bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise enforcement in cities
Authors: Zwerling Eric
Published: September 2013

Noise enforcement programs (NEPs) in cities face a number of unique obstacles, including the necessity to conduct sound level measurements in a complex acoustical environment. It is important to regularly and objectively review the efficacy of the program in totality. A successful NEP consists of the following interactive components: the ordinance, trained enforcement personnel, sound measurement equipment, and prosecutorial mechanisms. If any of these components are not working in harmony, the NEP may not deliver the desired results. The NEP should be designed to reflect the realities of field enforcement, and should be tailored to the specific agency that will be conducting the enforcement, mindful of the differences between environmental compliance officers and police officers. This begins with the crafting of an ordinance that is appropriate for the unique conditions within the jurisdiction. The sound measurement equipment should be the least complicated necessary to take the specified measurements, and should be as durable as possible. Enforcement officers require proper training. Noncompliance must be addressed in a constructive and meaningful manner. A number of jurisdictions with active noise enforcement programs have been interviewed to determine the status of the program, and their strengths and weaknesses have been honestly assessed.
Noise impact evaluation method for supermarket sites
Authors: Tocci Gregory , Su Rose Mary
Published: September 2013

A large food supermarket chain is currently in a large store-building program involving several project managers who identify prospective sites, retain A/E design services, and obtain local permits for construction. There is a variety of environmental and planning issues that sometimes need special consideration; among these is environmental noise. Supermarket management has asked that consultants representing each discipline, and who work with project managers on specific projects as needed, issue guidelines as to when special consideration of their disciplines is required. This presentation describes a simple method developed for the supermarket owner that allows their project managers to judge whether there is a need for special consideration of environmental noise in store design by an acoustical consulting firm.
Numerical modeling of infrasound propagation at very long distance
Authors: Piserchia Pierre-Franck , Roche Roger
Published: September 2013

Compliance with the CTBT in the atmosphere will be monitored by a world-wide network of infrasound stations consisting of 60 stations equipped with microbarographs in order to measure small changes in the air pressure in the frequency range 0.02 to 4 Hz. They are characterized by a good sensitivity, and by a large dynamic. By the application of array techniques, it is possible to determine the direction of pressure pulses caused by small explosions in the atmosphere, as well as shock waves caused by supersonic aircraft or meteorites. To take into account the nonlinear phenomena at the source and during the propagation, we are developing a numerical approach to solve the Euler nonlinear equation. In a first step, in the linear domain, this method is compared with two other numerical modeling approaches based on the ray tracing technique and the parabolic approach. In our test case, the source is on the ground and generates a 1-Pa pressure pulse centered at the frequency of 0.1 Hz. We considered an infrasound propagation over a distance of 500 km and an atmosphere height of 200 km. In a further step, the source level will be increased to study nonlinear phenomena.
Broadband time reversed acoustic focusing and steering system
Authors: Sutin Alexander , Sarvazyan Armen , Montaldo Gabriel , Palacio Delphine , Bercoff Jeremy , Tanter Mickael , Fink Mathias
Published: September 2013

We present results of experimental testing and theoretical modeling of a time reversal acoustic (TRA) focusing system based on a multifaceted aluminum resonator with 15 piezoceramic transducers glued to the resonator facets. One of the facets of the resonator, a pentagon with characteristic dimension of about 30 mm, was submerged into a water tank and served as a virtual phased array which provided ultrasound focusing and beam steering in a wide frequency band (0.7–3 MHz). Ultrasonic pulses with different carrier frequencies and various complex waveforms were focused; the focal length was varied in the range of 10–55 mm and the focused beam was steered in a range of angles of ±60 deg. The amplitude of the signal in the focal region reached 40 MPa. A theoretical model was based on an assumption that the radiating part of the resonator works as a phase conjugation screen for a spherical wave radiated from the focal point. Theoretical dependencies of the field structure on the position of the focus point and ultrasound frequency are in a good agreement with experimental results. TRA based focusing of ultrasound has numerous applications in medical diagnostics, surgery and therapy. [Work supported by NIH grant.]
Acoustic tomographic array simulation
Authors: Collier Sandra L. , Ligon David A. , Noble John M.
Published: September 2013

Acoustic travel-time tomography of the atmosphere allows one to retrieve the virtual temperature and wind velocity fields, and to monitor their evolution in time. The temperature and wind velocity fields in a horizontal slice near the ground have been successfully retrieved by several research groups. One future direction for acoustic tomography of the atmosphere is the retrieval of detailed time-varying volumetric wind and temperature fields. The ability to retrieve these fields is strongly dependent upon the system configuration, e.g., the number and placement of sources and sensors, the geometry of the array, the environmental effects, and the type of the source. A sensitivity analysis for the retrieval of the temperature and wind velocity fields as a function of sensor configuration has been performed using an acoustic tomographic array simulator. We discuss the simulation model and results of the sensitivity analysis to some baseline propagation cases.
The time-reversal effect at sound scattering by a rough surface
Authors: Fuks Iosif , Naugolnykh Konstantin
Published: September 2013

