bluuebunny/crossref_metadata_2025 huggingface dataset:
Engine configurations for the Silent Aircraft
Authors: Hall Cesare
Published: October 2013

The Silent Aircraft Initiative is a Cambridge-MIT Institute research project aimed at reducing aircraft noise to the point where it would be unnoticeable in the urban areas around airports. This talk investigates viable engine and installation options that can meet the Silent Aircraft noise requirements. To reduce the transmitted jet noise sufficiently, it is found that a very large exhaust nozzle area is required. If this is achieved with a conventional turbofan it leads to a very high engine diameter and low fan pressure ratio. The large diameter results in greater engine weight and unacceptably high installation drag at cruise. The low fan pressure ratio makes the engine more susceptible to operability problems such as fan stall and vibration, which lead to a further increase in weight. This presentation demonstrates how these problems can be mitigated with a propulsion system that has a variable cycle combined with a novel installation that is embedded into the airframe. Several suitable engine concepts are considered in detail and each configuration is assessed in terms of its relative performance, weight, noise emission, and operability.
Innovative aircraft design for step changes in noise reduction
Authors: Spakovszky Zoltan S.
Published: October 2013

Low-noise integrated propulsion system concepts are proposed for functionally silent aircraft with the goal to reduce airframe and propulsion system noise by as much as 30 dB. Silent in this context means sufficiently quiet that the aircraft noise is less than that of the background noise in a typical well-populated environment. The theme of the technical approach for this multi-disciplinary problem is based on a systems view rather than an individual component view of the airframe and interacting propulsion system. Simple analytical modeling and existing semi-empirical noise prediction methods and scaling laws are used to predict the acoustic signature of low-noise airframe and propulsion system concepts envisioned for a functionally silent aircraft. The design study and acoustic analysis is based on an aerodynamically clean blended-wing-body-type airframe configuration. A distributed propulsion system is proposed to facilitate airframe boundary layer ingestion and to take advantage of shielding effects by embedding engines in the airframe. Ultra-high bypass ratio engines are necessary to reduce jet noise and multiple small engines or a multi-fan engine system is envisioned to enable integrating the propulsion system with the airframe. Results from the noise assessment studies are discussed and preliminary design implications for a functionally silent aircraft are given.
Control of supersonic jet noise with a spherical reflector
Authors: Islam Md. Tawhidul Khan , Seto Kunisato
Published: October 2013

Jet screech is considered to be generated from a feedback cycle in an underexpanded supersonic jet. Experiments were carried out to control the screech tone by placing a spherical reflector at the nozzle exit. The reflector controlled the location of the sound image-source and minimized the sound pressure at the nozzle exit. The weak sound could not excite the unstable disturbances at the exit and the feedback mechanism was cancelled and finally screech tone was eliminated. The new technique suppressed not only the screech tones but also the broadband noise and reduced the overall sound pressure of the jet. The performance of the proposed technique was checked with different sizes of reflectors by placing the reflectors at different upstream positions of the nozzle exit for different pressure ratios and the result was very good. [The research was supported by a grant from JSPS of the government of Japan.]
The effect of surfactants on inertial cavitation activity and sonoluminescence intensity in aqueous solutions
Authors: Ashokkumar Muthupandian , Lee Judy , Kentish Sandra , Grieser Franz , Matula Thomas J.
Published: October 2013

The understanding and influencing of bubble clusters in an ultrasonic filed is important for many applications. We have investigated the various concentration-dependent effects of sodium dodecyl sulfate (SDS), an anionic surfactant, in aqueous solutions on bubble coalescence, stability of bubble nuclei and rate of bubble growth in an ultrasonic field. For example, the addition of low concentrations of SDS has been found [J. Phys. Chem. B, 101, 10845 1997] to enhance the intensity of multibubble sonoluminescence (MBSL). Further investigations on the effect of SDS on MBSL intensity have revealed that the SL enhancement observed is highly dependent on the ultrasound pulse length. We have observed that there exists a critical (ultrasound) pulse length below which the addition of SDS in fact lowers the MBSL intensity relative to that observed from water. The inertial cavitation activity has been experimentally measured under similar conditions to that of the SL experiments and has been found to correlate with MBSL results. Both MBSL and inertial cavitation activity results suggest that the presence of SDS at higher concentrations could also enhance the rate of bubble growth by rectified diffusion. This presentation will focus on how specific surfactants influence bubble cluster dynamics and bubble coalescence.
Temporal evolution of sigle bubble sonoluminescence spectra: From bubble creation to stabilization
Authors: Young Jeremy , Matula Thomas
Published: October 2013

