bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas-Turbine Peaking Power Plants and Future Outlook
Authors: Bruce D. F. , Morrash J.
Published: May 2015

The considerations justifying peaking power plants have been discussed in numerous publications, some of which are referenced in the Appendix. With the acceptance of the gas turbine by various utilities as a suitable prime mover for use in peaking service, a relatively inexpensive machine became available in reasonably large blocks of power. The most recent concept in peaking service is equipment for peak shaving. This is that facet of a utility operation of shaving the peak off the top of a load duration curve. This involves equipment that can be installed at a very nominal investment per kilowatt and maintained at a minimum cost; for example, a remote unattended unit with low standby cost and an overhaul period of 5 years or more. This is readily obtainable with a normal operating period of 500 to 1000 hr per year in peak shaving service.
Design and Test of the First Aerodynamic Torque Converter for Gas Turbines
Authors: Hill Charles C. , Mercure Robert A. , Cole Charles D.
Published: May 2015

A first of its kind — 100 hp aerodynamic torque converter (ATC) was designed, built and tested. The ATC which closely resembles hydrodynamic torque converters in principle of operation uses a compressible fluid as a working media instead of an incompressible liquid. Since an ATC operates at gas turbine speeds, it is particularly suited for gas turbine powered vehicles. Classical techniques in aero-thermodynamics were used to design a simple three element coverter. Performance testing to date has demonstrated peak transmission efficiencies of 77%.
A Unique Application of Gas Turbines in a Coke and Coal Chemical Plant
Authors: Amatangelo C. J. , Busa J. V. , Wilson W. B.
Published: May 2015

The basis for selection and application of 7 combined energy cycle systems, (natural gas and steam) is presented. The gas turbines are used as the prime energy source for the production of electrical power and the operation of gas compressors in a coke and coal chemical plant. The unique features discussed are the production of variable frequency electrical power and the utilization of the steam produced in the waste heat boilers for direct process requirements.
Material Characterization Results for a Selected Graphite Fiber/Epoxy Composite
Authors: Molter G. E. , Rothman E. A.
Published: May 2015

Static and dynamic strength tests and modulus data are reported for a uniaxial graphite yarn reinformcement impregnated with an epoxy matrix by the vacuum injection molding technique. All testing was done at room temperature. An inherent tendency to fracture in inter-laminar shear was observed.
C. I. T. Sensors: A Design Evolution
Authors: Dugar Alvin B.
Published: May 2015

The paper explains the need for C.I.T. sensors; describes the operation of the various types of C.I.T. sensors that have been developed; and discusses the design characteristics of these sensors.
Heat Transfer in the Oscillating Turbulent Boundary Layer
Authors: Miller J. A.
Published: May 2015

Measurements of local heat transfer coefficients in the fully established oscillating turbulent boundary layer over a flat plate are reported. In the range of frequencies from 0.1 to 200 cps and amplitudes from 8 to 92 percent of the freestream mean velocity increases in local Nusselt numbers of 3 to 5 percent were found. It is concluded that substantial increases in local coefficients sometimes reported in oscillating flows of low standing wave ratio may be traced to reduced transition Reynolds numbers.
Emulsified Fuel and Fuel Control Systems
Authors: Lamart R. M. , Mello J. D.
Published: May 2015

Chandler Evans Engineering conducted a test and evaluation program to uncover problem areas of fuel control systems using emulsified fuel. Basic control components and a complete control system were tested as were fuel characteristics pertaining to a control, exposure effects of typical control system materials to the fuel, and temperature and pressure properties of emulsified fuel. Since the absolute quantity of fuel (1000 gal) made available for the program limited testing, no endurance tests were performed. General variations in control component and system performance when operated with JP-4 and emulsified JP-4 appear to be minor. Exposure of typical fuel-control materials indicates the fuel’s highly corrosive nature, which requires special consideration in material selection. The temperature and pressure properties of this fuel, although evaluated from testing, may be used as order of magnitude indication only, based on the one batch of emulsified JP-4 fuel tested. The results, which could be quite different on other batches of the same fuel — or on any of the many other emulsified-type fuels under development, indicate the general field of emulsified fuels.
Process Plant Application of an Aircraft-Type Gas Turbine
Authors: Yancy H. B.
Published: May 2015

