bluuebunny/crossref_metadata_2025 huggingface dataset:
Power transmission variance predictions in complex systems with dissipation
Authors: Burkhardt John , Weaver Richard
Published: October 2005

The eigenstatistics of damped complex systems are examined for the purpose of improving statistical response predictions such as those formulated in statistical energy analysis and statistical room acoustics. Both the statistical distribution of modal decay rates and the effect of dissipation on the intermodal correlation of the natural frequencies described by the gaussian orthogonal ensemble (GOE) of random matrix theory are explored. It is found that the modal decay rates are distributed according to a chi-square distribution whose degree depends on the distribution of damping in the system and the wavelength of the disturbance. The intermodal correlations of the natural frequencies are found to be unaffected by the presence of moderate damping. Level repulsion (the absence of near degeneracies) and spectral rigidity (the near regularity of the spectrum) are found to conform to the prediction of the GOE provided the system is reverberant. The variance of the power transmission function for an irregularly shaped membrane is formulated using a GOE-type natural frequency spectrum and chi-square distributed modal decay rates. Numerical simulations of membranes are performed which confirm the calculated effect of a distribution of decay rates on power transmission characteristics.
Constraints on the sound production mechanism of blue whales
Authors: Clark David S. , McDonald Mark A. , Hildebrand John A. , Webb Spahr C.
Published: October 2005

Broadband, high-fidelity recordings of blue whale calls are used to model parameters of the sound generation mechanism. Arrays of sonobuoys have been used to characterize and localize calling whales, providing broadband (10–2400 Hz), high dynamic range (90 dB) recordings. Blue whales typically produce 15- to 20-Hz sounds of up to 30-s duration at levels of 185 dB re: 1 μPa@1 m. The observed sound levels, frequencies, and harmonic content have implications for the sound generation parameters. Source levels provide constraints on volume displacements. Frequencies and harmonic content relate to resonant structures and their means of excitation. The data show harmonic series with selected overtones emphasized. The relative amplitudes of the overtones vary between different parts of the call.
The use of passive towed arrays for surveying marine mammals
Authors: Norris Jeffrey , Evans William , Sparks Troy , Benson Robert
Published: October 2005

The first marine mammal acoustic survey using a towed passive hydrophone array was recently completed. Other cetacean surveys have used static, low-frequency arrays; the array used is a broadband, mobile system, receiving both baleen and toothed whale signals. For acoustic censusing and tracking (ACT) to become an accepted technique, it’s biases and assumptions must be described. ACT has a number of advantages, including a permanent record of all effort, compared to visual methods which are instantaneous samples, with no permanent record. This record permits measurement of perception and availability biases. A dynamic strip width can be calculated by continuously recording SPL. An area of 154 621 km2 was surveyed in the north central Gulf of Mexico during seven cruises, recording 1431 tapes. Recording effort occurred over 11 997 km of a total transect distance of 12 580 km, corresponding to a 95.4% level of effort; a concurrent visual survey yielded a 48.5% level of effort. A total of 157 contacts from 13 cetacean species were recorded, including 67 sperm whale (Physetermacrocephalus), 22 pantropical spotted dolphin (Stenellaattenuata), one baleen whale, 327 unidentified dolphin, and 30 unidentified cetacean contacts. Three-dimensional distributions were determined for sperm whale and pantropical spotted dolphin. Estimates of cetacean populations were computed based on this effort.
Three-dimensional localization of a blue whale using broadband matched-field processing for range and depth, and plane-wave adaptive beamforming for azimuth
Authors: D’Spain G. L. , Kuperman W. A. , Hodgkiss W. S. , Berger L. F.
Published: October 2005

During a recent shallow water experiment conducted 10–15 km west of San Diego, blue whale calls were recorded simultaneously on two underwater hydrophone arrays, an 18-element, 205-m-aperture horizontal line array, and a 64-element, 115-m-aperture vertical line array. These data are used to localize the calling whale in 3-D space and then to make estimates of its source level. First, adaptive plane-wave beamforming is used with the horizontal line array data to obtain finely resolved bearing estimates. Then, the bottom bathymetry profiles along these bearing estimates are used as input to a 2-D full-wave-field normal mode code (written by Mike Porter) for generating ‘‘replica vectors’’ (i.e., predictions of the acoustic field) received by the vertical line array. A search in range and depth for the best match between the replica vectors and the actual field measured by the vertical array (‘‘matched-field processing’’) then is performed to obtain the best-fit position of the whale in 3-D space. Finally, estimates of the source level of the whale calls are made. [Work partially supported by ONR, Code 321.]
Simultaneous source panging and bottom geoacoustic inversion using shallow water, broadband dispersion of fin whale calls
Authors: D’Spain G. L. , Kuperman W. A. , Clark C. W. , Mellinger D. K.
Published: October 2005

