bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of Caribbean music
Authors: Davis Martha Ellen
Published: October 2013

To frame the 2001 meeting of the ASA within the soundscape of the region, this paper offers an overview of the diversity of musical sounds and sound-makers, i.e., instruments, of the Caribbean and Circum-Caribbean region. Many are in fact present in the Miami–Dade/Fort Lauderdale–Broward area because of the growing presence of immigrant populations, as well as the influence of some of their traditions on ‘‘world beat’’ music (the subset of ‘‘world music’’ with African influence). The survey of sounds of the Caribbean, illustrated audiovisually, will include both the commercially disseminated genres (‘‘popular music’’), and others which are not marketed or marketable, although in some cases the roots of popular music. The ‘‘unknown’’ genres include social dances, as well as work songs, sacred drumming, ritual songs, and more. The paper proposes African culture influence as the common denominator which musically unifies the region and explains why.
Traditional Junkanoo music instruments of the Bahamas
Authors: Wood Nina
Published: October 2013

Junkanoo is a carnival-like parade that takes place twice a year in the Bahamas. The parade grew out of the music practices of Africans who had been enslaved in the Bahamas during the nineteenth century. Today, the parade incorporates large, elaborate costumes, and music played on traditional instruments. The number of participants in Junkanoo has grown tremendously, and moves have been made to incorporate amplified, electronic music in the parade in order to project the volume of the music over the sounds of the participants and spectators. Despite attempts to incorporate amplified music, however, acoustic instruments have remained primary. Junkanoo music performance has retained many of its African characteristics in terms of timbre, percussion, and density, and throughout the past two decades adjustments have been made to the instruments to enhance these characteristics. In this discussion the instruments of the Junkanoo music tradition will be introduced, their timbral qualities will be examined, and their particular functions and relationships within the tradition will be explored.
The Steelpan Development Centre at The University of the West Indies
Authors: Copeland Brian , Imbert Clément , Gay Derek
Published: October 2013

This paper describes the Steelpan Development Centre (SPDC) of The University of the West Indies (UWI), a specialist center created to explore, support, and develop all aspects of the technology of the steelpan. The SPDC places special emphasis on the development on steelpan manufacturing technology and performance in the Caribbean region. While the major focus of the center is pan technology, its mission also includes consideration of other aspects that impact on the growth of the instrument, in collaboration with the UWI Center for Creative and Festival Arts. In particular, the SPDC has strong interest in providing technical, business, and administrative support to the many regional tuners who, by and large, still operate at the craft level. The paper looks at the motivation for the formation of the center, a few of the developments to date and some of the projects listed for consideration.
Materials and manufacturing of steelpans
Authors: Imbert C. A. C.
Published: October 2013

The musical instrument referred to as the Caribbean steel drum (called the steelpan or simply pan by true aficionados) is traditionally hand-crafted from 55 U.S. gallon oil drums. These drums are made to satisfy certain physical and mechanical properties but certainly not for musical instruments. As a result pan builders/tuners have to reject a relatively large number of drums because they do not respond well enough to produce fine quality lead instruments. In this paper the results of the mechanical/metallurgical investigation of several drum steels are reported—steels that respond well and others that do not—as well as the process of hardening steelpans by nitriding. Also reported are the results of mechanized methods of sinking the pan compared to the traditional manual process.
Sound radiation from Caribbean steelpans
Authors: Copeland Brian , Morrison Andrew , Rossing Thomas D.
Published: October 2013

Besides radiating sound from the note area being struck, a steelpan radiates from neighboring note areas that vibrate sympathetically, from the areas between notes, and from the skirt [Rossing et al., Phys. Today 49, 24–29 (1996)]. We have used a two-microphone intensity probe to measure the sound field around steelpans when various note areas are excited with swept sine wave force in an anechoic room. The radiation patterns in planes parallel and perpendicular to the surface of the pan are plotted and analyzed.
Feasibility of a phased acoustic array for monitoring acoustic signatures from meshing gear teeth
Authors: Hood Adrian A. , Pines Darryll J.
Published: October 2013

This research investigates the feasibility of sensing damage emanating from rotating drive train elements such as bearings, gear teeth, and drive shafts via airborne paths. The use of a planar phased acoustic array is evaluated as a potential fault detection scheme for detecting acoustic signatures radiating from gearbox components. Specifically, the use of beam focusing and steering to monitor individual tooth mesh dynamics are analyzed, taking into consideration the constraints of the array/gearbox geometry and the spectral content of typical gear noise. Experimental results for a linear array are presented to illustrate the concepts of adaptive beam steering and spatial acoustic filtering. Also, a comparison is made between the radiated spectrum of a damage free system and one with seeded faults using spur gears. This feasibility study indicates that the planar array can be used to track the acoustic signatures of gear mesh dynamics of typical helicopter systems at higher harmonics of the mesh frequency.
Machine vision improves sound level meter calibration
Authors: Arcas Guillermo , Ruiz Mariano , Pagan Raul
Published: October 2013