The installation to be discussed in this paper was one of the first gas generator, power turbine, centrifugal compressor design combinations to be put in ground (as opposed to airplane) power applications. As a consequence the control systems, waste heat boiler installation and other parts of the facility proved to be other than adequate for continuous duty industrial plant use and as such, has gone through a subsequent development period to overcome the many problems that were encountered. This should be kept in mind as one reads the article. The present-day industrial gas generator units incorporate simplified and reliable control systems and other successful features as a result of this earlier experimental and prototype installation. Revisions to the Phillips Petroleum Company Dumas Helium Plant Pratt Whitney GG3C gas generator and related equipment have greatly increased onstream capabilities. Replacement of unreliable controls and electrical relays has decreased unwarranted shutdowns from 80 hr in 1963 to 8 hr in 1967. Improvements in lubricating oil have increased the time between oil changes from 300 to 3000 hr. Design changes in bearings, exhaust hood, and the lubricating oil system have increased the gas generator’s reliability. The Cooper-Bessemer RT-48 free power turbine has operated maintenance-free since startup. Cooper-Bessemer’s latest design has solved the reaction turbine hood stress cracking problem. Use of this type facility in helium plant service offers advantages, but lack of flexibility has caused a considerable amount of product loss at Dumas Helium Plant.
The Development of Supersonic Axial Compressor Boost Stages for Small Gas Turbines
Authors: Muller C. H. , Sabatiuk A.
Published: May 2015

The axial supersonic compressors of the “shock-in-rotor” type are under development for application to small gas turbines. A passage flow approach and passage criteria were used to design and develop the airfoils for the highly loaded rotor and stator blading of these 4 lb/sec machines. The overall stage performance values demonstrated to date are 2.06:1 pressure ratio at 78 percent adiabatic efficiency and 2.56:1 at 74.4 percent efficiency. The loss data and static pressure rise measured for the rotors and exit stators provide ample evidence that the higher design performance goals can be met.
The Gas Turbine’s Application in Central Chilled Water and Heating Plants
Authors: Viera S.
Published: May 2015

The author has reviewed the basic design concepts of central chilled water and heating plants and the gas turbine’s application to the concept. Advantages of the central plant are detailed. Available types of equipment are discussed. Gas turbine applications are thoroughly reviewed with comments regarding actual design experience for several large central plants. The importance of heat recovery equipment selection and application has been thoroughly considered. Two large plants, constructed in California, designed under the engineering supervision of author, are discussed throughly with appropriate comment regarding concept, selection of equipment, expansion potential, thermal efficiency as well as other salient features.
Ten-Year Process Gas Turbine Experience
Authors: Kevil C. G. , Drost J. G.
Published: May 2015

The Columbian Carbon Company Petrochemical Plant, formerly known as PCI or Petroleum Chemicals, Inc., has now operated three 13,000-hp class gas turbines for ten years. This paper reviews the overall plant arrangement and application of the units. The paper then discusses operating experience and points out on-stream innovations developed over this operating period. Parts life and reliability are touched upon. A critical path maintenance program is discussed. The required high degree of process reliability of the three gas turbines has been established as set forth in this paper.
Superalloy Development for Aircraft Gas Turbines
Authors: Quigg R. J. , Collins H. E.
Published: May 2015

The creep resistance of nickel-base superalloys has progressed consistently over the past two decades. These improvements have been accomplished through the use of three principal strengthening mechanisms, solid solution strengthening, intermetallic (gamma prime) strengthening, and carbide strengthening. Most recently statistical regression analysis has been employed to predict the influence of alloying ingredients in nickel, and an alloy (TRW-NASA VI A) has been designed through this procedure. Superalloys, along with appropriate cooling mechanisms, appear to be entrenched as the materials of construction for the hotter portions of aircraft gas turbines for at least the next ten years.
Some spatial analysis of the room impulse response
Authors: Meyer Jens , Elko Gary W.
Published: May 2015

The room impulse response (RIR) and measures derived from it have been a powerful tool for room characterization. Traditionally, these measures are based on time domain characteristics like reverberation time or clarity. By recoding a group of RIRs with microphone arrays, one can add the spatial dimension to the RIR. Spherical microphone arrays are of special interest since they can give equal weight to all directions. In this paper, we explore an adaptive cardioid beampattern algorithm for its suitability as a tool for the spatial analysis of RIRs. The algorithm uses the spherical harmonic base patterns (“Eigenbeams”) of a spherical microphone array to form and steer a cardioid beampattern. The steering is automatically adjusted to minimize the output power in a specific time region. Due to the cardioid beampatterns sharp null in the beampattern, an adaptive cardioid algorithm can provide detailed spatial information on reflections as a function of time for impulse responses.
An open-source spherical microphone array design
Authors: Granzow John , O'Brien Tim , Ford Darrell , Yeh Yoo H. , Hur Yoomi , Mostowfi Darius , Abel Jonathan S.
Published: May 2015

We present an open-source design for producing a spherically baffled, 32-channel microphone array having elements aligned with the vertices and face centers of a dodecahedron, and fabricated using additive manufacturing (3-D printing). The design approach emphasized low cost, assembly ease, and acoustic integrity. Mechanical, electrical, and acoustical design considerations are discussed, as are assembly and calibration details. The baffle is a 10-cm-radius sphere, built from separable hemispheres, and supported by a 2-cm-diameter cylindrical stand that serves as a conduit for the microphone signal cables. Microphone capsules are mounted on preamp boards, which provide balanced line level outputs, and press fit to the baffle. The performance of the array is characterized, and an example application to spatial room impulse response measurement is provided. Design documents, including the enclosure model and preamp electrical design and board layout, are provided at https://ccrma.stanford.edu/~granzow/sphericalmicarray/
Equivalence of plane wave and spherical harmonics rendering of binaural room impulse response
Authors: Ben-Hur Zamir , Sheaffer Jonathan , Rafaely Boaz
Published: May 2015