Beamformed time series of fin whale calls from the North Atlantic recently have been obtained. Spectrograms of these recordings have an unusual appearance—three to four downsweeping clicks occur in rapid succession, almost as if the whale was stuttering. These arrivals can be explained in terms of the differences in group velocity between the lowest-order modes that propagate in the shallow water (about 350 m) waveguide. By matching predicted spectrograms calculated from a shallow water waveguide model with actual spectrograms, estimates of both the range of the whale and the compressional wave velocity in the ocean bottom are obtained. The approach makes various assumptions, including that the whale emits a signal with a downsweep rate of 25 Hz per second. However, known deviations from the assumptions can be incorporated into the modeling. The results have several implications such as that whale signals may provide loud, broadband, tomographic sources of opportunity for determining oceanographic/geophysical properties, and that some differences in whale call recordings from different populations of the same species may be caused by propagation effects. Might whales take advantage of propagation-induced distortions in order to learn something about the ocean medium? [Work partially supported by ONR.]
The study of acoustic interactions of territorial song sparrows, Melospiza melodia, using passive acoustic tracking
Authors: Bower John L.
Published: October 2005

A passive sparse acoustic array of eight microphones was used to characterize the patterns of acoustic interactions of territorial song sparrows. The rectangular array was placed in a four hectare open field (near Ithaca, New York) that contained 11 song sparrow territories. Recordings were made approximately every 3 days from early April, when male song sparrows arrived back from their wintering grounds, through July, when the breeding season ended. Computer analysis of field recordings showed that the array was able to capture vocalizations of all 11 territorial males in the field, and that these vocalizing males could be accurately located. Data were taken during three critical periods of the breeding season: (1) territory establishment, (2) settlement of territories by females, and (3) nesting. For each period, the timing of song, inter-song intervals, and song-type matching were discerned for males. Patterns of acoustic interactions recorded during periods of visually observed male–male conflict were also investigated. These patterns were used to evaluate several hypotheses that seek to explain the function of acoustic interactions in song sparrows.
Acoustics of guitars
Authors: Rossing Thomas D.
Published: October 2005

The guitar can be considered to be a system of coupled oscillators. The plucked strings excite the top plate, which in turn transmits vibrational energy to the air cavity and back plate. Sound is radiated quite effectively by the vibrating plates and through the sound hole. The considerable amount of research on the guitar during the past 20 years, especially as it reflects on further development of this popular instrument, will be reviewed.
The guitar: Air modes and radiated sound fields
Authors: Bork Ingolf , Heise Ulrich , Hansen Uwe J.
Published: October 2005

The experimental technique of modal analysis is generally used to display normal modes of structural vibrations. It provides a phase sensitive method of representing a slow motion animated display of the standing waves supported by the structure. The technique also allows exaggerated displacement representation on the computer screen for ease of observation. An essential element in the technique is associated with its ability to retain spatial phase information for a predetermined geometrical point distribution on the structure in relation to the point of excitation. The work discussed in this paper utilizes this ability to retain phase information and extends the technique to represent the radiated sound field. The grid of observation points is removed from the structure and is replaced by a grid covering the space where the sound field is to be modeled. The excitation point is retained on the structure. This will be illustrated by observing air resonances in a guitar in computer animation, and by representing the radiated sound field of that guitar at various frequencies.
Designing and testing of new guitars by criteria of applied physics and psychoacoustics
Authors: Kasha Michael
Published: October 2005

This program represents the interaction of the authors as designer of new guitars, with skilled luthiers as developers, and musicians as evaluators. The ultimate goal is the development of the full brilliance and power which the instrument should be capable of, using models derived from the elementary laws of vibration mechanics. The aim is to enhance the response of the four-octave range of the classical six-string guitar by introducing structural asymmetry, borrowing the principle inherent in the violin family of instruments. As a guide, the standard formulation of the boundary conditions, and the frequency dependence of mechanical impedance, are incorporated—all this within the construction limitations imposed by the luthier, the materials, and the aesthetics of the instrument. The Backhaus criterion of brilliance is adopted, wherein the harmonic spectral intensity distribution is targeted in which the fundamental is dominant, and with decreasing intensity of higher harmonics. A specially designed anechoic chamber has been constructed for testing real-time harmonic spectra of string instrument pairs: conventional versus new designs (taking into account variations of player technique). Measurements will be made to compare with the Backhaus criterion. Ultimately, the judgement of musicians and of the general spectrum of musical auditors will decide the success of this program.
Progress report and discussion on the continuing activity on ASA’s role in noise and its control
Authors: Hoover Robert H.
Published: October 2005

A discussion meeting is being sponsored by the Technical Committee on Noise to review progress made to date on the actions initiated at the Denver, 1993 meeting to increase the role of the ASA in noise and noise control. Much of this action evolved out of an all-day workshop held at the Ottawa, 1993 ASA meeting. Members of the steering committee and others involved in related supporting activity will review specific progress made in the areas of education, increasing public awareness about noise and noise control, and encouraging joint activity in this area with other professional organizations. Included will be a report on a trial presentation on acoustics and noise given to 6 high school classes. Discussion about, and review of opportunities for involvement with, these activities will be encouraged.
Harvey Fletcher: Friend and scientific critic
Authors: Beranek Leo L.
Published: October 2005

