bluuebunny/crossref_metadata_2025 huggingface dataset:
Preventing compensable on-the-job noise-induced hearing loss
Authors: Royster Larry H. , Royster Julia Doswell
Published: October 2005

To prevent a significant on-the-job noise-induced hearing loss, management must ensure that hearing conservation program (HCP) activities include the following efforts (as appropriate): pre- and postemployment audiograms, annual audiograms for employees with TWAs of 85–99 dBA and semiannual audiograms for employees with TWAs of 100 dBA and higher, use of a threshold shift criterion more strict than the OSHA STS to flag the most noise-susceptible employees, documentation of adequate hearing protector fitting, issuing, replacement, and user training, and annual updating of auditory history information. The HCP's level of effectiveness should be evaluated annually using the recommendations of ANSI S12/WG12; if the program is found ineffective, corrective measures should be implemented immediately. When employees file for compensation, the appropriateness of their claims is evaluated by taking into consideration the level of effectiveness and completeness of the HCP, comparing their TWA exposure level against the real-world protection capabilities of the hearing protection utilized, and comparing their hearing losses against the range of hearing loss predicted using the ISO 1999 (1990) model for a noise-susceptible population with the same exposure. If an employee's hearing loss is judged to be non-work-related, then all company personnel and other professionals who will be involved in the judicial process should be adequately trained in preparation for the hearing or trial.
Sediment properties derived from shear and interface waves
Authors: Ewing John I. , Sutton George H. , Carter Jerry A.
Published: October 2005

Bottom-mounted sources and receivers have been used to measure shear wave velocity and attenuation in sediments of the U.S. East Coast continent shelf. Experimental results are compared with borehole and other subseafloor geologic information. Shear sources were designed primarily for generating SH waves but also produced SV and P waves. Receiver nodes containing orthogonal geophone or accelerometer sensors, plus hydrophone, provided four-component data, each component producing unique information on wave type, velocity/attenuation structure, scattering, lateral heterogeneity, and anisotropy. Measurements were made with two systems; one with a large source and 4–8 m sampling interval to a maximum range of 200 m, the other with a smaller source and 1-m sampling to a range of 30 m. Velocity and attenuation are estimated by matching recorded data with full-waveform synthetic seismograms. [Work supported by ONR.]
A pseudo-underway geophysical technique for quantifying seabed sediment properties
Authors: Davis Angela M.
Published: October 2005

A towed geophysical device has been developed that will allow the rapid quantification of seafloor sediment properties for engineering and other purposes. The seabed hardware consists of seismic sources, a focused electrode pad (all sledge mounted), and a string of gimballed triaxial geophones. The seismic sources are impulsive devices that are essentially electromagnetic hammers that can preferentially generate shear or compressional waves dependent on their mode of operation. Travel time relationships obtained for seismic waves propagating through the sediment body to the geophone array allow the velocity structure to be defined to a depth dictated by the maximum receiver offset. Of particular interest to the engineers are the velocity gradient effects that for shear waves are indicative of the seabed sediment rigidity. The device can be used to construct distribution maps of geophysically related physical properties of the sediment body, and their variation with depth. Surveys carried out with the device in well-documented test-bed sites have produced significant correlations between the geophysical parameters and the known sediment variability.
High-frequency acoustic penetration of sandy ocean sediments
Authors: Chotiros Nicholas P. , Ramaker Michael L.
Published: October 2005

High-frequency acoustic signals, from 5 to 80 kHz, were projected from a point in the water to an array of hydrophones in a sandy sediment. The data were processed to yield acoustic wave speeds and directions. For normal and near-normal incidence, the results are in good agreement with liquid-viscoelastic solid propagation models. For grazing angles less than the critical value, the results cannot be explained in terms of a viscoelastic medium; a slow wave is observed that can only be explained in terms of Biot's theory. [Work supported by ONT under NOARL management.]
Laser generation and detection of ultrasound and applications
Authors: Monchalin Jean-Pierre
Published: October 2005

Ultrasound is generally generated and detected by using piezoelectric transducers bonded or fluid coupled to the specimen under investigation. Such a method requires a good bond or precise transducer orientation, is essentially limited to samples with planar surfaces, and can hardly be applied at elevated temperature. These limitations are circumvented by using lasers to generate and detect ultrasound. This technique, called laser ultrasonics, has the advantage of being noncontact, permits probing off curved surfaces and complex shapes and allows the generation and detection of low frequencies as well as high frequencies. In this presentation, the various physical principles used for laser generation and optical detection will be outlined. Several interferometric detection systems that have been developed in this laboratory will be reviewed and their merits and limitations for laboratory investigation or industrial inspection will be discussed. Several applications now being persued will be presented, including various thickness gaging applications, the generation and detection of plate waves and their use for evaluating plate anisotropy, the determination of ultrasonic attenuation, and its use for evaluating steel grain size.
The generation of narrow-band and directed ultrasound using spatially and temporally modulated arrays
Authors: Wagner J. W. , Spicer J. B. , Deaton J. B.
Published: October 2005