In this paper, important improvements in sound level meter (SLM) calibration are presented. One of the most important problems that the calibration laboratories are facing today is the long time required for calibrating certain SLMs. Instruments without a dc output require that an operator reads the SLM response in every test. This makes the process slow and tedious, and induces errors due to the operators fatigue. By using an image acquisition card with a low cost analog camera to acquire an image of the sound level meters display, calibration time can be reduced significantly. Once an image of the SLMs display has been acquired, machine vision techniques (OCR) are used to recognize the sound level meter indication. This process reduces calibration time and errors produced by operators fatigue.
The software architecture for an analyzer sound level meter with DSP-bios
Authors: Lopez Navarro Juan M. , Ruiz Gonzalez Mariano , Recuero Lopez Manuel , Pagan Muoz Raul
Published: October 2013

This paper shows the software architecture implemented for the accomplishment of an analyzer sound level meter in one-third octave based on a Digital Signal Processor TMS320C6701 of Texas Instruments. In order to minimize the cost of the equipment, it has been done without the elements of interface with the user (keyboard and displays). For the operation and control of the equipment a laptop, or a PDA may be used. A communication RS232C is used in the local way; and in a remote way, a connection through built-in MODEM GSM. The sever application is executed in the signal processor. It has been implemented in C language and it runs on an real time operating system (DSP-Bios provided by Texas Instruments). DSP-Bios provides the management of events, queues, and timings. The application has the necessary algorithms to make the measures and sends the results to the visualizer, or to a center of remote operation by means of the GSM. The client application that is executed in the visualization element (Laptop or PDA) is developed in Visual Basic. This application can run on any Windows operating system depending on the terminal used: Windows 9x or Windows 2000 for portable ones and on Windows CE for mobile ones.
Airfoil vibration in the wake of an obstacle: Effects of inflow nonuniformity and vortex sheet
Authors: Kovinskaya Svetlana , Amromin Eduard , Avilova Genrietta
Published: October 2013

Obstacles in flow produce wakes that can cause significant vibration of devices located within the wakes. Such vibration appears in many situations, from landing an aircraft on a ship deck to operations of rotating machinery. There are two principal singularities of these wakes that define incoming flow for the downstream devices. First, the time-average velocity profiles are highly nonuniform. Second, flow separation from obstacles is accompanied by generation of large vortices. An initial mathematical study of this flow-induced vibration of the devices includes quasipotential approach in determination of time-averaged flow parameters and determination of amplitude response of elastic airfoils (device cross sections) on perturbation. Perturbation frequencies depend on the obstacle drag, size and free-stream speed. Vortex sizes depend also on Reynolds number. Numerical modeling shows a certain difference between the foil response on gust flow and its response on excitations caused by the obstacle wakes.
Suppression of nonlinear energy decrease by linear absorption and enhancement of resonant properties of nonlinear systems
Authors: Rudenko Oleg
Published: October 2013

A general question of nonlinear vibration and wave theory is discussed which is of special interest for nonlinear acoustics and technologies. Examples of nonlinear systems of different physical nature are given to illustrate how the properly introduced additional absorption can decrease the nonlinear losses and improve the resonant properties of nonlinear systems. Both traveling and localized standing waves are considered. The possibilities to enhance the Q-factor of acoustic resonators are discussed in detail, as well as links to the turbulence, solid state physics, and electronics. [Work supported by CRDF, INTAS, and RFBR grants.]
Wet-walled thermoacoustics
Authors: Slaton William , Raspet Richard
Published: October 2013

An analytic solution of sound propagation in wet-walled tubes with a temperature gradient will be presented. The tube contains an inert gas–vapor mixture with a thin layer of condensed vapor coating the tube wall. The vapor phase condenses and evaporates from this layer during an acoustic cycle. This phased evaporation and condensation modifies traditional energy density and wave number equations. It is found that mass and heat transport act in parallel thereby increasing the acoustic energy density for proper choice of gas mixtures. This increase in energy density due to inert gas–vapor working fluids can be quite large and even dominate the traditional thermal transport contribution. The use of phased evaporation-condensation in gas mixtures provides a path to higher energy density in thermoacoustic systems. The effects on sound propagation, energy density, and efficiency due to the presence of an inert gas–vapor working fluid in tubes with wet walls will be discussed. Also, computational modeling of thermoacoustic refrigerators utilizing an inert gas–vapor working fluid will be presented. Modeling is done using DeltaE software with modifications made to explore inert gas–vapor mixtures. Design of a practical thermoacoustic refrigerator utilizing wet-walled thermoacoustics will be presented. [Work supported by ONR.]
Reduced onset temperature difference in wet thermoacoustic engines
Authors: Slaton William V. , Rayburn John W. , Hiller Robert A. , Raspet Richard
Published: October 2013

