bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of occupational noise exposure limits for very high intensity impulses when hearing protection is used
Authors: Patterson James H. , Johnson Daniel L.
Published: October 2005

The U.S. Army needs validation of safe limits for exposure to impulse noise produced by heavy weapons. Current impulse noise limits are based on data from small arms. Recent studies indicate these standards may be overly conservative. In order to define new limits, a systematic study of the effects of high-intensity impulse noise on human volunteers is underway. The number of impulses, the peak pressure level, and spectral distribution of energy are being varied systematically. Four groups of at least 60 volunteers will be given a series of exposures to one of four impulse types. The impulse spectrum is varied by changing the distance between the volunteer and an explosive detonation. The peak pressure level is varied in 3-dB steps by changing the weight of the explosive charge. The number of impulses is 6, 12, 25, 50, or 100. Volunteers wear hearing protection for all exposures. After each exposure, TTS is determined. Each volunteer starts with an exposure of six impulses at the lowest intensity. If the TTS is less than 15 dB, the subject receives six impulses at the next higher level the next day. This continues through all intensities. Then the number of impulses is increased using the maximum intensity permitted by nonauditory injury limits. The first group, using an earmuff as a protective device, has completed all exposures at the first impulse detonation distance of 5 m. The peak sound pressure levels varied from 172 to 192 dB with A durations of approximately 3 ms and B durations of approximately 20 m. No TTS in excess of 15 dB was observed for any condition. The percentages of volunteers unwilling to undergo the higher intensity exposures also will be presented.
Acoustical model studies of the Escondido Civic Center
Authors: Siebein Gary W. , Chiang Wei-Hwa , Cervone Richard P. , Talaske Richard
Published: October 2005

A 1:24 scale model of a proposed design for the Lyric Theater in the Escondido Civic Center was constructed. Acoustical tests were performed in the model early in the design process to facilitate discussions among the design team. Modifications to the model were made as the design progressed and several subsequent series of tests were performed. The acoustical effects of the design changes were documented. The theater was tested at several source and receiver locations in configurations for theater and concert. The paper will show the progressive changes made in the building as the final design evolved.
Effects of cable scattering on underwater acoustic measurements
Authors: Arveson Paul T. , Johnson Stephen J.
Published: October 2005

In many situations, cable scattering can be a major contribution to errors in underwater acoustic measurements, far exceeding the errors due to electronic sources. When a cable passes near a hydrophone, the cable generates a scattered wave, which can add to the incident signal to create a standing wave pattern. The amount of deviation of pressure from free-field values depends on frequency, separation distance, and the impedance of the cable. In this work, a computer model of an infinite rigid or soft cylinder has been developed, which provides a contour map of the sound field around the cylinder. The calculations are nondimensionalized in terms of ka and r/a, where a is the cable radius, k is the wave number, and r is the distance of a field point from the cable center. These results are compared with measurements on common types of real hydrophone cables and strength members. In general, the comparisons show that real cables have an effect that is somewhat greater than theoretical values for a rigid cylinder. Guidelines are provided for designing measurement arrays with a specified maximum measurement error. [Work supported by DARPA.]
Analysis of the scattering of a plane acoustic wave by a doubly periodic structure using the finite-element method
Authors: Hladky-Hennion A. C. , Decarpigny J. N.
Published: October 2005

In an attempt to design low-frequency nonreflecting or nontransmitting coatings for underwater applications, many new heterogeneous multilayer structures have been studied in recent years. In the general case, each layer is homogeneous and more or less complex models can be built using a standard transfer-matrix approach. However, in some cases, one or several constitutive layers contain doubly periodic inclusions, such as spherical or cylindrical cavities, used to enhance energy absorption via resonance effects. Then, the modeling requires a larger effort to take account of this periodicity and of the actual displacement field inside each elementary cell. To do this, a finite-element approach has been set up, using the ATILA code and following the method already developed to analyze wave scattering by compliant tube gratings [A. C. Hennion et al., J. Acoust. Soc. Am. 87, 1861–1870 (1990)]. Within this approach, only the unit cell of the structure, including a small part of the surrounding fluid domain, has to be meshed, while the acoustic field on both sides of this mesh is described by a plane-wave expansion, with progressive, as well as evanescent, contributions. Internal losses and anisotropy of the materials, as well as normal or oblique incidence of the wave, can be described in the model. In this communication, the general method will first be presented. Then, several applications will be given, related to classical Alberich coatings made up with different viscoelastic materials. Finally, comparisons with insertion loss measurements will demonstrate the accuracy of the whole approach. [Work supported by D.R.E.T, Paris.]
Composite smart skin systems
Authors: Howarth Thomas R. , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