Single bubble sonoluminescence (SBSL) is generated by creating and levitating a bubble at the pressure antinode of a standing wave. Previously, it was determined that the SBSL total light intensity evolves during the stabilization process [T. J. Matula and L. A. Crum, Phys. Rev. Lett. 80, 865–868 (1998)]. The evolution process was used to confirm a theoretical hypothesis that chemical diffusion effects were important for stable SBSL. In this talk we report how the emission spectrum evolves over time, from bubble creation to stabilization. SBSL was generated in a 100-ml spherical cell filled with degassed (air) filtered water. Boiling from a nichrome wire created bubbles which were then forced to the pressure antinode. Spectra were recorded with a multichannel PMT (Burle Industries) using 16 color channels in a 4×4 grid with 20-nm bandwidth interference filters covering the range from 250 to 625 nm. Continuous recording of the spectra (with a 192-ms integration time) was performed until the bubble stabilized. Spatial, crosstalk, filter, and tube response calibrations were performed. Temporal evolution measurements showed evidence of an early-stage emission band near 300 nm, suggesting that hydroxyl emission becomes swamped by the continuum during stabilization. [Research was funded by NASA.]
Relative contribution of temporal cues and spectral profile to voice gender discrimination
Authors: Chinchilla-Rodriguez Sherol , Nogaki Geri , Fu Qian-Jie
Published: October 2013

Despite limited access to spectral and temporal cues, cochlear implant (CI) users are somewhat able to discriminate voice gender. The present study explored the relative contributions of spectral and temporal cues to normal-hearing (NH) subjects’ voice gender discrimination, while listening to multi-channel simulations of CI processing. The output spectrum was either matched (relative to normal) or upwardly shifted to simulate the spectral shift associated with CIs; the envelope filter in each channel was varied to examine the contribution of temporal cues. Voice gender discrimination was tested with two talker sets, in which the mean fundamental frequency (F0) between male and female talkers was either widely or narrowly separated. Results showed that for both talker sets, 16 spectral channels were needed before subjects could use the spectral profile to identify voice gender; when the speech spectrum was shifted, 32 channels were needed. Given enough temporal cues, the spectral profile had a relatively small effect on discrimination when the F0 was widely separated between male and female talkers. When there was little F0 separation between male and female talkers, the spectral profile had a much stronger effect; however, 16 or more channels were needed before listeners could attend to the profile. [Work supported by NIDCD-RO1-DC004993.]
Vocal tract influence on medial surface dynamics of the vocal folds
Authors: Doellinger Michael , Berry David , Montequin Douglas
Published: October 2013

In previous work, quantitative measurement of the medial surface dynamics of the vocal folds was reported using a hemilarynx methodology. The technique was applied to excised larynges from both humans and canines, as well as to in vivo canine larynges. In the present investigation, a vocal tract was attached to the excised hemilarynx preparation, and systematic changes were made in vocal tract shape to study its influence on the medial surface dynamics. In particular, the width of the epilarynx was varied across experiments. Previously, in a similar experiment, phonation threshold pressure was investigated as a function of epilarynx width. It has also been shown that epilarynx width has an influence on glottal volume velocity and the acoustic output [I. R. Titze and B. H. Story, J. Acoust. Soc. Am. 101, 2234–2243]. However, the direct influence of the epilarynx width on vocal fold vibration has never been quantified. The present investigation considered the impact of epilarynx width on the medial surface dynamics, including the underlying empirical eigenfunctions which make up the vibration patterns. Further, quantitative measures such as displacement and velocity were reported and compared. [Work supported by NIH/NIDCD Grant No. R01 DC03072.]
A comparison of three algorithms for estimating aspiration noise in dysphonic voices
Authors: Goor Mina , Shrivastav Rahul , Harris John G.
Published: October 2013

Dysphonic voices are frequently characterized by increased aspiration noise. Several algorithms have been proposed to quantify the noise present in such voices. Yet, an independent analysis of these algorithms has not been reported. These algorithms differ in a number of aspects such as the theory underlying these measurements, the procedures used for estimating the noise, and the nature of their output. Three different algorithms for estimating noise in dysphonic voices were implemented in MATLAB and their output for synthetic and natural voice samples compared. These algorithms include: (1) the pitch-predictive signal-to-noise ratio reported by Milenkovic [Workshop on Acoustic Voice Analysis: Proceedings (1994)], which analyzes signals in the time domain and provides a time waveform of the aspiration noise: (2) the harmonics-to-noise ratio reported by deKrom [J. Speech Hear Res., 36, 254–266 (1993)], which performs a cepstral analysis to provide the spectrum of the aspiration noise; and (3) the glottal-noise excitation reported by Michaelis, Frohlich, and Strube [J. Acoust. Soc. Am. 103, 1628–1639 (1998)], which measures the correlation of the Hilbert transform of different frequency bands. The result of the study will help identify the algorithm(s) most suitable in the prediction of the listener judgments of voice quality. [Research supported by NIH/R21DC006690-01.]
Boundary array size for teleconferencing
Authors: Macomber Dwight F.
Published: October 2013

