstructure
Authors: Flatté Stanley M.
Published: October 2005

The general theory of sound transmission through a fluctuating ocean is reviewed. The connection between sound fluctuations and the underlying ocean-medium fluctuations is described in terms of a physical picture derived from the path-integral technique. Quantitative comparison between the theory and several recent ocean-acoustic experiments is discussed, as are limits of validity and accuracy of the theory in the face of experimental uncertainty in the deterministic sound-speed profile. Prospects for future use of sound transmission as a probe of ocean statistical processes are summarized.
Fluctuations of resolved acoustic multipaths at long range in the ocean
Authors: Spiesberger John L. , Worcester Peter F.
Published: October 2005

A phase-coded signal centered at 220 Hz with 64-ms resolution was transmitted at 10-min intervals between an acoustic source moored at 2-km depth and a bottom-mounted receiver at ∼3-km depth and at ∼900-km range. A variety of fluctuation statistics (pulse and CW) are computed for three resolved multipaths from a 32-day record. The fluctuations are compared with theoretical predictions based on internal wave scattering. Some measurements agree with theory; measurements that disagree differ by amounts that are statistically significant but not large. Uncertainty of the internal wave energy level could account for some discrepancies. Some theoretical results are very sensitive to small changes of the second derivative of the mean sound speed profile. There are substantial fluctuations at frequencies below those that can be accounted for by internal waves.
Acoustic tomography applied to imaging the oceanic mesoscale field
Authors: Cornuelle Bruce
Published: October 2005

In the spring of 1981, an acoustic tomography experiment consisting of 4 moorings with low-frequency (224 Hz) sources and 5 moorings carrying receivers was deployed as an array about 300 km on a side centered at approximately 26 N, 70 W. Subsurface moorings were used in order to minimize motion, so that the acoustic instruments were placed at about 2100-m depth, well below the sound channel. The array was sited in a region of moderate mesoscale activity, overlapping the MODE region somewhat, and CTD surveys during the experiment showed a cold eddy in the experimental area, with 2- to 3-degree amplitude at 500-decibars depth. Rays traveling from a source to a receiver within a volume of ocean sample the velocity and sound speed of the water along their propagation paths. The fields of dynamic significance are coupled to the acoustic fluctuations primarily through sound speed changes, so that the ability of a tomographic array to directly measure a given feature is partly limited by the degree to which the feature affects the sound speed. At present, acoustic travel times from source to receiver are the primary data to be used for the estimation of the mesoscale fields. Estimates are produced using both statistical optimal estimation and deterministic linear inversion. These are similar techniques with somewhat different limitations and capabilities. The performance of the inverse methods can be evaluated relative to each other and to the CTD data to yield checks of resolution, accuracy, and noise sensitivity. This array thus provides a theoretical and experimental test of tomography as a system for studying the mesoscale variability.
Theory of propagation in fluctuating oceans using the radiation fransport equation
Authors: Tappert F. D.
Published: October 2005

A new theory of low-frequency deep ocean propagation has been developed based on the radiation transport for randomly fluctuating oceans. Using the Fokker-Planck approximation and a novel ray-bundle approximation, we have derived analytic solutions for the means and spreads of arrivals. The mean arrival is predicted to differ significantly from the unscattered arrival, but the spreads are predicted to be greatly suppressed relative to spreads in an unchanneled medium. Thus the “3/2 law” of Chernov becomes a “1/2 law” due to the sound channel itself. Further, a new Λ parameter has been derived which is nonsingular at caustics and saturates at small values at large range. [Work supported by ONR and NSE.]
Measurements of transmissions fluctuations for three long ranges in the deep ocean
Authors: DeFerrari H. A. , Davis R. I.
Published: October 2005

Pulse-like signals were transmitted continuously between a moored source and a fixed bottom-mounted receiver located 700 m below the deep sound channel axis. The source was deployed at three ranges: 210, 412, and 563 km. A second mooring measured temperature fluctuations caused by internal waves and source mooring motion was also measured. The duration of the transmitted pulse was approximately 9 ms (4 cycles of 459-Hz carrier). Several distinct RR arrivals have travel time consistent with ray theory predictions. Statistics of fluctuations for the individual paths and the combined multipath are computed and compared with predictions of the theory of scattering from internal waves. Those fluctuations associated with travel time (Phase pulse-to-pulse coherence, etc.) are consistent with a priori model predictions. Statistics of intensity fluctuations for all paths are typical of saturated multipath interference, a result difficult to reconcile with model prediction even when ambiguities in the computation of the defraction parameter are taken into account.
A reconsideration of acoustic invariance for place of articulation in stop consonants: Evidence from cross-language studies
Authors: Lahiri Aditi , Blumstein Shiela E>
Published: October 2005