Harvey Fletcher was active in World War II both in the early days of defense research under the auspicies of the National Defense Research Committee and later as Chief of Section 17.3 of the Office of Scientific Research and Development. He was a member of the National Research Council committee that started and oversaw the research of the Electro-Acoustic Laboratory at Harvard University of which I was named Director. Within a year or so Dr. Fletcher’s OSRD Section 17.3 took over the supervision. In the latter part of World War II, I was named Director of the Systems Research Laboratory under the Office of Field Research. Dr. Fletcher was appointed as one of a group of five to oversee the activities of this Laboratory. This paper is a collection of anecdotes and remembrances of Fletcher in the fast-moving and important military research and development period from 1940 until 1945 when I reported often to him. Personal contacts with him continued after the war, frequently at first, and sporadically for the next three decades. ‘‘Uncle Harvey,’’ as I came to call him, was both a friendly guide and a demanding scientific critic.
Harvey Fletcher: Some personal recollections
Authors: Harris Cyril M.
Published: October 2005

The author of this paper describes his first visit with Harvey Fletcher in 1940 at the Acoustical Research Department of Bell Telephone Laboratories, then located on West Street in New York City. Five years later, he was invited by Dr. Fletcher to join the Laboratories. A brief description is given of some of the work carried out in Acoustical Research at that time. Upon his mandatory retirement at age 65, ‘‘Uncle Harvey’’ accepted the position of Visiting Professor in the Department of Electrical Engineering at Columbia University. In 1951 the author left Bell Labs for a teaching position in Europe; on his return to the U.S. a year and a half later, he again sought Dr. Fletcher’s counsel and it was suggested he take Fletcher’s place at Columbia University. This made it possible for Dr. Fletcher to return to Utah, where he devoted the rest of his distinguished career to research in musical acoustics at Brigham Young University.
Harvey Fletcher and auditory theory
Authors: Kiang Nelson Yuan-sheng
Published: October 2005

Harvey Fletcher was an original thinker whose career is worth examining for future scientists. Trained as a physicist, he developed a pragmatic approach to psychophysics that virtually defined the engineering approach to acoustic communication. Although his practical achievements were considerable, he also tried to integrate all that was known about hearing in the 1953 version of his ‘‘space-time pattern theory of hearing.’’ It is instructive to compare that formulation with the ideas of today after more than four decades of intense research. Many of the issues that concerned Fletcher have been resolved; many others remain uncertain. For example, the observation that low-frequency stimuli can mask high-frequency stimuli whereas high-frequency stimuli cannot mask low-frequency stimuli was accorded great significance by Fletcher. It is now known that a key factor lies in the asymmetry of tuning curves for basal and apical turn auditory-nerve fibers. On the other hand, the full implications of these phenomena, especially for central processing mechanisms, is virtually unexplored. What is clear is that a major effort to produce a unified theoretical framework for research in hearing is long overdue and a modern Fletcher would be welcome today.
Fletcher and pitch
Authors: Pierce John R.
Published: October 2005

Preparing remarks on Fletcher’s work on pitch changed drastically. My view of the development of our present understanding. In 1940 Jan Schouten showed that canceling out of the fundamental of a pitched tone did not change pitch. Schouten called the surviving pitch residuepitch. This inspired a spate of papers by people ignorant of earlier work. I had known Fletcher [Phys. Rev. 23(3), 427–437 (1924)] had shown that filtering out the fundamental and lower harmonics of a variety of musical sounds did not change the pitch, and, through synthetic sounds, that mere equal frequency spacing of tones did not give a pitch equal to the spacing. Thus, the pitch heard was evoked by harmonic partials. Unhappily, Fletcher proposed an unsound explanation in terms of production of the fundamental in the ear by nonlinearities. In a latter report, Fletcher [ 311–343 (1930)] gave an incomplete analysis of the functioning of the cochlea. Among his valid conclusions he said ‘‘the pitch of a tone is determined both by the position of its maximum stimulation on the basilar membrane and also by the time pattern sent to the brain. The former is probably more important for high tones and the latter for low tones.’’ That is our present understanding. Fletcher [ 637–645 (1951)] subsequently gave a ‘‘correct’’ analysis of the functions of the cochlea, agreeing with the experimental work of von Bekesy, and going a little beyond papers a year earlier by Peterson and Bogert and by Zwislocki.
From Fletcher to Knudsen
Authors: Levitt Harry
Published: October 2005