The scattering of the time-reversed wave by a rough surface is considered in the present paper. Using the Green function theory the point source field scattering by the rough surface in the Kirchhoff approximation is considered and the equation for the time-reversed and retransmitted back to the rough surface wave is obtained. The spatial distribution and the intensity spectrum of the scattered wave are evaluated for the Gaussian model of the rough surface and their features are examined. The modifications of the spectrum of the time-reversed wave as a function of the relation of the propagation time of the wave to the source-receiver array to the characteristic period of the surface roughness variation are discussed.
Perceptual scaling of room reverberation
Authors: Zahorik Pavel
Published: September 2013

Recent evidence suggests that reverberant energy can provide listeners with important spatial information regarding the distance of a sound source. However, relatively little is known about the perceptual attributes of the reverberation itself, and how these attributes may be related to physical properties of the environment that also potentially impact perceived spatial location. Here, perceived similarity among 15 reverberant rooms simulated using virtual auditory space techniques was examined. Room size and surface absorption properties were varied, along with aspects of the virtual simulation including the use of individualized head-related transfer function (HRTF) measurements and properties of the room acoustic simulation. Seven listeners rated perceived similarity on a 100-point scale between all possible pairs of simulated rooms using a speech source signal. Multidimensional scaling techniques were used to estimate scales of perceived room reverberation. Although the resulting scales were complex and somewhat unique to individual listeners, it is clear that the perceptual effects of manipulating properties of the reverberant sound are much larger than the effects due to either nonindividualized HRTFs or nonoptimal room simulation methods. [Work supported by NIDCD.]
A real-time virtual auditory system for spatially dynamic perception research
Authors: Scarpaci Jacob W. , Colburn H. Steven
Published: September 2013

A Real Time Virtual Auditory System (RT-VAS) is being developed to provide a high-performance, cost-effective, flexible system that can dynamically update filter coefficients in hard real time on a PC. An InterSense head tracker is incorporated to provide low-latency head tracking to allow studies with head motion. Processing is done using a real-time Linux Kernel (RTAI kernel patch) which allows for precise processor scheduling, resulting in negligible time jitter of output samples. Output is calculated at a sample rate of 44.1 kHz and displayed using a National Instruments DAQ. Object oriented approach to system development allows for customizable input, position, and calculation routines as well as multiple independent auditory objects. Input and position may be calculated in real-time or read from a file. Calculation of output may include filtering with spatially sampled HRTFs or analytic models and head movements may be recorded to file. Limitations of the system are tied to the speed of the processor, thus complexity of experiments scales with speed of computer hardware. The current system handles multiple moving sources while tracking head position. Preliminary psychoacoustic results with head motion will be shown, as well as a demonstration of the system. [Work supported by NIH DC00100.]
Scaling the perceived fluctuation strength of frequency-modulated tones
Authors: Wickelmaier Florian , Ellermeier Wolfgang
Published: September 2013

Fluctuation strength is one of the major psychoacoustic variables considered in sound-quality evaluation. Zwicker and Fastl [Psychoacoustics (Springer, Berlin, 1999)] summarize recommendations for its computation, which have already been implemented in various software applications, even though the data basis is rather limited. In particular, the dependency of fluctuation strength on modulation frequency and modulation depth has seemingly never been tested in a factorial design. Therefore, in experiment I both of these factors were varied simultaneously in order to create 54 different frequency-modulated sinusoids. The task of the subjects was to directly estimate the perceived magnitude of fluctuation strength. The results do not conform well with the prevalent model of fluctuation strength. In experiment II this finding was further investigated by varying only one factor at a time. The results show that large individual differences, particularly in the effect of modulation frequency, persist. Thus, in experiment III the interaction of both factors was analyzed on an individual basis. By employing a 2AFC procedure, matches in fluctuation strength were obtained. The results suggest that most listeners are not able to integrate modulation frequency and modulation depth additively into a unidimensional percept. [Work supported by Centercontract on Sound Quality, Aalborg University.]
Effect of noise on the detection of intensity increments
Authors: Jesteadt Walt , Nizami Lance , Neely Stephen T. , Schairer Kim S.
Published: September 2013

The detection of an increment in a longer duration tone is often used as a measure of intensity resolution. Many studies of increment detection have used background noise, but few have varied the level of the longer duration tone relative to the noise or have compared results obtained with or without the noise. To explore this space in more detail, thresholds were obtained by adaptive tracking from four subjects for detection of a 50-ms increment in a 350-ms, 4000-Hz tone presented in quiet or in broadband noise of 0, 10 and 20 dB spectrum level. Tone levels ranged from 15 to 75 dB SPL in quiet and from approximately 0 to 30 dB above the tone’s detection threshold in the noise. Increment detection thresholds expressed as values of the difference in overall level of the tone resulting from addition of the increment increase as tone sensation levels decrease and are greater in noise than in quiet, but increase only slightly as a function of noise level. The data are well fitted by a model that assumes a specific form of nonlinearity motivated by loudness-matching data. [Work supported by NIDCD.]
The effect of modulation maskers on the detection of second-order amplitude modulation in the absence and presence of notched noise
Authors: Uchanski Rosalie M. , Moore Brian C. J. , Glasberg Brian R.
Published: September 2013