Measurements of the onset temperatures of a standing-wave thermoacoustic prime mover in air show a dramatically decreased onset temperature difference when liquid water is present on the stack surfaces. These data may be explained by considering the condensation and evaporation of water during the acoustic cycle [W. V. Slaton and R. Raspet, J. Acoust. Soc. Am. 108, 2569 (2000)]. The inert gas–vapor mixture thermoacoustic propagation equations are integrated through the resonator/stack system to determine the quality factor and resonant frequency using complex frequency analysis. In addition the 1-D thermoacoustic modeling code deltae was modified to include these effects in the stack to predict onset temperatures.
One-dimensional acoustic streaming instabilities in traveling-wave thermoacoustic devices employing jet pumps
Authors: Backhaus Scott , Swift Gregory W.
Published: October 2013

Traveling-wave thermoacoustic devices employ a Stirling-type thermodynamic cycle and thus enjoy an inherent efficiency advantage over standing-wave devices. However, if the regenerator of the traveling-wave device is embedded in a loop, acoustic streaming around the loop can cause a heat leak that greatly reduces the efficiency. In several traveling-wave devices, asymmetric nozzles, or synthetic-jet pumps, have been successfully used to suppress the streaming and, therefore, the heat leak. However, in one traveling-wave refrigerator, an instability that precludes streaming suppression is driven by the interaction between the synthetic-jet pump and the thermoacoustic system. Calculations showing how this instability arises will be presented. [Work funded by the Office of Basic Energy Sciences within the U.S. DOE.]
A study of thermoacoustic instabilities in a resonator with heat release
Authors: Matveev Konstantin I. , Culick Fred E. C.
Published: October 2013

Excitation of acoustic modes in systems with heat release is a complex process, involving coupling between the heat transfer rate and the acoustic pressure. The Rijke tube is the simplest device for studying the fundamental principles of thermoacoustic instabilities both experimentally and theoretically. In our investigation, special attention is paid to reproducibility and precision of the measurements. Experimental results for transition to instability are obtained when controlled parameters (flow rate, heater position, and supplied power) are varied in a quasisteady fashion. The stability boundaries exhibit hysteretic behavior not previously reported. Properties of the limit cycles in the region of instability have also been determined. A mathematical model is developed that incorporates heat transfer, acoustics, and thermoacoustic interactions. An energy balance, accounting for all types of heat transfer, allows for the determination of temperature variations and heat flux along the tube. The acoustic modes, generally nonorthogonal, corresponding to particular experimental thermal conditions, are computed. Solutions of the linearized wave equation with both loss and heat source terms determine the stability of acoustic modes. Hysteresis effects at the stability boundary and amplitudes of the limit-cycles are calculated from the nonlinear model.
Saturation of the thermoacoustic separation of a binary gas mixture
Authors: Geller Drew A. , Swift Gregory W.
Published: October 2013

Spoor and Swift have previously shown [Phys. Rev. Lett. 85, 1645–1649 (2000)] that sound waves can produce the separation of a binary mixture of gases in a duct. This phenomenon is caused by the conspiracy of two effects at the thermoviscous boundary layer: (i) oscillating temperature gradients drive thermal diffusion perpendicular to the direction of sound propagation; and (ii) viscosity sets up a time-averaged counterflow process. In order to assess the relevance and potential uses of this mechanism, it is important to determine the concentration gradient at which the separation process saturates. Here, it is shown that the saturation is determined primarily by ordinary diffusion and by a remixing flux due to the oscillatory motion. Both of these remixing processes are proportional to the concentration gradient, but only the latter process depends on the acoustics, being proportional to the squared volume flow rate and inversely proportional to the frequency. For He–Ar mixtures, saturation concentration gradients near 10%/m have been achieved, in agreement with detailed calculations of these processes. Evidence to date supports the possibility of more challenging separations, e.g., of isotopes. [Work supported by the DOE Office of Basic Energy Sciences.]
The effect of pinna protrusion angle on localization of virtual sound in the horizontal plane
Authors: Gupta Navarun , Ordonez Carlos , Barreto Armando
Published: October 2013

The transformation of a sound from its origin to each of the eardrums of a listener, due to the head, torso, and outer ear of the listener, are modeled by the so-called head-related transfer functions (HRTFs) for each individual and each location around the listener. These HRTFs can be used to transform a monoaural sound into left and right sounds that will give the subject the illusion of a virtual sound placement, at the location associated with the HRTF used. However, subjects tend to confuse sounds virtually placed in the front hemisphere with sounds placed symmetrically in the back hemisphere, i.e., points that lay in a cone of confusion. This paper reports on a study that involved the measurement of the HRTFs of 20 subjects, and the analysis of their performance in locating virtual sources in a horizontal plane. The subjects were tested using their own individual HTRFs and also using the HRTFs of a prototype subject who has particularly protruding pinnae. Results indicate that the additional shadowing of sounds from the back hemisphere encoded in the HRTFs of the prototype subject aided some of the test subjects in resolving the front–back confusion observed when tested with their own HRTFs.
Determining the influence of visual stimuli on the peception of surround sound using data mining algorithms
Authors: Odya Piotr , Czyzewski Andrzej , Kostek Bozena , Smolinski Tomasz
Published: October 2013