Boundary arrays for teleconferencing require large numbers of sensors to be effective. The paper describes efforts to estimate the number of microphones required for an effective teleconference boundary array. Measurements of many source-to-sensor room transfer functions (RTF) were made in a conference room of moderate size. The direct arrivals of these RTFs were time aligned in software to estimate the transfer function of a delay-and-sum boundary array. Using the image method of Allen and Berkley, another set of RTFs was generated for a virtual room acoustically similar to the measured room. These RTFs were time aligned to create a second virtual array. The S/Rs of these two virtual arrays compare favorably. The image method was used to estimate transfer functions of virtual boundary arrays of different sizes for a 60-cubic-meter room. Standard beamforming and matched-filter processing were used. TIMIT speech was convolved with the virtual array transfer functions to generate audio used for evaluation. A listening test ranked the auditory performance of four single-microphone reference systems and eight test arrays in the virtual room. For rooms of roughly 100 cubic meters, boundary arrays with approximately 100 microphones may provide good subjective performance.
Beam summation algorithm for wave radiation and propagation in stratified media
Authors: Heilpern Tal , Heyman Ehud
Published: October 2013

An efficient Gaussian beams summation (GBS) algorithm for tracking source excited wavefields in plane stratified media is introduced. It has two important features: (a) it involves an efficient calculation of the GB propagators, and (b) it involves rather sparse lattice of beams. For (a) we approximate the medium using layers with constant wavespeed gradient, and derive an efficient recursive algorithm for tracking the GB through such medium. This model not only reduces the number of layers, and thereby the algorithm complexity, in comparison with the conventional uniform layers model, but it also eliminates the reflection artifacts at layers interfaces. Property (b) is achieved by determining the beam expansion parameters for an efficient discretization of the source-excited beam spectra using a sparse lattice of beams. The algorithm has been validated and calibrated via thorough numerical comparisons with closed form ray solutions for source-excited fields in layered media. Perfect agreement between these independent solutions has been obtained in regions where the ray solution is valid, but the beam formulation also provided smooth and physically meaningful solutions in caustic regions where the ray solution fails.
Fluctuations in sound transmission through velocity profiles that are periodic in range and in geo-time
Authors: George Jacob , Field Robert L.
Published: October 2013

The lunar M2 tides cause variations in sound velocity profiles that are periodic in range and in geo-time. Acoustic transmissions through such an environment exhibit fluctuations at the primary tidal frequency as well as its overtones, due to nonlinear dependence on sound speeds. The number of tidal cycles within the source-receiver range is found to be a major factor that determines the magnitude and nature of the fluctuations. This has been investigated using parabolic equation (PE) models and by modal analysis. In the WKB model the important phase factor consists of a range integral of the horizontal wave number of each mode. A study of this integral has revealed a dramatic decrease in fluctuations when the number of tidal cycles within a constant source-receiver range increases. This result directly impacts transmissions that are at variable angles measured from the direction of the tides. Pulse transmission through the tidal environment has also been investigated, and the results are similar to those described above. [Work supported by ONR.]
Time-domain sound propagation through a ship wake
Authors: Di Xiao , Culver Lee , Bradley David
Published: October 2013

A time-series model has been developed to visualize high-frequency pulses propagating through the bubbly wake of a ship. The wakes can have very large void fractions, and thus strong inhomogeneities in sound speed, scattering cross section, and acoustic attenuation. The model uses the Green’s function PE to calculate the pressure field at frequencies within the bandwidth of the acoustic pulse, followed by Fourier synthesis to calculate time-domain solutions over a range of times. Special care was required to preserve the phase of the pressure at each frequency. Our concern is with quasihorizontal propagation and source–receiver ranges from about 100 to 1000 m, which contain effects of bubbles on propagation including attenuation, refraction, and scattering. We show predictions using a simple model for the distribution of bubbles in a ship wake. We find a very interesting frequency dependence for refraction and scattering. [Work supported by ONR Code 321.]
Comparison of real world measurements and computer model results for a dedicated coupled volume system
Authors: Bradley David T. , Wang Lily M.
Published: October 2013

A dedicated coupled volume system consists of a larger main space connected through an opening, or coupling aperture, with a smaller auxiliary space specifically designed to produce a double slope effect (DSE). DSE can be achieved if the absorption characteristics in the secondary space are such that its decay time is longer than that of the main space, which in turn causes late-arriving energy to be fed back into the main space. This project focuses on the verification of computer modeling as an accurate method for analyzing dedicated coupled volume systems. Impulse response measurements were taken in a real world coupled volume hall. The amount of absorption in the main hall and the number of open apertures were systematically varied to create a series of configurations for which the impulse responses were measured. The same configurations of the hall were modeled in the computer aided acoustical modeling program, ODEON. Comparisons of the impulse responses from the real world measurements and the computer model are presented both qualitatively and quantitatively through examining pertinent objective acoustical measures, such as reverberation times (T30, T15) and clarity index (C80).
Decay time uncertainty analysis in acoustically coupled spaces
Authors: Xiang Ning , Kleiner Mendel , Jasa Tomislow
Published: October 2013