A smart skin system for inclusion into composite structures is presented. The composite structure can be considered for both underwater and air-borne applications. Individual component designs in the skin include a piezoelectric SAW sensor for the characterization of both the local and global boundary flow layer, piezocomposite sensors and actuators for noise and vibration control, and an array of piezocomposite shear transducers for local damage assessment. Recent research results of the components will be presented. Conceptual system designs will be discussed.
Measurement of the mutual radiation impedance of loudspeakers from electrical input power and diaphragm velocities
Authors: Suzuki Hideo , Anzai Masazou , Ono Takahiko , Herve Patric
Published: October 2005

In a previous paper [Suzuki et al., J. Acoust. Soc. Am. Suppl. 1 86, S21 (1989)], a technique to obtain self and mutual radiation impedances from the measurement of radiated power and diaphragm velocities was reported. However, the measurement of acoustical power is time-consuming and less accurate compared to the measurement of electrical parameters. A method presented here is to obtain the mutual radiation impedance from the measurement of electrical input power and diaphragm velocities. This technique allows a better understanding of how the input electrical power is distributed in the loudspeaker and the effect of the mutual interaction. A difficulty of this technique is that the electrical power consumed by the voicecoil resistance is much larger than the mechanical and acoustical powers. Another disadvantage is that the self-radiation resistance cannot be measured separately from the mechanical resistance. A result of the mutual radiation resistances obtained from the previous and present techniques is compared.
Finite- and infinite-element approaches for low-frequency noise field in a thermal power plant
Authors: Hiramatso Tsutomu , Ikeda Yoichi
Published: October 2005

The finite- and infinite-element methods are applied in order to analyze the diffraction effects of low-frequency noise radiated from a boiler wall surface around a turbine house and an obstacle such as a water tank. The method used in this study is called a hybrid-type infinite-element method in which the elements are combined with the finite elements. The building and the other obstacles treated as a calculation model are situated in a finite domain, which is divided into many isoparametric cubic elements with 20 nodes, and an infinite domain which is divided into many hybrid-type infinite elements with eight nodes and has no noise source or obstacle. The illustrative numerical result of this method is compared with an experimental result that was obtained for a low-frequency noise field around a turbine house, substation buildings, and water tanks radiated from the noise source of the boiler of a thermal power plant, and the results obtained are in good agreement with each other. Prom these studies, it must be pointed out that the hybrid-type infinite-element technique is well adapted to the prediction of a low-frequency noise field around large-scale buildings.
Acoustic tomography using widely distributed vertical arrays and matched-field processing
Authors: Tolstoy A. , Diachok O. , Frazer L. N.
Published: October 2005

This paper suggests a new approach based on single, low-frequency data using air-deployed shots recorded on widely distributed large-aperture vertical arrays. This approach uses fast, cheap, and high S/N data. Results to date with a simulated three-dimensional (3-D) eddy environment show that efficient characterization of the environment plus careful selection of the source/array geometry can lead to highly accurate estimates of the 3-D sound-speed profiles, e.g., maximum errors less than 0.2 m/s.
Focalization: Matched-field processing with environmental focusing
Authors: Kuperman W. A. , Perkins John S. , Collins Michael D.
Published: October 2005

Matched-field processing (MFP) methods can provide accurate estimates of the positions of submerged acoustic sources. If there is uncertainty in the a priori information regarding the speed of sound in the ocean and the geoacoustic parameters of the sediment, however, MFP can be partially or completely degraded. Focalization is an approach for reducing the problem of mismatch by treating the ocean as an acoustic lens that is out of focus and adjusting the acoustic parameters until the sources come into focus with high-resolution MFP methods. With localization, which has been implemented successfully in simulations for a single source, the acoustic parameters must be determined at most along the propagation paths between the sources and the array of hydrophones. Simulated annealing, an efficient method for solving optimization problems involving large numbers of parameters, has been applied to search the space of environmental and source parameters for optimal solutions. The ocean parameters that bring the sources into focus may not be unique. If the primary objective is to determine source location, this type of ambiguity is acceptable and probably even desirable. If a sufficient volume of data is available, focalization can determine sound speed unambiguously.
Modeling of bottom-limited acoustic transmission in the Florida Straits
Authors: DeFerrari H. A. , Monjo C.
Published: October 2005

