bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of aircraft noise during thrust reverser engagement
Authors: Gutierrez Remy M. , Atchley Anthony A. , Hodgdon Kathleen K.
Published: October 2013

Airport noise impact on communities has been an area of considerable study. However, it has been determined that thrust reverser engagement is an area requiring further research. This paper presents findings on thrust reverser from a noise study done at Washington-Dulles International Airport (IAD) in October of 2004. Previous studies have found that high levels of acoustic energy in commercial aircraft during takeoff are contained below 300 Hz [Sharp, Ben H., Guovich, Yuri A., and Albee, William, W., ‘‘Status of Low-Frequency Aircraft Noise Research and Mitigation,’’ Wyle Report WR 01-21, San Francisco, September 2001]. Preliminary analysis of thrust reverser signatures indicates similar findings. A categorization of aircraft noise during thrust reverser engagement is given and looks at factors that may affect the noise characteristics. Some of these factors include: plane type, engine type, and thrust ratings. In addition, a brief analysis of frequency weightings of the Equivalent Sound Level (Leq) and Sound Exposure Level (SEL) metrics, and their application to thrust reverser noise is discussed. [Work supported by the Federal Aviation Administration.]
William W. Lang’s days at the Massachusetts Institute of Technology, Bolt, Beranek and Newman, founding of the Institute of Noise Control Engineering and his efforts at creating a national noise policy
Authors: Beranek Leo L.
Published: October 2013

William Lang entered acoustics through his master’s degree program at MIT and through becoming the second full-time employee at Bolt Beranek and Newman. Bill stimulated the start of the Institute of Noise Control Engineering and this paper covers the early days of that organization and his contribution to its success. Finally, covered are his efforts to promote a national noise policy.
William W. Lang’s contributions to the development of the International Institute of Noise Control Engineering
Authors: Kihlman Tor
Published: October 2013

Bill Lang has been a member of the Board of I-INCE since its first meeting in 1975 in Sendai, Japan. From 1988 to 1999 he served as the President, and to this day remains a very active member of the Board. The INTER-NOISE congress series has been the core activity of I-INCE, and in every case Bill has contributed very actively to secure an excellent congress. He has also taken a number of initiatives both to improve the organization itself and to develop new activities, especially the Technical Study Groups that have prepared consensus reports on important issues such as noise barrier effectiveness and industrial noise hearing conservation policy. At present, he is very active in attempting to develop a global noise control policy.
Validating a new approach for predicting the degree of speech security
Authors: Gover Bradford N. , Bradley John S.
Published: October 2013

The new method of estimating the speech security of meeting rooms first predicts transmitted speech levels at spot positions 0.25 m from the outside boundaries of a meeting room. The degree of speech security at each spot measurement position is related to this transmitted speech level and to the ambient noise level at the same location. This information can be used to calculate new signal/noise ratio measures that indicate the degree of speech security [J. Acoust. Soc. Am. 116(6), 3480–3490 (2004)]. The values of these indices will indicate whether speech will be audible or intelligible, and to what degree. This paper reports validation studies of the prediction of transmitted speech levels at points 0.25 m outside the meeting room, and the effects of varied room absorption on these predicted levels. It also reports on subjective evaluations of the transmitted speech sounds, in terms of the audibility and intelligibility of the transmitted speech, to validate expected judgments in realistic acoustical conditions.
Inversion of bottom sound speed and dispersion using boat noise
Authors: Tang Dajun
Published: October 2013

An experiment was conducted near shore in water depth between 2 and 10 m. The sediment consists of uniform sand. A lone hydrophone was moored 2 m above the bottom at 6 m depth. A small boat traveling at constant speed was used as the sound source, and ran both parallel and perpendicular to shore. Thus, both the range-independent as well as range-dependent cases can be investigated. Environmental parameters in both the water column and the sediment are independently measured. We first will study the propagation of broadband noise from bubbles emitted from a small boat in this special environment, especially the interferences of modes in the wedge-shape waveguide. Both analytical and numerical approaches are used to simulate the field experiment and to obtain general conclusions concerning mode interference in range-dependent environments. Then we will use the data to invert for sediment sound speed as a function of frequency. This is achieved by investigating mode cut-off for different frequencies at different water depths. In the present work, sediment sound speed is estimated over the frequency range of 500 C–4500 Hz. [Work supported by the U.S. ONR.]
Geoacoustic inversion using broadband noise from surface ships
Authors: Koch Robert A. , Knobles D. P.
Published: October 2013