A short description of experiments that aim to determine visual cues influence on the perception of spatial sound is provided in the paper. The earlier stage of the carried out experiments showed that there exists a relationship between the perception of video presented in the screen and sound signals reproduced in a surround system. However, this relationship is dependent on the type of audio–visual signals. Thus a series of subjective tests has been performed on dozens of experts in order to discover these dependencies. The main issue in such experiments is the analysis of the influence of visual cues on the perception of the surround sound. This problem is solved with the application of genetic algorithm and rule searching mechanism to the processing of subjective test results. Some results and conclusions concerning the complexity of the investigated problem are included. [Research sponsored by the Committee for Scientific Research, Warsaw, Poland, Grant No. 8 T11D 00218.]
Interaural coherence and the lateralization of noise by interaural level differences
Authors: Hartmann William M. , Constan Zachary A.
Published: October 2013

Coherent noise, with an interaural cross correlation of unity, and incoherent noise, where signals to left and right ears are independent, sound very different. The former produces a compact lateralized image. The latter produces a diffuse image that fills the head. Nevertheless, listening experiments show that coherent and incoherent noise images seem to be equally affected by small interaural level differences (ILD). The ILD threshold for lateralizing incoherent noise is less than half a dB greater than the threshold for lateralizing coherent noise. In this sense, the human binaural system appears to behave like an ideal level meter, insensitive to the wave form and envelope fine structures that determine coherence. The small discrepancy (less than 0.5 dB) can be understood from a standard model of loudness perception—incorporating critical band filtering, half-wave rectification, amplitude compression (0.6 power law), and temporal integration (300 ms). The same model can also account for the small observed difference in lateralization ILD thresholds for coherent noise (N0) and antiphasic noise (Nπ). It can further account for the observed noise bandwidth dependence of lateralization ILD thresholds. [Work supported by the NIDCD.]
Effect of pitch fluctuation of vowels on vowel perception under a noisy environment
Authors: Ishizuka Kentaro , Aikawa Kiyoaki
Published: October 2013

Previous paper reported that natural vowel identification scores were higher under harmonic complex tones than under a white noise, in spite of the tone and the noise having the same flat spectral envelope [K. Ishizuka and K. Aikawa, J. Acoust. Soc. Am. 109, 2439 (2001)]. Natural vowels have pitch fluctuation. This paper reports a new finding that the pitch fluctuation has the effect of improving vowel identification under noisy environments. An experiment was conducted to examine the effect of pitch fluctuation of vowels on vowel perception under a harmonic complex tone at SNRs ranging from −10 to −15 dB. The Japanese female vowels were synthesized with the pitches fluctuated according to the 1/f characteristics [N. Aoki and T. Ifukube, J. Acoust. Soc. Am. 106, 423–433 (1999)]. Five pitch fluctuation bandwidth conditions for vowels were tested. The bandwidths ranged from 0 to 4.3% (F0 = 255.3 Hz). The harmonic complex tone was composed of the same F0 of the vowels and 21 components in the cosine phase. The subjects were forced to choose the vowel they heard for each stimulus. The mean vowel identification scores increased from 33.2% to 46.5%, proportional to the increase of the pitch fluctuation bandwidth.
Digital USB audiometer with noise-shaping techniques for signal generation
Authors: Minguez Antonio , Sancho Juan , Grundman Jorge , Ulin Vladimir
Published: October 2013

A digital audiometer has been implemented on a personal computer with new features to make a low cost and simple equipment. The signals are generated digitally (digital samples) by a recursive algorithm that shapes the spectrum of the quantization noise of the digital samples in order to: (1) eliminate the harmonic distortion at low levels and (2) to increase the signal-to-noise ratio of every tone generated, as the standard EN 60645-1 requires for tone audiometers. Besides, the digital output of the personal computer (PC), the universal serial bus (USB), is used to link the PC with a compatible USB headphones so the transducer can get the original signal in a digital format, avoiding all the analog and electrical noise and distortion in the PC environment, so the proposed audiometer does not need any external equipment to generate the test signals, reducing the total cost of the product.
Absorption and trapping of vibration energy by complex resonators
Authors: Carcaterra Antonio , Akay Adnan
Published: October 2013