Most tomography experiments rely on a ray interpretation for inversions. Ideally, separable and stable pulse arrival patterns can be used to measure arrival time along identifiable ray paths, but many areas of oceanographic interests have more complicated acoustic transmission that cannot be precisely modeled with ray theory. Acoustic transmission in the Florida Straits is complicated by multiple interactions with an irregular bottom, a strong range dependence of sound speed, and very energetic oceanographic variability that results in an order of magnitude greater fluctuation in sound speed than observed in the deep ocean. Yet, many experimental observations dating from the sixties reveal a remarkable temporal stability of acoustic transmission and a strong correlation between fluctuations of acoustic travel time and oceanographic variables, such as transport and temperature. In 1983, two 3-point reciprocal transmission tomography experiments were conducted for a period of 1 month, each over a short range of 25 km in 250-m water depth and a longer range of 45 km in 400 m. Channel pulse responses were measured at 12-min intervals for 30 days, along with temperature and current measurements along the path of propagation. Neither the short or long ranges exhibit clean identifiable arrivals associated with an individual ray path that can be used for inversions. The short range is characterized by a single spread out arrival composed of numbers of RBR path arrivals that overlap in time. The long range exhibits a similar RBR group, but with an additional six distinct earlier arrivals associated with the surface duct. After some temporal averaging, channel pulse responses are very stable and inversions appear to give precise measurements of average current and temperature. Presented here are broadband modeling results using normal mode, parabolic equation, and ray models with environmental measurements as imputs. For all ranges the forward problem can be solved with precision, and inversions are possible. The shortcomings of ray theory in describing this type of propagation become apparent, even for those ranges having negligible range dependence. While all the data and model predictions are for the Florida Straits and conditions of relatively short range and shallow water, results and methods may be transferable to long-range, deep-ocean experiments in situations where ray arrivals are closely spaced in time and cannot be separated or identified, or in the presence of a surface duct or other strong stratified channels.
Acoustic remote sensing in the Straits of Florida
Authors: Palmer D. R. , Georges T. M. , Jones R. M.
Published: October 2005

Ocean acoustic remote sensing is the only viable technology for monitoring the ocean interior on the spatial and temporal scales of the signals associated with climate change. The simplest inversion schemes for acoustic remote sensing are based on ray theory because oceanographic variations can be directly related to features in the time-of-arrival pattern. Using computer simulations, the sensitivity of ray-path parameters to small-scale, range-dependent ocean structure and the implications of this sensitivity for data inversion schemes are being studied. Here, monitoring the Florida Current in the Straits of Florida is discussed. The range dependence is due to large-scale, average bathymetry and, more importantly, small-scale bathymetric structure or bottom roughness. Exponential sensitivity to changes in either initital conditions or ocean parameters and the related exponential proliferation of eignerays are found. To properly interpret the results, it is necessary to consider the validity conditions for ray theory.
Applied tomography: Monitoring the Gulf Stream extension
Authors: Howe B. , Mercer J. , Odom R. , Spindel R. , Birdsall T. , Metzger K. , Worcester P.
Published: October 2005

From July to October of 1990, an applied tomography demonstration experiment was conducted in the North Atlantic in the area between Bermuda and North America. The highly variable eastward extension of the Gulf Stream Current was of particular interest. Acoustic sources placed on the bottom near Bermuda transmitted every 4 h, and at times every 40 min, to bottom hydrophones north of the Gulf Stream. The signals were replica processed and the results relayed to the Applied Physics Laboratory in an unattended near real-time mode of operation. In addition, a ship towing a hydrophone array on the northern side of the Gulf Stream received the tomography transmissions during a 1 week period. Sample data results for a single slice through the Gulf Stream are presented. The results show consistent and trackable multipaths that are used to monitor the position of the Gulf Sream. Furthermore, a high-resolution image of the Gulf Stream between 60 and 70 deg west longitude was obtained from the towed array data. Independent comparison data are also presented. [Work supported by the Oceanographer of the Navy and ONR.]
Experimental techniques for studying slow wave propagation in fluid-saturated porous media
Authors: Nagy Peter B. , Adler Laszlo
Published: October 2005

Since 1980, when Plona observed slow wave propagation in water-saturated artificial rocks made of sintered glass beads, numerous attempts have been made to increase the sensitivity of his bulk wave techniques so that other materials of much smaller permeability (e.g., natural rocks) can be investigated also. Three of these experimental methods will be reviewed in this presentation. First, different ultrasonic interface waves propagating along a slightly corrugated fluid/fluid-saturation porous solid boundary are considered. Experimental results are presented to demonstrate the existence of Rayleigh- and Stonely (Scholte)-type leaky interface modes as well as a slow compressional skimming wave. Second, leaky Lamb modes propagating in a fluid-saturated porous plate are discussed. Both theoretical and experimental results indicate the existence of particular modes associated with slow wave propagation in the porous plate. Third, a novel technique based on the transmission of airborne ultrasound through air-filled porous plates was introduced. Experimental results on different artificial and natural materials show the presence of a strongly dispersive, highly attenuated, slow compressional wave predicted by Biot's theory. [This work was sponsored by the Department of Energy Basic Energy Sciences Grant No. DE-FG-02-87ER13749.A000.]
Parameter deduction by matched-field processing near soil, snow, and pervious asphalt layers subject to acoustic excitation from a point source
Authors: Attenborough Keith
Published: October 2005

