bluuebunny/crossref_metadata_2025 huggingface dataset:
Using spatial coherence to improve the performance of underwater acoustic communications
Authors: Yang T. C. , Siderius Martin
Published: July 2012

Phase-shifted keying modulation schemes offer an efficient use of signal power for a given bandwidth in a communication channel. Successful communication often requires multichannel data (spatial diversity) to combat the signal fading due to random fluctuations in the channel. For each channel, a signal-to-noise ratio (SNR) of >10 dB is often required to estimate the channel impulse response for proper placement of the tap coefficients. Array beamforming can be used to improve the SNR, but when to use spatial diversity or beamforming is an issue long debated but not yet satisfactorily answered. It is shown with at-sea data that an effective use of beamforming versus spatial diversity depends on the phone spacing relative to the signal coherence. Beamforming requires the signals to be correlated between the sensors, whereas spatial diversity requires the opposite. Neither can fulfill the job of the other. By choosing phones according to spatial coherence and combining beamforming with diversity, bit error rates of the order of ∼0.001 were demonstrated using Advent 99 data over a period of ∼ 9 hours with an SNR as low as ∼1 dB at the phone level. [This work is supported by the Office of Naval Research and SACLANTCEN.]
Electronic architecture: Historical perspectives, current thinking, and future implications for architectural acoustic design
Authors: Scarbrough Paul
Published: July 2012

Few subjects in acoustics generate more controversy than electronic architecture, that is, the use of electronic tools to alter the acoustics of a performance space, church, rehearsal hall, or other facility. And yet, few advances in acoustics offer the promise of electronic architecture. This paper will trace the development of electronic architecture from the first tentative and highly creative experiments in the 1930s to the mature technologies that have evolved in recent years. What precipitated the development of electronic architecture? Who were the pioneers? How did the technology develop? And where do we stand today? Paralleling these technological advances has been an on-going philosophical debate. Is there ever a place for electronics in the concert hall or opera house? When and where should these systems be used? What obligations do acoustical design professionals have to performers? To the concert-going public? To the art of acoustical design? Finally, what does the continuing evolution of these techniques hold for the future of architectural acoustic design?
Characteristics of chorusing sounds of humpback whales wintering in waters off western Maui
Authors: Au Whitlow W. L. , Lammers Marc O. , Nachtigall Paul E. , Mobely Joseph , Burgess William C.
Published: July 2012

The dominant biological sound in the waters of west Maui during the humpback whale winter season in Hawaii is the chorusing sounds of singing humpback whales. A portable data logger was used to record chorusing sounds during most of the 1998 season. Sounds were digitized for 4 min every 1/2 h and the data were stored on a hard disk. The results showed a peak in the sound pressure level between mid-February and mid-March coinciding with the peak in the number of whales sighted by aerial surveys. Significantly higher levels of chorusing sounds were also recorded at night. Sound levels began to increase during sunset, raising to a peak near midnight and remained relatively high until sunrise, after which the levels progressively decreased to a minimum between 11:00 a.m. and 3:00 p.m. That more humpback whales appear to sing at night may reflect a switch to sexual advertisement as the primary male mating strategy at this time; it may also indicate that daylight and vision play key roles in the formation of competitive groups. It is suggested that the relative number of humpback whales may be estimated by monitoring changes in sound pressure levels.
Three-dimensional localization of blue whales using matched-field processing techniques: Unusual behavior, unanswered questions
Authors: Thode A. M. , D’Spain G. L , Kuperman W. A.
Published: July 2012

Recently, matched-field processing (MFP) and global inversion methods were used to track the three-dimensional trajectories of six blue whales, during a 1996 experiment off San Miguel Island in California, conducted off the research platform FLIP, using a 48-element, tilted vertical hydrophone array. Once the animals’ positions and the propagation environment were determined, source levels were obtained for individual animals, and potential propagation effects were removed from their sounds. Out of the six whales studied, one showed unusual behavior. Initially it swam directly towards FLIP, while producing a diverse set of calls that included three strong FM sweeps. It then fell silent, altered its course to avoid FLIP, and began calling again as it swam away. Its closest point of approach to FLIP coincided with the arrival of a powerful tidal bore. The maximum source levels estimated from this animal were 10 dB lower than those from the other animals, and the FM sweeps showed signs of a possible resonance, which remained even when possible propagation effects were removed. The ability to precisely position blue whales has raised interesting questions about baleen whale sound production, the purpose behind these sounds, and the potential association between feeding animals and internal waves. [Work sponsored by ONR.]
TRIDISMA: An EU program for utilizing acoustics for measuring suspended sediment processes
Authors: Thorne Peter D. , Taylor Jon J. , Humphrey Victor F. , Vincent Christopher E.
Published: July 2012

