bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic power output measurement by pulsed radiation pressure
Authors: Fick Steven E.
Published: October 2005

Direct measurements of time-average spatially integrated output power radiated into reflectionless water loads can be made with high accuracy by exploiting the radiation pressure which causes an absorptive target intercepting the entirety of an ultrasound beam to experience a force proportional to the total beam power, which, in turn, is readily determinable as accurately as the radiation force can be measured in isolation from confounding forces arising from such effects as buoyancy, surface tension, and vibration. A radiation force balance (RFB) constructed at NBS in 1974 is the first and only RFB known to be designed to employ simultaneous mechanical and electrical signal processing based on temporal modulation of the incident ultrasound at a frequency well above those characteristic of confounding phenomena. Equipped with purpose-built electronics, the RFB is operated by manually equalizing the radiation force and a counterforce generated by an actuator calibrated against reference masses using dc current as the transfer variable. Improvements made to the RFB during its one overhaul in 1988 have nearly halved its overall measurements uncertainty, and extended its capabilities to include measuring the output of ultrasonic systems with arbitrary pulse waveforms.
Effects of structure sensitivity of linear and nonlinear elastic moduli in built-of-contact systems
Authors: Zaitsev V. Yu.
Published: October 2005

Acoustical properties of built-of-contact systems are rather interesting both from the viewpoint of general physical acoustics and applied problems. Such structures can often demonstrate rather unusual acoustic properties (in this sense they are similar to such a popular object in acoustics as bubbly liquid). On the other hand, built-of-contact systems correspond to real physical structures, e.g., grainy media and rough contacting interfaces. Manifestations of their structural changes in linear and nonlinear acoustic properties are important for the creation of new methods of acoustical diagnostics. The results of numerical simulation of nonlinear harmonic generation under the action of an external sinusoidal drive in a model built-of-contact system with different initial compression is presented. The model has allowed experimental explanation of observed ‘‘unusual’’ nonlinear elastic properties of real grainy materials, which cannot be explained by known theoretical models, which do not take into account nonideality of packing, i.e., the presence of intergrain contacts with significantly different initial compression. It was revealed that higher-order elastic parameters are much more sensitive to the material structure changes than the liner modulus. This fact is rather encouraging for the creation of new nonlinear acoustic structure diagnostics methods.
Quantitative calibration and characterization of marine seismic sources
Authors: Fricke J. Robert
Published: October 2005

In the mid ’80s the offshore seismic exploration industry needed a standard procedure for describing transient seismic source signatures. The need was motivated by several issues including a need to specify performance criterion to the operations crew, a need to evaluate one source versus another for a particular seismic program, and the need to determine performance for new seismic source designs. Prior to that time, seismic source signatures were usually described in the time domain in terms of peak-to-peak pressure (bar-m) and peak-to-bubble ratio. Spectral characterization, if it existed, was relative to the peak value, which was usually set to 0 dB. These measures do not provide quantitative descriptions of source energy or spectral energy density, hence a quantitative standard was needed and developed. The standard focused on a spectral, rather than a temporal, description of the seismic signature and allowed for a detailed analysis of the total source energy and the distribution of that energy as a function of frequency. This approach opened the way for a consistent and quantifiable description of the source signature. Using this description, the above mentioned needs regarding performance and evaluation could be addressed.
Fourier and direct time-marching methods for transient signals
Authors: Porter Michael B. , Michalopoulou Zoi-Heleni
Published: October 2005

The ocean normally vibrates in harmony with the hum of anarrow-band sound source. Thus, for modeling such signals, time can be removed from the wave equation reducing it to the simpler Helmholtz equation which in essence governs only the intensity of the hum. Computational ocean acoustics has most often focused on this latter case. Broadband signals such as pings, clicks, chirps, and gurgles require far more work. For researchers accustomed to narrow-band models the fastest approach is usually to simply add a frequency loop to their narrow-band codes. (Of course, the run time goes up in accordance with the number of frequencies required.) Others have advocated the development of new models that solve the wave equation directly in the time domain. These options are surveyed and illustrative examples are provided using both idealized test cases and measured data from a recent experiment in the Gulf of Mexico.
Low-frequency ambient noise: Long time series and statistics
Authors: Curtis Keith R. , Howe Bruce M. , Leach Shaun
Published: October 2005

Low-frequency ocean ambient noise spectra have been collected at U.S. Navy Pacific SOSUS sites during the last year as a background com- ponent of the Acoustic Thermometry of Ocean Climate (ATOC) Program. Preliminary results are presented. Three-minute averaged spectra were obtained every 5 min; only the relative noise level as a function of frequency is presented because (at this time) unknown offsets prevent determination of absolute levels. One important statistic estimated is the probability as a function of frequency that the noise level exceeds a specified spectral level. [Work supported by the Strategic Environmental Research and Development Program through ARPA.]
Influence of local static stress on structural acoustics: Experiment and modeling
Authors: Gangala Hareen K. , Mann J. Adin
Published: October 2005