It has been claimed that the gross shape of the onset spectrum provides invariant properties for place of articulation in stop consonants [Blumstein and Stevens, J. Acoust. Soc. Am. 66, 1001–1017 (1979)]. We have examined the gross shape of the onset spectra for diffuse stop consonants (labial, dental, and alveolar) in French and Malayalam to test these theoretical claims across different languages and found that (1) although alveolar consonants in Malayalam had the diffuse-rising shape, contrary to theoretical predictions, the dental consonants were diffuse-flat (2) French dental consonants were also diffuse flat and could not be distinguished from labial consonants. We explored whether an alternative measure could capture the theoretical claims that (1) there is acoustic invariance for place of articulation, and (2) the properties for such invariance reflect a predominance of low-frequency energy for labials and a predominance of high-frequency energy for alveolars and dentals. We compared the change in distribution of energy from stimulus onset relative to the onset of the vowel steady state. After visual inspection, a set of measurement procedures were developed and tested on 300 utterances from French, Malayalam, and English. Over 85% of the data was correctly. classified. [Supported by an NIH Grant.]
Deep-to-shallow water sound propagation: A comparison of model predictions
Authors: McDaniel Suzanne T. , Lee Ding
Published: October 2005

In many ocean environments, the major range-dependent feature is the variation in water depth with range. There are presently several wave theoretic means of modeling transmission loss in range-dependent environments. These include various implementations of the parabolic approximation, adiabatic normal-mode theory, and solutions to the coupled mode equations. In this paper, we consider sound transmission in an environment in which the coupling between modes plays a dominant role in propagation. Numerical results are obtained using four different transmission loss models, the results are compared, and the limitations of each model discussed. [Work supported by NAVSEA.]
Numerical calculation of bounds on array performance using the parabolic-equation technique
Authors: Palmer David R. , Blodgett Marilyn L.
Published: October 2005

The standard approach to the problem of determining the effects of ocean variability, i.e., internal waves, on system performance is to measure or calculate the mutual coherence function for the acoustic field since it enters directly into measures of system performance such as array gain. Because of difficulties in determining this quantity, we have taken a different approach. Rather than attempting to calculate, e.g., array gain, we seek only to bound it. Consequently, we calculate a limit on the degradation in system performance. The advantage of this approach is that the limit depends only on the mean pressure field, a quantity easier to calculate than the mutual coherence function. The calculation of the mean field does require, however, the use of a generalization of the Markov approximation appropriate when diffracting and refracting effects are present. With this approximation the calculation of the mean field can be carried out with a slightly modified version of the parabolic-equation technique of Tappert and Hardin. A case study is made for propagation in the Western North Atlantic.
Adiabatic modes for up-slope propagation in a wedge-shaped ocean
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

Recent numerical studies of upslope propagation in a wedge-shaped ocean with penetrable bottom [F. Jensen and W. Kuperman, J. Acoust. Soc. Am. 67, 1564–1566 (1980)], have revealed that intermode coupling is negligible for small bottom slopes but that each range-dependent adiabatic trapped mode field is strongly perturbed when that mode passes through cutoff. This observation has revived interest in extending the description of an adiabatic mode field through the transition region from trapped to radiating [A.D. Pierce, J. Acoust. Soc. Am. Suppl. 1 69, S69 (1981)]. We present a procedure of inherent general validity for range-dependent waveguides whereby an initial ray-acoustic field undergoing multiple reflection is converted into local mode fields by Poisson summation. Before the conversion, a plane-wave spectrum is fitted to the ray family, and the resulting Poisson-transformed spectral integrals, after asymptotic evaluation by the stationary phase method, are found to produce the conventional adiabatic trapped modes downslope from their cutoff points. As mode cutoff is approached, the simple stationary phase procedure must be modified, and the transformed spectral integrals become “canonical integrals” that trace the transition of a mode uniformly from the trapped to the radiating (leaky) regime. Results are shown for the transition function and its connection to the trapped and leaky mode fields downslope and upslope from the cutoff region. [Work supported by ONR Ocean Acoustics Branch.]
A real-time voice fundamental frequency acquisition and processing system
Authors: Stilwell Donald J. , McCutcheon Martin J. , Hasegawa Akira , Fletcher Samuel G. , Smith Stephen C.
Published: October 2005