Spatiotemporal techniques developed for geoacoustic inversion using broadband noise from surface ships will be discussed. Inversion processing will be demonstrated with data obtained from a bottom-mounted horizontal line array at a depth of 110 m in the Gulf of Mexico near Corpus Christi, TX. The inversion solutions for the geoacoustic solutions are validated by comparing modeled transmission loss at several frequencies with loss from a towed source that was measured in another portion of the experiment. The first step in developing the inversion algorithm was to obtain consistent results for geoacoustic parameters when the source track reconstruction is available. That such robustness requires temporal samples in the cost function is established from the results of inversions from normalized cross spectra. The next step in the algorithm development was to perform simultaneous inversion for geoacoustic and uniform source motion parameters to examine complications that might arise when source track reconstruction is unavailable. Examples showing the effect on robustness due to violations of uniform motion are presented. Also, the advantages and applications of alternative cost functions that match the structure in received level data and modeled fields will be described. [Work supported by ONR.]
Method for calculating directivity index of a directional microphone in a hearing aid on a manikin
Authors: Dittberner Andrew , Bentler Ruth
Published: October 2013

A method for computing a directivity index (DI) on a manikin for directional microphones in hearing aids is proposed and investigated. Test devices included first- and second-order directional microphones in hearing aids. Signal presentation involved a single noise source rotated completely around the directional microphone, in free field and on a manikin, at a defined radius. The area covered was equivalent to the approximate surface area of a sphere. It was anticipated that an equal angular resolution of 10 deg (elevation and azimuth) would effectively estimate the DI of first-, second-, and higher-order directional microphone systems located in a hearing aid on a manikin. A total of 450 spatially varied presentation points was analyzed, each weighted in reference to direction of arrival on the directional microphone. The absolute difference between the Directivity Index derived from the modified method proposed in this investigation and the conventionally derived Directivity Index on a manikin were as large as 3.8 dB in the higher frequencies, depending on the device under test. The magnitude of these differences was dependent on microphone location. In other words, the further the microphone was placed into the ear of the manikin, the larger the absolute difference.
Study on sound quality evaluation of fan noise
Authors: Minorikawa Gaku , Suzuki Shoji , Nagamatsu Akio , Irikado Hiroshi , Ito Takahiro
Published: October 2013

This study is to establish new evaluation scales of sound quality which is more suitable for the human sense of hearing than the conventional evaluation scales such as A-weighted sound-pressure level. The authors focus on fan noise and have investigated the meaning space of its sound quality by hearing tests and factor analyses. The hearing tests were performed using semantic differential (SD) method and their test results were analyzed to extract dominant factors of the fan noise sound quality. The factor analyses, influence of noise level and 1/3 octave band level on sound quality of fan noise were also investigated. It was found that the sound quality of fan noise had two major factors; ‘‘offensive’’ and ‘‘booming-powerful’’ factors. The evaluation of hearing test using a paired comparison method was performed in order to investigate the correlation of these two factors with physical quantities that represent noise level and quality such as A-weighted sound pressure level and loudness level. Analysis of hearing tests results revealed that ‘‘offensive’’ factor has positive correlation with the physical quantities such as A-weighted sound pressure, but ‘‘booming’’ factor has negative correlation with them.
Design and analysis of a hemi-anechoic chamber at Michigan Technological University
Authors: Dreyer Jason , Jangale Ashish , Rao Mohan D.
Published: October 2013

A four-wheel chassis roll dynamometer test facility was installed on the campus of Michigan Technological University (MTU). The chassis dynamometer was enclosed in a soundproof hem-anechoic room in order to conduct noise radiation measurements on test vehicles. All surfaces of the room, except the floor and control room window, were acoustically treated with donated tetrahedral acoustic cones and panels. The acoustic absorption properties of these materials were characterized through reverberation chamber and impedance tube testing, and the effects of air gaps, cone orientation, and cone mounting materials were qualitatively evaluated. The design of the wall, ceiling, and door treatments of the chamber was based on the sound absorption properties of these materials, in addition to spatial constraints and cost considerations. The treated chamber acoustics were predicted based on the amount of acoustic material that could be applied to given chamber dimensions and would still preserve the functionality of the room. These predictions were validated through evaluation of the actual room treatment based on average reverberation time at 100-Hz third-octave band, free sound field characteristic 6-dB reduction in sound pressure level (SPL) per doubling in distance from source, noise reduction at the chamber boundaries, and background SPL Noise Criteria (NC) Rating.
Diel patterns in underwater sounds by Weddell seals during two breeding seasons
Authors: Coulombe Charisse , Thomas Jeanette
Published: October 2013