Owing to their generally poor sensitivity relative to conventional contact ultrasonic methods, laser-based ultrasonic systems have proven to be effective for only a limited range of applications, and only then with very careful and specific designs. Recent investigations at The Johns Hopkins University have been directed at the use of spatial arrays and temporal laser beam modulation to generate ultrasonic signals which are both narrow band and may be directed over some angle within the test piece. The degree to which sensitivity may be enhanced by these methods, however, is a strong function of the temporal and spatial nature of the laser array source as well as the acoustic mode one wishes to excite. For example, variations in the dimension of each element in an array, array spacing, and array source rise time may all affect dramatically the degree to which one is able to generate narrow-band signals for high-sensitivity detection. Ultrasonic directivity issues are also somewhat more complicated than they are represented in much of the current literature. In fact, the degree to which the ultrasonic energy may be directed by laser array sources of any type is a strong function of the wave shape generated by each element in the array. Consequently, individual features such as pulse height or pulse repetition, which may be derived by superposition of the signals from elements of an array, may be directed over a range of angles in a solid material while total far-field energy directivity may remain unchanged.
Photoacoustic frequency-domain depth profiling of continuously inhomogeneous solids. Theory and quantitative profilometry of octyleyano-biphenyl (8CB) liquid crystals
Authors: Mandelis Andreas , Scoubs Els , Peralta Samuel B. , Thoen Jan
Published: October 2005

An application is presented of the Hamilton-Jacobi formulation of thermal-wave physics [A. Mandelis, J. Math. Phys. 26, 2676 (1985)] to the problem of photoacoustic depth profiling in inhomogeneous solids with arbitrary, continuously varying thermal diffusivity profiles. Simple expressions for the modulation frequency dependence of the photoacoustic signal in the case of exponential thermal diffusivity profiles are obtained, and a working general method for solving the inverse problem and obtaining arbitrary diffusivity depth profiles is demonstrated through computer simulations. The method was found to possess excellent profile reconstruction fidelity. As a first experimental application of the theory, an observed change in the photoacoustic signal frequency response upon the application of a transverse magnetic field across octylcyanobiphenyl (8CB) samples in the nematic phase at 37°C is reported. The theory has given quantitative profiles of thermal diffusivity decreases extending to 20–30 μm below the liquid crystal surface. These decaying depth profiles are qualitatively consistent with earlier photoacoustic temperature scans of liquid crystals and are a measure of the extent of bulk reorientational effects due to the magnetic field, as well as the extent of the influence of the surface as a domain reorientation inhibitor in the kG range.
Laser generation of ultrasound for process control using optical fiber arrays
Authors: Umeagukwu Charles , Jarzynski Jacek , de Ridder Nick , Yang Jr-Syu
Published: October 2005

This paper reviews recent work on the use of optical fiber arrays to enhance laser generation of ultrasound. Experimental and numerical directivity patterns are presented, obtained using optical fiber arrays to generate longitudinal, shear, and surface waves. Comparisons of the directivity patterns for a single light source and for the fiber array will be presented and discussed for each of the above waves. Also shown will be some experimental results on array gains. This discussion will be limited to sound generation in the thermoelastic (linear) range. The optical fiber array can be used to control both the directivity and the type of elastic wave generated by the laser light. The noncontact fiber array generation can be combined with a noncontact EMAT or laser Doppler receiver to achieve a system for ultrasonic on-line inspection and control of manufacturing processes. The above technique for sound generation and reception is particularly useful in hostile and hard to reach environments. [Work supported by the National Science Foundation.]
Resonant photoacoustic measurements of very low optical absorption in piezoelectric and dielectric crystals
Authors: White J. D. , Yu C. , McKenna M. J. , Maynard J. D.
Published: October 2005

The photoacoustic effect is one of the most sensitive methods for measurements of the low optical absorption in glasses and crystals. Traditional methods using high-powered pulse lasers and attached piezoelectric transducers are limited by noise and scattered light at the transducer. Recently, a new resonant photoacoustic technique has been developed for highly transparent solids, where a cw laser modulated at the acoustic resonant frequency of the sample generates an acoustic signal amplified by the quality factor (Q) of the resonance. This technique is several orders of magnitude more sensitive than conventional pulse techniques. Noncontact capacitive transducers eliminate the problem of scattered light. Two different transduction mechanisms are important in the detection of the acoustic wave at the sample surface. First, the displacement of the surface of the dielectric sample in the electric field of the capacitor results in small changes in the capacitance. Second, through the piezoelectric effect, the strain generates a small electric field at the sample surface; here, the transducer acts as an rf receiver, detecting the changes in the electric field intensity. Based on recent measurments on single crystals of calcium fluoride and quartz, the relative contributions of these two mechanisms will be discussed. [Work supported by the Office of Naval Research.]
Spectral shape discrimination of narrow-band spectra
Authors: Berg Bruce G. , Green David M.
Published: October 2005