In this paper the application of high-frequency acoustic remote sensing is discussed with respect to the development of an instrument capable of resolving the dynamics of the benthic boundary layer, in response to the interaction of waves and currents, using sound backscattered by the sediments entrained by the flow. Within the TRIDISMA project an acoustic instrument has been developed which combines three distinct approaches to the analysis of backscattered signals in order to extract information on flow structure and the response of the sediment bed to the overlying flow. The TRIDISMA instrument combines pulse coherent Doppler and acoustic cross-correlation techniques to the problem of extracting profiles of velocity, while the amplitude of the backscattered signal measured at three frequencies is used to investigate the response of the suspension field in terms of both size and concentration profiles. In the present paper we describe the hardware and software architecture of the prototype instrument and demonstrate the systems capabilities with results obtained from flume studies of waves, currents, and combined flows.
Acoustic measurements of boundary layer turbulence, sediment concentration and sediment flux using the Bistatic Coherent Doppler Velocity and Sediment Profiler (BCDVSP)
Authors: Stanton Tim
Published: July 2012

A pulse-to-pulse coherent acoustic doppler using a bistatic transducer configuration has been developed to study oceanic boundary layers. The instrument uses a central narrow-beam transceiving transducer, with three surrounding fan-beam response receiving transducers directed toward the narrow volume ensonified by the central transducer. Short acoustic pulses ensonify approximately 1-cm-long sections of the water column below the 2-deg-width transmitter transducer, and acoustic energy reflected from scatterers in the water column are received by all four transducers. Coherent sampling methods provide high resolution doppler frequency measurements. The four doppler estimates allow three component velocity vectors to be estimated concurrently with the backscatter amplitude in the same small volumes over a 75-cm range, at 1-cm resolution and 20-Hz sample rate. Laboratory calibration of the acoustic backscatter using in situ sand samples provides sediment concentration profiles over a 0.001 to 25 g/l concentration range. The BCDVSP has been used in two ONR studies of the oceanic bottom boundary layer (BBL) on the inner shelf. Examples of BBL turbulent structure and sediment concentration will be shown from the SandyDuck near shore experiment in 1997, and from two inner shelf sites during the Shoaling Waves Experiment.
Field observations of bedforms in high sediment transport conditions
Authors: Crawford Anna M. , Hay Alex E.
Published: July 2012

In the first reported use of MHz-frequency acoustics to study small-scale bedforms in the near shore zone, Dingler and Inman were able to observe the evolution of transition ripples under energetic groupy waves near the flat bed threshold. They found that these low-relief, long-crested bedforms appeared to be obliterated under the largest waves in a group, and subsequently reformed in one or two wave periods [J. Dingler and D. Inman, Proc. 15th Coastal Conf., Vol. II, 2109–2126 (1976)]. More recently, measurements of linear transition ripples were made during an autumn storm event using scanning wide beam and fixed narrow beam sonars, as well as a high resolution laser-illuminated video system. These observations also indicate the occasional apparent disappearance of these ripples, and also their reformation at the same locations. The question arises as to whether the disappearance is apparent (the result of increased near bed sediment concentration and the definition of bed elevation based on reflection amplitude) or real (planing off of the ripple crests by sheet flow).
An overview of the brass collection in the Kenneth G. Fiske Museum
Authors: Rice Albert
Published: July 2012

The Kenneth G. Fiske Museum of Musical Instruments at The Claremont Colleges is one of only seven comprehensive musical instrument museums in the United States. Its collection of brasses and cup-mouthpiece instruments made of wood consists of over 400 instruments dating from the 18th through the 20th centuries. It includes cornets, trumpets, bugles, trombones, French horns, mellophones, euphoniums, tenor horns, ophicleides, keyed bugles, over-the-shoulder horns, serpents, cornettos, Russian bassoons, bass horns, tubas, instruments from Africa, Tibet, China, and other countries. The collection is especially rich in its representation of important 19th century American makers and of examples of valve designs such as Stoelzel, Berlin Pumpen, Vienna, Allen, and various designs of the Perinet valve. Valves were initially introduced by German makers in 1818, and were gradually accepted by players during the 1830s and 1840s. The Perinet valve of 1838 emerged as the standard design only by the 1870s and 1880s. With the use of slides of several instruments the presentation will illustrate four broad aspects of the collection: (1) the development of the low brasses; (2) types of valves; (3) brasses in Asia and other countries; and (4) unusual designs.
The evolution of lip-reed instruments and their manufacture
Authors: Pyle Robert W.
Published: July 2012

Lip-reed instruments began in prehistory as animal horns and tusks and have evolved into the brass instruments of modern orchestras and bands. After a brief look at instruments of biblical times and earlier, this paper will concentrate on developments from the 15th century to the present. By the mid-18th century, the typical trumpet bell contour had changed from an ‘‘animal horn’’ shape to something very close to that of the present-day trumpet and players had achieved remarkable technical proficiency, as shown in the compositions of Bach, Handel, and others. On the other hand, manufacturing techniques had changed hardly at all and the instruments were still mechanically simple. The introduction of steam power in the late 18th century profoundly changed metal-working techniques and, with the invention of the valve, led to an explosion in the variety and complexity of brass instruments. Of the numerous dead branches and twigs on the brass family tree of the 19th century, some were killed by bad acoustics, some by economics, and some by poor marketing. In our own day, computer-controlled machining not only has changed traditional manufacturing economics, but also has allowed the production of new components that would formerly have been prohibitively expensive.
A survey of the historical and acoustical development of the horn
Authors: Holmes Brian
Published: July 2012