Automated underwater recordings of Weddell seal (Leptonychotes weddellii) vocalizations were made continuously once per hour for 2.5 min during the austral breeding season. Recordings were made during two breeding seasons: October 1976 through December 1976 and October 1977 through January 1978 at Hutton Cliffs, Antarctica. From radio-telemetry studies this species is known to exhibit a diel pattern in haulout on the ice. From census studies of tagged seals it is known they exhibit seasonal fluctuations in the number of seals hauled out on the ice. We studied how variations in the rate of different underwater call types reflected the haulout pattern and the changes in the colony associated with territorial defense, underwater breeding, and dispersal from the colony. The 34-call repertoire was evaluated for hourly, weekly, and annual variations in usage. The trill vocalization and the serial chug vocalization had the most significant variation for both the weekly and hourly analysis. The trill call type is thought to be important in mate attraction by underwater territorial males. The chug call is thought to be important in aggressive encounters between males. An increase rate of these call types might be a useful predictor of the onset of the mating period.
Diel patterns in underwater sounds produced by beluga whales and Pacific white-sided dolphins at John G. Shedd Aquarium
Authors: Brickman Jon , Tanchez Erin , Thomas Jeanette
Published: October 2013

Diel patterns in underwater sounds from five beluga whales (Delphinapterus leucas) and five Pacific white-sided dolphins (Lagenorhynchus obliquidens) housed at John G. Shedd Aquarium in Chicago, IL were studied. Underwater sounds were sampled systematically over 24-h periods by using a battery-operated cassette recorder and an Ithaco 605C hydrophone controlled by a digital timer, which activated every hour and then shut off after 2.5 min. Belugas had 14 sounds and Pacific white-sided dolphins produced 5 sounds. For each species, the use of some sounds was correlated with other sounds. The diel pattern for both species was similar and mostly affected by the presence of humans. Sounds gradually increased after the staff and visitors arrived, peaked during the midday, gradually decreased as closing of the aquarium approached, and was minimal overnight. These data can help identify the best time of day to make recordings and perhaps could be used to examine social, reproductive, or health changes in these captive cetaceans.
Automatic detection of regularly repeating vocalizations
Authors: Mellinger David
Published: October 2013

Many animal species produce repetitive sounds at regular intervals. This regularity can be used for automatic recognition of the sounds, providing improved detection at a given signal-to-noise ratio. Here, the detection of sperm whale sounds is examined. Sperm whales produce highly repetitive ‘‘regular clicks’’ at periods of about 0.2–2 s, and faster click trains in certain behavioral contexts. The following detection procedure was tested: a spectrogram was computed; values within a certain frequency band were summed; time windowing was applied; each windowed segment was autocorrelated; and the maximum of the autocorrelation within a certain periodicity range was chosen. This procedure was tested on sets of recordings containing sperm whale sounds and interfering sounds, both low-frequency recordings from autonomous hydrophones and high-frequency ones from towed hydrophone arrays. An optimization procedure iteratively varies detection parameters (spectrogram frame length and frequency range, window length, periodicity range, etc.). Performance of various sets of parameters was measured by setting a standard level of allowable missed calls, and the resulting optimium parameters are described. Performance is also compared to that of a neural network trained using the data sets. The method is also demonstrated for sounds of blue whales, minke whales, and seismic airguns. [Funding from ONR.]
Time reversal for ultrasonic transcranial surgery and echographic imaging
Authors: Tanter Mickael , Aubry Jean-Francois , Vignon Francois , Fink Mathias
Published: October 2013

High-intensity focused ultrasound (HIFU) is able to induce non-invasively controlled and selective destruction of tissues by focusing ultrasonic beams within organs, analogous to a magnifying glass that concentrates enough sunlight to burn a hole in paper. The brain is an attractive organ in which to perform ultrasonic tissue ablation, but such an application has been hampered by the strong defocusing effect of the skull bone. Our group has been involved in this topic for several years, providing proofs of concept and proposing technological solutions to this problem. Thanks to a high-power time-reversal mirror, presented here are in vivo thermal lesions induced through the skull of 12 sheep. Thermal lesions were confirmed by T2-weighted magnetic resonance post-treatment images and histological examination. These results provide striking evidence that noninvasive ultrasound brain surgery is feasible. A recent approach for high-resolution brain ultrasonic imaging will also be discussed with a skull aberration correction technique based on twin arrays technology. The correction of transcranial ultrasonic images is implemented on a new generation of time-reversal mirrors relying on a fully programmable transmit and receive beamformer.
Adaptive refocusing of dual-mode arrays
Authors: Ebbini Emad
Published: October 2013

Advances in piezocomposite transducer technologies have allowed for the development of dual-mode ultrasound phased arrays (DMUAs) for noninvasive surgery. The imaging and therapeutic capabilities have been experimentally demonstrated. One major advantage of DMUAs is the use of image feedback for optimal refocusing to maximize the power deposition at the target while minimizing it to any critical structures in the intervening and surrounding tissues. The use of the same array elements in imaging and therapy allows for the development of image-based refocusing algorithm that employs a propagation operator from the array to the target point(s). In addition, a number of critical points can be identified from the DMUA image of the treatment region. The optimal complex driving signals to the array elements are obtained from a weighted solution employing an inverse spatial filter. The inverse is a cascade of a decorrelation step and a backpropagation step with a weighting matrix obtained from an auxiliary propagation operator from the array to the critical points. The theoretical formulation of the image-based optimal refocusing of DMUAs will be presented. Experimental results from refocusing experiments in the presence of ribs and the application to liver cancer treatment are presented and discussed.
Theoretical analysis of a cell’s oscillations in an acoustic field
Authors: Allen John S. , Zinin Pavel
Published: October 2013