Previously, it was demonstrated that spectral pitch is used to discriminate three-component, narrow-band spectra when tones are separated by 40 or 80 Hz, but not for a 10-Hz separation. Here, discriminations are investigated based on the temporal envelope. The standard consists of three, equal-intensity sinusoids, with respective frequencies 990, 1000, and 1010 Hz. Presentation level is a random variable with a range of 20 dB and mean 55 dB. Thresholds for an intensity increment of the central tone range from −10 dB to −1 dB re: the standard. Thus, performance is as good as that obtained in profile tasks for which components are separated by two or more octaves. Because performance is unaffected by (1) the addition of a modulated masker centered at 4000 Hz [W. A. Yost and S.S. Sheft, J. Acoust. Soc. Am. 85, 848–857 (1989)], or (2) randomization of each component's phase as opposed to the same, fixed phase for each, it does not appear that modulation depth is a critical variable. It is believed that discriminability is related to the spectrum of the envelope. [Work supported by AFOSR, ONR, and NIH.]
Psychoacoustic evaluation of random-like deviation changes in FM signals
Authors: Ozimek Edward
Published: October 2005

The detection threshold for frequency modulation was measured at several carrier frequencies. The standard (unmodulated) waveform was a sinusoidal signal of fixed amplitude and fixed frequency. The comparison waveform was frequency modulated. The modulating signal had constant frequency, but the amplitude was a random variable. The amplitude of each successive period was the absolute value of a Gaussian random variable with mean, 0, and standard deviation, σ. The ability of listeners to detect the FM modulation by adaptively varying σ in a two-alternative forced-choice procedure was determined. An increase in the carrier frequency from 120 to 1000 Hz causes, on average, a three-fold increase in the threshold value of σ. Changes in modulation frequencies from 4 to 16 Hz increase the threshold by twofold at the highest carrier frequency. At low-modulation frequencies, different amplitude samples produce statistically different discrimination thresholds. Compared with the classical data for FM signals, the random deviations are easier to hear at higher carrier frequencies and harder to hear at lower carrier frequencies. [Research supported by the Kosciuszko Foundation and the NIH.]
Scalp potentials elicited using AM acoustic signals
Authors: Dolphin William F. , Mountain David C.
Published: October 2005

Temporal information is one of the most fundamental aspects of an acoustic signal extracted by the auditory system. Especially as regards communication sounds, temporal patterning is an extremely important information carrying feature of complex signals. Modulation of signal amplitude, at frequencies up to several hundred Hz, is common in many species specific vocalizations as well as in human speech. Scalp potentials which follow the low-frequency envelope of an amplitude-modulated (AM) stimulus waveform were evoked and recorded from anesthetized gerbils. This envelope following response is presumably due to the synchronized discharge of populations of neurons in the auditory pathway. When the carrier frequency (fc) of an AM constant-frequency acoustical stimulus is greater than the electrical cutoff frequency of the inner hair cells and the modulating frequency (fmod) is much below this cutoff, the instantaneous firing rate of the auditory nerve approximately follows the envelope of the stimulus. As the maximum amplitude of the basilar membrane response occurs at the region corresponding to fc, it is hypothesized that inner hair cells in this region are preferentially stimulated. To test this hypothesis, AM stimuli in the presence of pure-tone maskers of varying frequencies were presented and scalp potentials recorded. A strong envelope following response, at the frequency of the modulator, was obtained to AM stimuli alone. The response was quite robust and could be elicited using a wide range of fc's, modulation frequencies, and stimulus intensities. The response could be eliminated by the simultaneous presentation of a pure-tone masking stimulus (fmask). When fmask was close to fc, responses at the modulation frequency were diminished by up to 25 dB. Measurements of the group delay, determined from the phase of the response relative to the stimulus phase, indicate at least three separate brain regions as the site of this response. The responses come from progressively more central regions as the modulation frequency is reduced. Such studies may yield valuable insights to the processing of complex stimuli by the auditory system.
The role of envelope cues for the detection of a tone added to a narrow band of noise
Authors: Richards Virginia M. , Nekrich Robert D.
Published: October 2005

Using a 21FC paradigm, psychometric functions for the detectability of a tonal signal added to a 40-Hz-wide band of Gaussian noise was measured using signal and center frequencies of 600, 1800, and 5400 Hz. In a second condition, the noise-alone and the tone-plus-noise stimuli were scaled so as to yield identical energy values across the two intervals of each trial. Under the assumption of optimal combination of independent cues, a comparison of these conditions allows an estimate of the relative contribution of energy-based and non-energy-based cues for the detection of a tone added to noise. In a third condition, the envelopes of the scaled noise-alone and tone-plus-noise stimuli were extracted, and used to modulate tones of either 600, 1800, or 5400 Hz. The ability to discriminate between envelope patterns was measured, and that measure used to estimate each observer's reliance on envelope-based cues. Large individual differences were obtained. For one observer, the detection of a tone added to Gaussian noise was determined to rely equally on envelope-based and energy-based cues. A second observer was found to depend almost wholly on changes in energy. None of the observers appeared to rely on changes in fine structure that occur when a tone is added to noise, and consistent with that observation, no differential effect of frequency region was obtained. [Work supported by the National Institutes of Health.]
Detecting the temporal asynchrony among components of multicomponent complexes
Authors: Zera Jan , Green David M.
Published: October 2005