An experimental setup was designed to locally introduce stresses in a steel beam. The far-field sound power radiated by the beam was experimentally calculated for various magnitudes of the induced stresses. As a model, a finite element code was developed for the equation of motion due to a modified theory of acoustoelasticity [Pao etal., J. Appl. Mech. 58, 11–17 (1991)]. The theory allows the static stress components to be additions to the elastic moduli of the body. The sound power radiated by a beam was calculated from the FEM model results for axial, transverse, shear, and combined distributions of the stress components. Experimental results showed that the sound power increased by up to 1 dB as the static stress was varied. Results from the FEM model showed that all the individual stress components contribute to the radiation and the combined effect was about a 1 dB increase in the radiated power. Both experimental and model results suggest that static stresses induced by discontinuities such as welding and bolting can play a role in the mechanisms of the sound radiation at a discontinuity in a structure. [Work supported by ONR.]
Effect of thickness variations on the sound radiation from beams
Authors: Slaughter Julie C. , Mann J. Adin , Adams Daniel O
Published: October 2005

The effect that spatial thickness variations of a beam has on the beam’s far-field sound radiation was studied. The steel beams that were used in the initial tests show that at low-frequency ranges (500–1500 Hz) the thickness variations acted as discontinuities along the beam that increased sound radiation. However, at higher frequency ranges (2000–4000 Hz) the thickness variations, when spaced at certain intervals, acted as global stiffness changes and decreased the sound radiation. This decrease occurred when the spacing of the variations corresponded to a structural wavelength. Composite beams with thickness variations have also been built and tested. The spatial thickness variations appear to have a similar effect on the sound radiation as in the steel beams. The two data processing techniques used to evaluate the influence of the spatial thickness variations were a phase-speed tracking filter to quantify wave propagation in the structure and a wave-number domain filter to quantify far-field radiation. Results from these tests will be used to help determine how quieter materials can be designed. [Work supported by NSF.]
Structural vibration noise from open grid bridge decks
Authors: Cuschieri J. M. , Tournour M.
Published: October 2005

The contribution to the overall tonal component of the noise from the vibration of the grid section of an open grid bridge deck due to excitation by the interaction with the vehicle tires is investigated. Using vibration field measurements of the grid and laboratory measurements of the acoustic radiation efficiency, it is shown that the contribution to the overall noise level measured at the curb from the vibrations of the grid is insignificant. The main reason for this result is the poor acoustic radiation efficiency of the grid. Because of the large percentage of open area, the plate-like modes of the grid deck have very poor radiation efficiency. Similarly, the individual grid elements, based on their size and the frequency range where the predominant excitation from the tire takes place, are also very inefficient acoustic radiators. The significance of this result is that mitigation procedures that only reduce the vibration of the grid will not significantly reduce the overall radiated noise. [Work sponsored by FDOT.]
Tire noise from open grid bridge decks
Authors: Cuschieri J. M. , Gregory S.
Published: October 2005

Having identified that the contribution to the overall noise from the grid vibrations is insignificant, the attention is focused on the noise radiated from the vibrations of the tire. Field measurements of tire vibrations are rather difficult, therefore laboratory measurements and analytic modeling were used to understand the contribution from the tire vibrations. The laboratory measurements of both vibration and radiated noise compare well with the estimates from the analytic modeling. Using an estimate of the interaction force between the tire and the grid, from the field vibration data, it is shown that the estimated radiated noise level is comparable to the field measured noise level at the curb. This leads to the conclusion that the noise from the tire vibrations is the dominant source, and mitigation procedures must consider ways of reducing the excitation of the tire. This conclusion is verified by sound level measurements performed with the contribution from the grid vibrations removed. [Work sponsored by FDOT.]
Combined large area sensor—actuator tile for the NRL-ABC platform
Authors: Corsaro Robert D. , Houston Brian
Published: October 2005

A new research platform has been constructed for underwater studies of sensor/actuator coupling mechanisms. It consists of a 15-tile array of ‘‘ABC’’ tiles, where each tile contains a large area actuator, pressure sensor, and velocity sensor, where the latter is constructed by summing and integrating the outputs of four accelerometers. This paper presents details of the tile design and the predictive models used. Issues addressed include spatial sampling, near-field sensing, internal resonances, and both direct and extraneous coupling mechanisms, all of which can contribute to complicate the system transfer functions. Acoustic characteristics of the ABC tile were evaluated in the NRL Large Pool Facility, both in the free field and when mounted on a backing structure, and these results are compared with predictions. Implications for local control of the actuator’s surface are also discussed.
Lexical distinctiveness in lipreading: Effects of phonemic equivalence classes on the structure of the lexicon
Authors: Auer Edward T. , Bernstein Lynne E.
Published: October 2005