The analysis and deformation of an individual cell in a high-frequency acoustic field is of fundamental interest for a variety of applications such as ultrasound cell separation and drug delivery. The oscillations of biological cells in a sound field are investigated using a shell model for the cell following an approach developed previously [Zinin, Ultrasonics, 30, 26–34 (1992)]. The model accounts for the three components which comprise the cell’s motion: the internal fluid (cytoplasma), the cell membrane, and the surrounding fluid. The cell membrane whose thickness is small compared to the cell radius can be approximated as a thin elastic shell. The elastic properties of this shell together with the viscosities of the internal and external fluids determine the oscillations of the cell. The dipole oscillations of the cell depend on the surface area modulus and the maximum frequency for the relative change in cell area can be determined. Moreover, the higher order oscillations starting with the quadrupole oscillations are governed by the shell’s shear modulus. Induced stresses in bacteria cell membranes in the vicinity of an oscillating bubble are investigated and cell rupture with respect to these stresses is analyzed.
Chirped-excitation contrast imaging
Authors: Sun Yang , Kruse Dustin E. , Dayton Paul A. , Ferrara Katherine W.
Published: October 2013

Ultrasound contrast agent oscillation and echoes are investigated optically and acoustically following insonation with a high time-frequency bandwidth pulse. Results of a numerical evaluation of the modified Rayleigh–Plesset equation are used to predict the dynamics of a microbubble and compared with experimental observations. Two confocally aligned transducers transmitting at 10 MHz and receiving at 5 MHz are used, and a chirp waveform is transmitted with −6-dB bandwidth from 7.5 to 12.5 MHz. With a simple bandpass filter, subharmonic echo components can be detected using the return from a single pulse, as the power ratio of subharmonic components to fundamental components ranges up to −7 dB. A high-speed camera system, which provides 2D frame images and streak images, is used in optical experiments. From the optical observations of a single microbubble, nonlinear oscillation, destruction, and radiation force are observed. For an initial diameter ranging from 1.5 to 5 μm, a maximum diameter below 8 μm is observed during insonation with a 20-cycle 10-MHz linear chirp, with a peak negative pressure of 3.5 MPa. High-frequency pulse transmission may provide the opportunity to detect contrast echoes resulting from a single pulse in vivo. [Work supported by NIH CA 76062.]
The ping-pong cannon demonstration: Optical studies and numerical simulation
Authors: Peterson Richard , Stein Keith
Published: October 2013

This presentation describes the use of laser pulse photography, optical timing, pulsed Schlieren, and heterodyne interferometry to look more closely at the fluid dynamics of a recently popular lecture demonstration—the so-called ‘‘ping-pong cannon.’’ Optical diagnostic techniques have been applied to two types of these cannons, and led to greater knowledge of the kinematics of the accelerating ball, along with some insight into the exit mechanism and subsequent target interactions. Also will be described how a 1D numerical simulation allows visualization of shock wave formation within the tube during ball acceleration. Solutions of the Euler equation are obtained using the method of space-time finite elements, while the ball is tracked as an interface in the compressible fluid mesh. [Work supported in part by the MN NASA Space Grant and the Carlsen-Lewis Endowment of Bethel University.]
Report on a workshop for construction of acoustic demonstration apparatus
Authors: Poese Matthew E.
Published: October 2013

A workshop where over 20 participants built two acoustical demonstration devices was organized by the author and sponsored by the Central Pennsylvania Chapter of the Acoustical Society of America. This talk will show construction details of the cavitation stick and the thermoacoustic engine (‘‘acoustic laser’’) that graduate and undergraduate students, faculty and community members built at the workshop as well as demonstrate the finished products. In order that participants can finish the workshop in an evening, the level of preparation required for such an event will be discussed as will the shop facility used in this case.
Sound decay of notes from acoustic guitars
Authors: Galazen Erika , Nordberg Joni , Huber Thomas M.
Published: October 2013

The acoustic guitar produces tones by transferring energy from the strings, through the bridge to the top plate, back, and air cavity of the guitar. The vibrations are ultimately radiated into the air as sound. The air-cavity and body resonances of the guitar play an important role in both the tone and the sustain (the time it takes notes to decay) produced by the guitar. To study the relationship between resonances of the guitar and the sustain of notes, the resonance frequencies were measured using a mechanical shaker attached to the body of the guitar and laser Doppler vibrometer to measure its vibration. A string was tuned to different frequencies and plucked. The decay of the note was measured with an electromagnetic pickup that measured the vibration of the string, a vibrometer to measure vibration of the top plate, and microphones located inside and outside the guitar. As expected, when the fundamental frequency of the string was near one of the resonances of the guitar, the decay rate was faster (shorter sustain) than when the string was between resonances. The relationship between the decay rates of the different parts of the system will also be discussed.
Input impedance of brass instruments from velocity measurement
Authors: Ludwigsen Daniel O.
Published: October 2013