For many purposes the influence of porous ground surfaces on outdoor sound propagation is calculated adequately by assuming that the ground behaves as a semi-infinite or layered viscous fluid. Such calculation relies upon the dominance of the induced Biot slow wave traveling mainly in the air-filled pores. This assumption may be used in inversion processes whereby porosity, air permeability, tortuosity, and ground structure may be deduced from measurements of near-surface interference or penetration. Such a method has been tolerably successful when used on cultivated soils [Hess et al., J. Acoust. Soc. Am. 87, 1975–1986 (1990)]. This paper will describe attempts to use inversion processes on a variety of natural and artificial ground surfaces.
Dynamic permeability in porous media
Authors: Norris Andrew
Published: October 2005

The propagation of the acoustic slow wave at high frequencies and fluid transport at quasistatic frequencies are governed by the high- and low-frequency limits of the dynamic permeability in a porous medium. Recent numerical and experimental studies of the frequency dependence of the dynamic permeability have shown that it displays an almost universal behavior, except at low frequencies for media with pores that have characteristically sharp corners. This discrepancy is caused by the effect of the low-frequency inertial factor that is the first correction to the static permeability. This parameter can be calculated for a given pore geometry, and when its effect is properly taken into account, it is possible to express the dynamic permeability over the full frequency range in terms of a simple scaling function.
Acoustic transmission through layered porous and nonporous structures
Authors: Cops A. , Lauriks W. , Vervoort L. , Allard J. F.
Published: October 2005

A matrix formalism will be presented to describe the propagation of plane compressional waves in layered, fluid-loaded materials using the Biot theory. The three Biot waves have been taken into account and measuring equipment to determine the different elastic parameters of porous materials has been established. The model is then extended to include fluid and solid layers. Due to the matrix formalism, the reflection and transmission of plane acoustic waves on an arbitrary number of layers can easily be calculated. The model will be compared with measured data of the acoustic impedance of a layered system and with results for the transmission through a solid/porous/solid system. The proposed model can also be used to calculate the acoustic impedance of soil surfaces, which can be considered as a number of layers on an elastic half-space.
Cochlear waves in historical perspective
Authors: Zwislocki Jozef J.
Published: October 2005

The successive development of our understanding of cochlear waves is traced from Békésy's experiments on postmortem preparations to current experiments on live animals. The significance of the interaction between experimental and theoretical approaches is documented, and it is shown that experiments were not always right, and theories, not always wrong. Tonndorf's experiments on enlarged cochlear models elucidated some early contradictions between experiments and theory and showed that the long-wave approximation is acceptable in the basal part of the cochlea relative to the cochlear vibration maximum, and the short-wave approximation, near the maximum. Tonndorf also demonstrated that some cochlear nonlinear distortions were propagated along the cochlea. [Work supported by NIDCD Claude Pepper Award DC00074-28.]
In pursuit of Tonndorf's ideas: Cochlear distortion
Authors: Dallos Peter
Published: October 2005

In 1958 Juergen Tonndorf pioneered the use of CM measurements for assessing the spatial distribution pattern, and presumed origin, of cochlear harmonics. Subsequent results and ideas are reviewed with particular emphasis on the likely dominance of the production of cochlear distortion by outer hair cells.
Tonndorf and acoustic impedance
Authors: Allen Jont
Published: October 2005

Juergen was full of ideas that reflected his excellent understanding of the limits of technology and science. At first many of his ideas seemed impractical, but in my experience, he was usually right on target and got the results or data he was after. I learned many practice things from him in the lab; almost every encounter brought a new point of view or idea that had a long-term impact on my work. The most important project he introduced me to was that of measuring the eardrum impedance, with progressive damage to the cochlea and middle ear. I will describe this impedance measurement system, which is a one-microphone method, and discuss Juergen's and my results for the cat. The measurement system is presently the most accurate and quickest known method of measuring acoustic impedance in cavities, and it works to frequencies limited only by transducer bandwidth. The method uses four calibration cavities to find the source pressure (or velocity) and source impedance (or admittance) as a function of frequency. The losses in the cavities are included in the calibration calculation, and the method recovers automatically, using a minimization technique, the acoustic lengths of the four calibration cavities.
Predictions of the dependence of the difference limen on d′
Authors: Hellman William S.
Published: October 2005

The variation of the difference limen, ΔL[= 10 log(1 + ΔI/I)], with d′ is determined from requiring consistency between the relation d′σ = ΔN, and the observation that the neural count at a given level cannot depend on the choice of d′ used to determine ΔL. Here, ΔL is the change in neural count arising from a change in level, ΔL. These considerations place strong constraints on the dependence of ΔL on d′. The results follow from a Taylor-series representation for ΔN in powers of ΔL. The first-order approximation produces a linear relation between ΔL and d′; the second-order approximation generates small deviations from linearity for d′ < 3. These predictions are in agreement with experiments of Buus et al. [J. Acoust. Am. Suppl. 1 82, S25 (1987)], who report that the sensitivity d′ is nearly proportional to ΔL over the entire range of difference limens, and with the earlier work of Rabinowitz et al. [J. Acoust. Soc. Am. 59, 1506–1509 (1976)]. The results of the second-order approximation are exact when Weber's law holds.
The crack of the bat: Material properties, dynamic response, and sound radiation of baseball bats
Authors: Collier Robert D. , Dresens Paul
Published: October 2005

