bluuebunny/crossref_metadata_2025 huggingface dataset:
Active control of the headpiece of noise barriers
Authors: Möser Michael , Koh Hyo-In
Published: October 2013

A theoretical and numerical study of the sound field around an active controlled edge of a noise barrier is described. Studies about noise barrier with passive methods have shown improvement in reduction of the sound level in the range of middle and high frequencies. In this work the sound field on the surface of the headpiece is controlled in such a way that the tangential power transport parallel to their surface is lowered by means of secondary sound sources. First the sound field on the surface of the cylindrical headpiece is locally minimized. The effect of the control position and number of the control point on the sound field near the headpiece and in far field at various frequencies is discussed. The radiated power in the far field of the shadow region is globally minimized, which is the target to reduce, and compared to previous results. Afterwards the method of modal restructing is shown whereby each modal amplitude is controlled individually. Theoretical computations show improved levels in the shadow zone. Optimal active control methods are discussed and a practically oriented simulation is planned.
Amplitude modulation encoding in different auditory nuclei of the frog
Authors: Bibikov G. Nikolay
Published: October 2013

Since R. R. Capranica published his pioneer articles dealing with the amplitude modulation (AM) encoding, we have explored the reproduction of sine AM in a thousand single units of the medullar, isthmal, and midbrain acoustical centers of the European frogs. Typically, it was phasic units that demonstrated the best phase-locking to the 80%–100% modulated tone. However, onset units usually did not reproduce modulation with low modulation indexes (10%–20%). Medullar tonic units moderately reproduced deep AM and scarcely reproduced the 10% AM. However, the population response to a simple AM tone demonstrated a reliable reproduction of 10% modulated signal and a slight tendency to increase phase-locking from the first to the last modulation period. In the superior olive and lateral lemniscus nuclei this tendency became more evident. In torus semicirdularis a large population of the units increase their phase-locking response during the short-term (tenth of second) and long-term (tens of seconds) adaptation. In many units a dramatic enhancement of the mean firing rate in the sustained state was observed after noise addition. Morever, the amplitude of the sine modulation of the instantaneous spike rate was enhanced on some levels of the noise. [Work supported by the RFBR Grant No. 02-04-48236.]
Multiple components in distortion product otoacoustic emissions from the amphibian ear
Authors: Meenderink Sebastiaan W. F. , Van Dijk Pim
Published: October 2013

Distortion product otoacoustic emissions (DPOAEs) are weak intermodulation distortions generated in the inner ear in response to two stimulus tones. Both the amphibian papilla and the basilar papilla in the inner of the frog may generate DPOAEs [Van Dijk and Manley, Hear. Res. 153, 14–22 (2001)]. Here, we measured the level and phase of DPOAEs in the Leopard frog, Rana pipiens, in response to stimulus tones between 40- and 90-dB SPL. Results show that for stimulus tones in the amphibian papilla frequency range, two components contribute to DPOAEs. One component dominates for stimulus levels below about 70-dB SPL, while the other is most prominent at higher levels. The transition between both components is accompanied by a conspicuous phase change, and sometimes by a notch in the amplitude response curve. Similar results were obtained in the basilar papilla frequency range, but in addition a third component was present for stimuli below about 55-dB SPL. With the exception of this third component, our findings are remarkably similar to those in mammals, despite the structural differences between the mammalian and amphibian inner ear. [Work supported by NWO.]
Comments on ‘‘ray chaos’’ and ocean acoustic tomography
Authors: Dushaw Brian , Colosi John
Published: October 2013

Recent publications describe ‘‘ray chaos’’ in the context of long-range acoustic propagation in the ocean. This work is relevant to long-range tomography, which relies on the identification of specific ray paths with pulse arrivals. However, the ‘‘ray chaos’’ work has mainly had a theoretical or numerical focus. Of necessity, artificial assumptions have been made as to internal-wave spectrum, infinite acoustic frequency, background sound speed profile, etc. The discussions of ‘‘ray chaos’’ have rarely incorporated the results of the long-range propagation experiments that have been conducted over the past 15 years. In spite of this disassociation between theory/numerics and experiment, discussions involving ‘‘ray chaos’’ have been critical of tomography/thermometry. One claim is that acoustic rays employed for purposes of tomography are an inappropriate description of the acoustic sampling associated with measured arrival patterns. Such criticism has occasionally implied that tomography cannot be employed for ocean studies at ranges larger than about 1 Mm as a result of ‘‘ray chaos’’ and other issues. Some aspects of the ‘‘chaos’’ view are obviously correct, while other aspects require a more rigorous test of modeling by experiment. However, the oceanographic measurements that result from using either ‘‘classical’’ or ‘‘chaotic’’ rays are practically indistinguishable.
Downslope measurements from a bottom mounted tomography source
Authors: Heaney Kevin D. , Castille Brett , Teranishi Arthur , Sternlicht Daniel
Published: October 2013