This presentation examines conditions that can enhance apparent damping of a master structure due to its coupling with a complex resonator that does not exhibit classical dissipation properties. The model uses a set of multistage parallel oscillators within which energy is trapped. The method presented here for predicting the apparent damping is based on evaluation of the asymptotic response of the master structure utilizing the Hilbert transform. The result is a functional relationship between the frequency distribution within the system and the resulting apparent damping. This study leads to a nonclassical dynamic absorber, consisting of a multistage parallel oscillators, in terms of its absorption and trapping characteristics. The energy is absorbed from the master at a rate determined by the apparent damping and trapped for a given time interval as measured by the return time. The theoretical results suggest optimal configurations to decrease the absorption time and to increase the trapping time (up to an infinite delay). The results of numerical simulations performed on complex vibro-acoustic systems support the proposed theoretical approach. [Research sponsored by INSEAN and NSF.]
Non-native speech production I: Listener–talker adaptation
Authors: Bradlow Ann R. , Bent Tessa
Published: October 2013

To assess native listener adaptation to foreign-accented speech, we submitted 16 sentences produced by three talkers of Chinese-accented English to intelligibility testing. First, the test sentences were orthographically transcribed by native English listeners in a single-talker format in which the test sentences from one talker were preceded by 32, and followed by 16, other sentences produced by the same talker. Second, the test sentences were presented to native listeners in a multiple-talker format in which the test sentences from one talker were interspersed with 48 similar sentences produced by 31 other non-native talkers from various language backgrounds. Within the single-talker condition, the native listeners’ transcription accuracies for all three talkers improved from the beginning to the end of the test session. The magnitude of this improvement was similar across all three talkers. Furthermore, for all three talkers, intelligibility was better in the single-talker condition than in the multiple-talker condition; however, this difference depended on the talker’s overall intelligibility. The ‘‘best’’ and ‘‘worst’’ talkers showed smaller single- versus multiple-talker differences than the ‘‘medium’’ talker. These findings demonstrate that foreign-accented speech intelligibility can improve as the listener gains experience with the voice and speech patterns of the individual non-native talker. [Work supported by NIH-NIDCD Grant No. DC03176.]
Perception and production of English consonants by Japanese adults and children
Authors: Aoyama Katsura , Guion Susan , Flege J. E. , Yamada Tsuneo , Akahane-Yamada Reiko
Published: October 2013

This study examined perception and production of English consonants by native Japanese (NJ) adults and children (16 subjects in each group, mean age=39.9 and 9.9 years). The subjects were tested 2 times (T1, T2), when their mean lengths of residence in the U.S. were 0.5 years and 1.6 years. Age-matched native English (NE) controls (16 adults, 16 children) also participated. A categorial discrimination task was used to assess the perception of the English contrasts /b/–/s/, /b/–/v/, /ɹ/-/l/, /ɹ/–/w/, and /s/–/θ/. For three groups (NE adults, NE children, NJ adults), the T1 and T2 scores did not differ significantly on any contrast. The NJ children’s scores were significantly higher at T2 than at T1 on the /ɹ/–/l/ and /ɹ/–/w/ contrasts. A picture naming task with auditory cues were used to elicit the production of English words containing consonants of interest. Twelve NE listeners identified the subjects’ production of /ɹ/, /l/, and /w/ in word-initial position. Only the NJ children’s scores improved significantly from T1 to T2, and their improvement was the greatest on the production of /ɹ/. Several possible explanations will be offered for why there seems to be more improvement from T1 to T2 for /ɹ/ than /l/.
Perception of English vowels by native Korean and Japanese speakers
Authors: Nozawa Takeshi , Frieda Elaina M.
Published: October 2013

Native speakers of Korean and Japanese were assessed in their ability to perceive English vowels categorically. These two languages were chosen because they differ in the size of their vowel inventories with Korean containing more vowels than Japanese. The Korean vowel space is presumably partitioned more so than the Japanese and this may facilitate Korean speakers’ discrimination of English. This hypothesis is in keeping with Best’s Perceptual Assimilation Model (PAM). PAM states that non-native speakers’ discrimination of non-native sounds can be predicted by differing degrees based on whether the new non-native sounds are assimilated to one or more native phonemic categories. Further, discrimination is mediated by how well the non-native category fits the native category. Both subject groups completed the following tasks: the Categorical Discrimination Test (CDT, designed by J. Flege) which tested their discrimination of English vowels; and an assimilation task where subjects equated English vowels to their native vowels and rated each for category goodness. A’ scores were calculated for each contrast in the CDT. In addition, confusion matrices were calculated for each group. For both subject groups, the English vowels assimilated to a single vowel category were found to be more difficult to discriminate.
The ancient and selective history of the development of high frequency, short range, high resolution active sonars
Authors: McKinney Chester M.
Published: October 2013