Binaural technology has various applications in virtual acoustics, architectural acoustics, tele-communications, and auditory science. One key element in binaural technology is the binaural room impulse response (BRIR), which represents a continuum of plane waves spatially filtered by head related transfer functions (HRTFs). Such BRIRs can be rendered from spherical microphone array recordings and free-field HRTFs, either in the space domain using plane-wave composition or in the spherical-harmonics domain using order-limited spherical harmonics representation of the sound field. While these approaches have been individually employed in a number of recent studies, it appears that the literature does not offer a comprehensive analysis or a theoretical framework relating the two representations with respect to binaural reproduction and perception. In this paper, we provide a mathematical analysis showing that when certain sampling conditions are maintained, the plane-wave and spherical-harmonics representations are equivalent. Further, we show that under these conditions, resulting binaural signals are independent of the employed spatial sampling schemes. The analysis is complemented by a listening experiment, in which both plane-wave and spherical-harmonics representations are perceptually evaluated for different spatial sampling schemes and spherical harmonic orders.
The effect of playback method on listeners' judgments of concert hall auralizations
Authors: Clapp Samuel W. , Guthrie Anne E. , Braasch Jonas , Xiang Ning
Published: May 2015

Previous studies of the perception of concert hall acoustics have generally employed one of two methods for soliciting listeners’ judgments. The first is to have listeners rate the sound of a hall while physically present in that hall. The second is to record the acoustics of a hall and later simulate those acoustics in a laboratory setting. While the first method offers a completely authentic presentation of the concert experience, the second allows for more direct comparisons between different spaces and affords the researcher greater control over experimental variables. Higher-order spherical microphone arrays offer a way to capture the spatial components of a concert hall’s acoustics, which can then be reproduced using a loudspeaker array. In this study, eight different concert and recital halls were measured using both a spherical microphone array and binaural dummy head as receivers. Listeners were then presented with auralizations of the halls using an ambisonic loudspeaker array and headphones, and asked to rate the halls based on subjective preference and on similarity to one another. The responses were analyzed using multidimensional scaling methods in order to examine the effect of the auralization system on the listeners’ judgments.
Individually distinctive parameters in the upcall of the North Atlantic right whale (Eubalaena glacialis)
Authors: McCordic Jessica A. , Parks Susan E.
Published: May 2015

According to the source-filter hypothesis proposed for human speech, physical attributes of the vocal production mechanism combine independently to result in individually distinctive vocalizations. In the case of stereotyped calls with all individuals producing a similar frequency contour, the filtering of the signal resulting from the shape and size of the vocal tract may be more likely to contain individually distinctive information than parameters measured from the fundamental frequency resulting from the vibrating source. However, the formant structure resulting from such filtering has been historically undervalued in the majority of studies addressing individual distinctiveness in non-human species. The upcall of the North Atlantic right whale (Eubalaena glacialis) is characterized as a stereotyped contact call, and visual inspection of upcall spectrograms confirms presence of a robust formant structure. Here we present preliminary results testing individual distinctiveness of upcalls recorded from archival, suction cup mounted tags (Dtags). Parameters measured from the fundamental frequency contours as well as the formant structure of the calls are used in assigning upcalls to individual whales. These results provide a baseline for further development of acoustic detection techniques that could be used to noninvasively track movements of individual whales across habitats.
Objective analysis of vocal sequences using nested self-organizing maps
Authors: Mercado Eduardo
Published: May 2015

Traditional approaches to analyzing vocal sequences typically involve identifying individual sound units, labeling identified sounds, and describing the regularity of label sequences [A. Kershenbaum et al., “Acoustic sequences in non-human animals: A tutorial review and prospectus,” Biol. Rev. (2014)]. Although this method can provide useful information about the structure of sound sequences, the criteria for determining when distinct units have been successfully classified are often subjective and the temporal dynamics of sound generation are usually ignored. Self-organizing maps (SOMs) provide an alternative approach to classifying inputs that does not require subjective sorting or isolation of units. For instance, SOMs can be used to classify fixed duration frames sampled from recordings. Once an SOM has been trained to sort frames, the temporal structure of a vocal sequence can be analyzed by training a second SOM to sort spatiotemporal patterns of activation within the frame-sorting SOM. Analyzing humpback whale “song” using this technique revealed that: (1) perceptually warped spectra from frames varied uniformly along several continua; (2) a subset of frame patterns (sound types) was more prevalent; and (3) produced features varied systematically as a function of sequential position within a song for some sounds, but not others.
Using helium as the working fluid to improve efficiency of high-frequency thermoacoustic engines
Authors: Wells Nathaniel , Andersen Bonnie
Published: May 2015