Long-range tomography experiments seek to measure the temporal acoustic fluctuations due to thermal changes in the ocean structure. To map these changes to specific depths in the ocean, accurate travel times, and the ability to predict ray paths are required. Both of these become difficult in an environment that is bottom interacting (even though the water may be deep). To examine near source effects of interaction with the bottom for a tomographic source set on the bottom (at a depth of 800 m) measurements were taken off of Kauai. A short VLA was deployed from a small vessel and broadband recordings were taken at 6 ranges, from directly overhead to 55 km away. The issues to be addressed are the accuracy of the source timing and the relative strength of the bottom bounce and direct path. Evidence exists that interaction with the sea-floor can lead to up to a 0.5 s delay in the measured travel time, from that predicted.
Free-field calibration of measurement microphones at frequencies up to 80 kHz
Authors: Zuckerwar Allan J. , Herring Gregory C.
Published: October 2013

Civil-aviation noise-reduction programs, that make use of scaled-down aircraft models in wind tunnel tests, require knowledge of microphone pressure (i.e., not free-field) sensitivities beyond 20 kHz—since noise wavelengths also scale down with decreasing model size. Furthermore, not all microphone types (e.g., electrets) are easily calibrated with the electrostatic technique, while enclosed cavity calibrations typically have an upper limit for the useful frequency range. Thus, work was initiated to perform a high-frequency pressure calibration of Panasonic electret microphones using a substitution free-field method in a small anechoic chamber. First, a standard variable-frequency pistonphone was used to obtain the pressure calibration up to 16 kHz. Above 16 kHz, to avoid spatially irregular sound fields due to dephasing of loudspeaker diaphragms, a series of resonant ceramic piezoelectric crystals was used at five specific ultrasonic frequencies as the free-field calibration sound source. Then, the free-field sensitivity was converted to a pressure sensitivity with an electrostatic calibration of the reference microphone (an air condenser type), for which the free-field correction is known. Combining the low- and high-frequency data sets, a full frequency calibration of pressure sensitivity for an electret microphone was generated from 63 Hz to 80 kHz.
Education in acoustics in Argentina
Authors: Miyara Federico
Published: October 2013

Over the last decades, education in acoustics (EA) in Argentina has experienced ups and downs due to economic and political issues interfering with long term projects. Unlike other countries, like Chile, where EA has reached maturity in spite of the acoustical industry having shown little development, Argentina has several well-established manufacturers of acoustic materials and equipment but no specific career with a major in acoustics. At the university level, acoustics is taught as a complementary—often elective—course for careers such as architecture, communication engineering, or music. In spite of this there are several research centers with programs covering environmental and community noise, effects of noise on man, acoustic signal processing, musical acoustics and acoustic emission, and several national and international meetings are held each year in which results are communicated and discussed. Several books on a variety of topics such as sound system, architectural acoustics, and noise control have been published as well. Another chapter in EA is technical and vocational education, ranging between secondary and postsecondary levels, with technical training on sound system operation or design. Over the last years there have been several attempts to implement master degrees in acoustics or audio engineering, with little or no success.
Efforts regarding acoustical education for architectural students at the Universidad Peruana de Ciencias Aplicadas (Peruvian University of Applied Sciences), UPC
Authors: Moy Jorge
Published: October 2013

The lack of knowledge in acoustics among the vast majority of Peruvian architects results in acoustical problems in buildings from a lack of such considerations in the design stage. This paucity of knowledge on the part of the architects may be attributed to the lack of emphasis on the role of acoustics in most architectural curricula in Peruvian universities. A purpose in this paper is to present a brief report on last year’s efforts to implement courses in Architectural Acoustics and Noise Control for architecture students at UPC.
On helping Latin American countries in education in acoustics
Authors: Raichel Daniel R.
Published: October 2013

The science and applications of acoustics are just as important in Latin America as they are in North America and elsewhere. However, resources in academia are harder to come by in nearly all of the Central American and South American nations; and therefore it would behoove U.S. and European acousticians to help their Latin-American counterparts in achieving their goals of quality education in acoustics, particularly in architectural acoustics, noise control, biomedical usages of ultrasound, signal analyses, and measurement techniques. Among the means of helping are scholarly exchanges, more support by the U.S. government for such exchanges (particularly through Fulbright programs—it is unfortunate that the Fulbright Senior Specialist Program does not recognize acoustics as being one of the environmental sciences), collaboration on research projects, long-term equipment loans and/or outright donations, etc. Advice by experienced practitioners in establishing or improving acoustics laboratories can optimize equipment selection and development of the curriculum.
Easily extensible unix software for spectral analysis, display, modification, and synthesis of musical sounds
Authors: Beauchamp James W.
Published: October 2013