The crack of the bat on contact with a fastball is one of the special effects that contribute to the enjoyment of baseball. The objective is to establish relationships between the dynamic mechanical material properties, vibration characteristics, and acoustic radiation of hardwood, aluminum, and composite material baseball bats. Results of structural analyses are compared with laboratory and field experimental vibration and acoustic measurements. The aluminum bat characteristically exhibits a series of lightly damped resonant frequencies, relatively high handle vibration levels, and a distinct narrow-band radiation signature. Traditional hardwood bats have fewer, lower Q, low-frequency resonances, resulting in relatively low handle vibration levels and an impulsive sound signature governed by low-frequency components. A recently developed composite materials hat has a specially configured high-strength core integrated with a hardwood exterior shell. The dynamic and acoustic response of the composite bat is similar to that of hardwood bats. Field testing of the three types of bats provides performance measures that can be related to structural acoustic and vibration characteristics for parameter modifications and design improvements.
Sensitivity analysis of an algorithm for applying the time-temperature superposition principle
Authors: Dlubac J. J. , Deigan R. J.
Published: October 2005

The measurements of the dynamic complex modulus of viscoelastic materials on any apparatus is confined to a limited frequency and temperature range. It has been observed that an increase in temperature produces an identical effect in a viscoelastic material as a decrease in frequency and vice versa. Empirically, then, there is a correspondence between temperature and frequency. The time-temperature superposition principle with reduced variables provides a method of extending the effective frequency range of the dynamic modulus and loss factor. This technique involves measuring the complex modulus over a limited frequency range and a variety of temperatures. The data at different temperatures are then plotted versus frequency and shifted along the frequency axis until a smooth curve results over a broad frequency range at some fixed temperature. This paper reviews the time-temperature superposition principle, and presents an implementation algorithm and an ad hoc error analysis.
Perceptual shift of accent in English
Authors: Hasegawa Yoko , Hata Kazue
Published: October 2005

It has been found that the perception of an accentual high tone (H) in Japanese is determined by both the F0 peak location and the F0 drop rate thereafter. The actual F0 peak need not occur on the accented syllable: If the peak is approximately within the first half of the postaccent syllable, and the drop rate is greater than a certain value, the H will be associated with the accented syllable [Y. Hasegawa and K. Hata, J. Acoust. Soc. Am. Suppl. 1 83, S29 (1988); K. Hata and Y. Hasegawa, J. Acoust. Soc. Am. Suppl. 1 84, S156 (1988)]. The preliminary experiment indicates that this perceptual accent shift is also observable in English; therefore, the effect must be taken into consideration in synthesizing English utterances. The present study investigates the case where the intonational H occurs on the utterance-final syllable, e.g., “This is my nét.” In such a case, due to the exaggerated F0 lowering at utterance end, the drop rate after the peak may be so great that the perceptual shift can occur, i.e., the utterance may be perceived as “This is mý net.” Listening to synthesized utterances with varying drop rate on the final syllable, the subjects judged whether each utterance is more appropriate to responding to “What is it?” (inducing the accent on “net”) or “Is it her net?” (inducing the accent on “my”). The approximate value at which the shift occurs will be reported.
Acoustic effects of combining phrase-final and focal stress in English
Authors: Behne Dawn M.
Published: October 2005

In English, sentence stress is used both to mark a phrase boundary and to provide focus for new discourse information. The goal of this study is to describe the behavior of the acoustic signal when phrase-final and focal stress occur in the same sentence. Two questions were addressed: (1) How do acoustic correlates of stress behave when phrase-final and focal stress converge within a sentence? (2) How do acoustic correlates of stress behave when phrase-final and focal stress occur separately in a sentence? Subjects produced sentences containing monosyllabic works in phrase-initial and phrase-final position which were either focused or non-focused by the discourse. Fundamental frequency change, vowel duration, amplitude, and the position of the maximum amplitude were measured. The results indicate that for the parameters investigated (1) the acoustic correlates of stress are additive when phrase-final and focal stress converge in a sentence; and (2) the acoustic correlates of stress are more dominant for phrase-final stress than for focal stress when they occur separately in a sentence. These findings suggest that sentence stress simultaneously signals phrase-final and focal stress by superimposing one on the other.
The effect of rate of speech on perception of syllabicity
Authors: Taub Sarah F.
Published: October 2005