Previous work on thermoacoustic engines with bottle-shaped resonators has been done to improve performance by varying geometric parameters, using air as the working fluid. This study is focused on transitioning from air to helium for the working fluid to further improve device performance. The theoretical ratio of efficiencies was derived for the two operating fluids. The existing engine was redesigned for evacuating the air and introducing helium into the resonator and six different types of heat shrink tubing used to hold the heat exchangers in place were tested for effectiveness with a vacuum and ease of removal. The optimal stack masses for this engine operating with air and helium were theoretically estimated and tested with air using six different stack masses from 50 to 62 mg. The resonator had a cavity with a length of 10 cm and ID of 4.13 cm and a neck with a length of 2.62 cm and ID of 1.91 cm and used steel wool for the stack material. The engine was supplied 12 W from a heating element applied above the hot heat exchanger in the neck. The engine was allowed to run for 40 s after the temperature had reached a steady state and the acoustic pressure at the bottom of the cavity was measured. The optimal amount of stack in air was found to be 56 mg, and the acoustic pressure was 206 Pa, Pk-Pk. The adhesive heat shrink tubing was found to be the most effective for use with helium and ease of removal.
High frequency oblique-angle acoustic reflections from an air-snow interface
Authors: Albert Donald G. , Song Arnold J. , Courville Zoe R.
Published: May 2015

Fresh natural snow is a difficult material to characterize, as any mechanical interaction is likely to damage the fragile pores and grain bonds. Because acoustic waves are sensitive to the porous material properties, they potentially can be used to measure snow properties in a non-destructive manner. Such methods have already been demonstrated on cohesive porous materials including manufactured foams, porous metals, and sintered glass beads. As a first step toward developing a portable method that can be used outdoors, we conducted high frequency oblique-angle reflection measurements on snow samples in a cold room. We compare the acoustically derived parameters with microcomputerized tomography (CT) methods and with standard (but destructive) laboratory measurements. [This research funded by the U.S. Army Corps of Engineers.]
Rotating sound sources and listeners: Sound source localization is a multisensory/cognitive process
Authors: Yost William , Zhong Xuan , Najam Anbar
Published: May 2015

When sound sources or listeners rotate, the acoustic cues used for sound source localization change, but in the everyday world listeners perceive sound rotation only when the sound source rotates not when the listener rotates. That is, in the everyday world, sound source locations are referenced to positions in the environment (a world-centric reference system). The acoustic cues for sound source location indicate a sound source’s location relative to the head (a head-centric reference system), not locations relative to the world. To compute world-centric locations of sound sources, the auditory spatial system must have information about the acoustic cues used for sound source location and cues about the position of the head. The use of visual and vestibular information in determining head position in sound rotation perception was investigated in four experiments. The experiments clearly show, for the first time, that sound source localization when sound sources and listeners rotate is based on acoustic and visual, and sometimes vestibular information. Sound source localization is not based just on acoustics. It is a multisensory process. [Research supported by an AFOSR grant.]
Changes in the integration of self motion and auditory spatial cues with age, hearing impairment, and use of hearing devices
Authors: Brimijoin W. O. , Akeroyd Micheal A.
Published: May 2015

To resolve a front/back confusion, listeners may use both the spectral cues associated with the pinnae and they may turn their heads and note the direction in which the signal moves. Since hearing impairment typically involves the loss of high frequency information, one might expect that hearing impaired listeners would be more reliant on self-motion cues. Such listeners, however, often wear hearing aids that alter binaural level cues, suggesting they may distort dynamic self-motion-related cues. To examine these interactions, we utilized a previously published front/back illusion [W.O. Brimijoin and M.A. Akeroyd, iPercept. 3(3), 179–182 (2012)]: the perceptual location of signals whose position is moved at twice the angular rate of head movements is opposite to its physical location. In normal-hearing listeners, the illusion is powerful but weakens with increasing low-pass filter cutoff frequency. We found that for hearing-impaired listeners, the illusion was effective at all cutoff frequencies. The effect of hearing aids was heterogeneous across listeners, but in no case was a listener returned to normal performance, suggesting that hearing aids are not only failing to provide the listener with spatially-informative spectral cues, but they may interfere with self-motion-related cues. [Work supported by MRC (U135097131) and the Chief Scientist Office (Scotland).]
On the importance of information-bearing acoustic changes for understanding speech in simulated electrical-acoustic stimulation
Authors: Stilp Christian , Donaldson Gail , Oh Soohee , Kong Ying-Yee
Published: May 2015