Software has been developed which enables users to perform time-varying spectral analysis of individual musical tones or successions of them and to perform further processing of the data. The package, called sndan, is freely available in source code, uses EPS graphics for display, and is written in ansi c for ease of code modification and extension. Two analyzers, a fixed-filter-bank phase vocoder (‘‘pvan’’) and a frequency-tracking analyzer (‘‘mqan’’) constitute the analysis front end of the package. While pvan’s output consists of continuous amplitudes and frequencies of harmonics, mqan produces disjoint ‘‘tracks.’’ However, another program extracts a fundamental frequency and separates harmonics from the tracks, resulting in a continuous harmonic output. ‘‘monan’’ is a program used to display harmonic data in a variety of formats, perform various spectral modifications, and perform additive resynthesis of the harmonic partials, including possible pitch-shifting and time-scaling. Sounds can also be synthesized according to a musical score using a companion synthesis language, Music 4C. Several other programs in the sndan suite can be used for specialized tasks, such as signal display and editing. Applications of the software include producing specialized sounds for music compositions or psychoacoustic experiments or as a basis for developing new synthesis algorithms.
Musical sound analysis/synthesis using vector-quantized time-varying spectra
Authors: Ehmann Andreas F. , Beauchamp James W.
Published: October 2013

A fundamental goal of computer music sound synthesis is accurate, yet efficient resynthesis of musical sounds, with the possibility of extending the synthesis into new territories using control of perceptually intuitive parameters. A data clustering technique known as vector quantization (VQ) is used to extract a globally optimum set of representative spectra from phase vocoder analyses of instrument tones. This set of spectra, called a Codebook, is used for sinusoidal additive synthesis or, more efficiently, for wavetable synthesis. Instantaneous spectra are synthesized by first determining the Codebook indices corresponding to the best least-squares matches to the original time-varying spectrum. Spectral index versus time functions are then smoothed, and interpolation is employed to provide smooth transitions between Codebook spectra. Furthermore, spectral frames are pre-flattened and their slope, or tilt, extracted before clustering is applied. This allows spectral tilt, closely related to the perceptual parameter ‘‘brightness,’’ to be independently controlled during synthesis. The result is a highly compressed format consisting of the Codebook spectra and time-varying tilt, amplitude, and Codebook index parameters. This technique has been applied to a variety of harmonic musical instrument sounds with the resulting resynthesized tones providing good matches to the originals.
The role of bubbles and cavitation in the production of thermal lesions from high-intensity focused ultrasound
Authors: Roy Ronald A. , Holt R. Glynn , Yang Xinmai , Edson Patrick
Published: October 2013

Rapid hyperthermia resulting in tissue necrosis is a key physical mechanism for focused ultrasound surgery (FUS). At therapeutic intensities, tissue heating is often accompanied by cavitation activity. Although it is well known that bubbles promote mechanical damage, in vitro and in vivo experiments have shown that under certain conditions bubble activity can double the heating rate. With a view towards harnessing bubbles and cavitation for useful clinical work, we report the results of in vitro experiments and modeling for the dynamic and thermal behavior of bubbles subjected to 1-megahertz ultrasound at mega-pascal pressures. The dominant bubble-related heating mechanism depends critically on the bubble size distribution which, in turn, depends on insonation control parameters (acoustic pressure, pulse duration), medium properties (notably dissolved gas concentration), and bubble-destroying shape instabilities. The evidence points to a range of control parameters for which bubble-enhanced FUS can be assured. [Work supported by DARPA and the U.S. Army.]
A theoretical model for bubble enhanced ultrasound heating due to time-dependent bubble size distributions
Authors: Xinmai Yang , Holt R. Glynn , Edson Patrick , Roy Ronald A.
Published: October 2013

Substantial in vitro and in vivo evidence shows that cavitation activity can affect tissue heating in focused ultrasound surgery and acoustic hemostasis applications. In particular, the heating rate in tissue increases significantly after cavitation sets in. Exploitation of this phenomenon for clinical use requires knowledge of, among other parameters, the time-dependent bubble size distribution sustained during insonation. Difficulties associated with the measurement of bubble sizes during in vitro or in vivo experiments call for a theoretical approach to the problem. We will present a theoretical model that estimates the time-dependent distribution of bubble equilibrium radii. Shape instability thresholds and rectified diffusion thresholds bound asymptotic bubble size distributions, and the instantaneous size distributions are governed by growth rates. The temperature rise caused by such bubble activity is calculated and compared with experimental data. [Work supported by DARPA and the U.S. Army.]
A novel cavitation probe design and some preliminary measurements of its application to megasonic cleaning
Authors: Crum Lawrence A. , Ferrell Gary
Published: October 2013

An initial prototype design for a cavitation probe that uses the property of a collapsing cavitation bubble to produce visible photons (sonoluminescence) has been designed and constructed. These light emissions can be easily detected within a small, finite volume and thus this probe provides a direct means of measuring the cavitation density (activity/per unit volume) within a cavitating fluid and the delivery of ultrasonic energy at an engineered surface. As a result, ultrasonic methods treating a surface can be directly monitored and controlled in real-time, leading to the ability to improve and predict the performance of the resulting structure. This probe provides the potential for constructing a real-time monitor of ultrasonic/megasonic cleaner efficiency and effectiveness. In addition, because the entire three-dimensional cavitation field can be measured with this probe, it can also serve as a useful tool in ultrasonic/megasonic cleaner design. A real-time cavitation-density measuring device would have great utility in the semiconductor cleaning industry and thus this probe provides considerable promise for commercial development. A description of the probe will be presented as well as some preliminary data on cavitation density within a commercial megasonic cleaner. [Work supported in part by the NSF.]
Auditory localization in the horizontal plane with single and double hearing protection
Authors: Brungart Douglas S. , Kordik Alexander J. , Simpson Brian D.
Published: October 2013