In the 17th century, the hunting horn entered the orchestra. With its shallow mouthpiece and rapidly flared bell, the baroque horn had a bright sound like that of the trumpet. Indeed, the same musicians often played either instrument. In modern authentic performances, players use side-vents or hand-stopping to improve intonation, though no evidence suggests that 18th century players used these techniques. When the hand entered the bell, the bell was widened and the mouthpiece deepened, giving the instrument its modern character. Despite the invention of the valve, acoustics requires that the hand remain in the bell. The modern double horn, with its wider bell and rotary valves, was introduced by Kruspe in 1902. Older designs (such as the Vienna horn, with its narrower bell, terminal crook, and curious Vienna valves) persist in some areas. The drive to compete with trumpets for volume and recordings for accuracy has led some modern players to adapt higher pitched descant horns.
Pitch drift as a result of just intonation
Authors: Mullen Patrick K.
Published: July 2012

The most easily recognized difficulty with just tuning is the large and confusing array of pitches that must be made available on a keyboard instrument in order to allow modulation to several keys. A given note name may have more than one pitch associated with it, sometimes several, depending on the context in which it is used. Using computer-generated instruments that provide a limitless supply of unique pitches, just intervals can be used exclusively and explored thoroughly. When applied to Giovani Gabrieli’s Sonata Pian’ E Forte, the strict use of just tuning forces the pitch center to drift lower as the music progresses. When pitches are held across certain chord changes, lower versions of previous pitches must be used in order to maintain just tuning. Though most nonkeyboard acoustic instruments, the brasses in this case, can vary the tuning of each pitch somewhat, most cannot match the degree of drift that occurs in the Gabrieli (‘‘A’’ begins the piece at 440 Hz and ends it at ∼398 Hz!). For players of these instruments a compromise between physical tuning limitations and the ideal of just intonation must be made. Players use just intervals wherever possible, until the pitch drift forces a decision as to where the ‘‘rub’’ will be. The pitch-drift phenomenon will be demonstrated.
Measurement and classification of hearing protectors in New Zealand and Australia
Authors: Bellhouse George
Published: July 2012

An overview of the method of the measurement of the attenuation of hearing protectors using the subject-fit protocol according to the Joint Australian/New Zealand Standard AS/NZS 1270-1999: ‘‘Acoustics—Hearing Protectors’’ is presented including a comparison with ANSI S12.6-1997: ‘‘Methods of Measuring the Real-Ear Attenuation of Hearing Protectors’’; Method ‘‘B’’: Subject Fit. In this Australian/New Zealand Joint Standard, hearing protectors are rated in terms of a ‘‘class’’ rather than given an attenuation value. The system of classifying hearing protectors is detailed including the actual method of the determination of the ‘‘class’’ of a hearing protector. The use of the Australia/New Zealand ‘‘class’’ system in the workplace is illustrated by way of an example. This describes the use of LAeq,T, the determination of LAeq,8h and how these parameters relate to the ‘‘class’’ of a hearing protector. The benefits and drawbacks of the system used are compared with other rating systems.
Now what do we do with these good numbers?
Authors: Franks John R. , Murphy William J.
Published: July 2012

Present ANSI and ISO standards suggest calculating the mean real-ear-attenuation at threshold (REAT) and the standard deviations as well. These are used for calculating assume protection values (APVs) that are incorporated in calculations of the NRR in the United States and the SNR and HML in Europe and elsewhere. One of the discoveries from intense analysis of both experiment-fit and subject-fit REAT values is that they are not always unimodally and normally distributed around a mean or median, thus weakening the statistical relevance of the mean and standard deviation of the REATs. Methods for determining APVs that take into account the distribution of REATs and yet allow the computations to be otherwise unaffected will be presented. Additionally, suggestions for ratings other than the NRR, SNR, and HML will be made.
Hearing protector performance for impulse noise
Authors: Johnson Daniel L.
Published: July 2012

Using Army volunteers, a series of studies were performed at the Blast Overpressure Test Site in New Mexico to establish safe exposure levels for impulse noise. The results of these studies demonstrated that for properly worn hearing protection, the limit of human exposure is set by the threshold of nonauditory damage. This nonauditory threshold can be depicted by a simple formula based on peak pressure, A-duration, and number of impulses. Using this information, a standard for impulse noise will be proposed in which the attenuation of the hearing protective need not be measured or predicted. The protector need only to be shown to protect adequately. One method for evaluating this adequacy is based on a procedure that verifies that Temporary Threshold Shifts of Hearing are not occurring. Another method is to measure the total A-weighted energy under the protection device or devices. The standard will also include a computer model that will provide the means for the user to predict the risk of hearing injury by analyzing the waveform of the impulse.
Laser-ultrasonic measurements of thin-film properties using surface acoustic waves
Authors: Hurley Donna C. , Richards Adrian J.
Published: July 2012