The system was designed to measure voice fundamental frequency by zero-crossing detection of the filtered output of a miniature piezoelectric accelerometer placed on the throat. Relatively inexpensive hardware provides a host computer with a cycle-by-cycle pitch period information with a resolution of 10 μs. Tests indicate the instrument operates reliably for male and female speakers of a wide variety of ages under varying phonatory conditions including breathy voicing. Performance evaluations and applications as a research tool and a speech training aid will be presented.
Acoustical characteristics of primary syllabic stress in excellent esophageal speakers
Authors: McHenry Monica , Reich Alan , Minifie Fred
Published: October 2005

Primary syllabic stress appears to be controlled by a complex interaction of fundamental frequency (∫0), sound pressure (SP), duration, and formant frequency position [D. Fry, Language and Speech 2, 126–151 (1959)]. Because esophageal speakers typically exhibit reduced ability to manipulate ∫0, SP, and duration, it seems unlikely that they would be able to approximate normal prosodic patterning. This study investigated the ability of excellent esophageal speakers to manipulate acoustical characteristics associated with primary syllabic stress. Five excellent esophageal speakers and five sex and age-matched normals produced 10 sentence pairs, each containing a bi-syllabic stimulus item differing only in primary stress placement. The mean ∫0, SP, and duration of the stressed and unstressed vowel nuclei were analyzed. Although some differences in absolute levels were apparent, only sound pressure level differences reached statistical significance. For both groups, primary stress was associated with a comparable pattern of increased ∫0, SPL and duration. The findings of this project were interpreted to mean that excellent esophageal speakers are capable of producing primary syllabic stress in a fashion that is remarkably similar to normals.
Coarticulation in French consonant clusters
Authors: O'Shaughnessy Douglas
Published: October 2005

Formant speech synthesis requires an adequate model of how formants vary with time in natural speech. While the general formant targets for phonemes in languages such as French are well known, the effects of coarticulation and undershoot of targets in various phonetic contexts are less well established. Toward the goal of French synthesis-by-rule with timing and formant transitions based on natural speech, 285 words were read in frame sentences by a French Canadian and analyzed via digital spectrograms for durations, formants, and bandwidths. Examples of all possible consonant clusters were examined, including those not found in English (e.g., “pluie”). While most formant transitions could be well modelled in terms of simple targets and time constants, the glides and liquids (/l, r, w, j, ɥ/) were highly variable in consonant cluster contexts. For example, /r/ was devoiced next to an unvoiced consonant, and the formants for /l/ indicated different articulatory positions depending on context. The presence of a liquid in word-final stop + liquid clusters (e.g., “tigre”) was noted primarily by extending the aspiration period following stop release, rather than releasing the liquid into a schwa vowel.
Spweech synthesis from measured vocal tract shapes
Authors: Sondhi M. M. , Resnick J. R.
Published: October 2005

The talk will describe our recent experiments on estimation of vocal tract area functions from acoustical measurements at the lips. Since the theoretical basis for such measurements has been discussed in several earlier publications, we will concentrate on the experimental aspects. The two main accomplishments we will report on are: (1) We are now able to make measurements, compute and display the area functions in real time (16–20 frames per second). This speed of reconstruction has never been possible before. (2) We have synthesized reasonable good quality speech from a number of sentence-length sequences of measured area functions. Some attempts at synthesizing steady vowels from such measurements have been reported in the past. However, to the best of our knowledge, this is the first instance of continuous speech synthesized from direct acoustical measurements of area functions. We will present examples of time-varying area functions and corresponding synthesized speech signals.
Analysis-by-synthesis method for determining optimal excitation for natural-sounding LPC speech synthesis
Authors: Atal B. S. , Remde J. R.
Published: October 2005