In order to guide acoustic design and to verify the design goals, evaluations of multiple decay times in coupled spaces are of practical significance when designing coupled volumes in performing art spaces. Traditionally, however, identification of double- or multiple-sloped decay in room impulse response measurement has been considered very challenging. Previous works [Xiang and Goggans, J. Acoust. Soc. Am., 110, 1415–1424 (2001); 113, 2685–2697 (2003)] have applied Bayesian framework to cope with the demanding tasks in estimating multiple decay times from Schroeder decay functions, evaluated from measured room impulse responses. The Bayesian approaches have also been applied in systematic investigation of double-slope decay in coupled volumes with respect to volume ratio, absorption ratio, and aperture size [Bradley and Wang, J. Acoust. Soc. Am. 113, 2188 (2003) (A)]. These recent applications of Bayesian approaches stimulate further study of uncertainties associated with decay time estimation. This paper discusses the estimation uncertainties and interrelationships between multiple decay times within Bayesian framework.
Reverberated sound field modeling in coupled rooms using a diffusion equation
Authors: Billon Alexis , Valeau Vincent , Sakout Anas , Picaut Judical
Published: October 2013

Sound modeling in coupled rooms has attracted considerable attention in the past, but accurate and operational models are still needed. In recent papers, a diffusion equation based model has been applied with success to unusual room shapes. This approach allows nonuniform repartition of energy, and is especially relevant in room acoustics for long rooms or complex spaces such as networks of rooms. The present work aims at validating the behavior of the diffusion model in the case of two acoustically coupled rooms separated by an open area. In this purpose, the time-dependent diffusion equation is solved in three dimensions using a finite-element solver. It allows one to predict both sound attenuation and reverberation time at any point of the coupled rooms. Parameters influencing the coupling, i.e., room relative sizes, aperture size and room absorption areas, are investigated. Results are then compared with the classical statistical theory of coupled rooms. Finally, a comparison with experimental data in two coupled classrooms is also provided.
Differential response by manatees to playbacks of sounds simulating approaching vessels
Authors: Miksis-Olds Jennifer L. , Donaghay Percy L. , Miller James H. , Tyack Peter L. , Reynolds John E.
Published: October 2013

One of the most pressing concerns associated with the endangered Florida manatee is mortality due to collisions with watercraft. Watercraft collisions are the leading identified cause of adult mortality, resulting in greater than 30% of manatee deaths each year. Reducing adult mortalities is critical to the recovery of the manatee population, as population trends are more sensitive to adult deaths than to those of other age groups. Acoustic playback experiments were conducted to assess the behavioral responses of manatees to watercraft approaches. Playback stimuli were constructed to simulate a vessel approach to approximately 10 m in seagrass habitats. Stimulus categories were (1) silent control; (2) idle outboard approach; (3) planing outboard approach; and (4) fast personal watercraft approach. These results are the first to document responses of wild manatees to playback stimuli. Analyses of swim speed, changes in behavioral state, and respiration rate indicate that the animals respond differentially to the playback categories. The most pronounced responses, relative to the controls, were elicited by the personal watercraft. Quantitative documentation of response during playbacks will provide data that may be used as the basis for future models to predict the impact of specific human activities on manatee and other marine mammal populations.
The sensitivity of far-field measurements in shallow water to the geoacoustic properties of the seabed
Authors: Poole Travis L. , Frisk George V.
Published: October 2013

Because sound propagating through shallow water interacts strongly with the seafloor, measurements of the pressure field can be used in geoacoustic inversion algorithms to determine the sound speed profile in the bottom. However, the sound most easily measured is that which is concentrated in the water rather than in the bottom. Furthermore, only sound that propagates at shallow angles reaches a receiver far from the source because only these shallow-angle paths undergo total reflection from the bottom as well as the surface. In light of this behavior, an investigation is made into the sensitivity of this shallow-angle portion of the pressure field to changes in bottom properties. Also addressed is the manner in which this sensitivity affects geoacoustic inversion schemes and their ability to accurately determine bottom properties from far-field pressure measurements. [Work supported by ONR.]
Musical effects of the digital pressure-controlled valve
Authors: Smyth Tamara , Abel Jonathan S. , Smith Julius O.
Published: October 2013

In computer music, a digital simulation of the pressure-controlled valve is required to model many wind instruments and vocal systems. The method used for simulating the valve usually depends on how closely it corresponds to any of three simple configurations for valves in acoustic tubes. The classification of the valve is determined by whether an additional upstream or downstream pressure causes the valve to open or close further on the corresponding side. In this work, a configurable model of a pressure controlled valve is implemented, allowing the user to design a valve simply by changing the model parameters. The user may design three simple models: one that is blown closed (like woodwinds or reed-pipes), one that is blown open (as in simple lip-reeds, the human larynx, harmonicas and harmoniums) and the transverse model (as in the bird’s vocal organ, the syrinx). Using the computer model, the musical applications of different valve configurations and topologies (where valves are arranged in series and in parallel) will be examined. For several cases, observations will be made on how the valve couples differently with the tube-resonator and how this affects the produced sound.
Unexpected elastic softening in delta-plutonium
Authors: Migliori A. , Ledbetter H. , Betts J. B.
Published: October 2013