High-frequency, laser-ultrasonic methods to evaluate the mechanical properties of thin films have been developed. The approach is based on the optical generation and detection of surface acoustic waves (SAWs) to determine the frequency dependence of the phase velocity (dispersion relation). Broadband or variable-frequency, quasi-plane wave SAWs are generated by a line-focused, 200-ps pulsed laser. The out-of-plane SAW displacement amplitudes are measured using a path-stablized Michelson interferometer with line-focus detection. The apparatus incorporates differential photodiode detection with a −3-dB bandwidth of 40 kHz–800 MHz. With this system, several displacement waveforms over a range of propagation distances are acquired and used to determine the SAW dispersion. Dispersion relations up to 200 MHz are presented for a variety of specimens, including a series of Si wafers with TiN films 0.2–1.3 micrometers thick and containing residual stress. The results illustrate the applicability of this technique to various conditions such as stiffening and loading films and isotropic and anisotropic substrates. The experimental dispersion curves obtained with this method are compared to theoretical predictions to evaluate the film elastic properties.
Optical matched-filter and phased-array detection of surface acoustic waves
Authors: Murray Todd , Krishnaswamy Sridhar
Published: July 2012

A method to optically measure surface acoustic displacements simultaneously over an array of detection points is described. Optical phase gratings are used to create a detection array of laser beams that is directed to the specimen. The scattered beams from the detection array are then collected and combined with a single reference beam in a photorefractive crystal in a multiplexed two-wave mixing configuration. The output beams of the resulting multiplexed photorefractive interferometer are imaged onto either a single photodetector (matched-filter scheme) or to separate photodetector elements (phased-array scheme). The optical matched filter requires less electronic overhead. By using different object beam footprints, it is possible to configure optical matched-filter receivers that selectively detect SAWs (broadband, narrow-band, chirped, etc.) with enhanced sensitivity. The responses of equispaced and chirped array receivers to propagating SAWs are discussed. The more general phased-array configuration, although requiring greater electronic overhead, provides time-domain signals from each element for postprocessing. This system can therefore be synthetically focused by applying appropriate phase shifts between the detected signals to create images of the acoustic scattering region. Both these multiplexed optical detection schemes, with their high spatial resolution and subnanometer displacement sensitivities, have applications in nondestructive testing and materials characterization.
Phase-amplitude-modulated laser and microwave vibrometers
Authors: Donskoy Dimitri , Sedunov Nikolay , Whittaker Edward
Published: July 2012

The paper presents results of a new development of remote vibration sensors using modulated electromagnetic (optical and microwave) signals. The microwave sensor (vibrometer) utilizes the effect of phase modulation of a cw microwave carrier reflected from vibrating surfaces or subsurfaces. The optical vibrometer uses a similar principle of phase modulation of the microwave frequency modulating envelope of the optical carrier. Both optical and microwave vibrometers can share the same signal, generating and receiving electronics and algorithms. Using different carriers but shared electronics, both sensors can be combined in one device offering versatile capabilities for various applications. The developed concept has been experimentally validated for both optical and microwave sensors. The 2.5-GHz portable vibrometer has been designed and tested. The description of the vibrometers, examples of their applications, and comparison with commercial LDV systems will be discussed in the presentation.
Measurement of grain size using diffused ultrasound energy
Authors: Lamouche Guy , Lord Martin , Moreau Andr
Published: July 2012

A new method is proposed to determine grain size in steel sheets by combining a laser-ultrasound technique with ultrasound energy diffusion. A short laser pulse impinging on a metal surface generates an ultrasonic wave packet that propagates through the material. This wave packet is scattered by the discontinuities it encounters at the boundaries of the metallic grains. At the beginning, this energy is quite localized near the generation point and then spreads in the sheet in a way that can be described as a two-dimensional diffusion process. This diffusion process can be followed by measuring the ultrasound field amplitude at the surface of the sheet at various distances from the generation point. This observation is performed remotely by using a laser light that is frequency shifted by the surface movement (Doppler effect). Theoretical considerations suggest that there should exist a relationship between the size of the grains responsible for the ultrasound scattering and the diffusion coefficient describing the ultrasound energy diffusion process. We present preliminary experimental results showing that such a relationship does exist, thus providing a method to remotely measure grain size in steel sheets.
Computational evaluation of satellite equipment panel modal densities and radiation efficiencies
Authors: Conlon Stephen C. , Hambric Stephen A.
Published: July 2012