Second-order amplitude modulation (AM) can be detected despite the absence of a component at the second-order modulation frequency in the modulation spectrum. This may depend on the detection of a modulation component at the second-order frequency produced by nonlinearities in the auditory system, or on the detection of a ‘‘beat’’ at the output of the modulation filter centered at the first-order rate. To assess these possibilities, and to explore the role of off-frequency listening, first- and second-order AM detection thresholds were determined for six listeners with normal hearing, in the absence and presence of a notched noise centered at the carrier frequency of 4 kHz. First-order thresholds were measured for f1=2, 10, 16, and 50 Hz. Second-order thresholds were measured for f1=16 and f2=2 Hz, and for f1=50 and f2=10 Hz. Then, using a second-order modulation depth giving about 80%-correct detection, performance for detecting second-order AM was measured in the presence of a modulation masker centered at either the first- or second-order rate. In the absence of notched noise, both modulation maskers impaired performance, for both second-order rates. In the presence of notched noise, for most listeners there was little effect of either modulation masker. [Work supported by MRC.]
Touch-induced scraping sounds and texture perception
Authors: Altinsoy M. Ercan
Published: September 2013

Sound is often the result of human–object interaction (touch, striking, scraping, etc.) and conveys to the listener required information about physical attributes of the interaction, and spatial properties of the sound event, e.g., location, geometry. People are highly skilled in using touch-produced sounds to identify texture properties. Loudness and pitch of the touch-induced scraping sounds are the important psychoacoustical determinants of the texture perception [S. J. Lederman, Perception 8, 93–103 (1979)]. In this study, psychophysical experiments were conducted to investigate the relationship between auditory properties (loudness and pitch) and texture perception. In order to control the psychoacoustical parameters, the scraping sounds were synthesized in computer environment. The results of the experiments show that subjects were able to differentiate the roughness of textures on the basis of pitch and loudness differences. Decreasing pitch tends to result in increasing magnitude of perceived roughness.
Proficient bilinguals require more information for vowel identification than monolinguals
Authors: Lopez Alexandra S. , Rogers Catherine L.
Published: September 2013

Even proficient bilinguals have been shown to experience more difficulty understanding speech in noise than monolinguals. One potential explanation is that bilinguals require more information than monolinguals for phoneme identification. We tested this hypothesis by presenting gated, silent-center vowels to two groups of listeners: (1) monolingual American English speakers and (2) proficient Spanish–English bilinguals, who spoke unaccented or mildly accented English. To create the stimuli, two American English speakers were recorded as they read the following items: ‘‘beeb, bibb, babe, bebb, babb,’’ and ‘‘bob.’’ Duration-preserved silent-center versions of three tokens of each item were created by retaining varying amounts of the CV and VC transitions (10, 20, 30, or 40 ms) and attenuating the remainder of the vowel center to silence. Duration-neutral versions of silent-center tokens were created by lengthening or shortening the silent portion to match the tokens vowel duration to the average for all the tokens. Listeners identified the unedited (full vowel), duration-preserved, and duration neutral silent-center tokens in a six-alternative forced-choice task. The two groups of listeners identified the unedited tokens with similar accuracy. In the silent-center conditions, however, the bilinguals identified the stimuli less accurately than the monolinguals. [Work supported in part by NIH-NIDCD Grant No. 1R03DC005561-01A1.]
Discrimination of synthesized English vowels by American and Korean listeners
Authors: Yang Byunggon
Published: September 2013

This study explored the discrimination of synthesized English vowel pairs by 27 American and Korean, male and female listeners. The average formant values of nine monophthongs produced by ten American English male speakers were employed to synthesize the vowels. Then, subjects were instructed explicitly to respond to AX discrimination tasks in which the standard vowel was followed by another one with the increment or decrement of the original formant values. The highest and lowest formant values of the same vowel quality were collected and compared to examine patterns of vowel discrimination. Results showed that the American and Korean groups discriminated the vowel pairs almost identically and their center formant frequency values of the high and low boundary fell almost exactly on those of the standards. In addition, the acceptable range of the same vowel quality was similar among the language and gender groups. The acceptable thresholds of each vowel formed an oval to maintain perceptual contrast from adjacent vowels. Pedagogical implications of those findings are discussed.
Visual contributions to talker attunement
Authors: Brancazio Lawrence
Published: September 2013