A velocity sensor known as the Microflown measures particle velocity from a difference in temperature between two MEMS-scale wires. With a small precision microphone in a package the size of a matchstick, simultaneous measurement of particle velocity and pressure can be accomplished in a tiny space such as the mouthpiece of a brass instrument. Traditional measurements of input impedance rely on a constant flow provided by a capillary tube or feedback loop control of the driver. This velocity sensor eliminates these technical requirements. The apparatus and calibration procedures will be described, and results of measurements of several instruments will be presented. In an easily used device, this approach could benefit instrument designers, makers, and repair technicians.
Measurement of underwater noise of the new National Oceanic and Atmospheric Administration (NOAA) Ship OSCAR DYSON
Authors: Bahtiarian Michael
Published: October 2013

The NOAA Ship OSCAR DYSON is the first-in-class fisheries research vessel (FRV) designed and built for National Oceanic and Atmospheric Administration (NOAA) for fish stock assessment. One of its most important contractual requirements was to meet the underwater noise limit of 1995 International Council for the Exploration of the Seas (ICES) report. This paper describes the efforts to conduct the underwater noise tests of the vessel. A commercial underwater measurement system was developed which was set-up off the Gulf of Mexico. The system consists of a small hydrophone array, signal conditioning, and data acquisition hardware. Field calibration was performed. Requirements for mounting the hydrophones and operation of a support vessel are discussed. In addition to measuring underwater sound, the distance between the source and receiver was also measured. Results are compared to the specification requirements and subsequent measurements performed by the U.S. Navy.
Noise control considerations for patient rooms
Authors: Davenny Benjamin
Published: October 2013

The patient room envelope is a path between outside noise sources and the patient receiver. Within the patient room there are several sources including televisions, clinical monitor alarms, medical pumps, etc. Noise control in patient rooms relies on a combination of the sound transmission loss of the patient room envelope and the level of background sound at the patient’s head. Guidelines published by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), American Institute of Architects (AIA), and the U.S. Department of Defense for background noise and sound transmission loss in patient rooms will be discussed. Appropriate levels, spectra, and temporal characteristics of background sound at the patient head location may be helpful in raising the threshold of annoying sounds. Various means of personal hearing protection for patients will be discussed. Sound-pressure levels in patient rooms reported in previous literature will also be discussed.
Federal Transit Administration’s noise and vibration Guidance Manual: Updates after 10 years of experience
Authors: Hanson Carl E.
Published: October 2013

In April 1995, the Federal Transit Administration of the U.S. Department of Transportation issued its guidance manual, ‘‘Transit Noise and Vibration Impact Assessment.’’ The manual was written to provide direction for the preparation of noise and vibration sections of environmental documents for public transportation projects in the interest of promoting quality and uniformity in assessments. In the 10 years since its release, the guidance manual has been used as the basis of noise and vibration assessments in over 80 environmental documents and has been used worldwide as a standard method for performing transit noise analyses. An updated version has recently been prepared that takes account of improvements in tools, changes in the environmental assessment procedures, modifications of impact criteria, and experience with mitigation measures. These factors, and other background information, will be discussed to provide insight regarding the revisions in the new edition.
Assessing of the solid-borne noise produced by the urban traffic. Case study: St. Giuseppe dei Teatini’s Church in Palermo
Authors: Barbaro S. , Barrera G. , Santamaria A. Sansone
Published: October 2013

In past years, the continuously increasing road traffic, correlated with both economical and social development, has improved the vibration rate upon the structures. Anyway often the component vibration is ignored, for different reasons. Today in Italy a law about vibration impact upon structures does not exist; we refer to the International Standard Organization. The vibration waves hitting the structures may cause damages, increasing at particular frequencies. There are other kinds of nonstructural damages, that are called cosmetic damages, such as cracks in the plaster and damages on architectural elements. In this work a survey protocol has been set up, with application to a busy street in the historical center of Palermo: Vittorio Emanuele street. In this street a church has been chosen like a case study: the St. Giuseppe dei Teatini’s Church, that is a heritage building. The case study includes at the same time measurements of both vehicular traffic and vibration on the ground floor and first floor.
Acoustical prediction methods for heating, ventilating, and air-conditioning (HVAC) systems
Authors: Ryherd S. R. , Wang L. M.
Published: October 2013