During the design phases of communications satellites Statistical Energy Analysis (SEA) methods are often used to predict critical equipment panel structural-acoustic vibration responses. Difficulties arise in the SEA modeling due to the nonhomogeneous nature of these complex equipment panels. Panel constructions are typically sandwich honeycomb (thick) cored panels with internal embedded heat pipes, external attached stiffeners, external thermal doubler plates, as well as the attached equipment itself. The resulting built up structure is very difficult to analyze using SEA theoretical asymptotic values. This work computationally evaluates the modal density and radiation efficiency of a typical communications satellite equipment panel utilizing a detailed finite-element model along with a lumped parameter radiation representation developed by Fahnline (1997). The full built up nonhomogeneous panel, as well as the uniform baseline panel, are evaluated using both idealized and realistic boundary conditions. The characteristics of the nonhomogeneous equipment panels are shown to vary significantly from commonly used SEA values. Simple curve fits are developed for future SEA evaluations of similar structures.
Introduction of complex layer analysis (CLA) for acoustic radiation problems
Authors: Feit David , DiPerna Daniel T.
Published: July 2012

The pressure radiated by a planar vibrating surface with a prescribed harmonic time-varying surface velocity can be represented as the inverse Fourier transform of the product of the velocity transform and the spectral form of the acoustic surface impedance. This integral representation usually cannot be evaluated in closed form, but can, however, be evaluated asymptotically in the far field, i.e., at field points large compared to the acoustic wavelength. In this note a novel approach, ‘‘complex layer analysis’’ (CLA) is introduced which involves an approximation of the acoustic impedance in terms of a rational function. Contour integration is then used to obtain an explicit expression for the near-field pressure distribution as a sum of waves propagating with wave numbers corresponding to the poles of the approximate acoustic impedance. Such an expression makes explicit the notion of pressure-field generation localizing to points of discontinuity in the velocity distribution. [Work supported by the Carderock Division Naval Surface Warfare Center ILIR Program.]
Predictive approaches and measurements of far-field radiation from submerged partially coated (compliant layer) cylindrical shells
Authors: Herdic Peter C. , Houston Brian H. , Photiadis Douglas M. , Williams Earl G.
Published: July 2012

In-water laboratory experiments involving spatially dense near-field and far-field responses (ka=1 to 20) are reported for a number of point driven cylindrical shells with varying amounts of compliant material attached to the exterior. The first framed shell has a square opening in the otherwise fully coated surface. Two modeling approaches are employed to predict the far-field radiation from this opening. The first method is based on the Helmholtz Integral Equation (HIE), using a simple baffled plate model where only surface quantities around the opening are projected. A square piston in a cylindrical baffle is also implemented as a second predictive approach. The predictions are found to be in general agreement with the actual radiated values determined through holographic projections to recover the off-board quantities. The discussion includes the conditions necessary for an accurate model. Additionally, two shells with different levels of interior structural complexity are each investigated using near-field acoustic holography (NAH) where the degree of compliant material coverage is varied. The physics of these systems will be discussed, including the nature of the normal modes, the energetics, and the degree to which interesting phenomena such as ‘‘tunneling’’ are observed.
Numerical and experimental characterization of the transmission loss of complex composite panels
Authors: Bolduc Maxime , Panneton Raymond , Atalla Noureddine , Wojtowicki Jean-Luc
Published: July 2012

The noise reduction in aircrafts is one of the top priorities for the aerospace industry. In this paper, a thorough investigation is done on the reliability of numerical FEM/BEM methods to predict the sound transmission loss of aircraft-type panels. The investigation is based on the comparison between numerical predictions, using commercial and in-house software, and measurements for different configurations of panels: single plate, double plate with air cavity, and double plate with cavity absorption. Clamped boundary conditions are used for both the simulation and experiments. The porous material is modeled following Biot theory and the diffuse sound field is simulated as a superposition of plane waves at various directions. For the experimental part, the transmission loss is obtained by setting the panel between a reverberant and an anechoic room. The transmitted power is measured with an intensity probe allowing fine characterization of the effects of complexities such as the boundary conditions and leaks. Furthermore, the quadratic velocity is measured as a means of validation for the mode shapes. Discussions on the numerical procedure to follow for providing reliable transmission loss predictions and a discussion on the discrepancies between the experiments and the numerical simulations will be done.
Dynamic structural–acoustic–piezoelectric finite-element analysis of a sonar array for a supercavitating high-speed underwater vehicle
Authors: Koch Robert M.
Published: July 2012