Listeners can attune to talker-specific speech patterns, as demonstrated by findings of greater accuracy in spoken-words-in-noise identification for words spoken by familiar voices [e.g., Nygaard and Pisoni, Percept. Psychophys. 60, 355–376 (1998)]. In previous demonstrations of this effect, talker familiarity was produced by auditory speech exposure. The purpose of the present study was to examine the contribution of visible speech information to talker attunement. First, the auditory attunement effect was replicated: Participants were given extensive exposure to auditory words spoken by different talkers, and were subsequently tested on novel words in noise spoken by one of the familiar talkers and by a talker not previously heard. Identification of the words was more accurate for the familiar talker. This procedure was then extended to include video presentations of the talker’s articulating face along with each word during the exposure phase. To control for familiarity with the faces, a separate condition included presentation of static images of the talkers’ faces. Visual articulations were not presented during the identification-in-noise task. Thus, the experiment tests whether visual exposure to talker’s articulatory patterns contributes to talker attunement, and, specifically, whether any such visual contributions to talker attunement generalize to auditory speech perception. [Work supported by NICHD.]
Effects of speaking rate on the acceptability of change in segmental duration within a phrase
Authors: Muto Makiko , Kato Hiroaki , Tsuzaki Minoru , Sagisaka Yoshinori
Published: September 2013

To contribute to the naturalness criteria of speech synthesis, acceptability of changes in segment duration has been investigated. Previous studies showed context dependency of the acceptability evaluation such as intraphrase positional effect, where listeners were more sensitive to the phrase-initial segment duration than the phrase-final one. Such contextual effects were independent of the original durations of the segments tested [Kato et al., J. Acoust. Soc. Am. 104, 540–549 (1998)]. However, past studies used only normal-speed speech and temporal variation was limited. The current study, therefore, examined the contextual effect with a wide variety of speaking rates. The materials were three-mora phrases with either rising or falling accent that were spoken at three rates (fast, normal, and slow) with or without a carrier sentence. The duration of each vowel was either lengthened or shortened (10–50 ms) and listeners evaluated the acceptability of these changes. The results showed a clear speaking-rate effect in parallel with the intraphrase positional effect: the acceptability declined more rapidly as the speaking rate became faster. These results, along with those of Kato et al., suggest that acceptability is evaluated based on the speaking rate rather than on the original duration itself. [Work supported by TAO, Japan.] a)Currently at GITI, Waseda University.
Medial surface dynamics of the vocal folds in an in vivo canine model
Authors: Doellinger Michael , Berke Gerald S. , Chhetri Dinesh K. , Berry David A.
Published: September 2013

Quantitative measurement of the medial surface dynamics of the vocal folds is important for understanding how sound is generated in the larynx. However, such data are hard to gather because of the inaccessibility of the vocal folds. Recent studies have applied hemi-larynx methodology to excised human larynges, to visualize these dynamics. The present study extends this methodology to obtain similar quantitative measurements using an in vivo canine hemi-larynx setup, with varying levels of stimulation to the recurrent laryngeal nerve. Use of an in vivo model allows us to examine effects of intrinsic muscle contraction on the medial surface of the vocal folds, to provide greater insight into mechanisms of vocal control. Data were collected using digital high-speed imaging with a sampling frequency of up to 4000 Hz, and a spatial resolution of up to 1024×1024 pixels. Three-dimensional motion will be extracted, computed, visualized, and contrasted as a function of the level of stimulation to the recurrent laryngeal nerve. Results will also be compared to patterns of vibration in excised larynges. Finally, commonly applied quantitative analyses will be performed to investigate the underlying modes of vibration. [Work supported by NIH/NIDCD.]
Flow characteristics in a scaled-up glottis model
Authors: Barry Michael , Wei Timothy , Krane Michael
Published: September 2013

Measurements of the velocity field of the flow through a scaled-up model of the vocal folds are presented. Scaling up the model ten times life size and using water as a working fluid enables temporally and spatially resolved measurements of the velocity using digital particle image velocimetry, making use of dynamic similarity. The Reynolds number (based on maximum glottal width and maximum jet speed) is 3000, and the Strouhal number (based on glottis length, maximum jet speed, and opening/closing time) ranges from 0.01 to 0.1. Prescribing the motion of the model vocal folds allows phase averaging of the flowfield. Measurements presented focus on the time intervals just after vocal fold opening and just before closure. [Work funded by NIDCD of NIH.]
Passive acoustic localization with an AUV-mounted hydrophone array
Authors: D’Spain Gerald L. , Terrill Eric , Chadwell C. David , Smith Jerome A. , Zimmerman Richard
Published: September 2013