Harvey Fletcher was not only an outstanding researcher and director of one of the world’s leading research laboratories, but was also an inspiring teacher and mentor. Vern Knudsen was one of many outstanding researchers who were deeply influenced by Fletcher. Knudsen’s contributions in architectural acoustics, psychoacoustics, audiometry, hearing aids, and tactile stimulation were of groundbreaking importance and reflected Fletcher’s remarkable influence. As a close disciple of Fletcher, Knudsen was also in a position to learn about many of Fletcher’s other accomplishments which were substantial, but unknown to the outside world.
Physical parameters of a welded t-joint that impact structural acoustics
Authors: Mann J. Adin , Carney Matthew , Driesch Patricia
Published: October 2005

The influence of welded joints on the accuracy of analytical structural acoustic models is investigated. A beam with a T-shaped rib attached to it is studied. Welding a t-joint causes geometry variation, static stress, and material variations that are not currently included in computational models of the structural acoustics of a t-joint. Two techniques of processing the experimental data are used to show that the geometry and the static stresses caused by welding can have a significant impact on waves propagating past the joint and the resulting radiated sound power. Likewise experimental results show that the material variation caused by the welding of the joint has minimal impact on the wave propagation and sound radiation from the beam. The processing techniques are a phase-speed tracking filter and wave-number filtering. The phase-speed tracking filter shows an increase in the phase speed of propagating waves near the joint. There is also a reduction in the group delay of wave packets propagating past the joint and a change in the reflection coefficient of structural waves incident on the joint. The wave-number filtering is used to quantify the amount of far-field sound radiation from the area of the t-joint on the beam. Finally an analytic model that describes a rib as imparting a force and moment on a beam in reaction to the incident structural waves is modified to include the influence of the weld fillet geometry and static stress induced by welding. [Work supported by ONR, Dr P.B. Abraham Scientific Officer.]
The response and radiation of ribbed panels
Authors: Dickey J. , Maidanik G.
Published: October 2005

The dynamic response of a panel with an infinite number of regularly spaced line impedances (i.e., regularly ribbed), or a finite number which may be irregularly spaced and nonidentical, is a system which can be solved ‘‘exactly.’’ Exact, that is, to within the approximations employed in developing the equations of motion for the panel and the ribs. Even though these approximations may preclude realistic modeling in some (usually high) frequency ranges, or with some configurations (e.g., wide ribs), these canonical models exhibit many characteristics of experimental and numerical data obtained on real and more complete structures. This makes them very useful and cost effective in identifying observed characteristics and evaluating noise control measures. Models which describe flexural or longitudinal waves on membranes or thin plates have been developed by the authors. These models are reviewed and used to describe the response and radiation of a panel into an adjacent fluid. The panel is driven either by a line drive parallel with the ribs or an incident plane wave. There are a host of phenomena which manifest themselves; some of which are: (1) pass and stop bands, (2) localization and de-localization, (3) aliasing, (4) free wave dispersion and the splitting of the dispersion curves due to fluid loading, (5) Bragg diffraction, and (6) radiation efficiency. Also presented is the effect on these phenomena of: (1) altering the strict periodicity or identity of the ribs, (2) the loss factor in the panel, and (3) the degree of fluid loading.
Cavity-backed simply supported plate for acoustic and structural response measurements
Authors: Champoux Yvan , Brunet Serge , Berry Alain
Published: October 2005

Originally, an acoustic cavity has been designed and fabricated to study active noise control strategies in a closed volume. It has a parallelepipedic shape of dimensions 0.868 m×1.15 m×1.0 m with walls made of 13-cm-thick reinforced concrete. The top is closed with a simply supported 6.63-mm-thick aluminum plate. The plate support was carefully designed to meet the simply supported boundary conditions. The plate is excited by a point force and its structural response is measured with force and accelerometer transducers. The acoustic field inside the cavity is also measured using microphones. Comparisons between calculated and measured natural frequencies of the plate shows that for most of the modes found in the 0–500 Hz range, the discrepancy is less than 1 Hz. Quadratic mean surface velocity and mean volume sound pressure have been calculated from frequency response functions measured for centered and off-centered point force excitations. Comparisons with calculated values shows very good agreement. The relative contribution of the various plate modes and cavity modes are well distinguishable.
Measured effects of orchestra shells
Authors: Bradley J. S.
Published: October 2005

The effects of adding orchestra shells or modifying orchestra shells were measured in six different concert halls varying in volume from 3000 to 32 000 m3. Early, late, and total sound levels were seen to increase with the addition of an orchestra shell. Effective orchestra shells were found to increase total sound levels by up to 2 dB at mid-frequencies in audience areas of halls. Average changes to measured clarity could be larger. The measured increases in sound levels varied with location in the halls, and in several cases sound level increases were greatest towards the rear of halls. In one case, adding an orchestra shell was found to decrease low-frequency levels due to a shift of the seat dip attenuation. On-stage, larger effects were measured. Support values increased by as much as 5 dB with the addition of an orchestra shell. Partial changes to shells generally produced much smaller effects. In audience seating areas the effects of partial changes and adjustments to orchestra shells were usually less than estimated just noticeable differences in the measured quantities.
Stage acoustics measurements with major orchestras
Authors: Kirkegaard Dana
Published: October 2005