Three-dimensional nonlinear dynamic finite-element analysis (FEA) is utilized herein in order to examine the coupled structural, acoustic, and piezoelectric noise propagation physics within a high-frequency sonar array for a supercavitating underwater research vehicle. Specifically, steady-state dynamic simulations of the sonar array’s coupled performance are carried out that model both (a) the acoustic radiation field resulting from electrically actuated ceramic array elements, and (b) the ceramic array element electrical response due to incident structure-borne excitation; fluid-borne excitation is being examined presently and may also be presented if completed in time. This paper focuses primarily on the interesting issues related to accurately modeling such a complex coupled system. For example, the frequency-dependent properties of a nonlinear elastomer absorption material within the array must be carefully characterized at very high frequencies in order to gain accurate results. Additionally, determining electrical properties of the piezoelectric ceramic material can pose a significant problem. Finally, performing a three-dimensional simulation at high frequencies with coupled physics analyses is not a trivial undertaking.. Laboratory shaker experiments performed in order to validate the modeling will also be presented.
Ken Stevens and cross-linguistic phonetic studies
Authors: Ladefoged Peter
Published: July 2012

Many years ago we realized that one person’s pathological voice quality might be a necessary part of another person’s phonological contrast. Some American English speakers may have a very breathy voice, but a Gujarati speaker may need that voice quality to distinguish the word meaning ‘‘outside’’ from the word meaning ‘‘twelve.’’ It was largely Ken Stevens’s work, in personal communications, that enabled us to quantify these distinctions. This led to the notion that it was possible to describe a continuum of phonation types: voiceless, breathy, voiced, creaky, glottal closure. Using a modified version of another notion suggested by Stevens, we were able to consider possible quantal states along the parameter of glottal stricture. Further investigation of different languages suggested that contrasts along a single parameter may not be as straightforward as they seemed, and a number of ‘‘helping features’’ (yet another Stevens notion) were often involved. Despite being misled by the binary notions of colleagues at MIT, Ken Stevens’s work has been of great help in linguistic phonetics.
Human communication with information systems
Authors: Flanagan James
Published: July 2012

As networked information systems increase in complexity, natural modes of communication assume a greater role in the design of human–machine interfaces. Modalities of sound, sight, and touch are largely favored by humans, with conversational interaction being a central medium for information exchange. The distinguished research career of Professor Kenneth N. Stevens, celebrated in this special session on speech communication, has contributed directly to the basic understanding that supports current capabilities in voice interaction. While as yet primitive in comparison to human versatility, the technologies for sound, in concert with those for sight and touch, can be prudently applied to transcend the functionalities of traditional mouse and keyboard. This report describes a research effort in simultaneous utilization and fusion of sound, sight, and touch signaling in a networked collaborative environment. The conversational interaction depends upon automatic speech recognition, speech synthesis, and ‘‘hands-free’’ sound capture. Automatic face recognition, visual gesture, and eyetracking serve the sight modality. A force-feedback tactile glove provides manual gesture and grasp of virtual objects. And, intelligent software agents fuse and manage the multiple modes to develop a context-aware estimate of user intent. An experimental system utilizing these interface modes is applied to crisis management, and is demonstrated by videotape. [Components of this research were supported by National Science Foundation Contract Nos. IRI-96-18854 (STIMULATE) and IIS-98-72995 (KDI), DARPA Contract No. N66001-96-C-8510 (DISCIPLE), the Intel Corporation, Texas Instruments, and the Rutgers Center for Advanced Information Processing.]
Robust speech recognition in adverse environments by separating speech and noise sources using JADE-ICA
Authors: Kadambe Shubha
Published: July 2012

Spoken dialogue information retrieval applications are the future trend for mobile users. The typical presence of background noise in mobile environments causes significant reduction in speech recognition accuracy unless the recognizers are trained explicitly for each environment. However, it is not practical to train recognizers for every environment. One solution to this problem is to use an array of microphones and then separate the speech signals from noise by applying Blind Source Separation (BSS) techniques. BSS based on Independent Component Analysis (ICA) is one of the efficient techniques to separate mixed signals and JADE-ICA is one of ICA’s variants that is applicable for non-Gaussian signals. The JADE-ICA is applied here, since generally speech and noise are non-Gaussian signals. An array of two microphones was considered and two signal sources: speech and in-vehicle noise were assumed. Recognition accuracy experiments were conducted on 1831 utterances from 1831 speakers after separating the speech signals from noise using the JADE-ICA. The word recognition accuracy for three conditions: clean speech, noisy speech (SNR = 0 dB) and noise separated speech are 91.9%, 45.2% and 91.9%, respectively. This indicates that using the JADE-ICA to separate speech from noise results in the same recognition accuracy as that of clean speech. The details on JADE-ICA and simulations will be provided in the full paper.
Convolutive blind source separation of speech signals based on amplitude modulation decorrelation
Authors: Anemüller Jörn , Kollmeier Birger
Published: July 2012

The problem of blind separation of a convolutive mixture of speech signals is considered. Signal separation is performed in the frequency domain. The amplitude modulation decorrelation algorithm for convolutive blind source separation of speech is described, the first ideas of which were presented by Anemüller at the joint ASA/EAA/DAGA meeting, Berlin, 1999. The algorithm is based on the fact that the frequency-specific envelopes of speech signals exhibit correlation across different frequencies. This feature can be used to solve the ‘‘permutation problem’’ of frequency-domain-based blind source separation algorithms. Furthermore, it leads to separation of good quality since it results in a high number of constraints which must be fulfilled by the unmixed signals. Results for the separation of speech signals are presented for different mixing scenarios, including real-room reverberant mixing.
Privacy with intelligibility—A novel electroacoustic solution
Authors: Mapp Peter A.
Published: July 2012