The goal of this project is to compare and contrast various aspects of acoustical prediction methods for heating, ventilating, and air-conditioning (HVAC) systems. The three methods include two commonly used software programs and a custom spread sheet developed by the authors based on the American’s Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) Applications Handbook. Preliminary results indicate relatively good agreement between the three methods analyzed. The degree of disparity is predominately effected by the assumptions required by the end user. Research methods and results will be presented. This project provides a greater understanding of these acoustical prediction methods and their limitations.
Multitrack analysis of amateur and professional choirs
Authors: Jers Harald
Published: October 2013

Many choir singers in the world know the fascinating phenomenon of choir sound, which is the result of multiple voices singing in an ensemble. This so-called chorus effect, where the normal mechanisms of auditory localization of the single voices are disrupted, may be caused by complex interactions between the choir singers, but has not been researched in detail. Each singer of an amateur and a professional vocal ensemble of 16 singers was recorded on separate tracks while singing in the choir. The evaluation of different choir pieces and exercises provided information and predictions about F0, SPL, timing/synchronization, vibrato behavior, and the produced choir sound. The results reveal differences between amateur and professional choirs for homophonic and polyphonic choir pieces, and suggest new considerations for choir rehearsals and concert performances.
Modeling volcanic infra-sound propagation
Authors: Lingevitch Joseph F. , Edelmann Geoffrey F. , Drob Douglas P. , Collins Michael D.
Published: October 2013

Active volcanoes are significant sources of infra-sound and can be exploited for studying atmospheric sound. The propagation is influenced by the vertical and horizontal wind structure where wind-induced refraction can trap or disperse sound energy, leading to large variations of propagation with wind conditions. Stratospheric winds influence long-range observations and exhibit variations on seasonal, diurnal, and semi-diurnal time scales. These effects impact the observability and interpretation of acoustic signals at remote listening stations. The propagation of infra-sound over propagation paths of several hundred kilometers from volcanoes in the Archipelago of Vanuatu in Oceania is studied over a frequency range of 0.1–4 Hz. Atmospheric wind and sound-speed profiles constructed every 6 h for a 2-year period are used as inputs to a parabolic equation propagation model. The results are compared with experimental observations and other models to assess the validity of our numerical simulations. [Work supported by ONR.]
Atmospheric sound propagation at higher altitudes
Authors: Di Xiao , Gilbert Kenneth E. , Clark Richard
Published: October 2013

During the daytime, upward refraction dominates atmospheric sound propagation. An elevated sensor can potentially give much higher sound-pressure levels and higher signal coherence. To understand daytime upward atmospheric sound propagation at higher altitudes, a comprehensive sound propagation experiment for receivers at various heights (up to 220 m) was performed in November 1998. In the experiment, both meteorological data and acoustic data were taken. Three single tone sources were used in the experiment (210, 380, and 600 Hz). The horizontal propagation distances were 300, 600, and 900 m. In this presentation, we will present the experimental results and calculations of sound-pressure level and coherence using the measured meteorological data as input. Numerical calculations are compared with the experimental data. Both experimental data and theoretical predictions show much higher sound-pressure levels and higher coherence at higher attitudes.
The pressure distribution around foam spheres outdoors
Authors: Webster Jeremy , Raspet Richard , Yu Jiao
Published: October 2013

A previous investigation of the pressure fluctuations around foam windscreens outdoors indicated both lower pressure levels and lower correlations between microphones than expected from wind noise theory [J. Acoust. Soc. Am. 116, 2517]. The measurement set was limited and suffered from uncertainty in the incoming wind direction. In this paper we show results from several new measurements which use a three-axis sonic anemometer to establish the wind direction and speed simultaneous to pressure correlation measurements. [Prepared in part through collaborative participation in the Collaborative Technology Alliance for Advanced Sensors sponsored by the U.S. Army Research Laboratory.]
Soaker hose versus compact nonporous windscreen: A comparison of performance at infrasonic frequencies
Authors: Zuckerwar Allan J. , Shams Qamar A. , Ahuja Krish K. , Funk Robert
Published: October 2013

A compact nonporous windscreen described previously [J. Acoust. Soc. Am. 114, No. 4, Pt. 2, 2323 (2003)] was tested in the field against a soaker hose array to compare performance at infrasonic frequencies. The cylindrically shaped compact windscreen, made of closed-cell polyurethane foam, had dimensions 0.0762 m i.d. ×0.2286 m height ×0.0127 m wall (3×9×0.5 in.). The low acoustic impedance of the foam permits the propagation of infrasound through the walls of the windscreen with a transmission coefficient near unity. The soaker hoses were 15.24-m (50 ft.) long and coupled to a Chaparral model 5 low-frequency microphone. The hose plenum was removed and replaced with the compact windscreen for testing. A sonic boom simulator, located at a distance of 400 m (1/4 mile) from the microphone, generated tones at 3, 4, 5, and 6 Hz. Analysis of the signals received by the interior microphone revealed that the tones transmitted through the windscreen, as well as the reduction of background noise due to naturally occurring wind-generated turbulence, were nearly identical for the two types of windscreen.
Outdoor sound propagation effects on aircraft detection through passive phased-array acoustic antennas: 3D numerical simulations
Authors: Roselli Ivan , Testa Pierluigi , Caronna Gaetano , Barbagelata Andrea , Ferrando Alessandro
Published: October 2013