Although most occupational noise problems can be adequately addressed with either earplugs or earmuffs, some extreme noise environments require listeners to wear both earplugs and earmuffs at the same time. However, little is known about the impact that double hearing protection has on sound localization. In this experiment, listeners wearing single and double hearing protection were asked to localize pink noise signals originating from 24 evenly spaced loudspeakers in the horizontal plane. In the single hearing protection conditions, localization accuracy was severely degraded with a short (250 ms) stimulus, but only modestly degraded with a continuous stimulus that allowed listeners to make exploratory head movements. In the double hearing protection conditions, localization accuracy was near chance level with the short stimulus and was only slightly better than chance with the continuous stimulus. A second experiment showed that listeners wearing double hearing protection were routinely unable to identify the lateral positions of stimuli originating from loudspeakers located at ±45° in azimuth. The results suggest that double hearing protection reduces the air-conducted signals in the ear canals to the point that bone and tissue conducted signals disrupt the interaural difference cues listeners normally use to localize sound. [Work supported by AFOSR.]
Pitch and loudness memory in musicians and nonmusicians
Authors: Bailey Peter , Dobinson Stuart
Published: October 2013

The finding that pitch and loudness traces decay at different rates [S. Clement, L. Demany, and C. Semal, J. Acoust. Soc. Am. 106, 2805–2811 (1999)] is one of several results indicating that the processes of pitch and loudness memory may be distinct. A speculation raised by Clement et al., among others, is that these specialized memory subsystems might be differently influenced by musical experience. To explore this hypothesis, difference limens (DLs) for the fundamental frequency (DLF) and intensity (DLI) of complex tones were measured for groups of musically-experienced and musically-naive participants, using a roving-standard, 2-interval procedure in which the duration and content of the interstimulus interval (ISI) within a trial were manipulated. In the first experiment ISIs were silent and 0.5 s or 2.0 s in duration. For both groups DLs increased with ISI; DLFs were smaller for musicians than nonmusicians at both ISIs, but DLIs were smaller for musicians only when ISI=0.5 s, and did not differ when ISI=2.0 s. In a second experiment the ISI included interpolated tones. DLFs were larger for nonmusicians than musicians, but DLIs were similar for both groups. The results suggest that musical experience has different effects on memory fo rpitch and loudness.
The intensity potential approach
Authors: Guyader Jean Louis , Thivant Michael
Published: October 2013

Sound intensity vectors can be decomposed into irrotational and curl components. The irrotational part describes intensity propagation, and the curl component vortices and near field of sources. To predict power flow one can limit the problem to irrotational intensity, that is to say to the determination of intensity potential. The resulting equation is analogous to heat transfer, permitting one to use standard heat transfer solvers to predict acoustic power flow. The intensity potential approach is presented for acoustic propagation from sources in cavities with apertures. The modelization of absorbing materials through thermal convection factor is discussed. Finally, comparison with exact prediction and experimental results are presented.
Active control of structural intensity and radiated acoustic power from an infinite point-excited submerged Mindlin plate
Authors: Won Jungyun , Hayek Sabih
Published: October 2013

In this paper, the active vibrational structural intensity (VSI) in, and the radiated acoustic power from an infinite elastic plate in contact with a heavy fluid is modeled by the Mindlin plate theory. The plate is excited by a point force, which generates a vector-active VSI field in the plate. The resulting acoustic radiation generates an active acoustic intensity (AI) in the fluid medium. The displacement, shear deformation, VSI vector map, radiated acoustic pressure, and the AI vector map are computed. One, two, or four synchronous point controllers are placed symmetrically with respect to the point force on the plate. Minimization of either the structural intensity at a reference point or the total radiated acoustic power is achieved. Below coincidence, a significant portion of the point force input power is trapped in the plate in the form of VSI. The total radiated power is calculated by use of the input power from the source, the controllers, and the VSI. Above coincidence, a significant portion of the input source power is leaked to the fluid in the form of AI, so that the acoustic radiated power is equal to the input power from the source and the controllers.
Active control of cantilever-beam vibration
Authors: Serbyn M. Roman
Published: October 2013