A mid-size Odyssey IIb autonomous underwater vehicle (AUV) was retrofitted with the advanced vectored-thrust system presently installed on AUVs manufactured by Bluefin Robotics, Inc. Subsequent modifications to this thrust system decreased the radiated acoustic and vibration noise levels recorded by an eight-element hydrophone array mounted on the AUV’s inner shroud by 20 to 50 dB across the 20 Hz to 10 kHz band. This reduction in self-noise levels to near, or at, background ocean noise levels permits the use of the vehicle-mounted hydrophone array in passive ocean acoustic studies. One example is the application of passive synthetic aperture processing techniques to provide greater spatial resolution estimates of the direction of low frequency sources. Doppler spreading caused by medium motion is a limiting factor in array gain. At mid frequencies (1–10 kHz), the complexity of the received acoustic field created by scattering off the AUV body is partly captured in the array processing by the use of replica vectors measured in a calibration tank. These empirical replica vectors decrease the azimuthally dependent degradation in beamforming performance over that of plane waves. [Work supported by ONR, Code 321(US).]
Surface ship wake remote sensing using an AUV-mounted multibeam sonar
Authors: Culver Lee , Bradley David
Published: September 2013

A 250-kHz multibeam sonar integrated into a high-speed autonomous underwater vehicle (AUV) has been used to image the wakes of two large surface ships from the underside. Using vehicle autopilot data (yaw, pitch, and roll) and acoustic tracking data, the multibeam sonar data were processed to produce 3D maps of the ship wake intensity. Also, the backscattered signal has been used to estimate the number of bubbles per unit volume (the bubble density), assuming a particular size distribution of the bubbles, using a technique that other researchers have employed to estimate the bubble density from single beam sonar data. These measurements have been discussed in two earlier ASA talks [J. Acoust. Soc. Am. 110, Pt. 2 (2001); 111, Pt. 2 (2002)]. The present talk focuses on how vehicle motion is used to process acoustic data from individual beams so as to produce a 3D map of the ship wake. Future plans involving a commercial multibeam sonar integrated into a high speed vehicle are discussed. [Work sponsored by NAVSEA PMS 415 and ONR Code 333.]
Concurrent detection and classification of targets with multistage signal-processing algorithms
Authors: Montanari Monica , Edwards Joseph R. , Schmidt Henrik
Published: September 2013

Concurrent detection and classification (CDAC) of targets stands as the goal in littoral mine-hunting missions. CDAC systems commonly apply model-based algorithms that include a priori known features of the target inside the detection algorithm. If the models are accurate, then this approach significantly reduces the false-alarm rate inherent in detection-only methods. When the possible targets are unknown, as may be the case in tactical situations, then these model-based methods not only fail to reduce the false-alarm rate, but may also reduce the probability of detection. Simultaneous optimization of detection and classification presents a challenge due to competing criteria; detection seeks to integrate signals to improve signal-to-noise ratio, while classification seeks to preserve small features of distinction within the signals. In this work, a method for robust CDAC is demonstrated that exploits the capabilities of autonomous underwater vehicles (AUVs) and multistage signal-processing algorithms to systematically investigate targets of interest in a single mission. The deformable geometry of the AUV-borne sonar network is exploited to provide favorable views of targets to achieve multiple objectives in series, and on-board computational facilities allow the implementation of multiple signal-processing regimes [Work supported by ONR and NATO Undersea Research Centre.]
Intervessel navigation using range and range rate
Authors: Bourgeois Brian S. , McDowell Patrick M.
Published: September 2013

A fundamental requirement for groups of unmanned underwater vehicles to work cooperatively together is the ability for each vessel to know the relative position of its neighbors. While external communication and positioning infrastructures can be used for this purpose, a more flexible approach is to give each vessel the ability to independently discern the location of its neighbors using its own communication and sensor systems. Recent developments in acoustic modems have included the ability to measure range between two vessels as well as the Doppler imparted on the signal by the relative motion between vessels. The measured Doppler shift can be used to compute the instantaneous range rate between two vessels; researchers at NRL are presently working to validate these measurements using GPS. Approaches to vessel relative positioning and navigation using successive range and range-rate measurements, along with directed vessel maneuvers, will be presented.
Sensitivity kernels of finite-frequency travel times in ocean acoustic tomography
Authors: Skarsoulis Emmanuel K. , Cornuelle Bruce D.
Published: September 2013

Wave theoretic modeling is applied to obtain travel-time sensitivity kernels representing the amount by which travel times are affected by localized sound-speed variations anywhere in the medium. In the ray approximation travel times are sensitive to medium changes only along the corresponding eigenrays. In the wave-theoretic approach the perturbations of peak arrival times are expressed in terms of pressure perturbations, which are further related with the underlying sound-speed perturbations using the first Born approximation. In this way, an integral representation of travel-time perturbations is obtained in terms of sound-speed perturbations; the associated kernel represents the spatial sensitivity of travel times to sound-speed perturbations. The application of the travel-time sensitivity kernel to an ocean acoustic waveguide gives a picture close to the ray-theoretic one in the high-frequency case but significantly differs at lower frequencies. Low-frequency travel times are sensitive to sound-speed changes in areas surrounding the eigenrays, but not on the eigenrays themselves, where the sensitivity is zero. Further, there are areas of positive sensitivity, where, e.g., a sound-speed increase results in a counter-intuitive increase of arrival times. These findings are confirmed by independent forward calculations.
A novel technique for measuring the rainfall from the rain noise
Authors: Thundiyil Mani , Pillai P. R. Saseendran
Published: September 2013