The listener's task was to detect onset or offset asynchrony among sets of equal-amplitude sinusoids. In the standard condition, all components were started (or stopped) at the same time. In the asynchrony condition, their onset (or offset) times were chosen from a Gaussian distribution with a certain standard deviation. The value of this standard deviation was adjusted in an adaptive 2AFC procedure to determine the asynchrony threshold. Parameters investigated, in addition to the differences between onset and offset asynchrony, were rise (fall) time of the components, frequency spacing (linear and logarithmic) of the components, and the number of components. The obtained asynchrony thresholds measured in 2AFC tasks ranged from 0.1 to 3 ms for 20-component complexes. In these experiments, the temporal events to be compared occurred in different frequency channels. A control experiment was conducted which indicated that the obtained results could not be explained on the basis of the perception of the wideband waveform.
Human auditory temporal summation in the presence of ipsilateral or contralateral continuous tones
Authors: Bhat Vishwa K. H. , Gerken George M.
Published: October 2005

The auditory temporal summation function was measured in 16 normal hearing human subjects using a set of five single-burst and seven multiple-burst tones of 2.0 kHz. In each of two experiments, thresholds were obtained: in the presence of a 60 dB SPL continuous tone one-third octave above or below the stimulus frequency of 2.0 kHz, and in the quiet condition. In experiment I, the continuous tone was presented ipsilaterally and in experiment II, the tone was presented contralateral to the stimulus. It was shown that the ipsilateral tone conditions significantly reduced the slope of the temporal summation functions, whereas the contralateral continuous tone conditions had no influence. Second, it was concluded that a common mechanism processed both single- and multiple-burst stimuli. Finally, it was concluded that a power function was a simple and adequate way of describing the temporal summation process.
Temporal effects obtained with signals of various bandwidths presented in notched and unnotched maskers
Authors: Wright Beverly A.
Published: October 2005

The temporal effect, or decrease in simultaneously masked threshold as signal onset is delayed relative to masker onset, was measured for signals centered at 2500 Hz that ranged in width from tonal to 7900 Hz. The masking noises covered the frequency range from 100 to 8000 Hz and either contained a spectral notch that always perfectly complemented the width of the signal, or contained no spectral notch. In the short-delay and long-delay conditions, the 20-ms signal was gated 1 or 250 ms, respectively, after the onset of a 420-ms masker. In the burst condition, the signal was gated 1 ms after the onset of a 23-ms masker. Although there were marked individual differences, with the notched masker, thresholds were as much as 7–17 dB higher in the short-delay condition, and 20–27 dB higher in the burst condition, than in the long-delay condition. With the unnotched masker burst/short-delay differences were minimal. Thus, only the magnitude of the temporal effect obtained with notched maskers was strongly influenced by the choice of reference condition. [Work supported by NIDCD.]
A wave-number domain approach to the active control of structure-borne sound
Authors: Fuller Chris R. , Burdisso Ricardo A.
Published: October 2005

Previous work has shown the possibilities of active control of structurally radiated sound by applying control forces directly to the structure while error information is taken from microphones placed in the radiated far field is impracticable in many applications. On the other hand, it has been demonstrated that simply minimizing the structural response, i.e., by using accelerometers as sensors, may lead to an increase in the radiated sound levels due to “control spillover.” Thus, this research work demonstrates for the first time the design of feed-forward controller in the wave-number domain for eliminating the use of microphones in the radiated far field. By using a stationary phase approach to evaluate sound radiation from panels, it is shown that only one spectral wave-number component of the structural response radiates towards one particular angle. Thus, by minimizing particular wave-number components on the structure, the sound radiation can be minimized at the corresponding radiation angles. A 2-D baffled simply supported beam example demonstrates this concept. [Work supported by ONR/DARPA.]
Active control of sound radiation from a uniform rectangular fluid-loaded plate
Authors: Gu Yi , Fuller Chris R.
Published: October 2005