This is a brief history of the development of a broad class of active sonars which generally have most or all of these characteristics: relatively high operating frequency (35–1500 kHz), short range (a few meters to 1.0 km), high range resolution (1.0 m to a few cm), and high cross range resolution (a few degrees to 0.1°). Emphasis is on such sonars developed by several navies to find small objects such as naval seamines although there are other important civilian applications. Beginning with the experimental work of Paul Langevin (France) in 1916–18, the development of three generic types of sonars is traced: ahead searching, multibeam, electronic scanning sonars; continuous transmission frequency modulated sonars; and side-scanning sonars. Other types such as small boat sonars, sonars for manned and unmanned small submersibles, and 3D or camera type sonars are covered briefly. Basic research to support the development of all these sonars, primarily target strength and echo structure and bottom reverberation, is discussed only briefly as are other topics such as techniques for high cross-range resolution, target classification clues, and uses for wide bandwidth. Sonars that have proven to be historically significant are identified. The period covered is primarily 1916–1980.
Oceanic ambient noise
Authors: Carey William M.
Published: October 2013

Ambient Noise (AN) research during World War II was facilitated by the availability of calibrated instruments and motivated by the necessity to understand AN levels in coastal waters. The state-of-the-art was reviewed by Knudsen in 1948 and later by Pryce and Urick in 1954. After the war, AN research waned until the classic paper by Wenz (1962) marked its renaissance. By 1976, a vast literature existed on measurements, theory and computational methods, and in the 1980s AN was the second largest area of underwater acoustics. Initially, emphasis was on the omni-directional properties of the field and later on vertical/horizontal directionality and the shipping-component statistical characteristics. Measurement arrays characterized the statistics of the AN, its persistent directionality, and benchmarked attempts to predict the AN-levels. Interest in AN sources re-emerged around 1985 with the identification oceanic bubble ensembles as a major contributor to deep and shallow water noise fields. This overview discusses fundamental AN sources, measurements, and the physics of the air–sea interaction boundary layer. Bubble, spray, splash, and rain noise are examined and ranked in order of importance. The production, absorption, and transmission of sound by bubble clouds and layers produced by breaking waves are examined. [Work sponsored by ONR.]
Advances in high-frequency underwater acoustics
Authors: Liszka Edward G.
Published: October 2013

Significant progress has been made over the past 3 decades in understanding the acoustic phenomena that affect the operation of high-frequency (i.e., 10 kHz–60 kHz) sonars utilized by systems in the undersea environment such as weapons and autonomous underwater vehicles. The specific underwater acoustic research interests have somewhat paralleled and been motivated by the technology developments for these applications. In the late 1960s and early 1970s, experiments and model development focused on understanding the processes of signal propagation, scattering from the ocean medium (reverberation), and target reflection to predict signal levels for energy detection systems. Recently, systems have evolved to exploit more advancd signal processing concepts that have established a new set of scientific issues. Accordingly, underwater acoustics research has been focused on time/frequency/spatial distribution of energy, temporal, and spatial coherence of signals and background, and a broader scope of complex environments. The increased understanding has been captured in models representing the physical phenomena and rather detailed simulations of the underwater acoustic picture. This paper will review some of the key results in high-frequency underwater acoustics research that have contributed to the current state of knowledge and an indication of the direction for future research.
From matched filter to matched field tracking
Authors: Bucker Homer
Published: October 2013

An old example of use of a matched filter in underwater sound is the quadrature detector. The signal from hydrophone ♯j is split, and one channel is matched with a cosine wave and the other with a sine wave. These channels are assembled as the real and imaginary parts of the analytic signal Fj. The next application of a matched filter occurs in plane wave beam forming where the signals {Fj} of an array are matched with signals {Gj(φ)}, which are expected if the incident signal is a plane wave with direction φ. The problem is expanded when a more precise form of {Gj} is used. In general, {G} will be a function of the location of the source. Therefore, in principle, the location of a sound source can be found by finding the coordinates of the best match between the F’s and the G’s (matched field processing). Several methods will be described showing how to do this in an efficient manner. Finally, there is further gain to be had by including many time values in matching the track of the acoustic source (matched field tracking). Examples will be shown illustrating results from sea tests.
Fifty years of measuring, modeling, and sometimes understanding the physics of sound in the sea
Authors: Walkinshaw Helen M.
Published: October 2013

By the end of the 1940s naval experience in World War II and progress in undersea physics and oceanogoraphy had brought about recognition of low frequency as a means of passive detection. The discovery of the deep sound channel was published in 1948, defining its role in long range propagation. In January 1950, the National Research Council’s Committee on Undersea Warfare recommended a study be made of these emerging concepts. What came to be known as the Hartwell Committee was formed. The Committee’s report included specific recommendation of real-time narrow band analysis of radiated sounds and exploitation of low-frequency signals. In October, the Chief of Naval Research was directed ‘‘to proceed with arrangements with Bell Laboratories to institute a program of research and development in the field of low frequency.’’ This directive, shared with naval laboratories and affiliated universities, initiated an intensive program of sea experiments that continued over four decades. The measurements were paralleled by computer codes developed to analyze and deconstruct data, and eventually model propagation and arrival structure in realistic, range-varying ways. The sequence of the discovery and validation of features that define the nature of undersea sound as now understood are outlined and discussed.
Good vibrations: Composed instruments integrating gestural control, and sonic display
Authors: Bahn Curtis
Published: October 2013