It has been observed that if water droplets are allowed to fall with terminal velocity, on to the water trapped in the chamber of a specially designed sensor assembly, the resulting acoustic signal generated from the drop impact is wideband and extends up to 100 kHz. The acoustic energy of the signal in the low-frequency range is seen to be vis-a-vis correlated to the kinetic energy of the drops. Such an assembly is exposed to the rain to pick up the rain-generated noise. The energy of the rain-generated noise is seen to be proportional to the kinetic energy of the rain. From the rain kinetic energy–intensity relationship, the rainfall rate is computed. This paper presents an experimental procedure for estimating the rain intensity from the rain generated underwater noise captured by the sensor assembly. Experiment has been carried out for various rainfall rates and the computed rain intensities were compared with the ones measured with a tipping bucket rain gauge. The results and inferences suggest that this approach is a simple, cost effective and computationally efficient technique to measure the kinetic energy of rain as well as compute the rainfall rate.
Acoustic cymbal performance under hydrostatic pressure
Authors: Jenne Kirk E. , Huang Dehua , Howarth Thomas R.
Published: September 2013

Continual awareness about the need to develop light-weight, low-volume, broadband, underwater acoustic projector and receive arrays that perform consistently in diverse environments is evident in recent Navy acoustic system initiatives. Acoustic cymbals, so named for resemblance to the percussive musical instruments, are miniature flextensional transducers that may perhaps meet the performance criteria for consistent performance under hydrostatic pressure after modifications in the design. These acoustic cymbals consist of a piezoceramic disk (or ring) bonded to two opposing cymbal-shaped metal shells. Operating as mechanical transformers, the two metal shells convert the large generative force inherently within the disk’s radial mode into increased volume displacement at the metal shell surface to obtain volume displacement that translates into usable source levels and/or sensitivities at sonar frequencies in a relatively broad band. The air-backed design for standard acoustic cymbal transducers presents a barrier to deepwater applications. A new acoustic cymbal design for high-pressure applications will be presented for the first time. This practical pressure compensation is designed to diminish the effects of hydrostatic pressure to maintain consistent acoustic cymbal performance. Transmit and receive performance data, determined at the Naval Undersea Warfare Center’s (NUWC) Acoustic Pressure Tank Facility (APTF), is presented.
An acoustic array to be towed behind an autonomous underwater vehicle
Authors: Holmes Jason D. , Carey William M. , Lynch James F.
Published: September 2013

The use of a towed array from a small autonomous underwater vehicle, AUV, such as the WHOI-Remus vehicle is discussed as a valuable ocean acoustics measurement tool for of 3-D characterization of shallow water regions. The feasibility of towing a 10-m-long, small-diameter fluid-filled hydrophone array behind Remus was investigated with a laboratory-prototype array and preliminary tests from the WHOI pier. Preliminary results on array self-noise are presented for low tow speeds. The flow noise, vehicle noise, and other unwanted signal degrading noise sources are examined, discussed, and shown by theoretical arguments to be reduced to low levels by proper array design. This paper examines current technology for such an array with digital sampling and recording equipment incorporated in the Remus vehicle. Consideration is also given to the deployment problem of array on an autonomous vehicle. [Work supported by the College of Engineering, Boston University.]
Evaluation of the noise pollution in urban parks of Curitiba, Brazil
Authors: Ferreira Andressa C. , Diniz Fabiano B. , Paz Elaine C. , Zannin Paulo T.
Published: September 2013

This work shows a study about the noise pollution found in six urban parks of Curitiba, Paran, Brazil. The equivalent noise levels (Leq) have been measured in points spread throughout the park, and interviews have been conducted with some park visitors. It has been found out that 52.48% out of the measurement sites did not satisfy the Municipal Law no. 10,625, which states the noise emission level of 55 dB(A) as the limit value for green areas. The results of the questionnaires applied to the local visitors have showed that 39% out of the interviewed people used to visit the park every day and that 75% out of them seek for the realization of a physical activity. During the realization of their activities in the parks, 22% out of the interviewed people pointed to the noise pollution as the source of annoyance and 28% out of them pointed the local security. In this sense, it has been verified that half of the analyzed parks were inserted in acoustically polluted areas, which incurs a real state depreciation in their vicinities.
Public acceptance of urban rotorcraft operations
Authors: Marcolini Michael A. , Powell Clemans A. , Posey Joe W.
Published: September 2013