Prior research indicates that a simple increase in the duration of sonorants such as /rln/ causes them to be perceived as syllabic, e.g., a lengthened /r/ in “prayed” causes it to be perceived as “parade” [P. J. Price, Phonetica 37, 327–343 (1980)]. This experiment investigated whether speech rate would influence the crossover from nonsyllabic to syllabic /l/. The sentence “Now I'm going to say blow again” was recorded spoken at fast and slow rate (1197 and 3524 ms total, respectively). Additional versions were created by lengthening the [1] to two, three, or four times its original duration. Eight single-word tokens were also created by splicing out the word “blow” (or “below”) from the sentence contexts. Twenty listeners identified the target words, in and out of sentence context, as “blow” or “below.” Results indicate that the rate of the isolated target word itself had little influence on the crossover but that the rate of the surrounding sentence had much more. The implications of this result will be discussed.
Non-F correlates of prosody in free conversation
Authors: Erickson Donna , Fujimura Osamu , Bauer Harold R.
Published: October 2005

Expressive features may have physical correlates of a large variety, including (1) formant patterns; (2) voice source spectrum slope; (3) other voice quality characteristics, e.g., vocal fry; and (4) phrasing. For a given sentence (for which the intonational pattern is described) can these articulatory and laryngeal variations be predicted, depending on expressive conditions, and if so, how? A number of free conversations were recorded and analyzed in terms of their F0, F1, F2, voice quality and durational characteristics. For a comparison with a similar, controlled set of utterances, the same speakers (a) read parts of their recorded conversations (from an orthographic transcription) and (b) imitated their own speech after listening to parts of their recorded conversation. The acoustic signals were analyzed, comparing the three different situations. Initial analysis suggests that indeed there is independent control of articulatory and voice quality correlates. The question whether these physical correlates are completely representable by the current intonation theory will be discussed.
P centers and temporal distortion
Authors: Lame Gerald D.
Published: October 2005

Most research on P centers relies on the implicit assumption that the time between P centers is perceived veridically. This is closely related to the claim that P centers are uninfluenced by context. However, temporal illusions are well known. If the duration of a syllable rhyme influenced the perceived duration of the interval it occupied, perceived isochrony adjustments would be affected. Like considerations apply to production. Work addressing this “temporal distortion hypothesis” will be presented. In a speech production task requiring the synchronization of monosyllables with a metronome, it was found that, while relative timing between syllables conforms to the P-center description, the alignment of a syllable with the metronome is influenced by the length of the preceding syllable's rhyme. Such behavior is consistent with the operation of an internal clock, used for perception and production of rhythmic intervals, which is phase shifted by acoustic events.
Shortening of feet in longer articulatory units
Authors: Campbell W. N.
Published: October 2005

A 20-min radio broadcast of a short story, digitized and measured for both syllable and pause durations, was studied with respect to the durational characteristics of both pause durations and rhythmic groups. Syllables were grouped into feet and foot durations were calculated. Feet were then grouped into interpausal units and the durations of these larger articulation groups were also calculated. The hypothesis that pause duration is a function of average foot length, determined over the previous n feet, was tested for different values but no supporting evidence was found. It has already been shown that the durations of both stressed and unstressed syllables in a foot tend to decrease as the number of syllables in the foot increases. Evidence was found here for a similar shortening of average foot durations as the number of feet per interpausal unit increases. This shortening indicates that an element of planning may be involved at higher articulatory levels. That the shortening is asymptotic lends support to the concept of a minimum duration at some level of the timing hierarchy.
An acoustic and perceptual study of undershoot in clear and reference speech
Authors: Moon Seung-Jae
Published: October 2005

The vowel reduction (or undershoot) phenomenon in “clear” (over-articulated: CS) versus “reference” (citation list: RS) speech was investigated by systematically controlling “locus-to-target” distance, lexical stress, and vowel duration. Speech samples from five American English speakers were measured. Each subject produced 12 words, consisting of a stressed [wV] syllable followed by 0, 1, or 2 unstressed syllables, five times each in the two speaking styles yielding 120 tokens per subject. Acoustic analyses were performed on the first three formants. For the perception task, the same tokens were embedded in noise (−6 dB/oct) with varying signal-to-noise ratios. The results from formant measurements showed that all speakers exhibited duration-dependent undershoot phenomenon. However, the degree of undershoot varied considerably between vowels, between speakers, and between speech styles. CS formant patterns were found to be closer to a null context [hVd] pattern than RS patterns were. This suggested that CS involves an active reorganization of phonetic gestures. The results from audibility and identification tests showed that CS is, in general, more audible and intelligible than RS under the identical signal-to-noise ratios. These results indicate that speakers change and modify their speech according to the needs of listeners. In other words, speakers show a successful adaptation to the on-line constraints/contexts of speaker-listener interaction.
Open ocean bubble measurements from multifrequency acoustic backscatter
Authors: Vagle Svein
Published: October 2005