The concept of electronic sound masking is a well-established and successful solution in helping to achieve adequate speech privacy either within or between office areas or similar spaces. In many instances, separate paging or voice-alarm systems are also installed. Whereas locating loudspeakers in the ceiling void or within a plenum assists sound diffusion and evenness of coverage, this also degrades speech intelligibility and causes significant nonlinear (frequency-dependent) transmission losses. Conversely, installing conventional loudspeakers directly into the ceiling can result in good intelligibility but poor sound diffusion, leading to uneven sound distribution and immediate localization of the loudspeaker as the sound source. The diffuse, substantially decorrelated and wide dispersion characteristics of the distributed mode loudspeaker suggests that systems employing this new class of device may simultaneously satisfy the requirements for both speech privacy and speech intelligibility. The paper presents the results of a study using a range of loudspeaker formats to establish whether these apparently opposing requirements can be achieved.
Architectural repair of the acoustics in Koubek Auditorium at the Catholic University of America
Authors: Ellis Donna A.
Published: July 2012

Koubek Auditorium is used as the main lecture space in the School of Architecture and Planning at The Catholic University of America in Washington, DC. The space is used for classes in physics, history, and issues in practice, to name a few. It is also regularly used for lectures by professionals from the architectural community. Acoustics in the auditorium are poor and result in ineffective use of the space as well as a poor teaching environment. The main problem areas are the noise levels of the HVAC, reverberation times, and sound distribution. The average noise criteria in this space is NC40. In some locations the maximum is 50–60. At Koubek Auditorium the RT’s range from 0.8 s, to 1.46 and higher. This paper will demonstrate how these numbers are brought down to acceptable levels to ensure effective learning in the space. [Work supported by ScantTek, Armstrong, Electro-Media Design.]
Differences in performance with different background sound and ambient noise in three open office plans
Authors: Yoon Heakyung C.
Published: July 2012

The effect of noise on the performance of workers is investigated in three types of open workplaces: a combination of open plan and closed offices, rectangular configuration in open plan, and triangular configuration in open plan. An open workplace is intended to increase workers’ performance by creating a knowledge-sharing environment informally and seamlessly, while it is also known to decrease workers’ performance for they are annoyed with or distracted by the sound from the workplace. According to interviews from and questionnaires completed by workers in these workplaces, the order of preference was the combination, the rectangular configuration, and the triangular configuration workplaces. Each subject took two proofreading tests for 10 min under two different sound conditions. One of these conditions was background sound only with quiet HVAC sound and the other was ambient sound, which was recorded from each workplace along with speech and the sound from other activities by a binaural artificial head measurement system. The result is the mean test score of subjects from the triangular configuration workplace is significantly different from the mean test scores of subjects from the combination type workplace and the rectangular configuration workplace, respectively. [Work supported by IBM-Toronto, Inc.]
Speech intelligibility in highway toll booths
Authors: Feist Jeffrey P. , Mongeau Luc , Bernhard Robert J.
Published: July 2012

The purpose of this study is to improve the working conditions at highway toll collection facilities. It is believed that the sustained noise levels create an unpleasant working condition and hamper communication between attendants and patrons. Controlling noise in this environment is particularly challenging because the toll booth is a partially open enclosure with reflecting walls which may amplify the traffic noise. Toll collection employees were surveyed in order to assess, among other factors, the influence of ambient traffic noise on speech intelligibility. The results suggest that communication problems exist and that active noise control (ANC) headsets are a potential solution. Low-frequency vehicular noises are believed to strongly contribute to the communication problem, and ANC systems are particularly effective at reducing such noise emissions. To adapt ANC headsets to this application, insertion loss measurements have been made for a variety of active headsets. Attention was given to the level of attenuation within the frequency range of speech intelligibility. Modifications are underway to optimize an active headset for speech intelligibility and noise reduction. Additional work includes modeling the acoustics of the environment with a ray-tracing software package. This modeling work will allow structural changes to be evaluated.
Investigation of speech intelligibility in building with curved surfaces by means of objective measures
Authors: Harun Mokhtar , Abd. Rahman Tharek , Ibrahim Md. Najib , Said Ahmad Khan
Published: July 2012