Even though tiltrotor operations from city center to city center could greatly shorten travel times over moderate ranges, public opposition to intense urban rotorcraft activity has kept this possibility from being realized. One significant factor in this opposition is rotorcraft noise. Over the last 25 years, NASA has explored the subjective response to rotorcraft noise and developed low noise design concepts and noise abatement flight procedures. While low noise designs can be applied for future rotorcraft, this is not an effective near-term means of reducing rotorcraft noise, because of the costs associated with replacement of helicopter rotor blades. Recent noise abatement research, which has been focusing on the development of tools and techniques to facilitate the design of quieter flight procedures for existing vehicles, has much more immediate application. While very little subjective response work has occurred recently, prior work at NASA in this area from the 1970s and 1980s is discussed. Lastly, thoughts on future research areas that might help improve the public acceptance of rotorcraft will be described.
Diffraction of plane waves having complex frequency and the excitation of transient leaky Rayleigh waves
Authors: Declercq Nico F. , Degrieck Joris , Leroy Oswald
Published: September 2013

Harmonic plane waves are not advantageous for stimulation of leaky Rayleigh waves whereas bounded beams are better suited. Furthermore, past studies have revealed that it is even better to apply incident harmonic inhomogeneous waves, both on smooth and on rough surfaces. If the right inhomogeneity is used, very strong excitation is to be expected. However, inhomogeneous waves are difficult to generate and are far from practical outside the laboratory boundaries. The current paper describes how incident harmonic plane waves having a complex frequency are also excellent tools for stimulating leaky Rayleigh waves, if the technique is combined with the use of a periodically rough surface. Such transient plane waves are much more practical to generate experimentally whence the usability of the technique is more realistic compared with the classical use of harmonic inhomogeneous waves. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]
Nonlinear modal method of crack localization
Authors: Ostrovsky Lev , Sutin Alexander , Lebedev Andrey
Published: September 2013

A simple scheme for crack localization is discussed that is relevant to nonlinear modal tomography based on the cross-modulation of two signals at different frequencies. The scheme is illustrated by a theoretical model, in which a thin plate or bar with a single crack is excited by a strong low-frequency wave and a high-frequency probing wave (ultrasound). The crack is assumed to be small relative to all wavelengths. Nonlinear scattering from the crack is studied using a general matrix approach as well as simplified models allowing one to find the nonlinear part of crack volume variations under the given stress and then the combinational wave components in the tested material. The nonlinear response strongly depends on the crack position with respect to the peaks or nodes of the corresponding interacting signals which can be used for determination of the crack position. Juxtaposing various resonant modes interacting at the crack it is possible to retrieve both crack location and orientation. Some aspects of inverse problem solutions are also discussed, and preliminary experimental results are presented.
Criteria for quasi-shear wavefront triplication in a tranversely isotropic material
Authors: Schoenberg Michael A. , Daley Thomas M.
Published: September 2013

Quasi-shear (qSV) wavefront triplication, classically known as shear wave bi-refringence, occurs in TI media when anellipticity parameter E2≡BC−A2 differs significantly from 0 (equality is the elliptic case), where A≡c13+c55, B≡c11−c55, C≡c3−c55 [Helbig and Schoenberg, J. Acoust. Soc. Am. 81, 1235–1245 (1987)]. The region of the slowness curve corresponding to the triplicating region of the wavefront curve must be concave. Most common hexagonal crystals and all TI media long wavelength equivalent to isotropic layering exhibit positive anellipticity. In general, the exact condition for positive anellipticity triplication (the triplicating region then is between the 3-axis and its normal) requires the solution of a cubic equation [Peyton, Elastic Wave Propagation in Transversely Isotropic Media (Martinus Nijhoff, 1983)]; however, a good approximation for triplication is that E2>KBCc55/(c11+c33), where K is almost always within a few percent of 1.39. For negative anellipticity media, a simpler case, triplication centers about the 3-direction when A2>c11C and/or about the normal to the 3-axis when A2>c33B.
Generalized paraxial ray tracing derived from Riemannian geometry
Authors: Bergman David R.
Published: September 2013

In 1973 R. White demonstrated that acoustic rays in a generic environment could be identified with the null geodesics of a pseudo-Riemannian manifold. A general set of paraxial (dynamic) ray equations, suitable for three dimensional ray tracing in a generic environment, is derived from the geodesic deviation equation used in general relativity and the geometric transmission loss of a ray bundle modeled from this equation. (When fluid motion is removed the paraxial ray procedure used in seismology emerges from the formalism.) The results are applied to time independent layered media where it is found that the standard ray integrals used in underwater acoustics as well as a generalized version of Snell’s law, originally derived by Kornhauser, emerge naturally as conserved quantities related to symmetries of the metric. Finally, when the results are applied to torsion free rays the deviation equation reduces to a scalar equation and the sectional curvature reduces to a simple expression depending on the derivatives of the sound speed and fluid velocity as well as the ray parameters allowing one to determine ray divergence or the development of focal points simply by checking the sign of a single term in the equation.
Preference patterns in infant vowel perception
Authors: Molnar Monika T. , Polka Linda
Published: September 2013