This paper examines electronic composed instruments which take as essential aspects of their design the full feedback loop of: acoustic sound production; physical interface/gestural sensing; computer interface (including sound synthesis/processing); and localized sonic display. Many issues relevant to architectural sonics are seen, including: the design of localized haptic/sonic feedback for the performer; the composition of relationships between gesture and sound production composing the sonic architecture of the body; and the inclusion of spherical speaker arrays to engage the natural acoustics of the hall. Conventional sound reinforcement techniques often draw acoustic instruments into an electronic sound space where artificial reverberation and other processing is added in an attempt to create a natural blend with electronic sound sources. This approach decorrelates instrumental gesture and original sound source, and most often conflicts with or undermines the acoustic design of the hall. The integration of sonic display into composed instruments reinforces the feedback loop between instrumental touch and sonic result, offers localized sonic feedback for the performers on stage, and creates a rich, acoustic ensemble blend. These extended instruments provide an extremely effective approach to integrating electronic musical performance into an acoustic context.
The manipulation of audio dynamics toward both technical and artistic goals in recorded music
Authors: Case Alexander U.
Published: October 2013

The musical dynamics of recorded sounds must be made to fit within the audio dynamic range of the recording and playback equipment. This constraint on dynamic range is presented track by track in the multitrack recording studio and at every stage of audio signal processing up to and including the end user’s system. Recorded orchestras must be made to sound good on clock radios. Audio compressors and limiters have been developed to help the recording engineer cope with this problem. Automatic, but careful, control of the signal gain during the course of music recording and playback is part of almost all music production styles, most notably pop music. In addition, these dynamics processors are used for purely aesthetic purposes. They shape the character, timbre, and emotional feel of a musical performance. These more innovative applications of compression become part of the music, creating effects that range from subtle to conspicuous. This paper reviews many compression techniques used in the production of recorded music and describes their technical and creative goals.
Synthesizer as processor: Flexibility in signal processing
Authors: Moorhead Jan P.
Published: October 2013

Creative use of the digital inputs available on many synthesizers offers a wide array of possibilities in digital signal processing. This provides the capabilities of standard rack-based processors as well as a great deal more. The most significant opportunities for new timbers come from modular synthesizers that allow you to design new instruments to suit your specific application. These techniques may easily be used in live performance as well as in the studio. When the unprocessed sound of the source is suppressed, it is possible to create entirely new timbers from standard acoustic or electroacoustic instruments. An advantage over typical MIDI-controlled synthesizers is that the performer need not necessarily learn a new interface or new techniques to optimize the expressiveness of the performance. Additionally, because the sound from the input instrument can be used as a controller for elements of the patch (in the synthesizer), the resulting output can be very responsive and expressive. In all, this provides a new class of nonstatic timbers for the performer, composer, engineer, and producer.
Surf zone bubble spectrometry: The role of the acoustic cross section
Authors: Leighton Timothy
Published: October 2013

Fifty years ago, there were doubts as to whether microbubbles existed in the sea at all. Herman Medwin settled the issue in the 1960s by showing that they were indeed present, and in very large numbers. He interpreted in situ measurements of backscatter and attenuation using the concept of the acoustic cross section. In essence that procedure forms the basis of the most popular ways of measuring microbubbles today, the two favored experimental layouts (measurement of attenuation and sound speed along a propagation path, and the acoustical resonator) being based on techniques pioneered by Medwin. In recent years attempts have been made to take these open ocean techniques and deploy them in the surf zone. Here the assumptions inherent in the standard form of the cross section can be violated. Specifically, the conditions may not relate to plane wave insonification of isolated bubbles undergoing steady state single-frequency linear pulsations in the free field in an incompressible liquid. This paper describes the attempts that have been made to produce cross sections which are not restricted by these limitations, and how these are exploited in determining the evolution, anatomy, and effects of bubble clouds. [The support of The Royal Society Leverhulme Trust is acknowledged.]
Vibration damping layer performance enhancement with an intermittent bond
Authors: Garrelick J.
Published: October 2013

Having arrived in the U.S. in 1941 and upon graduating from the MIT in 1944, Miguel C. Junger’s early contributions to structural-acoustics were predominantly structural. With war needs dominating, Miguel worked on aircraft engine testing at Wright Aeronautical Corp. and subsequently Naval ship shock mounts at Barry Controls. The clichéd ‘‘can do’’ attitude of these early war years may or may not have been the genesis of his much admired approach to technical problems of all stripes, a focus on fundamental physical principles and the utilization of rigor to extract the essence. In this talk, by example, I will attempt to illustrate how ‘‘Miguel’s acoustics’’ has influenced and benefited his colleagues. The example is a problem recently confronted by the author, the effect of an intermittent bond on damping layer performance. Damping treatments are typically uniformly bonded, with any irregularity in converage deemed shoddy. However, this need not be the case and an intermittent bond may actually enhance performance. This will be demonstrated for an unconstrained layer with the intermittency represented by periodic gaps. Numerical results are compared for two solution approaches, one a somewhat plodding viscoelastic layer analysis, the other a rather highly idealized asymptotic representation, to capture the essence.
Miguel Junger, Cambridge Acoustical Associates, and the U.S. Navy
Authors: Strasberg M.
Published: October 2013