A bang–bang control system previously developed for the stabilization of a rigid platform [ISA Trans. 21, 55–59 (1982)] has been adapted to the problem of reducing flexural vibrations of a beam. The electromechanical system develops an appropriate control signal for the actuator from samples of the disturbance by analog and digital signal processing using integrated circuits. The effectiveness of this approach is predicated upon the sampling rate being much higher than the maximum vibration frequency to be silenced. It is also robust with respect to the waveform of the disturbance. Noise reductions of 10–20 dB have been achieved, depending on the bandwidth of the noise. The cantilever, chosen because of its mechanical and theoretical simplicity, provides a good foundation for the study of more complex structures, like airfoils and nonrigid platforms. In both experimental and analytical investigations the emphasis has been on the optimization of control parameters, particularly with regard to the application of the cancellation signal. Reduction in size and cost of the control unit is possible by incorporating the latest technological advances in electronic and electromechanical devices, such as FPGA boards and MEMS components.
An active structural acoustic control approach for the reduction of the structure-borne road noise
Authors: Douville Hugo , Berry Alain , Masson Patrice
Published: October 2013

The reduction of the structure-borne road noise generated inside the cabin of an automobile is investigated using an Active Structural Acoustic Control (ASAC) approach. First, a laboratory test bench consisting of a wheel/suspension/lower suspension A-arm assembly has been developed in order to identify the vibroacoustic transfer paths (up to 250 Hz) for realistic road noise excitation of the wheel. Frequency Response Function (FRF) measurements between the excitation/control actuators and each suspension/chassis linkage are used to characterize the different transfer paths that transmit energy through the chassis of the car. Second, a FE/BE model (Finite/Boundary Elements) was developed to simulate the acoustic field of an automobile cab interior. This model is used to predict the acoustic field inside the cabin as a response to the measured forces applied on the suspension/chassis linkages. Finally, an experimental implementation of ASAC is presented. The control approach relies on the use of inertial actuators to modify the vibration behavior of the suspension and the automotive chassis such that its noise radiation efficiency is decreased. The implemented algorithm consists of a MIMO (Multiple-Input–Multiple-Output) feedforward configuration with a filtered-X LMS algorithm using an advanced reference signal (width FIR filters) using the Simulink/Dspace environment for control prototyping.
Acoustic correlates of English glottal [t] allophone
Authors: Kreitman Rina
Published: October 2013

This experiment investigates the acoustics of American English coda [t], which is often glottalized. A list of monosyllabic and bisyllabic words with matching vowel quality in target syllables across pairs was devised. The matching pairs were controlled for lexical frequency from the celex database. The words were read in isolation and in a frame sentence, where the target word was at the end of an intonational phrase. Results show that there is glottalization on the vowel preceding [t], which is interpreted as laryngeal coarticulation from the glottal allophone of [t]. Additionally, results show that for some speakers the proportion of the vowel that is glottalized is longer in sentences than in isolated words. Results of a cepstral measure of harmonics-to-noise-ratio (Hillenbrand et al., 1994) are different from what was found for Ju–hoansi glottalized consonants (Miller-Ockhuizen, 2002), but similar to results for glottalized vowels. That is, Gamnitude of R1 increased toward the end of the vowel. Since glottalization, as measured via a low H1–H2 (NiChasaide and Gobl, 1997) and aperiodicity seen through waveform inspection, does occur on the vowel, this suggests an articulatory mechanism for glottalization different from constriction of the glottis, such as false vocal-fold contraction (Fujimura and Sawashima, 1971).
Effects of frequency shifts on vowel category judgments
Authors: Glidden Catherine M. , Assmann Peter F. , Nearey Terrance M.
Published: October 2013

To investigate the effects of fundamental frequency (F0) and formant frequency shifts on vowel identification, a high-quality vocoder (‘‘STRAIGHT’’) was used to process the syllables ‘‘bit’’ and ‘‘bet’’ spoken by an adult female talker. From these two endpoints a nine-step continuum was generated by interpolation of the time-varying spectral envelope. Upward and downward frequency shifts in spectral envelope (scale factors of 0.75, 1.0, or 1.33) were combined with shifts in F0 (scale factors of 0.5, 1.0, or 1.25). Downward frequency shifts generally resulted in malelike voices whereas upward shifts were perceived as childlike. Matched frequency shifts, in which F0 and spectral envelope (i.e., formant frequencies) were shifted in the same direction, had relatively little effect on phoneme boundaries. Mismatched frequency shifts, in which F0 was modified independently of spectral envelope or vice versa, resulted in systematic boundary shifts. The changes in the identifications functions were qualitatively consistent with predictions of a model trained using acoustic measurements derived from a database of naturally spoken vowel tokens from men, women, and children. The empirical and modeling results are consistent with the idea that vowel boundary shifts are a consequence of listeners sensitivity to the statistical structure of natural speech.
Assimilation and discrimination of Canadian French vowels by English-speaking adults
Authors: Polka Linda , Escudero Paola , Matchett Shelly
Published: October 2013