Elastic-constant measurements on a Pu 2.4-at.-% Ga quasiisotropic polycrystal reveal remarkable elastic softening as temperature increases from ambient to 550 K. Unexpected softening appears in both the bulk modulus B and the shear modulus G, thus in all quasi-isotropic elastic stiffnesses Cij such as the Young modulus and the constants. The dB/dT slope gives a (lattice) Gruneissen parameter =6.0, enormously higher than a typical f.c.c.-metallic-element value of 2.4. Especially, this high value from dB/dT measurements disagrees strongly with the value from volume measurements of −0.26. The dB/dT slope exceeds that measured previously at lower temperatures. Also, it exceeds that expected from high-temperature Debye–Waller-factor measurements. A two-level model used successfully previously to interpret this alloy’s unusually low thermal expansion fails to explain the large dCij/dT. We comment on other possible explanations for plutonium’s odd anharmonic behavior. These concepts include magnetism, 5f-electron localization-delocalization, and vibrational entropy. Our measurements on a Pu–Ga polycrystal agree remarkably well with a Kröner-theory average of previous measurements on a same-composition monocrystal. [Work supported by the State of Florida, the National Science Foundation, and the NNSA.]
Bow-thruster noise remediation in R
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Authors: Brown Neal A.
Published: October 2013

A program was initiated for Scripps Institution of Oceanography, sponsored by ONR, to silence the bow thruster in the research vessel ROGER REVELLE, AGOR-24. The ship suffered habitability problems during long-term dynamic positioning operations. A one-half-scale mockup of the ship’s bow thruster, sea chest, guard grids, and local hull surfaces was constructed for air tests. By measuring velocity distributions at the (absent) impeller location while separately drawing air through the mockup system at high velocity, it was demonstrated by calculation that the offending noise originated in unsteady cavitation of the impeller of the vertical-axis thruster. Several modifications to improve the flow were designed and evaluated in the mockup. Further, a modified impeller was designed on the basis of cavitation avoidance. The new impeller was designed-in-detail, manufactured, and installed along with several structural modifications of the thruster and sea chest, approved by the thruster manufacturer, during ship overhaul. No additional acoustic treatments were applied. Quantitative measurements of compartment levels of noise and vibration, and structural and water-borne noise were carried out to compare with premodification measurements. Results now indicate an absence of bow-thruster cavitation noise in adjacent compartments during DP operations. Thrust performance was preserved.
Stability in perceptual assimilation: Talker and vowel context effects
Authors: Yeon Sang-hee , Wayland Ratree , Harnsberger James , Silver Jenna
Published: October 2013

A study was conducted to examine methodological and phonetic context variables in the discrimination and identification of non-native speech sounds and the stability of these patterns across experimental conditions. Native speakers of American English were presented with two voicing contrasts produced by three Hindi speakers, [k]–[g] and [t■]−[d■]. They appeared word-initially and in three vowel contexts [a, i, u] in a forced choice identification test and in a categorical AXB discrimination test. In the discrimination test, listeners were assigned to two conditions: (1) trials in which stimuli were produced by a single talker and (2) trials in which each stimulus was produced by a different talker. Single vs multiple talkers within trials were used to determine if a stronger correlation would be observed between identification and discrimination if listeners were forced to rely on more abstract representations in long-term memory when coping with talker variability. Multiple vowel contexts were employed to examine the stability of perceptual assimilation patterns. The results of pilot studies have demonstrated a significant vowel context effect on both identification and discrimination effect as well as a significant talker effect. The implications of the results for models of cross-language speech perception will be discussed.
Optimizing measures of the perceptual assimilation of stop consonants
Authors: Harnsberger James , Yeon Sang-hee , Silver Jenna
Published: October 2013

A study was conducted to examine methodological variables in the perceptual assimilation of non-native speech sounds. Native speakers of American English were presented with two voicing contrasts produced by three Hindi speakers, [k]–[g] and [t■]−[d■]. They appeared word-initially and in three vowel contexts [a, i, u]. Listeners were assigned to two groups. The first group was administered a categorical AXB discrimination test and a traditional forced-choice identification test in which stimuli were presented in isolation. The second group was administered the same discrimination test, but the identification test involved judging stimuli in the same context in which they appeared in the discrimination test (AXB identification). Pilot studies have shown a significant correlation with predicted discrimination scores based on the identification test, but the correlation was stronger between the AXB discrimination and AXB identification tests. A similar study was also conducted with Hindi listeners identifying and discriminating six Korean stop contrasts ([t–th], [t–t’], [t’–th], [k–kh], [k–k’] and [k’–kh] from one talker. These results highlight the importance of selecting optimized tasks in order to test hypotheses concerning the role of linguistic experience in speech perception.
The influence of language experience on perception: The case of Spanish and English
Authors: Hall Kathleen Currie , Hume Elizabeth , Johnson Keith , Boomershine Amanda
Published: October 2013