Speech perceived on the basis of viewing a talker’s face affords less phonetic distinctiveness than acoustic speech. Effects of this reduced distinctiveness can be estimated in relation to the structure of the mental lexicon. Based on empirical measures of phonetic confusability, recoding rules can be defined for mapping fully specified phonological forms into lexical equivalence classes. For example, under the recoding rule that /b/ and /p/ are in the same phonemic equivalence class the words ‘‘bat’’ and ‘‘pat’’ map into the same lexical equivalence class. After applying a set of recoding rules to a large online lexical database, the resulting structure of the lexicon can then be studied quantitatively. One such measure of the recoding effects on the lexicon is percent information extracted (PIE) [D. M. Carter, Comput. Speech Lang. 2, 1–11 (1987)]. Lexical statistics describing the results of applying sets of recoding rules derived from analyses of visual-phonetic confusability to a 30 000-entry lexicon will be presented. Implications for the use of top-down lexical constraints in resolving bottom-up visual-phonetic ambiguity during lipreading will be discussed. [Work supported by NIH.]
Multinomial models of speech perception
Authors: Crowther Court S. , Batchelder William H.
Published: October 2005

It is often the case that two different acoustic cues can influence perception of both of two adjacent phonemes within a syllable. In such cases, it is of interest to determine whether the cues are evaluated independently; that is, does a listener’s evaluation of one cue influence evaluation of the other cue? Another, related question is whether, as some researchers claim, phoneme decisions are dependent in the sense that, when cued by the same information, the decisions compete for the information. This study modeled data from a two factor, four category experiment in which F1 offset frequency and vowel duration cue both voicing and vowel identity in CVC syllables. A family of multinomial processing tree models [e.g., D. M. Riefer and W. H. Batchelder, Psychol. Rev. 95, 318–339 (1988)], of which the fuzzy logic model of perception for the two factor, four category design is a special case, was developed and tested to explore the independence issues. This modeling approach is highly flexible and allows one to test a wide range of hypotheses regarding speech cue processing.
Are coronals different? The influence of the lexicon on coronal identification
Authors: Newman Rochelle , Sawusch James R. , Luce Paul
Published: October 2005

In previous studies of lexical effects on phoneme identification, robust effects have been reported for voicing series with noncoronal places of articulation (e.g., /b/–/p/ or /g/–/k/). These same effects have been much more variable, smaller, and often absent for coronal voicing series (/d/–/t/). Previously, results were presented suggesting that neighborhood density could have effects similar to those of lexical status in phoneme identification tasks for noncoronals. For coronals, neighborhood density did not have an effect, again paralleling the lexical results. In new studies, additional coronal stimuli have been tested. Series have used word–nonword series to examine the influence of lexical status and nonword–nonword series to examine the influence of lexical neighborhood (the number of words similar to the target). The new stimuli included /d/–/t/ series where the initial stop is part of a consonant cluster. The results for /d/–/t/ series in clusters show robust lexical influences on phoneme identification. These results will be discussed in terms of their implications regarding the status of coronals and the nature of consonants in clusters. [Work supported by NIDCD Grant DC00219 to SUNY at Buffalo.]
Shifts in fundamental frequency and articulation resulting from intoxication
Authors: Alderman G. Allan , Hollien Harry , Martin Camilo , DeJong Gea
Published: October 2005

Two groups of subjects were administered controlled doses of alcohol while breath alcohol concentration (BrAC) measurements were made at regular intervals. They were recorded reading a 30-s passage when they reached preset BrAC windows. Fundamental frequency measurements were calculated and compared for sober (0.00 BrAC) and intoxicated (0.12 BrAC) productions. The number of misarticulations occurring during the readings also were assessed. In the first study, subjects were grouped on the basis of whether they were rated as sounding intoxicated at 0.12 BrAC (ratings were performed by 50 auditors using a 5-pt. scale). Subjects who sounded intoxicated were placed in one group, while those that did not were placed in a second. The first group showed a consistent, but statistically nonsignificant decrease in F0 as a result of intoxication; group 2’s F0 changes were not consistent. In addition, the first group showed a higher mean increase in misarticulations than did group 2. The second population was grouped by drinking level (heavy, medium, or light); none showed a statistically significant change in F0. Moreover, misarticulations increased (nonsignificantly) as drinking level increased. The results will be correlated with data from other studies. [Research supported by NIH.]
Predicting speech improvement from clinical profiles in stutterers
Authors: Howell Peter
Published: October 2005

Procedures for assessing dysfluencies in stuttered speech have the limitation that they show poor inter-judge agreement. This constitutes a serious problem for, amongst other things, assessing how a stutterer’s speech benefits from therapy. A critical review of alternative procedures that are available indicates that they do not offer any better prospect for assessing improvements due to treatment than do the traditional procedures. Several factors are identified which might lead to the limitation in agreement. A new procedure which overcomes some of the problems identified was devised and applied to a group of stuttering children before and after they received a 2-week intensive therapy course. The new procedure produced substantially higher levels of agreement than those reported in the literature. This procedure is used to measure the benefit each individual child achieved after treatment. Clinical review data on these children were then employed to see whether any aspect of the interview could have predicted the child’s response to treatment. The child’s general health and cognitive skills appear to be reliable indications as to treatment prognosis. [Work supported by MRC.]
Intraspeech masking in hearing-impaired listeners
Authors: Summers Van , Leek Marjorie R.
Published: October 2005