Listeners utilize information-bearing acoustic changes in the speech signal to understand sentences. This has been demonstrated in full-spectrum speech using cochlea-scaled entropy (CSE; Stilp & Kluender, 2010 PNAS) and in vocoded speech (CSECI; Stilp et al., 2013 JASA). In simulations of electrical-acoustic stimulation (EAS), vocoded speech intelligibility is aided by the preservation of low-frequency acoustic cues. The extent to which listeners rely on information-bearing acoustic changes to understand EAS speech is unclear. Here, normal-hearing listeners were presented noise-vocoded sentences with 3–6 spectral channels in two conditions: 1) vocoder-only (80–8000 Hz, filtered using third-order elliptical filters), and 2) simulated hybrid EAS (vocoded >500 Hz; original acoustic <500 Hz). In each sentence, four 80-ms intervals containing high-CSECI or low-CSECI acoustic changes were replaced with speech-shaped noise. As expected, performance improved with more channels and the preservation of low-frequency fine-structure cues (EAS). Relative to control vocoded sentences with no noise replacement, performance was impaired more when high-CSECI intervals were replaced by noise than when low-CSECI intervals were replaced in 5- and 6-channel sentences, but not at lower spectral resolutions. This effect maintained across vocoder-only and EAS sentences. Findings support the conclusion that EAS users make use of information-bearing acoustic changes to understand speech.
Predicting the timing of future events using sound: Bouncing balls and tone bursts
Authors: Shafiro Valeriy , Gygi Brian , Kharkhurin Anatoliy
Published: May 2015

Listeners can predict the timing of the next bounce of a bouncing ball by sound alone with high accuracy, relying primarily on temporal cues [Giordano et al., 2011, JASA, 129, 2594]. The present study investigated the role of temporal structure (natural bouncing patterns versus artificially reversed bouncing patterns) and event type (ball bouncing sounds versus similarly patterned tone bursts). After listening to two to four such sounds, listeners would indicate when they expected the next sound to occur (without hearing it). Results replicate previous findings of high accuracy in predicting the timing of natural bounce patterns regardless of event type. In contrast, accuracy was substantially poorer when pattern timing was reversed. Nevertheless, even for reversed patterns, listener accuracy improved as a greater number of bounces were heard prior to response time. This suggests that with additional information listeners were able to utilize veridical acoustic cues that best fit the temporal pattern. These findings demonstrate that in addition to being highly adept in estimating future timing of natural auditory events, listeners (a) tend to rely on temporal dynamics of everyday events in their timing estimates, and (b) can modify their response strategies for artificial timing patterns.
Relative weight of temporal envelopes across speech frequency regions for speech intelligibility in hearing-impaired listeners and cochlear implant users
Authors: Nie Yingjiu , Wheeler Harley J. , Short Alexandra B. , Harrington Caleb W.
Published: May 2015

The study was aimed to investigate, among three groups of listeners—normal-hearing, hearing-impaired, and cochlear implant users, the relative weight of temporal envelopes for speech intelligibility in each of the eight frequency regions ranging between 72 and 9200 Hz. Listeners were tested in quiet and in the presence of steady or amplitude modulated noise at two rates (4 and 16 Hz). An eight-band vocoder was implemented when testing the acoustic-hearing groups. Speech intelligibility of a given region/band was assessed by comparing scores in two conditions differing only by the presence or absence of the band of interest; the proportion of the derived score to the sum across the eight regions/bands was computed as the relative weight. Preliminary data showed the following: (1) in quiet, similar frequency-weighting pattern for all three groups with higher weight in the mid/mid-high frequency range; (2) in noise, for the normal-hearing group, different weighting patterns between steady noise and amplitude-modulated noise; for the other two groups, similar weighting patterns for all types of noise with comparable weight across bands # 2–7 and lower weight for the bands # 1 and 8. The contribution of each region/band to masking release will also be discussed.
Application of the WKB method for an active cochlear model
Authors: Nankali Amir
Published: May 2015

The Wentzel-Kramers-Brillouin (WKB) method has been used to approximate the solution for systems with slowly varying properties. The analytic method is computationally efficient and provides insights into the physical problem by decomposing the solution into a dominant wavenumber and the associated amplitude [e.g., Steele and Taber (1978)]. Because of its computational efficiency, this method provides a convenient means to estimate parameters in a complicated cochlear model, through variation and optimization. In turn, these parameters can be used in a more complete approximation technique (like a finite element or boundary element method) where parameter estimation can be more cumbersome. In this paper, we extend the WKB approximation to an active cochlear model, including the micromechanics of the organ of Corti (OoC) and electromotility. The model involves the OoC structural elements, basilar membrane (BM), and tectorial membrane (TM), coupled to the electrical potentials in the cochlear ducts and fluid pressure. Model predictions are compared to numerical approximations using finite elements. [Work supported by NIH-NIDCD R01-04084 and NIH NIDCD-T32-000011.]
Does providing more processing time improve speech intelligibility in hearing-impaired listeners?
Authors: Best Virginia , Mason Christine R. , Swaminathan Jayaganesh , Roverud Elin , Kidd Gerald
Published: May 2015