Native speakers can distinguish sounds that serve a contrastive function in their language better than those that do not, but the role of allophony in speech perception is understudied. The present study tests the influence of the allophonic/phonemic distinction on ratings of perceptual similarity given by Spanish and English listeners to pairs of stimuli contrasting [d], [r], and [■]. These sounds have different phonological relations in the two languages: [d] and [r] are allophonic in English and contrastive in Spanish, while [d] vs [■] are allophonic in Spanish but contrastive in English. The study also investigated to what extent, if any, degree of experience/proficiency with a non-native language influences perception. The results suggest that native language but not level of language proficiency in L2 affects rated similarity. In particular, whether or not sounds are in an allophonic or contrastive relationship in the native language shapes how these sounds are perceived. [Work supported by NIDCD Grant R01 DC04421-4.]
Training effects on native and novel linguistic categories
Authors: McGuire Grant L.
Published: October 2013

Categorical perception (e.g., Liberman et al., 1957) and the perceptual magnet effect (Kuhl, 1991) are frequently invoked to help explain how the perceptual system deals with highly variable speech input by warping the perceptual system in favor of native contrasts. Research into L2 acquisition demonstrates that this warping can be overcome and non-native categories can be introduced to listeners with extensive training (e.g., Logan et al., 1991); further studies into novel category acquisition have shown a perceptual magnet effect for nonspeech stimuli (Guenther et al., 1999). This paper addresses native English speakers’ acquisition of a novel category, the velar fricative /x/, by testing the effects of category labeling and discrimination training on subjects sensory trace and context coding auditory modes. The results demonstrate training affects the novel category differently from the native categories, with labeling training creating a perceptual magnetlike effect only in the novel category. Both types of training increased subjects’ abilities to discriminate categories, but mixed testing and training types (i.e., categorical testing with noncategorical training and vice versa) resulted in the greatest improvements.
Mandarin and English listeners’ perception of Mandarin tones in isolation and in context
Authors: Bent Tessa
Published: October 2013

A comprehensive model of cross-language speech perception must account for all aspects of phonological structure. However, current models focus primarily on phonemic categories and exclude cross-language perception of prosodic structure. The cross-language interaction of prosodic categories in non-native listeners is difficult to model in current frameworks because multiple prosodic units must be considered as possible sources of transfer and interference including lexical tone, word stress, pitch accent, and phrasal intonation patterns. This study tested the hypothesis that perception of non-native prosodic contours is affected by both the relationship between the native and non-native languages’ prosodic contour categories and the unit length over which the contours apply. Native English and Mandarin listeners’ discrimination of the four Mandarin lexical tones in isolated monosyllables and three-syllable sequences was tested. Reactions times to correctly discriminated ‘‘different’’ trials were entered into a multidimensional scaling analysis. In the English listeners’ similarity spaces, the configuration of the four lexical tones differed in the three-syllable context compared to their perception in isolation. In the Mandarin listeners’ similarity spaces, the isolated tones were arranged in triangular formation with the rising and dipping tones in close proximity, but for the three-syllable stimuli, all tones were well separated. [Work supported by NIH/NIDCD.]
The acquisition of absolute pitch for the mainstreamed, special educational needs and academically talented under Lau Chiu Kay Music Educatherapy
Authors: Lau C. Kay
Published: October 2013

Absolute pitch (AP) is an ability to identify or produce tones without references. It is rare among musicians. This study examined the effectiveness of Lau Chiu Kay Music Educatherapy in training students to develop AP and identified factors that exerted significant influences. Three academically talented, 103 mainstreamed and 38 special educational needs students at Music Home, with an age range of 2 to 25, constituted the sample. It was a case study incorporating a one-group-pretest-post-test quasi-experiment. An AP assessment and a questionnaire were utilized. Results showed that (a) Lau Chiu Kay Music Educatherapy helped all subjects to develop AP. (b) Singing absolute solfge, accurate tuning, interest and attention were influencing factors, whereas the gender, aptitude, age of onset, language background, acute memory, auditory sensitivity, pitch identification practice, inheritance, tinnitus and chromesthesia were not. (c) AP could be developed within one to two months and during the starting grade of the piano learning. (d) The verbal encoding strategy was the major processing strategy, etc. Following theories can be suggested: (a) AP is innate. (b) AP is a successful outcome of the tonal-absolute solfge with the octave designation labelling association. (c) AP may have a sensitive period. (d) AP is developmental etc.
Classifying sidescan sonar images using self organizing maps
Authors: Ioup Juliette W. , Gendron Marlin L. , Lohrenz Maura C. , Layne Geary J. , Ioup George E.
Published: October 2013