According to the Perceptual Assimilation Model (PAM) discriminability of non-native contrasts depends on the perceived similarity to native phonetic categories [Best (1994)]. With respect to vowel contrasts, it has been claimed that PAM predictions hold so long as context-specific realizations of a given contrast are considered [Strange et al. (2001); Levy (2002)]. To further assess these claims, English adults were tested on perception of Canadian French tense high vowels, /i/, /y/, /u/ and their respective context-conditioned variants [I], [Y], and [U]. Adults completed 2 tasks with both citation and sentence context stimuli; stimuli for both tasks were natural /bVs/ tokens, produced by male and female talkers. For each vowel, subjects completed an identification and rating task (using English vowel response categories) which provided data to assess the assimilation pattern for four non-native contrasts: /i-y/, /y-u/, /I-Y/, and /Y-U/. Discrimination was assessed for each contrast using a categorical AXB task, in which each token is produced by a different talker. The ability to predict discrimination differences from assimilation data was assessed. The findings were examined together with acoustic analysis to determine whether acoustic differences and assimilation differences are equally predictive of relative discriminability.
Effect of age and context on vowel area
Authors: Hodge Megan M.
Published: October 2013

Vowel quadrilateral area, based on first and second formant measures of the corner vowels, has been shown to be correlated positively with intelligibility scores in studies of adults with and without dysarthria [Weismer et al., 2001] and children with and without dysarthria [Higgins and Hodge, 2002]. This study compared vowel areas of three groups of typical talkers (3 year-olds, 5-year-olds, and women) using a log Hz scale in two different speaking conditions. The first speaking condition was production of multiple tokens of isolated /hV/ syllables for each corner vowel, and the second was production of single word items containing the four corner vowels taken from a childrens’ test of intelligibility [Hodge, 1996]. An interaction of age with phonetic context was found. Vowel areas for the 3-year-olds did not differ between the two conditions and were the largest of the three groups. The 5-year-olds’ and women’s vowel areas were of similar size and both were smaller in the word condition. The women showed the greatest effect of phonetic context with a significantly smaller mean vowel area in the word than isolated vowel condition. [Work supported by Glenrose Rehabilitation Hospital and Canadian Languaage and Literacy Research Network.]
Measurements of acoustic backscatter at shallow grazing angles at low kHz frequencies
Authors: Hines Paul C. , Osler John C. , MacDougald Darcy J.
Published: October 2013

The acoustic backscattering strength of the seabed has been demonstrated to be one of the key inputs required in sonar performance prediction models. Yet, direct measurement of acoustic scattering from the seabed at shallow grazing angles presents a considerable challenge in littoral waters. The DRDC Atlantic (formerly DREA) Wide Band Sonar system, which consists of a parametric transmitter and a superdirective receiver, is ideally suited to make this measurement. The system was used to measure backscatter as a function of grazing angle and azimuth on the Scotian Shelf off the coast of Nova Scotia and on the Strataform site off the coast of New Jersey. Interpretation of the data set is enhanced with swath bathymetry measurements made at one of the experimental sites. In this paper the experimental geometry is described and the backscatter measurements are presented and discussed in light of the swath bathymetry results.
Measurements of signal spread and coherence on the New Jersey Shelf and in the Straits of Sicily using time-forward and time-reversed signals
Authors: Gauss Roger C. , Menis Richard
Published: October 2013

Mid-frequency shallow-water propagation measurements were made at a variety sites on the New Jersey Shelf and in the Straits of Sicily during three joint trials with the SACLANTCEN (Boundary Characterization: 2000–2002) in order to extract measures of signal spread and coherence, and to evaluate the spatial robustness of time-reversal techniques. The experiments had the NRV Alliance periodically transmitting a 1-s, 200-Hz-bandwidth LFM while it traversed an arc about a stationary platform, which captured these signals and transmitted back time-forward and a set of time-reversed versions of them, as well as transmitting its own version of the original signal. Analysis of normalized matched-filter data indicate that while the two-way time spreads were generally modest, marked decorrelation was observed and that time reversal did well in reconstructing the original impulse response of the LFMs. As the various stored time-reversed versions of the original signals corresponded to different source–receiver paths, a comparison of their signal correlations provided a measure of the spatial robustness of phase conjugation in the different shelf environments. That statistically the stored time-reversed signals often did as well as in situ time-reversed signals suggests the potential for bistatic applications of phase-conjugation concepts. [Work supported by ONR.]
Measurements of mid-frequency boundary scattering on the New Jersey Shelf and in the Straits of Sicily
Authors: Kunz Edward L. , Gauss Roger C.
Published: October 2013

During joint trials with the SACLANTCEN, direct-path monostatic scattering measurements were conducted at 18 sites across the New Jersey Shelf (Boundary Characterization 2001) and at 9 sites in the Straits of Sicily (Boundary Characterization 2002). Using combinations of short duration cw and LFM signals, both the mean (scattering strength) and statistical (probability density function) characteristics of the bottom- and surface-interaction zones were measured at each site. Bottom-zone scattering strength results show that many sandy and rocky sites exhibited a generally flat dependence on grazing angle (over 20–70 deg) and a moderate dependence (∼5 dB) on frequency over 2.5–5 kHz. In contrast, the measured surface-zone scattering strengths exhibited a strong dependence on grazing angle (and a mild dependence on frequency), consistent with scattering from the rough air–sea interface. Using physics-based scattering models, coupled with the supporting environmental measurement results, estimates of both the relative contributions of different bottom-zone scattering mechanisms (water-sediment interface, sediment volume and, at low grazing angles, near-bottom fish) and geophysical quantities (such as bottom roughness spectral parameters) were derived and will be presented along with the acoustic data results. [Work supported by ONR.]
Bistatic reverberation modeling for range-dependent waveguides
Authors: LePage Kevin D.
Published: October 2013