There is ample evidence in the literature that hearing loss increases the time taken to process speech (e.g., increased response times for word discrimination, sentence identification, and passage comprehension). This has led to the assumption that providing hearing-impaired listeners with more time to process speech would be beneficial. For sentence identification, a number of studies have examined the effects of adding silent gaps, or using time-expansion, but the results have been mixed. This may be because the distortion of natural sentence structure counteracted any benefits, or because the tasks used were not sufficiently demanding. In the current study, we re-examined this issue in young hearing-impaired listeners. By using sequences of words spoken in isolation, we were able to insert pauses between words without disrupting natural word boundaries. Furthermore, we used speech tasks involving interference in order to reveal effects that might only be apparent when the processing load is high. Although we found a statistically significant benefit of providing silent gaps between words, it was modest and was only present for some listeners in certain conditions. Overall, there was little evidence that the benefit was larger for hearing-impaired listeners or under more challenging conditions. [Work supported by NIH/NIDCD.]
Experimental results on underwater communication using vector transducers
Authors: Zhang Erjian , Abdi Ali , Chen Chen
Published: May 2015

Recent studies show that a vector transducer which excites signals in acoustic particle velocity channels can serve as a compact multichannel communication transmitter (C. Chen and A. Abdi, “Signal transmission using underwater acoustic vector transducers,” IEEE Trans. Signal Processing, 61, 3683–3698, 2013). In this paper, performance of frequency shift keying modulation is studied, both theoretically and experimentally, for data transmission via underwater particle velocity channels using a vector transducer. Multiple test environments are considered. Comparisons are also made with systems that utilize scalar transducers only. System and transducer design considerations, implementation details, and experimental results are presented in the paper as well. [Work supported in part by the National Science Foundation (NSF), Grants IIP-1340415 and CCF-0830190.]
Inter-pulse noise field during an Arctic shallow-water seismic survey
Authors: Guan Shane , Vignola Joseph F. , Judge John A. , Turo DIego , Ryan Teresa J.
Published: May 2015

Marine seismic surveys using airgun arrays generate intense underwater acoustic pulses. Those pulses may cause hearing impairment and/or behavioral disturbances in marine mammals. Few studies have investigated the resulting multipath propagation and reverberation from these pulses. This research uses acoustic recordings collected in a shallow region of the Beaufort Sea during an open-water seismic survey to characterize the noise field between airgun pulses. The disturbances between pulses are collectively referred to as the inter-pulse sound. Two methods were used to quantify the inter-pulse sound: the incremental computation method and the Hilbert transform method. The incremental computation method calculates the root-mean-squared sound pressure level in various sub-intervals, and the Hilbert transform method is used to calculate instantaneous acoustic amplitudes. Analyses using both methods yield identical results, showing that the inter-pulse sound field exceeds ambient noise levels by as much as 9 dB during relatively quiet conditions. The results also indicate that inter-pulse noise levels are related to the source distance. These two methods can be used to quantify the impact of anthropogenic transient noises on the acoustic environment and to address acoustic masking in marine mammals.
Design optimization of low density parity check codes in multipath underwater acoustic channels
Authors: Liu Shengxing , Fu Qiang
Published: May 2015

We propose an iterative decoding and equalizing scheme using low density parity check codes and decision feedback equalizer for underwater acoustic communication system. The scheme decodes and equalizes iteratively by linking a LDPC decoder with an adaptive DFE and feeding output soft information of the LDPC decoder to the DFE as priori information. We extend extrinsic information transfer (EXIT) charts to analyze the performance of LDPC codes in multipath underwater acoustic channels. Furthermore, we introduce an EXIT aided method of optimally designing the parameters of LDPC codes using modified differential evolution algorithm in multipath underwater acoustic channel. Design example and simulation are presented in two different underwater acoustic channels which are generated by BELLOP ray tracing model. Bit error rate of the proposed scheme is less than 10-5 as signal to noise rate (SNR) is greater than 8.5 dB in the channels. Compared the regular LDPC code with degree 3 and the Turbo code with feedback and feedforward generator polynomials 1+D+D2+D3 and 1+D2+D3, the optimized LDPC codes achieve gains of about 0.5 dB and 0.8 dB, respectively, at BER= 10-4 under the same code rate and block length.
Evolution of ASTM E90 for measurement of sound transmission loss and related standards
Authors: Stewart Noral D.
Published: May 2015

The history ASTM E90 for measurement of sound transmission loss will be traced from the initial release of the first tentative standard in 1950, identifying significant changes that have occurred with each revision. To a lesser degree, the history of ASTM E413 on the sound transmission class, ASTM E1322 on rating outdoor-indoor sound transmission, ASTM E336 for measurement of sound isolation and insulation in the field, and ASTM E966 on outdoor to indoor measurements will be discussed.
Place specificity of dolphin auditory evoked potentials assessed with high-pass masking noise
Authors: Finneran James J. , Mulsow Jason , Houser Dorian S. , Burkard Robert F.
Published: May 2015