Miguel Junger and his associates at Cambridge Acoustical Associates have had a long, active, and fruitful relationship with the U.S. Navy and Navy acousticians. In this talk we will review some of the papers and reports published in the open literature during the 1960s and 1970s, describing their work on subjects of interest to the Navy.
Scattering by tilted cylindrical shells in water above the coincidence frequency
Authors: Marston Philip L. , Blonigen Florian J. , Morse Scot F.
Published: October 2013

Experimental, theoretical, and computational results indicate that flexural waves on bluntly truncated tilted cylindrical steel shells are a major contributor to the backscattering of sound at high frequencies over a wide range of tilt angles. Important contributions are associated with meridional rays and with helical rays [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998); S. F. Morse and P. L. Marston, J. Acoust. Soc. Am. 106, 2595–2600 (1999); S. F. Morse and P. L. Marston, IEEE J. Ocean. Eng. 26, 152–155 (2001)]. Successful development of a ray model for helical ray scattering contributions required the computation (at high frequencies) of the anisotropy of the flexural-wave velocity and radiation-damping parameters [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. (accepted for publication)]. In backscattering experiments with short and long tone bursts, the associated meridional and helical ray contributions are typically much larger than the scattering estimated for diffraction by a rigid tilted cylinder of the same size. The importance of the elastic response of shells was recognized in the early work of Junger [M. C. Junger, J. Acoust. Soc. Am. 24, 366–373 (1952)]. [Work supported by ONR.]
Computer simulation and virtual experiments for architectural acoustics education
Authors: Muehleisen Ralph T.
Published: October 2013

Computer simulation and virtual computer experiments are one way of introducing students to concepts without the high cost of traditional experimental equipment. Computer simulation can show students the effectsof room reverberation on different types of acoustic signals including speech and music and to show the noise control effects of absorptive materials. Computer based digital filters can be used with audio files to auralize the acoustic transmission loss of different materials and constructions. In this presentation the use of computers for simulation and virtual experiments in architectural acoustics is discussed. A variety of modern computer programs for acoustic prediction and simulation of room acoustics and noise control are reviewed.
Mechanisms affecting the propagation of sound through the atmosphere
Authors: Stinson Michael R. , Daigle Gilles A. , Havelock David I.
Published: October 2013

This talk will survey the various factors that affect the propagation of sound through the atmosphere. Ray-tracing software intended to predict community noise must accommodate these factors in some approximate yet realistic manner. The atmosphere is neither static nor uniform. Scattering by turbulence and refraction due to temperature and wind speed gradients must be considered. The impedance of the ground surface, the local topography (hills and valleys), and the presence of obstacles such as buildings have an important effect on the sound field. Barriers can reduce noise levels significantly, but the presence of turbulence and gradients can diminish their effectiveness.
Quirks, problems, and work-arounds with ray-tracing software
Authors: Hale Marlund
Published: October 2013

More and more, acoustical consultants and those in industry are turning to commercially available community noise prediction software to assist in assessing and mitigating community and environmental noise impacts. End users come from varied backgrounds that range from the novice to the expert in noise prediction or using noise ray-tracing software. What could start out as an expectation of a faster and more effective method of analyses, often turns into disappointment and frustration, if not total exasperation. Furthermore, hours upon hours of wasted effort and budget overruns can occur while learning to effectively use the software package chosen. This typically stems from a lack of adequate tutorials or training, apparent errors in the software, poor documentation, undocumented restrictions, lack of ease in learning and using the software, etc. This paper identifies some of the problems often encountered while modeling industrial facilities, propagation path influences, and receivers. In addition, some problems found in basic acoustic modeling are also identified and reviewed. In certain instances, work-arounds have been found, which allow the modeling process to continue with reasonable accuracy.
Nobelists in acoustics
Authors: Beyer Robert T.
Published: October 2013

The only Nobel Prize awarded specifically in acoustics was that to Georg von Bekesy in 1962 in medicine and physiology for his work on the ear, but there are at least ten other winners who did significant work in acoustics. The most famous and prolific of these was, of course, Lord Rayleigh, but the others include Pierre Curie (piezoelectricity), Peter Debye (the ultrasonic beam as a diffraction grating), C. V. Raman (mathematical analysis of the Debye–Sears effect), Albert Einstein (velocity dispersion of sound in gaseous mixtures), and Lev Landau (sound absorption in liquid helium). Their acoustical work and that of a number of other Nobel laureates will be discussed.