Upward spread of masking (USM), the masking of an acoustic signal by energy at lower frequencies, tends to increase with presentation level and is more pronounced in listeners with sensorineural hearing impairment (HI listeners) than in normal-hearing (NH) listeners. At high presentation levels, HI listeners may experience a decrease in the cues available from higher frequency regions due to masking produced by high-amplitude first formant (F1) resonances. In the present study HI and NH listeners labeled synthetic consonant–vowel stimuli at moderate and high presentation levels. F1 regions were attenuated by 0, 6, 12, or 18 dB to test whether F1 attenuation might reduce USM, making cues present at higher frequencies more available. Performance was tested in quiet and in broadband noise sufficient to mask initial consonantal bursts. For both groups of listeners, noise reduced labeling accuracy. For normal-hearing listeners, performance was not affected by presentation level or F1 attenuation. While some HI listeners showed clear improvements in labeling with F1 attenuation and/or increases in presentation level, the pattern did not hold across the entire group. The results will be discussed in light of the severity and configuration of the individual hearing losses.
Modeling pathologic vocal quality. Part I
Authors: Kreiman Jody , Gerratt Bruce R.
Published: October 2005

Previous studies of pathologic vocal quality have not yielded a standard set of scales for describing disordered voices, possibly due to the limited number of voices studied. The present study used large sets (n=80) of male and female voices, representing a broad range of diagnoses and vocal severities. Eight experts judged the dissimilarity of each pair of voices, and responses were analyzed using nonmetric individual differences multidimensional scaling. Results indicate that differences between listeners in perceptual strategy are so great that the fundamental assumption of a common perceptual space must be questioned. Group spaces revealed a single ‘‘feature’’ (severity of pathology). Spaces for individual listeners were characterized by clusters of voices which seemed structured by ‘‘family resemblances’’: Each voice in a cluster resembled others with rspect to some property, but the same property did not constitute the resemblance for all voice pairs. Further, voices did not appear consistently in the same clusters across listeners. In the absence of a common perceptual space—of a shared sense of how voices sound similar—valid perceptual scales cannot be defined. The results lead to the conclusion that standardization of perceptual labels for voice quality is theoretically impossible.
The French benchmark on computational methods and experiments in structural acoustics
Authors: Valor C.
Published: October 2005

The idea of creating a working group to perform benchmark on computational methods and experiments in structural acoustics originated as a conclusion of the congress ‘‘Prediction of the noise emitted by vibrating structures,’’ held in March 1991. This group was effectively created in 1993, by S.F.M. and S.F.A. and is constituted by researchers working in laboratories, industries, and consulting companies. The name of the participants with their affiliation will be given at the oral presentation. In order to simplify the publications of this working group, a fictitious name (C. Valor) has been created and represents the participants. Each year several one-day meetings are organized, they are devoted to the comparison of the different results obtained on each benchmark case. The discrepancies are analyzed, leading to new calculations if necessary. When a common agreement is obtained by the working group, each participant having performed the results writes a scientific report collected by the working group. The final goal is to publish a book giving the synthesis of all the work produced by the group. During the presentation, the computational and experimental benchmark will be presented and examples of results will be discussed.
Effects of low-frequency sound (ATOC) on marine mammals: An experimental approach
Authors: Costa Daniel P. , Goley Dawn , Waples Danielle , Croll Don , Le Boeuf Burney , Cascadia John Calambokidus , Harvey James
Published: October 2005

This presentation will outline the research program currently in place to study the effect of the California ATOC experiment on marine mammals. There are three phases to this research: (1) a preliminary baseline data collection period prior to any ATOC transmissions, (2) a pilot study (when ATOC transmissions would be manipulated to assess effects on marine mammals), and (3) a monitoring period (when transmissions are optimized for climate study, ATOC feasibility operations). During the pilot study ATOC transmissions would be 4 days on, 7 days off and changes in the animals distribution, abundance, and general behavior measured. This experimental pattern would be replicated to provide statistical power. Although the objectives are different for each period, the research methodology remains the same. Methods used will be aerial and shipboard surveys to assess distribution and abundance, shipboard observations to assess behavior, a towed array to assess acoustic behavior, photo-identification to examine long-term movements and stock identity, and very high frequency (VHF) radio tags and time depth recorders (TDR) to assess dive behavior and movements. Data collected during the preliminary period are being used to predict sample sizes necessary for studies that would be carried out during the pilot study.
Acoustic tracking of whales using hydrophone arrays: Implications for behavioral studies and population estimates
Authors: Clark Christopher W.
Published: October 2005