LPC speech synthesis uses two separate excitation signals—a delta-function pulse once every pitch period for voiced speech and white noise for unvoiced speech. This way of representing excitation requires that speech segments be classified accurately into voiced and unvoiced categories and the pitch period of voiced segments be known. It is now well recognized that such a rigid idealization of the excitation is often responsible for the unnatural quality associated with synthesized speech. We find that a more flexible representation of the excitation is necessary for producing natural-sounding speech. This paper presents an analysis-by-synthesis procedure for determining the optimal excitation for LPC synthesis (at different bit rates) without requiring prior knowledge of either the voiced-unvoiced classification or the pitch period. The excitation is found by minimizing the perceptual difference between waveforms of the original and the synthetic speech signals using a noniterative procedure. The perceptual difference metric takes account of the finite frequency resolution and the masking properties of the human hearing mechanism.
Modeling of reverberation rooms
Authors: Tichy Jiri
Published: October 2005

In recent years, progress in the knowledge of statistical properties of the sound fields allowed improvements in the precision of the measurements in reverberation rooms. A great number of experiments, particularly with rotating diffusers, has been conducted in down-scaled model rooms. This paper presents criteria for the scale modeling as well as comparison with the results obtained in full size rooms. Also, a summary of reverberation room properties will be given.
Evaluation of barrier shapes by acoustic scale modeling
Authors: Hajek Jerry J.
Published: October 2005

A 116 scale-model study (using a high-voltage spark as a noise source, and modeling typical highway situations and materials) was undertaken to compare the acoustical performance of several common highway noise barrier shapes, namely, reflective thin walls, earth berms, and in particular, the combination of the two. It was suspected that additional scattering and absorption losses, which can occur along the top of an earth berm, may be lost if a low thin wall is erected atop the berm. A change of several dB due to the change in the barrier shape may be considered significant, since the field insertion losses of noise barriers are usually in the range of 5 to 10 dB A. Thin reflective walls and earth berms of the same height were found to be equally effective. Results also indicate that the acoustical performance of an earth berm (a) is not compromised by erecting a relatively low thin wall on its top, and (b) may be improved by placing sound absorptive material atop the berm.
Demonstration of acoustical scale modeling
Authors: Cann R. G.
Published: October 2005

Acoustical scale modeling is possible because all the acoustical phenomena observed in the environment can be duplicated in scale. These can be clearly demonstrated using an impulsive sound source and an energy analyser. Absorption—The sound level reflected from a porous surface can be compared with the incident level to determine the noise reduction coefficient. Scattering—Multiple surfaces such as those forming the fenestrations of buildings, distribute sound but do not absorb it. The levels of specular and nonspecular reflections can be compared. Diffraction—For barriers, the relationship between noise reduction and Fresnel number can be seen. Factors that reduce the barriers effectiveness can be readily investigated. Reflection—The buildup of acoustical images can be observed as walls are added to form an interior space. Flutter, focussing and other characteristics can be observed. Ground effect—Sound traveling at grazing incidence across grassland can show a level reduction of up to 15 dB in mid- and low-frequency bands. In specific situations, obstacles reducing grazing may increase sound levels.
Ultrasonic backscattering from random rough solid interfaces
Authors: de Billy Michel , Quentin Gerard J. , Adler Laszlo
Published: October 2005

The angular variations of the mean backscattered intensity of ultrasonic waves by randomly rough surfaces of elastic solids are analyzed. The theoretical approach is based on the potential method. The calculations have been done for a normal distribution of heights and a Gaussian autocorrelation function. The experiences have been done at discrete frequencies and the roughness of the samples varied from 8 to 110 μm. (10−2 ⩽ g = k12h2γ2 ⩽ 90). A good agreement between theoretical and experimental curves is observed for the angles of incidence ⩽ 40°. Another feature of the experimental data is the increase of the backscattered intensity at the Rayleigh angle for k1h ⩽ 1. Results of this study have been applied to surface and bulk defects with rough surfaces.
Present status of elastic wave inverse scattering techniques
Authors: Thompson R. Bruce
Published: October 2005

Recent progress in the development of elastic wave inverse scattering techniques to size flaws in solids is reviewed. A summary of the underlying physical models for forward scattering is first presented. This is followed by a more detailed discussion of development and experimental evaluation of inverse scattering techniques, spanning regimes in which the wavelength is large, comparable, or short, with respect to the flaw size. Included are discussions of the sensitivity of the techniques to such nonideal conditions as irregularly shaped scatterers, material anisotropy, beam focusing, and finite measurement bandwidth and aperture. Throughout the paper, the similarities and differences between the elastic and acoustic wave cases are noted.
A comparison of ray tracing and exact methods for scattering from flaws
Authors: Chou C. H. , Khuri-Yakub B. I. , Kino G. S.
Published: October 2005