The BiStaR bistatic reverberation model has been developed at SACLANTCEN to model general reverberation scenarios in range-dependent waveguides. Features of the model include coherent propagation to and from the scattering patch, a coherent scattering patch model which includes anisotropy in the scatterer correlation length scales, and explicit inclusion of system parameters such as bandwidth and source and receiver directivity. The model is built upon the C-SNAP coupled mode model developed at SACLANTCEN by Ferla and Porter. In this talk the theoretical features of the model are presented and the characteristics of coherent and range-dependent bistatic reverberation predicted with the model are discussed. The model is also exercised to help interpret reverberation phenomena observed during the Geoclutter/Boundary Characterization Cruise conducted off the coast of New Jersey during the spring of 2001, including reverberation from beyond the shelf break and scattering from features buried beneath the sediment. a)Previously at the SACLANT Undersea Research Centre, La Spezia, Italy.
A comparison of high frequency acoustic transmission data from a smooth water/sand interface with a composite poroelastic model
Authors: Isakson Marcia , Weigl Daniel , Bigelow Erik , Chotiros Nicholas
Published: October 2013

Reflection data taken from a smooth water/sand interface have been successfully modeled using a composite poroelastic model. The model was able to account for a decrease in reflectivity at subcritical angles while maintaining physically realistic input parameters. In this study, transmission data have been measured at a number of grazing angles including subcritical angles through a smooth water/sand interface. Because of the flat interface, there should be no contribution to transmission from Bragg scattering or similar scattering effects. The data will be compared with simulations based on a composite poroelastic model using Biot parameters determined from the reflection data. The fit will be considered for its accuracy in predicting the arrivals of the fast, evanescent, and slow waves. [Work supported by ONR, Ocean Acoustics.]
The first vineyard concert hall in North America
Authors: Jaffe Christopher , Rivera Carlos
Published: October 2013

The first vineyard or surround concert hall designed and built in the Western Hemisphere is the Sala Nezahualcoyotl in Mexico City. The Hall was completed in 1976 and is part of the Cultural Center at the Universidad Nacional Autonoma de Mexico. The hall was named after a Toltec poet, architect, and musician who lived in the 15th century and was the Renaissance man of his day. In order to provide the familiar traditional sound of the rectangular (shoebox) European Hall, the acoustic designers set the criteria for reverberation times through the frequency spectrum and the Initial Time Delay Gap at every seat in the house to match the measurements taken at the Grosser Musik vereinssaal in Vienna and Boston Symphony Hall. In this paper we discuss the techniques used to create the traditional sound in a vineyard hall and the reaction of musicians and audiences to the completed facility. The Sala was the model for Suntory Hall in Japan which in turn spawned a number of vineyard halls in Japan. Most recently, the vineyard style seems to be appealing to more and more symphonic organizations in Europe and North America.
Sound perception in the mixing and mastering processes of recorded music
Authors: Meneses Jose Javier Muedano
Published: October 2013

This research work presents an analysis of the perceived musical sounds within the mixing process and computer mastering at the audio and video recording studio of the Acoustics Laboratory in ESIME, IPN, Mexico, working with the so-called plug-ins to process the audio signal. The analysis is made from a psychoacoustics standpoint. Samples analyzed include rock, tropical and classical music, and these experiences are part of the Audio course at the Acoustics option of the Electronics and Communications Engineers studies in the Mexican Polytechnic. (To be presented in Spanish.)
‘‘A’’ weighting curve algorithm
Authors: Redondo Jose de Jesus Negrete , Paulin Pablo Roberto Lizana , Rizo Isabel Elena Romero , Cervantes Igmar Moreno
Published: October 2013

The overall project was aimed to build a sound level meter, based on national and international standards. The instrument is being developed on a PC. For this section of the project, the sound signal is captured with a microphone, through an analog/digital converter to the computer. The weighted signal is obtained with a software which includes the equation for the ‘‘A’’ weighting curve to perform a convolution with the fast Fourier transfer of the sound signal. (To be presented in Spanish.)
Temporal call characters and vocal communication in the cricket frog (Acris crepitans)
Authors: Wilczynski Walter , Ryan Michael J.
Published: October 2013