Understanding how free-ranging whales use sound to communicate, navigate, and find food has been seriously hampered by the inability to consistently identify, locate, and track the animal producing the sound. Only in the most tractable situations (e.g., coastal species, shallow water, breeding/calving season) has it been possible to describe acoustic repertoires and prescribe biological functions. The potential use of such acoustic techniques, in combination with traditional visual observation methods, for population census efforts has been clearly demonstrated in the case of bowhead whales. Recent application of large aperture arrays and beamforming techniques has demonstrated the feasibility of using such systems for locating and tracking vocally active pelagic species. There is every reason to believe that a combination of acoustic tracking and visual observation techniques can be successfully extended for use as a census tool to produce meaningful estimates about relative abundance on blue, finback, and minke whales. Passive acoustic tracking methods, (towed arrays and fixed horizontal arrays) have now been successfully applied to follow individually vocalizing whales for many days, acoustically observe herds of animals, and describe species specific seasonal changes in distribution and relative abundance.
Using combined acoustic tracking and visual observation techniques to study humpback whales
Authors: Frankel Adam S. , Clark Christopher W.
Published: October 2005

The technique of acoustic location was combined with visual tracking and behavioral observation to study humpback whales on the winter mating grounds in Hawaii. The behavior and movements of nonvocalizing whales and singers could be studied simultaneously. Social interactions that had not been previously described were observed. These included affiliations of singers and nonsingers while the singer continued to sing. Visual tracking also allowed the comparison of visual and acoustic locations to verify the accuracy of the acoustic locations. Acoustic location allowed the simultaneous tracking of several humpback singers, and their relative distribution and orientations were examined. Results indicate that song mediates inter-singer separation and that 4 km was the preferred minimum spacing between singers off Hawaii. Humpbacks have been described as being distributed within the 100 fathom contour while on the mating grounds. However, singers were acoustically located up to 13 km offshore in water as deep at 305 fathoms. While singers are typically described as stationary, combined tracking techniques revealed singer speeds of up to 3.6 km/h. In conclusion, the combination of acoustic and visual tracking provided a more comprehensive view of humpback whale behavior and distribution than either technique separately.
The MAP tag: A new marine mammal tracking system
Authors: Bazeghi Cyrus , Oliver Guy W.
Published: October 2005

Development of the movement and position (MAP) tracking system was motivated by limitations of currently available tags for marine mammals. The MAP tag employs a global positioning system (GPS) receiver to accurately fix an animal’s position when it surfaces and a tri-axial magnetometer and velocity-time-depth recorder to track in three dimensions underwater movements between surfacings. The tag is microprocessor controlled allowing flexibility and user control of sampling regimes. Data are stored in a high capacity datalogger. To minimize the energy budget the GPS receiver is only switched on when the animal nears the surface and switched off when a fix is obtained. The unit is battery-powered, self-contained and capable of deployment on animals descending to 1500 m. By attaching a pinger to the animal it can also be tracked acoustically, allowing calibration of passive acoustic tracking systems. In its current configuration, the MAP tag is designed for deployment on elephant seals, but with relatively minor reconfiguration of the package it could be deployed on many large marine vertebrates. It is anticipated that the capability of the MAP tag will dramatically enhance future studies of marine mammal behavior, navigation, orientation, and foraging. [Work supported by ONR.]
Adapting intuitive ideas and applied mechanics to the improvement of guitar acoustics: The luthier’s view
Authors: Humphrey Thomas , Schneider Richard , Kasha Michael
Published: October 2005

The mechanical structure of the guitar underwent a sudden transformation about 150 years ago in the hands of Antonio de Torres Jurado, under the demand on the part of Julian Arcas, a virtuoso guitar performer of the day, for greater acoustical power and brilliance in the guitar. The Torres design features three revolutionary changes, (a) the transverse structural bars of the existing Mediterranean instrument were replaced by longitudinal functional bars, coupling the bridge action to the soundboard, (b) the body dimensions were greatly increased, lowering the body and cavity resonance frequencies, (c) the string length was greatly increased, leading to higher string tension requirements, thereby further increasing acoustical power. Each luthier will present his approach to understanding the mechanical action of the torres design, and its modifications for the acoustical requirements of modern musical performances. The presentation will be followed by live demonstrations of various guitars by musicians.
Harvey Fletcher: A son’s reflections
Authors: Fletcher Stephen Harvey
Published: October 2005