Active control of sound radiation from a simply supported rectangular one-side fluid-loaded plate is analytically studied. The plate is assumed to be excited by a point force at subsonic frequencies. The dynamic equation of the plate motion is based on the in vacuo eigen-functions of a homogeneous panel as the basis for Fourier decomposition of the fluid loading. Feed-forward control is applied by either point forces or piezoelectric actuators attached to the plate. The amplitudes of the control forces are determined by the optimal solution of a quadratic cost function which integrates the far-field radiated acoustic pressure in a hemisphere in the fluid half-space. The results show that for on-resonance frequencies, high global reduction in radiated pressure is possible with two active forces properly located on the plate. For off-resonance conditions in order to provide global control an increased number of control forces is required. However, for the low frequencies considered here four control forces proved adequate. The far-field directivity pattern, the modal amplitudes of the plate vibration, the plate power spectrum in a two-dimensional wave-number domain, and the near-field intensity distribution are extensively studied. The work confirms that the feed-forward control technique will work for heavy fluid loading where the plate modes are nonorthogonal and mode edge coupling is important. [Work supported by ONR/DARPA.]
Numerical simulation of active noise control for three-dimensional structures: Preliminary investigation
Authors: Ruckman Christopher E. , Fuller Christopher R.
Published: October 2005

In certain cases, low-frequency noise radiated by a structure into a surrounding fluid can be attenuated by applying harmonic “control forces” directly to the structure. If the system is controllable. i.e.. if the proposed control forces are sufficiently capable of influencing the radiation, then global radiation attenuation is possible. Recent studies show that some structures, including baffled flat plates, are indeed controllable in this sense. But analyzing a complex three-dimensional structure, particularly if it is immersed in a dense fluid, can be difficult because there usually is no analytical solution for the radiated field. The present research adapts NASHUA, a general finite element/boundary element computer program, to investigate whether radiation from three-dimensional structures can be controlled by harmonic forces. The preliminary test case to be presented is a thin spherical shell, chosen because it has an analytical solution. Control force locations are determined by examining the spatial Fourier transform of the surface velocity. Control force magnitudes and phases are found by minimizing the radiated power using quadratic optimal control theory. Also examined are sensitivity to control-force placement and phasing errors, and sensitivity to system identification errors. The numerical and analytical results are found to be in good agreement. [Work supported by ONR/DARPA.]
Active control of edge sound radiation from a clamped beam
Authors: Guigou Catherine , Fuller Chris R.
Published: October 2005

Active control of sound radiation from a thin semi-infinite beam clamped at one end is analytically studied. Active control is achieved by applying either control forces (approximating shakers) or control moments (approximating piezoelectric actuators) on the beam near the edge discontinuity. For a single frequency, the flexural response of the beam subject to an exciting point force and to the control forces or control moments is expressed in terms of waves of both propagating and near-field types. The control force or control moment magnitudes are derived by optimizing a quadratic cost function which is defined as the acoustic power radiated from one side of the baffled beam and obtained by integrating the far-field radiated acoustic intensity over a hemisphere. For single frequencies, large attenuation in radiated acoustic power and pressure is found when one and two control forces or two and four paired control moments are applied. The proper location of the control forces or control moments is determined in order to obtain the maximum decrease of the optimized radiated acoustic power. The influence of the control near-field component on the amount of attainable attenuation is studied and found to be important. The far-field radiated pressure directivity, the displacement of the vibrating beam, and the one-dimensional wave-number spectrum of the beam velocity are extensively studied. The work provides insight into active control of edge radiation from more complex 2-D structures. [Work supported by ONR/DARPA.]
Velar height and sentence length: Declination
Authors: Bell-Berti F. , Krakow Rena A.
Published: October 2005

Considerable evidence attests to the phenomenon of F0 declination during the course of an utterance. Recently, the question of whether upper articulators might show declination-type effects has been raised for the jaw [E. V.-Bateson and C. A. Fowler, J. Acoust. Soc. Am. Suppl. 1 84, S128 (1988)]. In previous studies, lower velar peaks were noted in sentence-final than -initial syllables, prompting a systematic investigation of velar declination. Thus peak velar height for early and late syllables in natural and reiterant-speech sentences of from three to nine syllables has been examined. Velar position and acoustic data were collected from three speakers of American English. Differences in velar height were examined with respect to number of syllables and acoustic duration. Possible interactions between declination-type processes and factors such as stress were also studied, since stress has been shown to have a strong influence on velar movement [R. A. Krakow, J. Acoust. Soc. Am. Suppl. 1 82, S17 (1987); J. Vassiere, Phonetica 45, 122–139 (1988)]. [Work supported by NIH Grants DC-00121 and RR-05596 to Haskins Labs.]
The F3 trajectories of American English /r/'s
Authors: Boyce Suzanne , Espy-Wilson Carol Y.
Published: October 2005