The present paper describes some of the main acoustic issues connected with the SAFE-AIRPORT European Project for the development of an innovative acoustic system for the improvement of air traffic management. The system sensors are two rotating passive phased-array antennas with 512 microphones each. In particular, this study focused on the propagation of sound waves in the atmosphere and its influence on the system detection efficiency. The effects of air temperature and wind gradients on aircraft tracking were analyzed. Algorithms were implemented to correct output data errors on aircraft location due to acoustic ray deviation in 3D environment. Numerical simulations were performed using several temperature and wind profiles according to common and critical meteorological conditions. Aircraft location was predicted through 3D acoustic ray triangulation methods, taking into account variation in speed of sound waves along rays path toward each antenna. The system range was also assessed considering aircraft noise spectral emission. Since the speed of common airplanes is not negligible with respect to sound speed during typical airport operations such as takeoff and approach, the influence of the Doppler effect on range calculation was also considered and most critical scenarios were simulated.
Analysis of broadband acoustic radiation from periodic structures
Authors: Danilov Pavel , Bliss Donald
Published: October 2013

Radiation from a 2D finite-length plate with periodic discontinuities modeled by line impedances, and with arbitrary boundary conditions, is considered. Under broadband excitation such structures often exhibit a fairly simple directivity pattern that is nearly symmetric and relatively smooth. The differences between single-frequency and broadband response are analyzed. Due to discontinuities the structure exhibits passband and stop-band behavior, with structural waves decaying in stop bands. This behavior leads to a different energy distribution between the structure and the acoustic field for frequencies in different bands. Acoustic radiation from periodic structures is characterized in terms of Bloch waves. Closed-form formulas for harmonic and broadband response from a single structural Bloch wave are obtained. Total response is recovered by superposition of Bloch waves. A single Bloch wave contains a primary harmonic, corresponding to a long-wavelength, smooth global solution, and higher spatial harmonics induced by discontinuities which describe the short-wavelength local solution. Radiation characteristics are discussed in terms of global and local solutions.
A boundary-element method using broadband vibrating-wall sources to predict high-frequency interior sound fields produced by wall vibration
Authors: Franzoni Linda P. , DuVall Tracy A.
Published: October 2013

In the high-frequency limit, vibrating panels subject to spatially random, temporally broadband forcing are shown to have broadband power and directivity properties than can be characterized by a limited set of parameters, based on numerical simulations. The radiated pressure field is parametrized in terms of direction, wave speed ratio, panel damping, and dimensionless frequency. A source directivity equation dependent on these variables is presented. The radiation properties of this equation are incorporated to simulate vibrating wall panels in an energy/intensity–based boundary-element method (BEM) developed for the prediction of steady-state, broadband, reverberant sound fields in enclosures having either diffusely or specularly reflecting boundaries. The BEM method uses uncorrelated broadband directional intensity sources to construct the source and reflection sound fields and predict mean-square pressure distributions in enclosures. Because uncorrelated broadband directional intensity sources are used, the system does not require a frequency-by-frequency-based solution, thereby reducing computational expense. Simulations are compared to exact solutions obtained by computationally expensive frequency-by-frequency modal methods. When fully developed, the directed application of this method is aircraft interior noise caused by exterior boundary layer excitation on fuselage panels.
Local parametric identification for in situ health monitoring of aircraft using distributed sensors
Authors: Micheau Philippe , Pinsonnault Jérôme , Masson Patrice
Published: October 2013

The objective of this study is to provide a strategy for in situ structural health monitoring with MEMS sensors in order to reduce the high costs associated with periodic prescribed inspections of aircraft. The presented strategy focuses on the flexural waves in the medium-frequency range in order to obtain a good trade-off between damage localization and distant propagation, and to be efficient for composite materials. The method consists of performing local parametric identification of equivalent MISO systems in order to detect a parametric discontinuity when a defect is present. Simulations were performed with a hierarchical trigonometric functions set on an aluminum plate (100 cm × 75 cm × 1 mm) with a crack (5 cm × 0.007 in.). For a chirp excitation in the medium-frequency range at 1 kHz, wave propagation simulation shows the scattering around the crack in the plate. A distribution of MEMS sensors over the plate is efficient to detect a significant change in the identified local parameters, and consequently to localize the crack. However, this approach is limited to configuration with high signal-to-noise ratio. Experimental validation of the model is conducted both in frequency and time domains for healthy and cracked beams and plates. [Work supported by the Consortium for Research and Innovation in Aerospace in Quebec.]
Betting on bits: Contextual influences on the perception of ‘‘phonetic categories.’’
Authors: Hawkins Sarah
Published: October 2013