The exact theory of Ying and Truell has been evaluated for scattering of waves from voids and inclusions in a surrounding isotropic matrix. The scattering has been determined both in the frequency domain and in the time domain for an incident band-limited pulse to provide a good comparison with experiment. The theory can be interpreted well by a ray tracing analysis. This ray tracing analysis has been carried out in some detail. We get good quantitative agreement with the exact theory for spherical voids and inclusions if the ratio of diameter to wavelength is sufficiently large. The advantage of the ray tracing theory is that it can also be used for other shapes. Some examples for ellipsoids will be given.
Effects of closure on the detection probability of fatigue cracks
Authors: Buck O. , Skillings B. J.
Published: October 2005

Fatigue cracks often can be (more or less) tightly closed. Under such “closure” conditions the crack may be transparent to ultrasound and actually form electrical contact between fracture surfaces, diminishing the eddy current response with respect to the fully open crack. In addition, external environments, which affect the crack propagation rate, also change the state of closure. The present paper reports on a recently developed model which seems to describe this closure phenomenon and aids in the interpretation of NDT data such that the crack size can be determined even for tightly closed cracks.
The full acoustic wavetrain in a laboratory model os a borehole
Authors: Chen S. T.
Published: October 2005

We have studied the characteristics of acoustic wave propagation in a fluid-filled borehole, using as a laboratory model a cement cylinder 2 ft in height and 2 ft in diameter with a 14 in. borehole at the center. We recorded a full wavetrain consisting of a refracted compressional (P) wave, a refracted shear (S) wave, a number of modal waves, and a Stoneley wave. Exploiting the dispersive properties of the modal waves and the source-receiver frequency characteristics, we were able to isolate the S wave, which has important applications in petroleum exploration, but which has not been widely used since it is difficult to extract from the full wavetrain in sonic logging. The observed Stoneley wave had a very high amplitude at low frequency and showed little dispersion. The Stoneley wave velocity is closely related to the S-wave velocity, and can be used as an indirect means to obtain the S-wave velocity. In general, the arrival time of each component wave agreed with theory, but the amplitudes of the component waves did not.
Transverse vibration of uniform and nonuniform, internally damped cantilever beams
Authors: Kerlin Roger L.
Published: October 2005

The driving-point impedances and transmissibilities of uniform cantilever beams in transverse vibration have been measured experimentally. Although the impedances were recorded with a commercial impedance head, the experimental procedures developed permitted measurements to be made through a far greater dynamic range (6 × 106) than reported hitherto. The measured impedances of metal alloy beams compare closely with the predictions of theory. The transmissibility of an aluminum beam has been measured in three reciprocal experiments that successfully substantiated the theoretical prediction that extensive regions of attenuation occur in the transmissibility of a beam (1) when it is driven by identical but suitably located dual forces, (2) when it is mass loaded at a point intermediate to these dual forces, and (3) when these forces originate from resilient mountings that support a force-excited mass. The driving-point impedances and transmissibilities of internally damped nonuniform cantilever beams have been derived in closed form and computed in representative cases. Truncated beams with rectangular cross section have been considered with linearly tapered depth and with breadth (1) constant, (2) varying parabolically, and (3) varying hyperbolically such that the beam cross-sectional area remains constant. A cantilever with three stages of arbitrarily different lengths and cross-sectional areas has also been considered. The measured transmissibility of one such beam, and the resonance frequencies of eight other nonuniform beams compare well with the predictions of theory.
Development of a community noise control program for the Universal Studios Amphitheatre
Authors: Davy Bruce A.
Published: October 2005

The Universal Studios Amphitheatre is a 5317-seat open-air amphitheater located in the vicinity of several residential communities. When the Amphitheatre began its program of summer evening rock concerts, noise complaints were received from the neighbors. A shielding wall was built in an attempt to contain concert noise, but complaints continued. An evaluation of noise levels in areas from which complaints were received was begun in 1973. The program was extended in 1974 to an evaluation of various techniques to contain the noise. Loudspeaker panels and baffles for exit doors were designed and installed. In 1973, a program of noise data collection was begun. Procedures were developed for data collection and for providing information to establish interior sound level limits. This data collection and evaluation continued for eight summer concert seasons from 1973 through 1980. In 1981, work began to completely enclose the Amphitheatre so it could be used year-round. The development of the noise control program and the eight-year data collection program is reviewed and summarized.