Self organizing maps (SOMs) can be used for computer-aided classification of objects found in two-dimensional snippets of sidescan sonar images. SOMs are briefly discussed, including the choice of features or attributes as well as various types of input data. The inputs can be, for example, the data values themselves, either raw or processed images; the amplitudes of the Fourier transform coefficients of the data; the wavelet transform coefficients of the data; the energies of the horizontal, vertical, or diagonal wavelet coefficients; the autocorrelation of the data; the Hartley transform coefficients of the data; the cepstrum; the dimensions of the object; or the sonar bright spot and shadow character. Tabular results and two-dimensional maps showing the groupings of measured and processed sidescan data are presented. Comparisons are made with human classifications of the same images. [Research supported in part by NRL-ASEE Summer Faculty Research Program.]
Digital algorithms for computing the time-corrected instantaneous frequency (reassigned) spectrogram, with applications
Authors: Fitz Kelly , Fulop Sean A.
Published: October 2013

The channelized instantaneous frequency of a signal x(t) is CIFx(ω,T)=(∂/∂T)arg(Fh(ω,T)), where Fh is the short-time Fourier transform of x(t) using window function h. The local group delay of a signal is LGDx(ω,T)=−(∂/∂ω)arg(Fh(ω,T)). For each point Fh(ω0,T0) in the STFT, the f−t coordinates [CIF(ω0,T0),t−LGD(ω0,T0)] pinpoint the local mean of the Rihacek distribution of complex signal energy, and this reassignment of the STFT magnitude yields a spectrogram from which a lot of blurriness is removed. Two algorithms which compute such a reassigned spectrogram are exemplified and evaluated. One is based on the theory of Nelson [‘‘Cross-spectral methods for processing speech,’’ J. Acoust. Soc. Am. 110(5), 2575–2592 (2001)]; the second implements the equations of Auger and Flandrin [‘‘Improving the readability of time-frequency and time-scale representations by the reassignment method,’’ IEEE Trans. Signal Process 43(5), 1068–1089 (1995)]. The empirical performance of each technique is qualitatively evaluated; both methods dramatically improve upon the standard spectrogram, and also surpass the naive benchmark provided by first-difference approximation of the phase derivatives. High-resolution spectrograms are provided for both music and speech signals; e.g., the time-frequency nature of a single glottal pulsation can be observed. Applications to sound morphing are also demonstrated, e.g., morphing voices and musical instruments.
Ten years of classroom acoustical design
Authors: Campanella Angelo J.
Published: October 2013

Bradley found [J. Acoust. Soc. Am. 80, 837–845] with word score tests that S/N and room reverberation time (RT) affect speech intelligibility, and that computed U50 [J. Acoust. Soc. Am. 80, 846–854] was maximum for rooms having RT<0.6 sec and quieter than 35 dBA. This was applied to teleconferencing rooms [J. Acoust. Soc. Am. 111, 2411(A)], and classrooms for distance learning [J. Acoust. Soc. Am. 107, 2861(A)]. Economic strategies to reduce classroom RT and HVAC noise were developed. RT from 0.5 to 0.7 s and NC less than 30 are economically achieved: Absorption is provided by acoustical ceiling tiles of NRC>0.6. Carpets help. Chalk and cork boards provide some wall absorption, while in-use posters and book storage add more later. Central air handling systems promote NC-25 HVAC design. Noisy supply (VAV) air boxes are placed in the corridor ceiling. The transmitting manifold is lined. A flexible duct link to diffusers provides more noise attenuation at no added cost. Larger supply air diffusers satisfy NC-25. Common ceiling return air plenums compromise noise isolation between classrooms. High CAC ceiling tiles and return air openings near the room center provide NIC>40 versus recommended NIC50. Sketches and some cost estimates are provided.
The study of whales with sound: the legacy of Paul Thompson
Authors: Hildebrand John A.
Published: October 2013

Passive acoustic monitoring of whales offers a complementary technique to traditional visual survey for assessment of whale populations. The development of whale acoustic monitoring techniques has proceeded over the last several decades. The work of Paul O. Thompson stands out for his pioneering contributions to the development of acoustic monitoring by: (1) identifying the variety of sounds produced by marine mammals and their mapping by species, (2) recognizing temporal patterns of sound production both on diel and seasonal cycles, and (3) demonstrating the value of long-term monitoring. The contributions of Paul Thompson will be discussed, and their connection to on-going work will be illustrated. The legacy of Paul Thompson’s work is that acoustic population estimation techniques are now being developed that offer the potential for efficient and economical monitoring of whale populations.
Remembrances of Paul O. Thompson at the Naval Ocean Systems Center
Authors: Moore Sue E. , Ridgway Sam
Published: October 2013