Harvey Fletcher was born on 11 September 1884, in Provo, Utah, of pioneer parents. He received a B.S. degree from Brigham Young University. He then entered the University of Chicago, where he worked with Robert Millikan on the determination of ‘‘e’’, and earned his Ph.D. in physics, summa cum laude, in 1911. He was made director of acoustical research at Bell Laboratories in 1928, and the following year, co-founded the Acoustical Society of America. By 1935 he was made director of physical research at Bell Laboratories. As such, he supervised the work of Shockley, Brattain, and Bardeen in the development of the transistor; Dean Wooldridge, James Fiske, Charles Towne, and many other outstanding physicists. Upon retirement from Bell Laboratories, Harvey Fletcher accepted a position as professor of electrical engineering at Columbia University, a position he held for 3 years. In 1952, he returned to BYU as director of research, and from 1960 until his death at the age of 96, he actively pursued the study of musical tones.
Prediction of articulation scores
Authors: Rankovic Christine M.
Published: October 2005

Harvey Fletcher developed articulation theory to enable the prediction of the speech transmission capacity of imperfect communication systems, thereby eliminating the need for the time-consuming speech recognition testing that is otherwise required to differentiate among systems. Two assumptions underlie the theory: (1) a speech signal in each of a number of contiguous frequency bands comprising the audible spectrum contributes independently to the articulation score (percent-correct for lists of nonsense syllables); and (2) the separate contributions are additive. The approach of Fletcher and his colleagues was to define the articulation index, A, an entity for which these assumptions hold true. The equations for calculating A contain variables representing hearing acuity, critical bandwidth, masking, loudness, perception, and frequency importance weights so that the communication system’s frequency response and gain are translated into perceptual terms. In addition to the derivation of the theory, Fletcher’s 1953 book provides a method for calculating A using charts and tabled data, as well as an extensive validation study that included a variety of suboptimal systems. Fletcher’s presentation of articulation theory is far more comprehensive than two popular versions [ANSI S3.5-1969; N. R. French and J. C. Steinberg, 90–119 (1947)]. Differences among these versions of the A calculation and consequences for predicting articulation scores will be discussed. [Work supported by NIH.]
Speech recognition at higher than normal speech and noise levels
Authors: Studebaker Gerald A. , Sherbecoe Robert L.
Published: October 2005

One finding of the early investigators at the Bell Telephone Laboratories was that the articulation index (AI) decreased when speech was amplified above normal conversational levels (French and Steinberg, 1947; Fletcher and Galt, 1950). Recent efforts to predict the performance of hearing-impaired subjects using hearing aids under real world conditions has produced a renewed interest in this phenomenon. A study will be described that attempts to quantify the effects of higher than normal speech and noise levels. Data for normal-hearing subjects revealed that raising the speech level from 65 to 100 dB SPL reduced the AI by about 0.003 units per dB and that this slope remained fairly constant for S/N ratios between −2 and +19 dB. Data on hearing-impaired subjects are currently being collected. Results for both subject groups will be compared with those obtained by Fletcher and his colleagues.
Harvey Fletcher and modern compression hearing aids
Authors: Villchur Edgar
Published: October 2005

Harvey Fletcher described the effect of a transmission channel on speech recognition in terms of the channel’s ‘‘articulation’’ plotted against channel gain. For normal listeners, articulation increases with gain to a maximum and then levels off or decreases. For hearing-impaired listeners, however, Fletcher noted: ‘‘... the gain αt corresponding to the tolerable level is reached before it is large enough (to bring articulation to a maximum).’’ This occurs in cochlear impairment because the dynamic range of hearing is reduced by recruitment. It is the problem to which the design of modern compression hearing aids is addressed. Compression aids compensate for recruitment by providing increased relative gain for weak speech sounds; thus they allow the articulation to reach higher values before tolerance levels are exceeded. An analysis of compression/equalization signal processing is presented. The essential elements of this processing are: (1) more than one channel of full-dynamic-range compression (the K-AMP design achieves similar results in a different way), (2) post-compression frequency-response shaping, and (3) adjustability of the compression in each channel, and of the equalization, to fit the amplified speech into the residual dynamic and frequency range of hearing of the individual patient.
Stage house coupled shells
Authors: Jaffe Christopher
Published: October 2005

In the early sixties, the American Symphony Orchestra League conducted a survey of American orchestras to determine their preference of material for demountable symphonic enclosures. Oddly enough, Fiberglass reinforced polyester shells manufactured by Stagecraft Corporation received the number one rating in the country. The Stagecraft shells, constructed of 0.0625- to 0.125-in. Fiberglass sheet, and edge framed in aluminum, were coupled to stage house volumes through openings between the ceiling sections. In the low frequencies some coupling was achieved through the panels themselves, in view of their low transmission loss at the bottom end of the spectrum. This paper will document the success of these enclosures, and explain why these shells worked so well for orchestras performing in the sixties and seventies. Basic changes in multi-use theater design in the eighties reduced the effectiveness of these designs. However, several practitioners have developed new design solutions that have returned stage house coupled shells to the forefront once again.
Adaptable acoustical shells incorporating modular reflective, absorptive, and diffusive surfaces
Authors: D’Antonio Peter
Published: October 2005