Auditory evoked potential measurements are commonly used for hearing assessment in marine mammals for which psychophysical testing is not practical. Evoked potential measurements typically employ electrical signals consisting of short-duration tone-pips or sinusoidal amplitude modulated tones, which are then presented to piezoelectric underwater sound projectors. Although tone-pip and short-duration tonal stimuli may possess relatively narrow frequency bandwidth, the resulting physiological responses may possess much greater bandwidth, especially for lower frequency stimuli at higher stimulus levels. In this study, high-pass masking noise techniques were used to examine the place specificity of auditory evoked responses from click, tone-pip, and sinusoidal amplitude modulated tones in bottlenose dolphins (Tursiops truncatus). The experimental methods for generating and spectrally equalizing masking noise and click stimuli will be presented, along with the effect of compensated clicks with uncompensated clicks and ABR latencies and amplitudes. [Funded by U.S. Navy Living Marine Resources Program.]
Continental scale acoustic monitoring program: One year of data
Authors: Denes Samuel L. , Parks Susan E. , Matthews Leanna , Blair Hannah , Varshney Pramod , Fristrup Kurt
Published: May 2015

A multiyear project is underway to demonstrate the benefits of incorporating acoustic monitoring into the National Ecological Observatory Network (NEON). The NEON project seeks to generate data for the study of continental scale phenomena. Acoustic recordings can be used to determine the presence of acoustically active biota without the presence of field technicians. We have deployed stand-alone acoustic recorders at four NEON sites. Data from these recorders can be used to document spatio-temporal shifts in the presence of acoustically active species of birds, anurans, and insects. Amplitude, frequency band energy, and statistical detection methods have been compared to demonstrate the implementation of automated detection algorithms. Results from acoustic biota surveys are compared with traditional biota surveys. Comparisons of the relative contributions of acoustic energy from geophysical, biotic, and anthropogenic sources within and between sites will be examined. Preliminary results from the first year and a half of acoustic data collection will be presented. [Project supported by NSF award #1340669.]
Improving knowledge and understanding of underwater sound from exploration and production activities and potential interaction with marine life: An overview of a research program
Authors: Voparil Ian
Published: May 2015

The International Oil and Gas Producers E&P Sound & Marine Life Joint Industry Programme (JIP), a partnership of 13 oil and gas producing companies, is the world’s largest non-governmental funder of research to increase understanding of the potential effects of E&P sound on marine life. The JIP provides objective, scientific information that: Informs and updates policy decision makers and regulatory development processes that affect E&P operations globally Determines the basis for mitigation measures that are protective of marine life, cost effective, and credible with outside stakeholders feeds into planning for efficient E&P project development that is environmentally protective. Since 2006, it has spent $25 million on research and in 2013, the program embarked on a new phase with an additional budget of $18 million. The JIP regularly consults with regulators regarding their needs for data, to enable development of fact-based regulatory decisions. The program co-funds selected projects with government agencies. Research is conducted by independent scientists who are encouraged to publish their results in peer-reviewed literature. To date, JIP-funded research has been published in 75 peer-reviewed papers and all final project reports publically available. During this talk, results of the previous JIP-funded research will be presented. Furthermore, an overview of ongoing and future studies is provided.
Inhibition of Rayleigh-Bénard convection via oscillatory acceleration
Authors: Swaminathan Anand , Garrett Steven L. , Smith Robert W.
Published: May 2015

The ability to dynamically stabilize Rayleigh-Bénard convection by imposition of sinusoidal acceleration is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the machine. These performance issues, tentatively attributed to convective instability, have been observed both in traveling wave thermoacoustic refrigerators and in pulse tube cryocoolers. This presentation discusses an ongoing experiment designed to determine the vibratory conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, to test the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135(2), 654–668 (2014)]. Measurement methods developed to determine the onset and inhibition of convection will be discussed. These include the measurement of heat transport employing a feedback thermal control loop and direct optical observation using a lightsheet produced by a laser diode source illuminating seeded particles. Preliminary results in both the static and vibratory conditions will be presented. [Work supported by the ARL Walker Graduate Assistantship, the Office of Naval Research, and ARPA-E.]
Numerical investigation of aeroacoustic characteristics of a circular cylinder in cross-flow and in yaw
Authors: Liu Xiaowan , Thompson David J. , Hu Zhiwei , Jurdic Vincent
Published: May 2015