It is well known that the coarticulatory influence of /r/ on preceding segments, as evidenced by a lower than expected F3 frequency, may be substantial. Researchers who have studied this phenomenon have found that this “spreading” occurs under a number of different conditions (cf. Espy-Wilson, 1987). A unifying explanation may be that the articulatory gesture for /r/ has a relatively incompressible trajectory whose timing “slides” with respect to other gestures in a sequence. This hypothesis was tested acoustically by analyzing the time course of the F3 trajectory in several American English speakers' production of the words “varam,” “vavram,” and “vavam.” In these data, previous findings of “spreading” to the preceding segments were confirmed. In addition, the /r/'s in “varam” and “vavram” showed a nearly identical time course. As a consequence, F3 during the post-vocalic /v/ of “vavram” is considerably lower than was seen in the post-vocalic /v/ of “vavam.” This suggests that the explanation for spreading of the feature retroflex into the /v/ is due to a constrained time course for /r/. This hypothesis will be further explored in words when /r/ cooccurs with /g/, a segment whose tongue-body requirement potentially conflicts with the articulatory requirement for /r/.
Voiced versus voiceless inaspirates: The perception of English stops
Authors: Lisker Leigh , Abramson Arthur S. , Koenig Laura L.
Published: October 2005

Preliminary data on four acoustic variables as possible cues to the contrast between voiced and voiceless unaspirated stops in fluent American English speech were reported at the 119th Meeting. They were burst amplitude, duration of the preclosure vowel, duration of the closure interval, and the nature of the closure signal. A single English speaker recorded the sentence pair He's known as Jack the Ribber and He's known as Jack the Ripper, which served as sources of waveform-edited stimuli that were identified by a jury of ten American English speakers. Additional word identification data have since been collected for three additional sentence pairs recorded by the same single speaker, with the new word targets chosen to include dorsal as well as labial stops after both the short vowel [ɪ] and the long vowel [o]. For each acoustic variable two values were tested, one normal for the word as originally produced and the other typical of the minimally contrasting word. The data allow us to rank the four acoustic properties in respect to their roles in perception: burst amplitude < vowel duration ⩽ closure duration < closure signal. [Work supported by NIH Grant HD-01994 to Haskins Labs.]
The production of “breathy voice.”
Authors: Davis Katherine
Published: October 2005

The nature of voicing in the Hindi “voiced aspirated” phonemes has been a subject of discussion in the literature for a number of years. In particular, the question of whether or not “breathy voice” or “murmur” is present during the aspirated portion of the stop has been at issue. The present study looks at productions of the velar voiced aspirated stop (/gh/) in initial position from the speech of ten adult female speakers of Hindi. Amounts of lead time (prevoicing) and lag time (post-release VOT) in the voiced aspirate were compared to lead and lag times in the voiced unaspirate (/g/) and the voiceless aspirate (/kh/). In addition, the presence or absence of voicing during the post-release portion of the stop was determined. Both lead and lag time values of the voiced aspirate were found to be significantly different from those of the other velar stop types, and the presence of voicing during aspiration (breathy voice) was found to be speaker dependent. Implications of these findings for a description of voicing contrasts in various languages will be discussed.
Production and perception of vowel duration as a cue to the word-final English /t/-/d/ contrast by native and Chinese subjects
Authors: Flege J. E.
Published: October 2005

Vowel duration was measured in seven minimally paired English words such as beat-bead and bat-bad as spoken by native English (NE) subjects and four groups of Chinese subjects (ten per group). The Chinese subjects were either relatively inexperienced (MA, TA) or experienced (TB) adult learners of English, or else had learned English as an L2 before the age of 12 years (TC). The early learners in TC closely resembled the NE speakers in making vowels much longer before /d/ than /t/. The inexperienced adult learners (MA, TA) produced a voicing effect, but one that was far smaller than that of the subjects in NE and TC. The experienced adult learners in TB produced a significantly larger voicing effect than the inexperienced subjects in TA and MA, but their effect was also smaller than that of the subjects in NE and TC. Sensitivity to vowel duration as a perceptual cue to the English /t/-/d/ contrast was investigated in three ways. The subjects identified the members of natural continua in which vowel duration was varied by deleting glottal pulses. One continuum ranged from bead to beat, the other from bad to bat. The subjects imitated the members of both continua, and also chose which members of the continua represented the best exemplars of bead, beat, bad, and bat. As expected from the production data, the early learners in TC resembled the NE speakers perceptually, whereas the inexperienced adult learners (MA, TA) showed little evidence of perceptual sensitivity to vowel duration. Some experienced adult learners in group TB, on the other hand, were perceptually sensitive to the vowel duration cue. The relationship between their production and perception will be discussed.
VOT values in bilinguals versus monolinguals of Hindl and English
Authors: Carey Carol E. , Gopal H. S. , Affentranger Heidi
Published: October 2005

This study compared the VOT values of stop consonants produced by bilingual speakers of Hindi-English with those produced by monolingual speakers of Hindi and English. Specifically, it investigated whether native Hindi speakers use their native VOT values of stop consonants when producing English stops, or if they use the correct/appropriate VOT values as produced by native English speakers. Two subjects in each of the three speaker groups (Hindi monolingual, English monolingual, and Hindi-English bilingual speakers) produced CVC test syllables in a sentence context. These sentences were acoustically analyzed for the VOT values of the initial stop consonants in the CVC syllables. Results will be discussed within the framework of the equivalence classification hypothesis which claims that, when there are similar phones between two languages, bilingual speakers of those languages will not produce the phones in the second language accurately as they will substitute the similar phone from their native language [J. Flege, J. Phon. 15, 47–65 (1987)].
A comparison of the first and second formants of vowels common to English and French
Authors: Behne Dawn M.
Published: October 2005