During intermale vocal interactions, male cricket frogs change the temporal, frequency, and amplitude characteristics of their calls. In playback studies, males changed the temporal structure of their calls in the direction of higher aggression to a greater degree when presented with calls having a high aggression temporal structure compared to a low aggression structure (with frequency and amplitude held constant). Hearing a low aggression call from the same location prior to a high aggression call resulted in a smaller change in the male’s call. Temporal structure degrades progressively between 4 and 16 m from the source over natural substrates. As distance-induced temporal degradation increases, males change temporal call characters progressively less. In sum, male cricket frogs respond to the temporal characteristics of other male calls by changing the temporal parameters of their own calls in a graded fashion. The magnitude of the change depends on the parameters of the challengers call, prior experience with calls from the challengers position, and temporal degradation (hence distance) of the challengers’ call. Phonotaxis experiments show that female cricket frogs prefer the high aggression calls. The call changes therefore seem to represent males increasing call attractiveness in response to increased competition from neighboring males.
Nonparallel coevolution of sender and receiver in the acoustic communication system of treefrogs
Authors: Schul Johannes , Bush Sarah L.
Published: October 2013

Advertisement calls of closely related species often differ in quantitative features such as the repetition rate of signal units. These differences are important in species recognition. Current models of signal/receiver co-evolution predict two possible patterns in the evolution of the mechanism used by receivers to recognize the call. (1) Classical sexual selection models (Fisher-Process, good-genes/indirect benefits, direct benefits models) predict that close relatives use qualitatively similar signal recognition mechanisms tuned to different values of a call parameter. (2) Receiver bias models (hidden preference, pre-existing bias models) predict that if different signal recognition mechanisms are used by sibling species, evidence of an ancestral mechanism will persist in the derived species, and evidence of a pre-existing bias will be detectable in the ancestral species. We describe qualitatively different call recognition mechanisms in sibling species of treefrogs. Whereas Hyla chrysoscelis uses pulse rate to recognize male calls, H. versicolor uses absolute measurements of pulse duration and interval duration. We found no evidence of either hidden preferences or pre-existing biases. The results are compared with similar data from katydids (Tettigonia sp.). The data are discussed with regard to current models of signal/receiver co-evolution.
Eight-year records of low-frequency ambient sound in the North Pacific
Authors: Andrew Rex K. , Leigh Charlotte , Howe Bruce M. , Mercer James A.
Published: October 2013

Spectra of omnidirectional ambient sound have been collected since 1994 at 13 locations around the North Pacific. Data were acquired for 3 minutes every 6 minutes and spectra calculated from 0–500 Hz in 1 Hz bands. With a million spectra per site, this database allows investigation into the statistical character of low-frequency ambient sound at multiple scales. At the shortest scales, the spectral levels in the shipping bands have a fluctuation spectrum similar to a 1/f process, with decorrelation times less than 20 minutes. At intermediate scales, the seasonal baleen whale component becomes the most dominant and repeatable feature. At the longest scales (averaging over the entire record) the ambient levels (at the Pt. Sur site) seem to have increased by up to 10 dB since the 1960s. The distribution of the levels (in decibels) generally indicates a short tail for quieter levels but a long tail for loud events. The Pt. Sur data set has also been used to validate the new dynamic ambient noise model (DANM), which shows good agreement in one-third octave bands to within a couple of decibels for January 1998. These and further results will be discussed. [Work supported by ONR and SPAWAR.]
Creating a web-based library of underwater biological sound
Authors: Bradbury Jack W. , Bloomgarden Carol A.
Published: October 2013

Establishing an archive of fish and other underwater biological sounds will meet many of the long-standing challenges faced by marine acousticians—the restoration and preservation of deteriorating recordings, the ability to catalog their sounds and data in a way that fosters the exchange and sharing of data, easy access to the sounds for analysis and identification, and the capacity to search through passive recordings for sounds of particular interest. The Macaulay Library of Natural Sounds, with a long history of working toward these goals in ornithology and animal behavior, recently launched into the realm of underwater sounds with the help of over 80 individual recordists and institutions worldwide. Researchers will be able to annotate their sounds through an online database application, summarize search results in exportable tables and maps, and download copies of recordings for research, teaching, and conservation. MLNS is committed to dual goals of maintaining open access to allow other researchers to listen and help identify sounds, while protecting recordists copyrights and restricting access during the publication process. Detailed and extensive metadata are needed, however, to create the functionality such an archive requires.
Monitoring air entrainment with breaking wave noise
Authors: Deane Grant B. , Stokes Dale M.
Published: October 2013

It is now known that the dominant component of wind-driven oceanic noise comes from breaking waves. Bubbles ranging in size from tens of microns to centimeters are forced into the water column during the first second or so of whitecap formation. At the moment of creation, each bubble emits a pulse of sound at a center frequency inversely proportional to its radius. The ensemble of such events amounts to a burst of noise that continues throughout the active phase of bubble creation within the whitecap. As the noise spectrum is related to the bubble size distribution within the whitecap, it is natural to explore the possibility that underwater oceanic ambient noise could be used as tool to remotely monitor air entrainment rates across the ocean surface. One of the problems with developing such a tool is understanding the relationship between bubble formation processes occurring within whitecaps and the concurrent noise emission. Here we will report recent progress in our understanding of bubble formation mechanisms in whitecaps, their role in ambient noise generation, and the implications for monitoring air entrainment rates.