Peter Ladefoged’s outstanding qualities include meticulous description of differences between ‘‘the same’’ phonetic categories in different languages, and a tendency to explore new research areas, not least by investigating things that others judge better left alone. This paper pays tribute to these qualities by discussing the phonetic category as a theoretical construct in speech perception. By demonstrating that F1 of a preceding phrase influences whether a word is heard as ‘‘bet’’ or ‘‘bit,’’ Ladefoged and Broadbent (1957) stressed that phonetic categorization is plastic: sense depends on context. Many other contextual influences on sound categorizaton have been identified, yet are poorly integrated into theory, especially when they extend over long durations, or indicate something other than lexical contrast. I argue from (human) perceptual and (animal) neurophysiological and behavioral data that category identification depends on context and perceived relevance—hence on potential meaning. Human data confirm the centrality of context and meaning to categorization. Animal data show that a sound which is behaviorally significant produces long-lasting changes to response characteristics of single neurons in the primary auditory cortex, and probably earlier. Such data encourage radical re-evaluation of how sensory information is used in understanding speech. [Funded by the Leverhulme Trust.]
Phonological acquisition of a Korean child: An acoustic study
Authors: Jun Sun-Ah
Published: October 2013

Studies on child phonology suggest that there exist phonological universals in the timing of phonological events and the ordering of phonological categories, but the acquisition of speech sounds is influenced by the language-specific aspects of the ambient language such as phonetics, phonology, and the frequency of the sound in child-directed speech. This study investigates a Korean child’s phonological acquisition based on tape recordings of longitudinal data (from 2 months to 2 years, recorded in 1- to 2-week intervals). Special attention is given to the change in prosody and the acquisition of the Korean three-way manner contrast (fortis, aspirated, lenis). It is known that Korean fortis and aspirated obstruents trigger high pitch at vowel onset while lenis obstruents trigger low pitch [Jun (1993), (1998)]. Preliminary results suggest that fortis obstruents are acquired first, followed by aspirated, and then lenis. The segmental properties (e.g., voice onset time, breathy phonation) appropriate for the lenis category were acquired later than the pitch. In addition, unlike the universal tendencies, velar and labial consonants were acquired earlier than alveolar consonants. Factors affecting the order of acquisition, including frequency effect and perceptual salience, will be discussed.
Identification of rapidly time-varying wideband acoustic communication channels
Authors: Li Weichang , Preisig James
Published: October 2013

Wideband acoustic communications in very shallow-water are typically confronted with channels that are both rapidly time varying and sparsely structured [J. C. Preisig and G. Deane, J. Acoust. Soc. Am. 116(4), 2067–2080 (2004)]. Techniques for coherent demodulation require either implicit or explicit identification of channel impulse response. Model based channel identification is able to capture the channel dynamics only when certain persistent excitation condition involving both the transmitted symbol sequence and the sequence of channel estimates holds. This is generally not the case for channels with highly sparse impulse response. On the other hand, dimension reduction techniques such as subspace decomposition and sparse processing, inherently assuming that the channel is stationary over certain time period, often fail to track the rapid channel fluctuations. Therefore both the channel dynamics and redundant dimension have to be addressed simultaneously in order to achieve accurate and robust channel identification. This paper presents methods of model based channel tracking with sparse preprocessing. The limitations of model based tracking and sparse processing when applied separately are derived. The performance gain obtained from the combining approach is then demonstrated through experimental results. [Work supported by ONR Ocean Acoustics.]
Thirty years since diffuse sound reflection by maximum length
Authors: Cox Trevor J. , D’Antonio Peter
Published: October 2013

This year celebrates the 30th anniversary of Schroeder’s seminal paper on sound scattering from maximum length sequences. This paper, along with Schroeder’s subsequent publication on quadratic residue diffusers, broke new ground, because they contained simple recipes for designing diffusers with known acoustic performance. So, what has happened in the intervening years? As with most areas of engineering, the room acoustic diffuser has been greatly influenced by the rise of digital computing technologies. Numerical methods have become much more powerful, and this has enabled predictions of surface scattering to greater accuracy and for larger scale surfaces than previously possible. Architecture has also gone through a revolution where the forms of buildings have become more extreme and sculptural. Acoustic diffuser designs have had to keep pace with this to produce shapes and forms that are desirable to architects. To achieve this, design methodologies have moved away from Schroeder’s simple equations to brute force optimization algorithms. This paper will look back at the past development of the modern diffuser, explaining how the principles of diffuser design have been devised and revised over the decades. The paper will also look at the present state-of-the art, and dreams for the future.