The optimum percentage and orientation of reflecting and diffusing surfaces in an acoustical shell was determined from objective and subjective measurements using conservatory students at the Cleveland Institute of Music comprising two string quartets, a brass quintet, and a horn duo. Objective impulse measurements were made with balloon bursts and five different microphone systems were used to obtain simultaneous DAT recordings. The Head Acoustics mannequin was placed within the group to determine ensemble blend without self-masking. Etymotic Research probe microphones were inserted into the ear canals of musicians to determine ensemble blend with self-masking, headband microphones were used to monitor ensemble blend with self-masking, an omnidirectional microphone was placed within the group as a monophonic control, and spaced omnidirectional microphones were placed in the front of the house to measure the projected sound quality. Analysis of these and other data led to the development of a variable acoustics modular performance shell utilizing reflecting, absorbing, and/or diffusing modules, which allows both variability and flexibility for different stage uses as well as sectional and personal acoustic environments for the performers. This approach was subjectively evaluated with the full Baltimore Symphony Orchestra with David Zinman conducting.
Orchestra shell design and manufacture: The Wenger way
Authors: Probst Ron , Benjamin Todd
Published: October 2005

Wenger Corporation has manufactured orchestra shells for educational and professional spaces for over 30 years. This paper will present the design philosophy behind the Wenger line of acoustic shells. Pros and cons of standardized equipment versus custom design and manufacture will be discussed. Also, the methodology behind the design and development of the Diva Acoustic Shell and many of its innovative features will be examined.
Simultaneous active/passive control of extensional and flexural vibrations in infinite thin beams
Authors: Deneufve Florence L. , Fuller Chris R.
Published: October 2005

Passive control techniques implemented using added damping, through mass discontinuities or material discontinuities in order to minimize structural vibrations, are limited concerning the amount of attenuation obtained especially in the low-frequency domain. Active control methods are effective for optimally reducing structural vibrations, but may require significant control energy, especially for large disturbance inputs. The combination of passive with active control has much potential for completely reducing vibrations propagating in structures as the control energy required for the active part is found to be reduced and the frequency ranges of operations are complementary. In this research, passive and active techniques are combined to control simultaneously extensional and flexural motions in an infinite thin beam. The passive control is implemented with a hard rubber discontinuity of various lengths and the active control is achieved with two co-located independent piezoelectric actuators bonded on each side of the rubber section. The disturbance is a harmonic point force applied at the origin at an angle in order to excite both extensional and flexural vibrations. The optimal control voltages are calculated to reduce both the extensional and flexural wave amplitudes to zero downstream of the rubber discontinuity. Results of a simulation on an infinite thin beam are presented and discussed.
Hot topics in structural acoustics
Authors: Norris Andrew N.
Published: October 2005

This talk surveys some key developments in modeling the acoustic response of fluid-loaded structures. Recent experimental and computational results indicate that wave interaction effects are very significant for structures with even a small degree of complexity. The complexity can be as simple as a few ribs or stiffeners which convert supersonic membrane-type wave motion into subsonic flexural energy, and vice versa. A great deal of effort continues to be put into developing efficient numerical methods in order to simulate greater complexity. At the same time, recent analytical findings have increased our understanding of the dynamic interaction at ribs and plate junctions, in terms of wave-like diffraction processes. Ray methods have been developed to handle the multi-wave nature of structural energy flow on nonseparable shapes, and provide a fast numerical method for dealing with high-frequency simulation. In general, the complexity of the substructures within the relatively well-defined ‘‘master’’ structure presents the most difficult challenge for modelers. Techniques are only now being developed to distinguish these effects in a logical manner. One approach of great interest is ‘‘fuzzy’’ structural acoustics. The idea is to replace the detailed dynamics of the internal by a smeared out effect, which still contains some of the physics of the internal such as the total mass, and the modal density per unit bandwidth. Fuzzies are also ‘‘hot’’ in that they are guaranteed to generate thermal energy among ASA participants concerned about energy effects.
Hot topics in underwater acoustics
Authors: Kuperman W. A.
Published: October 2005

Underwater acoustics is in a period of renaissance with researchers actively pursing studies in many areas from short-range high-frequency shallow water acoustics to global low-frequency acoustics. There has been renewed interest in inhomogeneous sediment acoustics as well as propagation in very shallow water bounded by these sediments. The recent Office of Naval Research ‘‘SRP’’ program studying deep water boundary reverberation has not only been fruitful, but has also laid the foundation for innovative research in the area of boundary scattering in coastal water acoustics. On the other scale, the Heard Island Feasibility Test as described by 18 papers in the October 1994 issue of JASA has re-awakened interest in the myriad of possibilities of monitoring all scales of the ocean using acoustic methods. In an expanding number of efforts, underwater acoustics is distinguishing itself as developing the most physically based signal processing schemes presently being considered in any field. These and other hot topics will be discussed.
Effect of ‘‘conditioning’’ on hearing loss from military noise exposures
Authors: Henselman Lynn W. , Henderson Donald , Subramaniam Malini , Hofstetter Philip , Sallustio Vincenzo
Published: October 2005