English vowels have been characterized as being lower, more central, and less rounded than the predominantly high, front, rounded vowels of French [P. Delattre, Comparing the Phonic Features of English, French, German and Spanish: An Interim Report (Groos Verlag, Heidelberg, 1965)]. In the present study, Delattre's description is experimentally investigated by comparing the first and second formant frequencies of English and French vowels that occur in both languages (i.e., /i,e,ɛ,u,o,ɔ,ɑ/). The results suggest that: (1) high vowels tend to be higher in French than in English; (2) /ɑ/ tends to be lower in English than in French; (3) high and mid vowels tend to be more central in English than in French; (4) rounded vowels tend to have greater liprounding in French than in English; (5) front vowels are higher and more fronted in French than in English; and (6) back vowels have greater pharyngeal constriction in English than in French. Although Delattre's description of English and French vowels is generally supported by the results, it does not fully characterize the differences demonstrated between the vowels common to English and French.
Effects of speaking rate on the vowel length distinction in Korean
Authors: Magen Harriet S. , Blumstein Sheila E.
Published: October 2005

Variations in speaking rate affect the perception of temporally defined phonetic distinctions in consonants, such as voicing in stops, and the stop-glide and stop-affricate contrasts. The production data on these contrasts show asymmetrical effects on temporally distinctive pairs, with the longer members showing the effects more markedly. These data further suggest that the shorter member of the pair serves as a phonetic anchor. This study investigates whether similar effects emerge for vowels. To this end, production of short-long vowel pairs was examined across speaking rates in Korean, a language that has phonemic vowel length. Results show that both long and short vowels vary across speaking rates, such that the symmetrical effects found for consonants are not found for vowels. Short vowels do not provide a phonetic anchor: In fact, the durations of short vowels produced at a slow rate nearly always overlap those of long vowels produced at a fast rate. [Work supported by NIH.]
Characterization of the dynamic response of buildings to ground-borne vibration
Authors: Carman Richard A.
Published: October 2005

A transfer mobility measurement procedure is proposed as a basis of characterizing the dynamic response of existing buildings to new ground-borne vibration sources. To demonstrate this technique, an empirical model was derived that can be used to predict the response of buildings to rail transit vibration. The proposed testing procedure and model are based on the comprehensive impact-testing procedure proposed by Nelson and Saurenman [Transportation Research Record 1143 (1987)] for predicting rail transportation ground-borne noise and vibration. The transit model for buildings is based on an analysis of measured transfer mobility for residential buildings using an instrumented impact device and an analytic comparison with actual train-induced vibration. Coupling loss between the ground and building foundation is incorporated in the model, as is amplification of building vibration by floor resonances. Examination of resonance conditions is made possible by modal testing. By making adjustments to the model, it is possible to extend the result to other sources, such as roadways.
Traffic-induced vibration study on residential structures in suburban Washington, DC
Authors: Harvey Scott , Capozello Bob
Published: October 2005

Based on residents' complaints of traffic-induced vibrations in single family dwelling units, vibration measurements were evaluated in terms of annoyance and structural damage. The study included 15 residences and measurements were made under a variety of traffic conditions. Measurement points within each residence included the foundation and utility pipes for determination of transmission path. Real time, 1/3-oct measurements were made in the range of 0.8–80 Hz and compared with criterion set forth by the Federal Highway Administration. It was found that all the residences were on local bus routes and that buses were the major cause of structural vibration. It was shown that vehicle suspension characteristics had greater influence on structural vibrations than gross vehicle weight. Pavement smoothness was the one controllable factor capable of reducing traffic-induced vibrations. Recommendations were made for decreasing the vibrations to a level lower than the threshold of annoyance.
Sound isolation design for cinemas below the roadway—A case study
Authors: Foulkes Timothy
Published: October 2005

The recently completed Tower City Cinema complex in downtown Cleveland is located below street level. Some of the 11 theaters are below an office building and several theaters are below an active street. Special construction was required to provide an acceptable theater environment. During design, two of the theaters were designated for THX certification requiring lower background noise than normal cinemas. All theaters achieved a background noise level of NC 30 with no discernible sound or vibration from the traffic. This paper will include preconstruction measurements and analysis, construction details, and postcompletion sound measurements.
New approach to designing low peak factor, discrete-time waveforms
Authors: Burgess John C.
Published: October 2005