This paper will address objective and subjective measures relating to the author’s work onstage with major orchestras. Based on this research, some of the design challenges and potential solutions, including the use of QRDs, will be diagrammed. A formal paper will be available for distribution.
Active and passive orchestra shells and stage acoustics
Authors: Prinssen W. C. J. M. , Kok B. H. M.
Published: October 2005

This spring the largest theater building of The Netherlands, the Chasse Theatre at Breda, was completed. Of the two main auditoria, which have similar stage houses, one has electronic variable acoustics by means of a SIAP system, including a stage system, and the other has mechanical variable acoustics which includes a large orchestra shell. It will be shown through measurements that active (electronic) stage acoustics can be at least as effective as passive (physical) stage acoustics. It is particularly interesting that loudness, reverberation time, and reflection patterns can be influenced independently with active systems. This flexibility is an advantage for meeting the needs of performers. Furthermore, active control of stage acoustics can also provide a significantly improved foldback to actors and singers for drama, opera performance, etc. when technical stage facilities and scenery make physical acoustic means difficult to apply. Since acoustic coupling of the stage to the auditorium main volume is an important factor, results will also be presented of the achievements of the SIAP system to correct auditoria which have spaces with (extremely) poor acoustic coupling such as balcony and under balcony areas. The orchestra pits, which are of different size and shape, but have the same passive acoustic treatment, will be compared.
Supplemental partial height concert shell incorporating quadratic diffusor panels
Authors: Hougland Dana S.
Published: October 2005

A recently completed project to modify the acoustical performance of Boettcher Concert Hall included the addition of several modifications to improve cross-stage hearing of the musicians. Boettcher Concert Hall utilizes an in-the-round seating arrangement, therefore, the enclosure design was restricted to partial height. Custom designed quadratic diffusors were incorporated into the concert shell design. Tests were conducted both on an individual panel section in an anechoic chamber and insitu. The results of the tests are presented.
The use of neural networks for optimum actuator grouping in time domain active control applications
Authors: Smith G. Clark , Fuller Chris R. , Silcox Richard J.
Published: October 2005

Previous work has demonstrated the benefit of grouping actuators to decrease the number of degrees of freedom in an active control system. In this work, a time-domain cost function was developed for on-line actuator grouping and active structural acoustic control (ASAC) of a simply-supported beam excited with a broadband disturbance. Actuators are considered grouped when their compensators are equal. Therefore, the cost function presented here incorporates a mean-square error term related to the structure-borne noise and an additional nonquadratic term which penalizes the controller for differences between respective compensator coefficients. The backpropagation neural network algorithm provides the proper procedure to determine the minimum of this cost function. The main disadvantage of using such a stochastic gradient technique while searching the prescribed control surface is converging to local minima. A resolution to this problem is discussed which incorporates using a variety of initialization conditions. Two scenarios are considered here: grouping actuators based upon weights determined by converging the filtered-x LMS algorithm and simultaneously grouping and controlling with the compensator weights started at zero. Computer simulations demonstrate the ability of this new form of the cost function to simultaneously group actuators and control the structure-borne noise with either initial conditions.
Vibration signature monitoring using analytical models of slotted beams
Authors: Man XiuTing C. , Finch Robert D.
Published: October 2005

Vibration signatures may be used in monitoring structural integrity. A procedure was established in which the experimental data were processed using analytical models of the physical structures. Steal beams were used as examples. Saw-cut slots of different sizes and locations were the ‘‘damage’’ to be detected. An analytical model based on a perturbation method was developed, which leads to direct relationships between the modal properties and the slot parameters. The modal frequencies were estimated experimentally using modal analysis techniques. The frequency reductions were computed as the difference between the experimentally estimated modal frequencies and the values theoretically calculated from a uniform beam of identical conditions. The first three modal frequency contours were calculated from the perturbation model and used to quantify the slot depths and slot locations. The slot locations were determined with great accuracy, although the slot depths were estimated lower than the actual values. The reason was that the perturbation model predicted the modal frequency shifts smaller than the actual values, and when used inversely, it tended to give a slot depth of higher value.
Active control of vibration of a magnetic levitation platform
Authors: Li Jiangxiong , Pan Jiaqiang , Hu Qiang
Published: October 2005

A study on active control of vibration isolation of a magnetic levitation platform used for the calibration of precision inertia instruments is presented in this paper. Nonlinear and linearized dynamic models of the system in state-space were deduced by using the theory of an electromagnetic field. The stability of both the open- and closed-loop system was investigated in the cases of different configuration of the current coils. A LQG optimal control strategy was employed in the control syntheses of the magnetic levitation system, since the system input perturbance is a stochastic excition acting on the fixed base from the ground. The transfer functions from the exciting current or the control current or the base displacement to the vibratory displacement of the levitation platform were verified experimentally. Open- and closed-loop vibration responses were calculated. The results show that compared to the base displacement, the vibration of the magnetic levitation platform can be attenuated more than 20 dB by using active control, over frequencies ranging from 0.1 to 10 Hz, which cover the main peaks of the ground perturbance.
Hot topics in speech communication
Authors: Whalen D. H.
Published: October 2005