It is well known that aerodynamic noise becomes dominant when the speed of high-speed trains exceeds about 300 km/h. The pantograph is one of the main aerodynamic noise sources, particularly in the presence of noise barriers which shield the sources on the lower part of the train more effectively. The pantograph consists of a number of slender bodies with different cross-sections. In the current research, the aerodynamic characteristics of a circular cylinder have been investigated through computational fluid dynamics simulations using a Delayed Detached-Eddy Simulation model. Then the aeroacoustic behaviour has been predicted by using Ffowcs Williams-Hawkings equation. Simulations have been carried out for various speeds, resulting in a wide range of Reynolds number, which includes subcritical, critical, and supercritical flow states. The results have been compared with experiments and give good agreement. As the pantograph arms are inclined to the flow, the effect of yaw angle is analyzed in this paper and the effect on vortex-shedding frequency and noise level is determined. Moreover, it is demonstrated that the critical Reynolds number, which determines the beginning of the critical flow state, is affected by the yaw angle. In addition, considering the high turbulence intensity on the train roof, a turbulent inflow with different levels of intensity has been considered and the results will be presented.
Pitch perception: Spectral and temporal integration at very high frequencies
Authors: Lau Bonnie K. , Oxenham Andrew J.
Published: May 2015

Recent work has shown that complex pitch can be extracted from spectrally resolved harmonics, even when all the harmonics are higher than 6 kHz, and so unlikely to be represented by a temporal phase-locked neural code. This study measured spectral and temporal integration of frequency and fundamental-frequency (F0) discrimination at such high frequencies and compared the patterns of results to those obtained at lower frequencies. Difference between the present and earlier studies included the use of level roving on individual components to reduce loudness cues, and the careful control of audibility at very high frequencies. The low and high spectral regions consisted of harmonics 6–10 of two nominal F0s (280 and 1400 Hz). F0 difference limens (DLs) of the complexes and DLs of each harmonic individually were measured at two durations (30 and 210 ms) to measure spectral and temporal integration effects. All tones were presented in background noise to mask distortion products. Preliminary data show similar temporal integration at low and high frequencies, but very different spectral integration, with high-frequency F0DLs generally lower than predicted by a simple detection-theory model. The results suggest different integration mechanisms in the two regions. [Work supported by NIH grant R01DC05216.]
Effects of resolved and unresolved harmonics in the perception of multiple pitches
Authors: Graves Jackson E. , Oxenham Andrew J.
Published: May 2015

The mechanisms underlying pitch perception have been studied for several decades. Most studies have concentrated on the pitch of single sounds, some have investigated the pitch of two simultaneously presented sounds, but few if any have investigated pitch perception with three or more simultaneous pitches. In contrast, in music it is rule, rather than the exception, that we are presented with multiple pitches. Here, pitch perception was studied with three simultaneously presented harmonic complexes, filtered into a single bandpass region to control the extent to which harmonics from each of the three tones were spectrally resolved. The tones comprised the three possible inversions of the major or minor triad, and the listener’s task was to discriminate between major and minor. Preliminary data suggest that subjects who could reliably discriminate major and minor triads in a pure tone training task were also capable of this discrimination when tone complexes were filtered such that the combination of harmonic components should have been unresolved on the cochlea. This finding suggests resolved harmonics may not be necessary to extract the pitch from multiple complex tones. Predictions from various spectral and temporal models of pitch were compared with the results. [Work supported by NIH grant R01DC05216.]
Sound source similarity influences change perception during complex scene perception
Authors: Dickerson Kelly , Gaston Jeremy , Foots Ashley , Mermagen Timothy
Published: May 2015

Everyday listening involves identifying an ever-changing milieu of sound sources in the environment. Recent studies have demonstrated that change perception during complex listening tasks is highly error prone; errors can exceed 30% for sounds that are clearly detectable and identifiable in isolation. This change deafness has been generally attributed to failures of attention or memory. The current study investigates the possibility that lower-level informational effects such as acoustic or semantic similarity are predictive of change perception errors. Listeners were briefly presented with pairs of auditory scenes. In experiment 1, the listeners’ were asked to identify if a change in sound source occurred. In experiment 2, listeners were asked to indicate where a change occurred across an array of loudspeakers. Results indicate that performance on the change identification and localization task was strongly influenced by the degree of similarity between the changed source and the “background” sources. Further, the semantic heterogeneity of the background seemed to be important predictor of performance on these change perception task.
Forward masking in children and adults with normal hearing and hearing loss
Authors: Brennan Marc A. , Jesteadt Walt , McCreery Ryan
Published: May 2015

The objective was to determine the extent to which childhood hearing loss can affect the development of temporal resolution. Participants were divided into those with and without hearing loss. Participants included 16 children per group (normal hearing, hearing loss) and 14 adults per group. Forward-masked thresholds for a 2 kHz masker and target (10 ms signal delay) were measured at similar points on the dynamic range for the participants with normal hearing and hearing loss. As expected, the amount of masking decreased with age. Due to their hearing loss, the participants with hearing loss were tested at lower masker sensation levels than the participants with normal hearing. For that reason, it was expected that less masking would occur for the participants with hearing loss, and this was observed in the data. It was hypothesized that age and hearing loss would interact, such that the younger children with hearing loss would show greater masking than younger children with normal hearing. Instead, both children with normal hearing and with hearing loss showed higher masking than their adult counterparts, suggesting that the amount of masking did not interact with age and hearing status. These findings suggest that children show less efficient temporal processing.