Breaking waves produce large numbers of gas bubbles immediately below the ocean surface. The effect of these bubbles on the sound speed is important in studies of sound propagation in the upper ocean. Recent studies have also indicated that the bubbles can play a major role in gas exchange through the air-sea interface. The bubbles are also being used as passive tracers to study the flow field in the upper ocean. For most studies involving the bubbles, it is of importance to determine the actual size distribution of the bubbles. Here, some results from the SWAPP and Critical Sea Test experiments, where a six-frequency acoustic backscatter technique was used, will be presented. Variability in the bubble size distribution will be related to the “age” of the bubble clouds as well as to the presence of coherent flows in the ocean, such as Langmuir circulation.
Preboundary lengthening and intonational and prosodic constituents
Authors: Rietveld Toni , Gussenhoven Carlos
Published: October 2005

An experiment was carried out in order to assess the relation between preboundary lengthening on one hand and intonational and nonintonational prosodic constituents on the other. A number of sentences, realized by an American female speaker, were recorded, manipulated, and subsequently presented to a panel of American listeners. The sentences in each set contained an identical string of segments that occurred before a foot boundary (F), word boundary (W), phonological phrase boundary (P), and an intonational phrase boundary (I). An example is the string [suwprst] in: It's these SUperSTitions that I dislike (F boundary); It's a SUper STAtion they've got there (W boundary); We gave the SUper STAtionary to write with (P boundary); And for the SUper, STEAK will be fine (I boundary). The duration of the preboundary strings was varied in six steps, by lengthening and shortening the original lengths. In addition to the durational makeup of the strings, the intonation contour of the sentences was manipulated. Each of the sentences was resynthesized with two intonation contours: one with rise-falls on the accented syllables and one in which the initial rise and final fall were bridged. The former contour was assumed to create an intonational boundary between the peaks [the association domain (AD) boundary]. Subjects were asked to rate the preboundary segments as “too long,” “just right,” or “too short.” It was found that the depth of the prosodic boundaries and the presence or absence of AD boundaries require different temporal structuring of the associated preboundary segments. The judgments of the subjects suggest that AD boundaries require longer preboundary segments, whereas the relation between depth of nonintonational boundary and lengthening is less direct. The “durational tolerance” appears to be larger before deeper boundaries. An additional finding was that before AD boundaries significantly more “just-right” judgments were given, which effect was progressive with prosodic boundary depth.
The effect of word length of segmental duration ratios in Estonian
Authors: Krull Diana
Published: October 2005

Estonian stressed syllables have three distinctive quantity degrees: short (Q1), long (Q2) and overlong (Q3). The duration of the vowel in the immediately following unstressed syllable is short to half-long depending on the quantity degree of the stressed syllable. The identification of quantity degrees is based on duration ratios between syllables and segments. For the differentiation of Q2 and Q3 additional cues are needed [I. Lehiste, FUSAC '88: Proceedings of the Sixth Annual Meeting Fenno-Ugric Studies of Canada, edited by J. Nevis (1988)]. In the present study, one to five derivational syllables were added stepwise to the words /sata/, /saate/, /sattu/, /saaat(u)/, /sattt(u)/, and /saaattt(u)/. The words were read by five native speakers with and without carrier phrase. Lengthening the word shortened and stressed vowel (V1), the following consonant (C) and unstressed vowel (V2) in about equal proportion. The V1/C and V1/V2 ratios were therefore usually preserved. An exception were words with a short V1 followed by an (over)long C where C and V2 tended to be slightly more compressed than V1 in longer words. Estonian thus differs from a language like Swedish where temporal compression tends to even out durational differences [B. Lindblom, B. Lyberg, and K. Rapp, Indiana University Linguistics Club, 1981].
Projection of the far-field target strengh of a continuously illuminated rigid sphere from the near field
Authors: Groutage F. Dale , Kollars Robert D. , Swenson Ernest
Published: October 2005

Simulated near-field measurements of composite scattered and continuous plane-wave illumination pressure fields were used to accurately predict the far-field target strengh of a rigid sphere. A theoretical diffraction model of a rigid sphere [R. V. Waterhouse, J. Acoust. Soc. Am. 75, 695–706 (1983)] was verified and used to simulate scattering in the geometric near field. Separation of the incident and scattered fields was based on wave-vector filtering where a two-dimensional spatial FFT was used to centralize the incident field. Following successful decompsition of incident and scattered fields, the complex near-field pressures were appropriately windowed and then projected to the far field via the Helmholtz integral [J. Hald, B&K Tech. Rev. 1, 5–9 (1989)]. Several supporting simulations were completed that optimized the parameters to allow a small measurement array for cost effective implementation.
Acoustic scattering from free field and buried spherical shells
Authors: Lopes Joseph L. , Todoroff Douglas G.
Published: October 2005

A measurement was conducted to investigate the effect of sediment loading on the characteristic elastic response of an object. Backscattered form functions were obtained for free field and buried 2% and 11% spherical shells. The results have shown that the free-field form function for the 2% shell is dominated by the nondispersive s0 mode while the 11% shell is dominated by the antisymmetric Lamb mode a0. Upon sediment loading, the a0 resonances shifted to higher frequencies. The results of this experiment are in good agreement with theoretical calculations.
A variational model for bubbly liquids: Reflection from a liquid-bubbly liquid interface
Authors: Hawkins J. A. , Bedford A.
Published: October 2005