In speech processing, mapping from acoustics to articulation is becoming more useful. While acoustically based recognizers have achieved impressive success rates, their limitations do not seem to be yielding to further acoustic manipulations. Recovering the articulation underlying the speech offers a way of decoding the complex acoustic manifestations of simple articulatory events. These results also offer benefits in bit-rate reduction and speech synthesis. In speech production, nonlinear dynamic models of speech articulation are beginning to bear fruit. The transition from stasis to vibration of the larynx (the voicing source in speech and singing) can be viewed as a switch from a point attractor (damped oscillator) to a limit cycle (self-sustained oscillation). The tools of nonlinear mathematics and chaos theory allow us to explore such topics as voice breaks, yodeling, and certain voice disorders, as well as normal phonation, Nonlinear techniques have also provided important insights into the production mechanisms of fricative consonants. In speech perception, one of the most interesting new developments is the patterns of brain activity (seen in blood flow) shown by PET scans and by functional MRI. Researchers have found that passive listening to speech activates the temporal lobe, but making judgments on that same speech also involves Broca’s area. Reading print also activates Broca’s area, indicating a crucial link between speech and reading. Another finding is that males rely mostly on the left premotor cortex in performing phonetic tasks presented in print, while females are not strongly lateralized. As acquisition time declines, fMRI promises to yield even more specific information on speech perception.
Investigation of the impact of changes in regulatory criteria on the daily noise dose (DND) of longwall coal mine workers
Authors: Burks J. Alton , Bartholomae Roy C.
Published: October 2005

The authors previously examined the impact of anticipated changes in noise regulations on the coal mining industry [R. C. Bartholomae and J. A. Burks, Noise-Con 94, 1017–1022 (1994)]. That analysis focused primarily on assessing the effect on the daily noise dose (DND) resulting from changing the current threshold level from 90 to 80 dBA. To more fully explore the effect of other regulatory parameters, as well as the threshold level, 59 sets of full-shift time-resolved dosimeter data were acquired on four occupations associated with longwall coal mining. After these data were downloaded to a computer, realistic combinations (a total of 12) of criterion level (80, 85, 90 dBA), threshold level (80, 85, 90 dBA), and tradeoff rate (3, 5 dBA) were applied to these data to compute DND’s. The results of this ‘‘what if’’ type analysis are presented. In general it was concluded that the magnitude of the computed DND resulting from changes in either the tradeoff rate or the threshold level is unpredictable; instead, it depends on the specific distribution of noise levels associated with a given worker’s noise exposure.
The effects of reverberant blast waves on hearing: Energy and spectral considerations
Authors: Ahroon William A. , Lei Sheau-Fang , Hamernik Roger P.
Published: October 2005

Chinchillas were exposed to 1, 10, or 100 reverberant impulses at 150, 155, or 160 dB peak SPL. The impulses were generated by one of two different shock tubes each producing blast waves having a different spectral composition; one emphasizing low frequencies (<0.5 kHz), the other mid-frequencies (2–4 kHz). Impulses were presented at the rate of 1/s. This parametric paradigm yielded 18 exposure conditions; 15 animals/condition. Hearing thresholds were measured using auditory evoked potentials and the sensory epithelium was evaluated with the surface preparation. In general, trauma increased as the total energy of the exposure, determined by the peak SPL and number of presentations, increased. The dependent variables (permanent threshold shift and sensory cell loss) varied in an orderly fashion across frequency as the peak and number of presentations was increased for both blast wave sources. There were, however, consistent differences between the effects of the low- and high-frequency energy ‘‘content’’ blast waves. Correlations between the dependent variables and the energy of exposure were highest for P- or A-weighted energies [Patterson etal., 2860–2869 (1993)]. [Work supported by U.S. Army Medical Research and Development Command.]
Validating a mathematical model of noise hazard with varying numbers of rounds and peak pressures produced by a rifle
Authors: Price G. Richard , Pierson Linda L. , Kalb Joel T. , Mundis Pam
Published: October 2005

A mathematical model of noise hazard [G. R. Price and J. T. Kalb, 219–227 (1991)] has correlated very highly with hearing loss to 50 Friedlander impulses from two sources at 5 different peak pressures (135 to 145 dB). In order to extend the model’s range four additional noise exposures were tested: two single impulse exposures (157- and 169-dB peak) and 6 or 12 impulses at 143-dB peak pressure. These specific conditions were also chosen to contrast the model’s predictions with the ‘‘CHABA’’ damage risk criterion (DRC). Four groups of ten anesthetized cats were exposed to each condition and ABR thresholds at 1, 2, 4, 8, and 16 kHz were monitored to establish hearing loss immediately and 2 months later. In each case the model’s predictions were upheld and rankings of hazard by the CHABA DRC were not. Furthermore, no simple linear frequency weighting would have predicted the losses. The model’s hazard rating correlated well with the group hearing losses (coefficient near 0.8) and refinement of the model’s annular ligament and the intracochlear hazard formula is expected to improve this correlation.
Mathematical formulas and summary measures for the audiometric database analysis procedures (ANSI S12.13-1991)
Authors: Adera Tilahun
Published: October 2005