Infants show directional asymmetries in vowel discrimination tasks that reveal an underlying perceptual bias favoring more peripheral vowels. Polka and Bohn (2003) propose that this bias is language independent and plays an important role in the development of vowel perception. In the present study we measured infant listening preferences for vowels to assess whether a perceptual bias favoring peripheral vowels can be measured more directly. Monolingual (French and English) and bilingual infants completed a listening preference task using multiple natural tokens of German /dut/ and /dyt/ produced by a male talker. In previous work, discrimination of this vowel pair by German-learning and by English-learning infants revealed a robust directional asymmetry in which /u/ acts as a perceptual anchor; specifically, infants had difficulty detecting a change from /u/ to /y/, whereas a change from /y/ to /u/ was readily detected. Preliminary results from preference tests with these stimuli show that most infants between 3 and 5 months of age also listen longer to /u/ than to /y/. Preference data obtained from older infants and with other vowel pairs will also be reported to further test the claim that peripheral vowels have a privileged perceptual status in infant perception.
The perceptual magnet effect reflects phonetic context
Authors: Hawkins Sarah , Barrett Jones Sarah
Published: September 2013

Two experiments demonstrate that the perceptual magnet effect is context sensitive. In experiment 1a, 24 participants rated goodness of synthetic /u/ in isolation (ooh) and in two consonantal contexts, /lu/, /ju/ (Lou, you), with nine versions per word, varying in F2 frequency. Their most (prototypical) and least (nonprototypical) preferred choices reflected expected differences between words, and individual differences within words. Experiment 1b demonstrated standard perceptual magnet effects for prototype and nonprototype /u/ in the three words. Unlike previous work, each participant discriminated his/her own prototype and nonprototype from experiment 1a, rather than the group mean. Experiment 2a replicated 1a with 40 new participants. Experiment 2b compared discrimination around participants’ prototypical F2 frequency for /u/ in one word (original) with discrimination around that same frequency in another word (transferred). Different original/transferred sets were heard by four groups (ten participants each): /u/ and /lu/; /lu/ and /u/; /ju/ and /u/; /ju/ and /lu/. Discrimination (d′) near the prototype was poorer for original than transferred contexts [for the four comparisons, t(9) ranged between 2.43–3.49, p<0.025–0.005]. Thus, the perceptual magnet effect is syllable specific: the vowel prototype for one word need not generalize to another. Implications for perceptual coherence and phonological representation are discussed.
On the categorical nature of Korean /pk/ place assimilation
Authors: Son Minjung , Kochetov Alexei
Published: September 2013

Korean exhibits regressive place assimilation in /pk/ clusters, which has been described as gradient and rate dependent. However, this assumption has empirically only been tested on the basis of air pressure data [Jun, 1996] which does not provide a direct record of articulator movement. The present study examines articulator movement using EMMA. For three Seoul-dialect speakers, stimuli containing /pk/ clusters were elicited word-medially (for words and nonwords) and in a phrase-boundary condition; two rates were employed. Results show that the labial can indeed reduce word medially, rendering [kk]. However, contrary to previous claims, the data demonstrate that reduction in /pk/ is always categorical, although it is optional or stochastic in its occurrence. Substantial interspeaker variation is observed, with the frequency of reduction being higher at fast rate and ranging overall from 6 at both rates and is never gradient. The lack of reduction in nonsense words and in the phrase boundary condition shows that the process is sensitive to lexical properties. The observed tendency for more gestural overlap word medially compared to the phrase-boundary condition supports the hypothesis that gestural overlap plays a role in the origins of place assimilation. [Work supported by NIH.]
Production of Mandarin tones by 3-year-old children acquiring L1 (Mandarin) in an L2 (English) environment
Authors: Wong Puisan , Schwartz Richard G.
Published: September 2013

Thirteen monolingual Mandarin-speaking children residing in the U.S. were recruited to examine their production of the four Mandarin lexical tones in monosyllabic words. A picture-naming task was used to elicit the children’s productions of lexical tones in isolated words and in sentence final position. Four mothers were asked to say the same set of words to their children in a picture reading activity. The children’s and the mothers’ productions were recorded and low-pass filtered at 500 and 400 Hz, respectively, to eliminate phonemic and semantic information. Ten Mandarin-speaking judges were recruited to identify the children’s and adults’ tone productions from the filtered stimuli. Contrary to the findings of L1 research conducted in countries where Mandarin is the language of the environment, the present results revealed that the lexical tones produced by 3-year-old children acquiring Mandarin as their first language in the U.S. were not yet adultlike. Children’s tone productions were more difficult to categorize than the mothers’ productions. The judges had significantly more difficulty identifying children’s dipping tones than the children’s level tones, rising tones, or falling tones, suggesting that the dipping tone posed the most difficulties for the children.