Recently, K. W. Commander and A. Prosperetti [J. Acoust. Soc. Am. 85, 732–746 (1989)] presented a model for the acoustics of bubbly liquids containing a distribution of bubbles sizes. They also analyzed the reflection and transmission of waves normally incident on a layer of bubbly liquid. In this paper the reflection and transmission of oblique plane waves at the interface between a liquid and a bubbly liquid are analyzed. The analysis is based on a variational theory for the acoustics of a bubbly liquid with a distribution of bubble sizes [J. A. Hawkins, Jr. and A. Bedford, J. Acoust. Soc. Am. Suppl. 1 86, S42 (1989)]. It is shown that the reflection and transmission coefficients are relatively insensitive to the bubble size distribution.
Reduction of plumbing noise in lightweight construction
Authors: Warnock A. C. C. , Morin M. J.
Published: October 2005

Noise from plumbing fixtures can be a source of great annoyance in single-family and multi-family homes. Noise-control articles and textbooks usually recommend the use of resilient supports for pipes and other fixtures as a means of controlling noise. A study recently completed at NRC examined the changes in noise level produced by different types of pipe. different methods of mounting pipes. different wall types. and the addition of sound absorbing materials in walls. Noise sources used included an ISO standard plumbing noise source, a toilet, a sink, and five common bathroom faucets. Closed cell foam rubber supports were found to be the most effective of the resilient materials tested, providing reductions in A-weighted noise levels of around 20 dB. This paper will give a summary of the results obtained. [The study was funded by Canada Mortgage and Housing Corporation.]
Sound transmission through very porous concrete blocks
Authors: Warnock A. C. C.
Published: October 2005

Sound transmission loss measurements through a wall constructed from very porous concrete blocks gave some interesting results. The unfinished block wall had a sound transmission class (STC) rating of 14. This was increased to only 29 by screwing a layer of drywall to one side of the block wall. The drywall, while it provides a sealed surface, is not well enough bonded to the blocks and can still vibrate fairly freely. Plastering increased the STC to 43. The porosity of the block increased the effective depth of the air space behind the drywall. This lowered the mass-air-mass resonance substantially and, with drywall supported on steel studs, plastered block wall systems gave very good STC ratings. Walls constructed using this type of block can give STC ratings about as high as those obtained with heavier normal weight blocks. Measurements were made down to 63 Hz and revealed that in many cases there are resonances occurring below 125 Hz that have a strong influence on transmission loss values at and above 125 Hz. Measurement to these low frequencies give a clearer picture of the effect of changes to the wall structure. The results obtained will be presented and discussed.
Suggested infrasound criteria for building spaces
Authors: Tocci Gregory C.
Published: October 2005

Work by Leo L. Beranek [“Application of NCB Noise Criterion Curves,” Noise Control Eng. J. (Sept.–Oct. 1989)] presents and discusses a set of “balanced noise criterion curves.” These are cited as an improvement in the widely used NC curves and extends them down to the 16- and 31.5-Hz octave bands. These curves are steeply sloped in the very low-frequency range and are intended to be based wholly on audibility. The author draws upon his experience and a paper by H. Dawson [“Practical Aspects of the Low Frequency Noise Problem,” J. Low Freq. Noise Vib. 1 (1) (1982)] to arrive at a modified set of NC curves extending down to 16 Hz that combine audibility and feelability affects. Examples of the application of these suggested criteria curves will be discussed.
Measurement metrics related to inception and development of cavitation of a low-frequeacy flextensional transducer
Authors: Collier Robert D. , Mazurek Jeffrey A. , Walters David L.
Published: October 2005

The objective is to establish cavitation limits for an operational transmit array. Measurements on a single 1-kHz Sanders model 30 flextensional transducer cover an input power range of 140 to 4860 W at pulse lengths of 20 ms and 2 s. Acoustic tank and lake measurements, supplemented by underwater television video recordings, indicate: (i) near-field pressure waveform distortion is the earliest indicator of localized bubble formation or “soft” cavitation (500 W); (ii) the steady reduction of electrical drive impedance (175 to 75 Ω) and a steady increase in near-field pressure harmonic distortion (0% to 50%) are directly related to the growth of the cavitation field as electrical drive power is increased; (iii) near-field pressure broadband energy increases with cavitation development; and (iv) at the highest drive levels, the expected bifurcation of the fundamental frequency is observed indicating the presence of “hard” or transient cavitation. Near-field acoustic holography data provide surface pressure distributions and correlation of cavitation inception predictions with the video data. The relationships of these metrics to far-field source levels and beampatterns will be discussed in the context of defining an overall operational transmit system drive levels.