Periodic waveforms can be designed to have the smallest possible peak (or crest) factors while having their power concentrated in a desired frequency band. A well-known approach is first to specify the magnitudes of the desired waveform harmonics, then to specify or search for a set of phase angles [M. R. Schroeder, Number Theory in Science and Communication (Springer-Verlag, New York, 1984); J. Pumplin, “Low-noise noise,” J. Acoust. Soc. Am. 78, 100–104 (1985)]. This approach requires a significant amount of computer time to search for sets of phases that provide waveforms with near-minimum peak factors. Another approach is to specify the waveform as a bandlimited, periodic chirp, x(n) = sin[a(n + n0)]2, 0⩽n <N. This approach has the advantage that the waveform has the smallest peak factor possible while allowing some control of the waveform spectrum. It has the disadvantage that the spectrum is distorted by leakage. The design approach, results, and some recent efforts to reduce leakage will be discussed. [Work supported in part by National Research Council of Canada and Lanikai Foundation.]
Effect of curvature discontinuities oil the vibrational modes of cylindrical shells
Authors: Bresnahan Michael J. , Jelatis George J. , Rossing Thomas D.
Published: October 2005

A study has been made of the modes of vibration of three brass cylinders with almond-shaped cross sections, formed by soldering together two sections of a circular pipe. These modes appear as doublets, with the higher frequency member of the pair having a node at each discontinuity. In uncapped shells, the frequency ratio of the doublet pair decreases rapidly with increasing m (the number of bending waves around the circumference) and less rapidly with increasing n (the number of nodal circles). Frequency splittings as large as 30% were observed in the m = 2, n = 0 mode, indicating a substantial decrease in bending wave velocity at the locations where the shell segments are joined. Measurements on capped shells are in progress. [Work supported by the Pew Foundation.]
Vibration analysis of shell structures based on a plate analogy
Authors: Kim Jeung T.
Published: October 2005

An approximated formula representing the vibration characteristics of a shell structure with finite curvature is proposed. The model is based on the dynamic analogy between a cylinder and a flat plate. In order to derive the formula, the dynamics of a shell with and without the curvature effect is introduced. Then, resonance frequencies, constant frequency loci, and number of modes in a flat plate and in a cylinder are also examined. After that, a simplified driving point mobility function of a shell with the plate mobility is derived. An experimental verification is conducted in order to examine the proposed formula. Cylinders having two different ring frequencies of 5.9 and 13.8 kHz are used as test structures. Comparisons are done for the resonance frequency and for the mobility function. The accuracy of the analysis falls within 6% error when resonance frequencies are compared with those of experimental data. The results show that the proposed mobility function predicts the vibration behavior for the frequency bandwidth below and above the ring frequency. The model is simple to use and could be easily extended to various boundary conditions for vibration and noise prediction purposes.
Hydrodynamic demonstration of the classical cochlea
Authors: Keolian Robert
Published: October 2005

The inner ear is a remarkable system for detecting and analyzing sound. To first approximation, it is a Fourier transform machine that utilizes a highly dispersive waveguide to localize the energy of each frequency of a traveling wave to a particular position. This will be demonstrated with the aid of a hydrodynamic analog. It consists of a 35-in.-long, 58-in.-i.d. horizontal tube (representing the scala) closed at one end and driven by a piston at the other. Projecting above this are about 100 closely spaced transparent vertical 14-in.-i.d. tubes (representing the cochlear partition) whose length varies exponentially from 8.25 in. near the piston to 33 in. near the closed end. Water poured into the apparatus fills the large horizontal tube, and rises up the vertical tubes to a height of 8 in. The tops of the vertical tubes are then sealed, and the air trapped above the water surface acts like a place-dependent spring. By driving the piston at various frequencies, one can see a wave in the free surface travel from the piston end toward the tube that is resonantly excited, where most of the energy will be deposited.
Demonstrations on the scattering of sound by bubble clouds
Authors: Korman Murray S. , Roy Ronald A.
Published: October 2005

A bubblemaker (which operates by regulating a transient volume of air stored in a chamber placed between two solenoid valves) is the heart of an experimental apparatus used to generate a transient bubble cloud in water. The apparatus can be adjusted to create a cylindrical bubble column terminating at the air-water interface. Sound pulses are generated by a circular plane array “transmitting” transducer driven by an electronic tone burst generator. Backscattering, at the angle θ = 180°, from the cloud is measured by a receiving transducer. Results are displayed to show any difference measured between scattering by the transient cloud and by the cylindrical column. [Work supported by the Naval Academy Research Council and by the National Center for Physical Acoustics.]
Acoustic levitation positioning of objects in water
Authors: Schemmann Gunter S. , Everbach E. Carr
Published: October 2005

Applications for the precise three-dimensional positioning of neutrally buoyant objects include the control of objects in space stations and the containerless processing of materials on Earth. There will be a demonstration of a microcomputer-controlled system for acoustically levitating an object and moving it to any point within a three-dimensional volume. The system uses a standing wave field in the vertical direction for levitation and a three-transducer traveling wave field to displace the object in the horizontal directions via radiation force. Pulse-echo transducers are used to provide continuous monitoring of position and a Macintosh Hex computer is used to control the position and provide user interfacing.