The concept of an audiometric database analysis (ADBA) method for evaluating the effectiveness of hearing conservation programs has been appearing in the scientific literature for more than 15 years. This concept was recently developed into a series of procedures and is currently being considered for acceptance as a U.S. National Standard (ANSI S12.13-1991). Although the method presents the various analytical procedures in a narrative fashion, mathematical formulas expressing the essential principles have not been provided. In addition, there currently is no method for determining the overall effectiveness of a hearing conservation program (HCP) following application of ADBA procedures to a set of audiometric data. This paper provides the mathematical formulas for four ADBA procedures including the percent worse sequential, percent better or worse sequential, standard deviation applied to single test frequencies, and standard deviation applied to averages of test frequencies. In addition, the paper introduces and illustrates two methods of summarizing results from ADBA procedures, which includes the standard score estimator and the score designator. Each of these methods consists of at least a median and a mean-based procedure. The strengths and limitations of these procedures in determining the overall effectiveness of an HCP are discussed.
A comparative study of occupational and nonoccupational noise regulations in South American countries
Authors: Arenas Jorge P. , Gutierrez V. Martin
Published: October 2005

The final aim of this work is to show a comparative study about the most important aspects of the noise regulations in some South American countries. It includes Argentina, Brazil, Chile, Peru, and Uruguay. Where national standards exist in a particular country, the area of application, and other details of the procedures, should be in accordance with the standards of that country. The differences between national standards are extremely significant for some types of noise. The most important parameters for nonoccupational noise considered when assessing the acceptability of a given noise exposure are: the time of the day (day time, evening, night time), the type of neighborhood, the use to which an area of land or building is put, and sometimes the indoor standards. The basic criteria is not to alter the character of an entire area and dominate its noise climate. In some countries the occupational regulations are combinations of ISO and OSHA standards. Differences were noted in some dose criterias and the trade-off between noise level and permitted exposure time is still the subject of some divergence of opinion. Some standards allows 3 dB (or 5 dB) increase in noise level per halving of exposure duration.
Modified method for determination of heightened human sensitivity to noise
Authors: Menshov Alexander A. , Lipovoy Vladimir V.
Published: October 2005

Occupational hardness of hearing occurs first of all in workers with heightened sensitivity to noise. Along with the objective method for determining higher excitability of the central structures of the auditory analyzer by means of the awaked brain potentials, the heightened sensitivity to noise can be determined by a simpler method [A. Peyser, Acta Oto-laryngol. (Stockh.) 28, 443–444 (1940)]. The experimental data have shown that a higher increase in TTS is observed at a tone of 2000 Hz instead of 1000 Hz according to A. Peyser. Such a modified method was approved at 42 young weavers. After 3 min of 100-dB noise load at the tone of 2000 Hz in 13% of weavers TTS was more than 12 dB (hightened sensitivity). After work for a year under the conditions of 98–100 dBA, in the weavers with hightened sensitivity, TTS at the tone of 2000 Hz was 11.9 dB, at the tone of 1000 Hz was 9.4 dB, and at the tone of 4000 Hz was 9.6 dB. In the weavers insensitive to noise, TTS at the tone of 1000 Hz was 7.0 dB, at the tone of 2000 Hz was 7.5 dB, and at the tone of 4000 Hz was 7.8 dB. In the sensitive to noise weavers, PTS at 1000 Hz was 2.3 dB, at 2000 Hz was 4.3 dB, and at 4000 Hz was 1.7 dB. In the insensitive to noise weavers, PTS at 1000 Hz was 1.1 dB, at 2000 Hz was 1.7 dB, and at 4000 Hz was 1.3 dB. The determination of human sensitivity to industrial noise by audiometry in this modification enables one to discover workers with heightened auditory sensitivity and predict the PTS auditory level.
Simulation of sensorineural hearing loss: Use of linear spectral smearing to reduce frequency resolution
Authors: Boothroyd Arthur , Mulhearn Bethany , Gong Juan , Ostroff Jodi
Published: October 2005