Paul Thompson spent 35 years working at the Naval Electronics Laboratory (later the Naval Ocean Systems Center) in San Diego and Hawaii. His research included psychoacoustics and animal bioacoustics. He authored 66 papers and reports, gaining the distinction of Fellow of the ASA. Paul was noted for painstaking data analysis, excellent aural memory, and outstanding skills at sound recording and processing. We present remembrances of Paul as a scientist, colleague, and friend during his years studying marine mammals for the Navy.
Acoustic localization of bowhead whales near a Beaufort Sea oil development, 2001–2003: Evidence of deflection at high-noise times?
Authors: Richardson W. John , McDonald Trent L. , Greene Charles R. , Blackwell Susanna B. , Streever Bill
Published: October 2013

Most bowhead whales migrating west along Alaska’s north coast during autumn pass 10–75 km seaward of BPs Northstar oil production island. Our objective was to determine the extent to which underwater sound from Northstar deflected the closest whales farther offshore. Whale calls were localized, via 11 DIFAR-based seafloor recorders, on 23–36 days per year while underwater sound was measured continuously 450 m from Northstar. Totals of 1121, 2057 and 14304 calls were localized within a 20×26 km analysis area seaward of Northstar. Quantile regression was used to relate the 5th quantile distance-from-shore to underwater sound. A permutation method allowed for lack of independence of closely spaced calls. In 2001, the closest calling bowheads tended to be slightly farther offshore at times with high industrial sound, which were mainly due to vessels near Northstar. The displacement effect was maximal if sound was averaged over 50–80 minutes preceding calls. In 2002, high sound levels were rare and results were inconclusive. In 2003, offshore displacement was not significant despite high sample size and a migration corridor unusually close to shore. The upper 90% confidence bound on the percentage of bowheads displaced 2+ km did not exceed 1.6% in any year. [Work supported by BP.]
Production of a noise level database of power tools used in the construction industry
Authors: Hayden Charles S. , Zechmann Edward , Verma Rohit
Published: October 2013

This study focused its efforts on sound power levels and noise reduction of power tools used by workers at both commercial and residential construction sites. The objective was to develop a noise control technology database consisting of power hand tools used in the construction industry with respective sound power levels and workers’ sound exposure level (SEL). The database and specific noise control applications information are made available to the public on a searchable web-site. Data includes a particular tool’s wavfile and time series signatures to be used for future qualitative and quantitative analysis by other acousticians accessing the database. With this information, reasonable assumptions can be made as to the potential occupational noise exposure expected for various occupations, tasks, etc. and as to potential sources of noise within the powered hand tool itself. The database captures tool types, tool models, tool manufacturers, and decibel power level. The database is expandable to include new tools and new manufacturers as the power tool population changes over time. These efforts support the reduction of noise induced hearing loss among construction workers by providing ‘‘buy quiet’’ and ‘‘designed quiet’’ information to power tool buyers and end users.
The glissando of colliding hard objects
Authors: Frey Benjamin , Hartmann William M.
Published: October 2013

When two hard objects are pressed together they alternately collide and rebound, leading to an audible, decaying sequence of pulses with a decreasing interpulse interval. Therefore, the sequence is heard as a rising pitch or glissando. Virtuoso performances of colliding hard objects (steel spheres) demonstrated a frequency rise that was accurately an exponential function of time over the span of more than three octaves. The amplitude decay also tended to be exponential, though less reproducibly so. Because successive decaying pulses were otherwise virtually identical functions of time, the spectra were harmonic. Four harmonics were clearly evident in spectrograms. Spectrograms also revealed a strong formant near 2000 Hz, presumably indicating the lowest mode of vibration of the steel spheres themselves. Formants had a Q of about 7. With the quantitative acoustical description well in hand, interest now centers on discovering the time-dependent force function employed by experienced performers of colliding hard objects when they achieve the most effective glissandos. [Work supported by the Michigan State University Professorial Assistant Program.]
A systems and neurobiological model of nucleus angularis and nucleus laminaris in the barn owl
Authors: Fischer Brian J. , Anderson Charles H.
Published: October 2013

The representation of binaural sound localization cues was investigated in a model of the barn owl’s auditory nerve, nucleus angularis (NA), nucleus magnocellularis (NM), nucleus laminaris (NL), and superior olivary nucleus (SON) using spiking leaky integrate and fire neurons. A phenomenological model of the barn owl’s auditory-nerve spike response was created to reproduce responses to tonal stimuli and exhibit two-tone rate suppression effects. The representation of stimulus level by NA was investigated by decoding the envelope of the input signal from populations of NA model neurons where the envelope was defined as in a previous computational model of sound localization in the barn owl [B.J. Fischer and C.H. Anderson, Adv. NIPS 16 (2004)]. Simulations demonstrated that inclusion of NA neurons with type IV responses increased the accuracy of the representation of the stimulus envelope. The effect of inhibition on the output of the population of NL model neurons was investigated and compared to a cross-correlation model. The output of the model SON provides inhibitory feedback to ipsilateral NA, NM, and NL model neurons. Simulations demonstrated that inclusion of inhibition of NL neurons by SON output increased peak–trough differences in ITD tuning curves.