There are two aspects in an acoustics design process that have to be taken care of in order for the room and the sound system to be intelligible. The first is the electronic part of the design. The second is the environment in which the system is to be installed. With the assumptions that the selection of sound system equipment and installation are correct and thorough, the sound reflection pattern and its delay in building with curved surfaces has to be investigated and understood. This paper investigates via measurements as well as through the simulation software the distribution of sound pressure level, sound delay (RT60), time and amplitude of early reflection (Rearly), and late reflection (Rlate) in a symmetrical room and in a room with curved surfaces. Rearly  is categorized as the first-arriving wave-front that happens before 35 ms and Rlate is that within 70 and 120 ms. Preliminary investigation has shown that the equal distribution of these objective measures is destroyed with the existence of curved surfaces in the room. This unequal distribution hints that speech intelligibility of a room with curved surfaces is also varied and altered.
On the disagreement between speech transmission index (STI) and speech intelligibility
Authors: Onaga Hiroshi , Furue Yoshihiro , Ikeda Tetsuo
Published: July 2012

The change tendency of speech transmission index (STI) was examined by calculation for several modeled sound fields. As a result, it has been revealed that STI contradicts the generally accepted concept of the importance of early energy for speech intelligibility. Namely, for single reflection fields, (1) STI takes the same value for positive and negative levels of reflection relative to direct sound, and for positive and negative delay times. (2) STI takes the lowest value when the reflection level is 0 dB (equal to direct sound), and the increase and decrease of reflection level from 0 dB causes a rise in STI. For multiple reflection fields, (3) STI evaluates only the degree of energy concentration or dispersion in the time domain. Also, energy concentration due to strong reflections with any delay time increases the value of STI. However, the already published experimental results of intelligibility on single reflection fields differ from the above-mentioned properties of STI, (1) and (2). Moreover, the authors’ intelligibility experiment with multiple reflections indicates the importance of early energy for intelligibility and shows the disagreement with the properties of STI (3). From the above findings, STI cannot be considered as corresponding to intelligibility.
Extraction and tracking of bottlenose dolphin whistle contours
Authors: Suzuki Ryuji , Buck John R.
Published: July 2012

The time-frequency contours of bottlenose dolphin (Tursiops truncatus) whistles are commonly extracted as features for the classification and comparison of these signals. This research presents a new method to extract and track the whistles’ fundamental frequency contours. This method takes a spectrogram as an input and uses a Bayesian inference approach with a random walk model for the frequency transitions. The output of the method is the maximum a posteriori probability estimate of the frequency contour. This technique is similar to the Kalman filter except that the states are probability densities, and it uses a probabilistic state transition model. For each time segment, the method combines the prior estimate of the probability distribution with the current observation to obtain the current estimate of the probability distribution. Experimental evaluation indicates that this method greatly improves the reliability of contour extraction from noisy signals when compared to the ad hoc contour extractor proposed by Buck and Tyack [J. Acoust. Soc. Am. 94 (1993)]. This technique has previously applied to target tracking in radar [Bethel and Rahikka, IEEE Trans. Aerosp. 23(6) (1987)]. [Work supported by NSF Ocean Sciences.]
Hector’s dolphin (Cephalorhynchus hectori) vocalizations and gillnet pingers
Authors: Cavagnaro Laura , Baldwin Kenneth , Stone Gregory
Published: July 2012

The effectiveness of acoustic gillnet pingers for eliciting a deterrent behavior in some marine mammals is well documented, although the reasons for this behavior are not clearly understood. Little is known about the mammals vocal response to these devices. The objective of the experiments defined here was to investigate the possibility of vocalization response changes due to the presence of a gillnet pinger. Three commercially available gillnet pingers were used as acoustic cues for Hectors dolphins (Cephalorhynchus hectori). The dolphins’ vocalizations were recorded with and without the pinger in the water. The records of the dolphin vocalizations were analyzed using digital signal processing techniques to determine whether the dolphin vocalizations changed with the presence of an acoustic cue from the pinger. Fourier analysis, wavelet analysis, and empirical orthonormal functions were used to analyze the vocalizations. No significant changes in the vocalizations could be found between the control and active gillnet pinger cases.
Use of actively tuned low-frequency transducers for high-power linear chirp transmission
Authors: Bernard Julien , Lesieutre George A.
Published: July 2012

To overcome the low-radiation resistance, low-frequency underwater transducers must be operated in the vicinity of resonance. To provide maximum displacement at resonance, they are often designed as high Q, hence narrow bandwidth, devices. Various approaches have been used to increase the bandwidth of these transducers, including impedance matching layers and velocity feedback, among others. However these approaches result in reduced peak sensitivity. In contrast, low-frequency transducers with a variable and controllable resonance frequency, which may be matched to the transmitted signal dominant frequency at all times, offer the double advantage of increased bandwidth and high sensitivity at almost all frequencies within the bandwidth. Variable frequency transducers have been used for the high-power transmission of consecutive single frequency pulses at various discrete frequencies, such as stepped frequency modulated chirps. This paper shows that they can also provide high-power transmission of continuously varying frequency pulses, such as linear frequency modulated chirps. Using a simple equivalent circuit model, the responses of a fixed frequency and a variable frequency piezoceramic tonpilz to a linear chirp are calculated and compared, in the time and the frequency domains. The results show that the variable frequency transducer can efficiently transmit linear chirps of much larger bandwidth.