Phoneme and word recognition, was measured in seven hearing adults under various conditions of spectral smearing—produced by multiplying the speech waveform by low-pass-filtered noise. Phoneme recognition fell from 97% for no smearing to 13% for complete smearing (±10 kHz). Smearing by ±600 Hz reduced group mean phoneme recognition to 50%—a score typical of hearing-impaired subjects with hearing losses around 80 dB, listening to amplified speech. In a second experiment, noise was mixed with the speech before spectral smearing was introduced. Noise susceptibility was measured as the S/N ratio required for a phoneme recognition score that was 50% of the score in quiet. Smearing at ±1 kHz increased noise susceptibility by 20 dB, an amount similar to that found in hearing-impaired subjects with losses in excess of 90 dB. As with hearing-impaired subjects, spectral smearing diminished the perception of consonant place more than the perception of consonant manner and voicing. Unlike with hearing-impaired subjects, however, smearing affected vowel perception more than consonant perception. This last finding may be attributed to the use smearing over a fixed bandwidth—producing a greater percentage smearing in the lower frequencies. [Work supported by NIDCD Grant No. 10078.]
Loudness functions in normal-hearing and hearing-impaired listeners
Authors: Lee Lidia W. , Humes Larry E.
Published: October 2005

This paper examined whether an excitation-pattern model of loudness could adequately describe the growth of loudness for complex stimuli presented to normal-hearing and hearing-impaired listeners in quiet and in noise. The loudness-growth functions were obtained for three synthesized steady-state vowels (/a,i,u/), each with two talkers (male: F0=120 Hz; female: F0=200 Hz), and for several pure tones (125–4000 Hz). All stimuli were presented, at random, from 2 to 90 dB SPL (in 4-dB steps) in quiet and in broadband noise. Magnitude estimation were used to measure the loudness of each stimulus. These data are used to evaluate the predictions of an excitation-pattern model [modified power-law model, L. Humes and W. Jesteadt, 1285–1294 (1989)]. [Work supported by NIA.]
Intensity discrimination of amplitude modulated stimuli in electric hearing
Authors: Zeng Fan-Gang , Shannon Robert V.
Published: October 2005

In cochlear implants loudness is a power function of electrical amplitude at low frequencies (<300 Hz) and an exponential function for higher frequencies [Zeng and Shannon, Science 264, 564–566 (1994)]. In addition, the just-noticeable-difference (jnd) in intensity is inversely proportional to the slope of the loudness function. Implant speech processors generally use low-frequency modulation of a high-frequency carrier. Because the loudness functions are different for the modulator and carrier frequencies, this raises the question: Do the loudness and jnd of a modulated stimulus follow the modulator or the carrier? Intensity discrimination was measured for a 100-Hz sinusoidally modulated 1000-Hz sinusoid or pulse train in implant listeners. The jnd was measured either as an increment in the carrier level for a fixed modulation depth or as an increment in the modulation depth for a fixed carrier level. The results showed that the jnd function of the modulated stimuli is similar to the jnd function of the high-frequency carrier. At high sensation levels, implant listeners can discriminate extremely small changes in modulation depth (1%–2%). This implies that modulated stimuli can produce more jnd steps across the dynamic range than either the modulator or the carrier alone.
Preliminary evaluations of cochlear implantees using a wearable CIS processor
Authors: Rabinowitz W. M. , Eddington D. K. , Tierney J. , Delhorne L. A.
Published: October 2005

Each channel of a continuous-interleaved-stimulation (CIS) sound processor uses the compressed envelope of its bandpass-filtered output to modulate biphasic current pulses that are delivered to an intracochlear electrode. Pulses are interleaved across channels to avoid simultaneous field interactions, and pulse rates are high (∼2000 pps/channel) to preserve temporal waveform cues. Using up to six monopolar electrodes directly accessible with the Ineraid implant, this strategy has shown considerable promise in acute evaluations conducted in the laboratory [Wilson etal., Nature 352, 236–238 (1991)]. In collaboration with a group in Innsbruck, a prototype portable real-time system has been developed (based on a DSP56001) that can realize some CIS implementations. Two subjects with 9 years of experience using the Ineraid analog sound processor are now wearing the CIS system on a full-time basis. After several weeks, one subject prefers the CIS strategy; however, objective measures of speech reception show no gains (re: the Ineraid processor). The second subject shows large gains with CIS and some evidence of continuing improvements. Without lipreading, he scores near perfect on relatively difficult (IEEE/Harvard) sentences in quiet; for speech reception in noise, he shows a deficit of 7 dB re: normal-hearing listeners. [Work supported by NIH.]
Combining ratings and paired comparisons in hearing aid evaluation
Authors: Levitt Harry , Neuman Arlene C. , Oden Christopher
Published: October 2005

The method of paired comparisons is a rapid and efficient technique which has proven to be useful in hearing aid evaluation. In the conventional application of the technique, the subject is limited to a binary decision. Greater efficiency can be obtained if, in addition, a confidence rating is obtained. A method for combining confidence ratings with paired-comparison data is provided. Data are presented in which a set of hearing aids differing in compression characteristics (compression ratio, release time) was evaluated by the traditional paired-comparison technique and the paired-comparison plus rating technique. Data will also be presented on the relative precision and efficiency of the two techniques.