It has been shown with chinchillas as subjects that prophylactic (‘‘conditioning’’) exposures to an interrupted OBN centered at 0.5 kHz for 10 days provide protection against permanent threshold shift (PTS) from high level impulse noise in chinchillas [L. W. Henselman etal., Hear. Res. 78, 1–10 (1994)]. The present investigation studied the effect of ‘‘conditioning’’ with helicopter noise on PTS resulting from high level impulse noise. Thirty-eight chinchillas were randomly assigned to one of four experimental groups (helicopter noise exposure prior to impulse noise exposure) or a control group (impulse noise exposure only). It was shown that (a) interrupted exposures over a 10-day period to helicopter noise presented at 112 dB SPL for 1.5 h/day caused TTSs to decrease as exposure days continued at the test frequencies of 0.5 to 8 kHz, and (b) after 4 weeks of recovery, subjects were protected from PTS after ‘‘conditioning’’ with helicopter noise (except the group with prolonged ‘‘conditioning’’). Histological results were consistent with audiological findings and revealed significantly less hair cell loss in the experimental groups that were protected from PTS. The results are discussed in terms of possible application to hearing conservation programs. [Work supported by the U.S. Army Medical Command.]
The effect of the level of impact noise on hearing loss
Authors: Levine Stephanie , Henderson Donald , Hofstetter Phillip
Published: October 2005

Impulse and impact noise found in industry may be particularly dangerous for workers’ hearing. This study examines the effect of the level of impact noise on hearing loss. Twenty four adult chinchillas were exposed to impact noise for 7.5 h. The subjects were divided into four groups and exposed to impulses delivered at 1/s at one of four different intensities: 113, 119, 125, and 131 dB. As the level of exposure increased, the permanent hearing loss of the animals increased. At lower levels, 113–125 dB hearing loss increased at approximately 1.8 dB for each dB of noise. These findings are consistent with studies using continuous noise which report a 1.7-dB increase in asymptotic threshold shift for every dB increase in exposure. However, as the level of the impact increases beyond a critical level, (125 dB) the resulting threshold shift increases dramatically i.e., 6 dB for each dB increase in exposure level. It has been shown in prior research [Hamernik etal., Hear. Res. 13, 229–247 (1984) and Henderson etal., Hear. Res. 76, 101–117 (1994)] that the anatomical damage to the cochlea at this critical level changes from metabolic to mechanical. [Research supported by NIOSH Grant No. 15034470.]
Relationships between simple reaction time and auditory stimulus intensity in people with sensorineural hearing losses
Authors: Seitz Philip F. , Rakerd Brad
Published: October 2005

Individual differences in reaction time (RT) to subjectively comfortable, loud, and soft tones were assessed for ten young adult subjects with longstanding, less-than-profound sensorineural hearing losses and ten normal hearing controls. To support estimation of the sensory, central, and motor components of RT, subjects were also tested using an equivalent protocol with bright and dim visual stimuli. Subjects with normal hearing listened to 500-Hz tones at fixed intensities that pilot testing established as corresponding to comfortable, loud, and soft levels. Prior to RT testing, subjects with hearing losses individually adjusted tone intensity to ‘‘most comfortable,’’ ‘‘very loud but not painful,’’ and ‘‘very soft but definitely audible’’ levels. Results show larger modality-dependent and level-dependent individual differences in RT than have been previously noted in the literature, pointing up a need for individual subject baselines in cognitive experiments that use RT as a dependent variable. Results also indicate that the typically small range between threshold and pain in listeners with hearing losses is, with respect to RT, functionally equivalent to larger ranges in normal hearing listeners in some individuals but not in others. [Work supported by NIH-NIDCD.]
Field trials of a portable prototype digital hearing aid
Authors: Gelnett Donna J. , Sullivan Jean A. , Nilsson Michael J. , Soli Sigfrid D.
Published: October 2005

A battery-operated digital processor connected to microphones and receivers located in left and right ear modules was built and used in a hearing aid field trial. Eight hearing impaired individuals with moderate to moderately severe hearing losses served as subjects. All subjects had symmetric hearing losses and were experienced binaural hearing aid users. Four binaural hearing aid algorithms were programmed into the processor for evaluation in the field trial. The algorithms all equalized the magnitude and phase insertion effects of the ear modules, but differed in their gain prescription. Two prescriptions based on the Articulation Index (AI), one on NAL-R, and a control prescription were evaluated in the two week field trial. Subjects rated each algorithm in seven categories. Objective measures of speech intelligibility in noise, including measures of binaural directional hearing, were taken before and after the field trial. Intelligibility and directional hearing was best with the AI prescriptions, although these prescriptions did not receive the highest subjective ratings. Details of the binaural algorithms and fittings, as well as objective and subjective measures of their benefit will be reported.