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  • 1
    Online Resource
    Online Resource
    Dichotic and Monotic Simultaneous and Time-Staggered Speech
    Acoustical Society of America (ASA) ; 1970
    In:  The Journal of the Acoustical Society of America Vol. 47, No. 1A_Supplement ( 1970-01-01), p. 76-76
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 47, No. 1A_Supplement ( 1970-01-01), p. 76-76
    Abstract: Twelve female normal listeners, all right-handed, heard rhyming pairs of (stop+/a/) nonsense syllables dichotically and monotically. Word onsets were simultaneous, then shifted by 15, 30, 60, and 90 msec. Each subject heard 600 pairs. Monotically, the lag-syllable discriminations were poor at all delays with differences leveling off at 30 msec (93% lead vs 19% lag). Dichotically, lag-ear discrimination was roughly 22% better for all lag times when the right ear lagged. [First found by Shankweiler and Studdert-Kennedy, personal communication.] Left-ear lag scores improved and overcame the right-ear advantage only after 30-msec delay. Total right-ear scores for entire dichotic portion of experiment (M=77%) exceeded total left-ear scores (M=66%) thus maintaining an over-all right-ear laterality effect. Thus, previous experimenters who allowed as much as 90-msec delay to be randomly distributed among their so-called “simultaneous pairs” might still have expected to find a right-ear laterality effect. [Supported in part by NINDS.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.1974712
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1970
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  • 2
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    Online Resource
    Nonlinear acoustic detection of weathered, low compliance landmines
    Acoustical Society of America (ASA) ; 2005
    In:  The Journal of the Acoustical Society of America Vol. 118, No. 3_Supplement ( 2005-09-01), p. 2022-2022
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 118, No. 3_Supplement ( 2005-09-01), p. 2022-2022
    Abstract: Two potential impediments to acoustic landmine detection are soil weathering processes and low compliance landmines. To bury landmines, the soil within a mine diameter is removed and replaced such that bulk density, compression, and shear strength all decrease, leaving an acoustic scar detectable with the linear acoustic measurement technique. After a few soil wetting and drying cycles, this contrast is reduced. Linear acoustic mine detection measurements were made on a low impedance contrast landmine before the first rainfall on several occasions over the subsequent 5 years. During this period of time, both the spatial and frequency resolution had to be increased to maintain an on/off target velocity ratio that allowed detection. In some cases, the landmine remains undetectable. To address this, two-tone nonlinear acoustic measurements have been made on these landmines. When the landmine is detectable with linear acoustics, two tones are broadcast at the frequency where the on/off target velocity ratio is the largest. For the cases when the landmine is undetectable, a two-tone sweep is performed and the operator observes the real-time velocity FFT, noting nonlinear sidebands. Next, two-tone tests are conducted at these sidebands to determine nonlinear velocity profiles. [Work supported by U.S. Army RDECOM, NVESD.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4785755
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2005
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  • 3
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    Online Resource
    The application of acoustic particle velocity sensors to airborne infrasonic signals
    Acoustical Society of America (ASA) ; 2018
    In:  The Journal of the Acoustical Society of America Vol. 143, No. 3_Supplement ( 2018-03-01), p. 1782-1782
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 143, No. 3_Supplement ( 2018-03-01), p. 1782-1782
    Abstract: Infrasound arrays, because of the wavelengths involved and the necessity for minimal spatial aliasing, can be quite large, e.g. an array layout often used for beamforming for frequencies up to 10 Hz is a centered, 17-m radius equilateral triangle. Available real estate is often limited such that optimally sized arrays are not possible. An acoustic particle velocity sensor, in principle, can perform the same job as a large infrasound array, but in a much smaller package (less than the size of a single infrasound sensor) since it provides, in post processing, a direct measurement of the wavefront normal. However, localized meteorological perturbations to the wavefront normal could cause significant bearing estimate errors when using a particle velocity sensor. Recently, as part of the characterization of a mobile infrasound source and during the collection of sounds from space station resupply rockets, acoustic particle velocity sensors were positioned next to infrasound sensors in order to test the concept of using these sensors for accurate pointing at infrasound frequencies. Results from these experiments will be discussed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5035835
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    Green’s function retrieval by crosscorrelation and multidimensional deconvolution: Application to atmospheric acoustics
    Acoustical Society of America (ASA) ; 2017
    In:  The Journal of the Acoustical Society of America Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3885-3885
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3885-3885
    Abstract: In this work, the Green’s function of an atmospheric acoustic propagation channel is extracted from experimental measurements. Of particular interest, is the accuracy of Green’s function retrieval methods in ideal and non-ideal situations. To this end, an emitting acoustic source (impulsive and audible) is placed at a distance of more than 90 meters from receiving tri-axis microphone arrays in open (ideal) and wooded areas (non-ideal) in southern Maryland. Green’s function retrieval methods are employed and investigated on the collected data. Green’s function retrieval by crosscorrelation has been successful in various applications despite the limitations of its lossless medium and equipartitioned wavefield assumptions. To overcome the violation of these assumptions, the multidimensional deconvolution has been proposed. Comparisons of the results between impulsive and audible sources using the two methods will be presented. The effects of multipath, source-receiver distance, temperature, and wind will be discussed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4988709
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2017
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  • 5
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    Online Resource
    Deduction of the acoustic impedance of the ground via a simulated three-dimensional microphone array
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 134, No. 5 ( 2013-11-01), p. EL471-EL476
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 134, No. 5 ( 2013-11-01), p. EL471-EL476
    Abstract: While commonly used ground impedance deduction methods often utilize pairs of vertically separated microphones, deployed arrays rarely have this configuration, which increases the difficulty in automatically deducing local ground impedance from these arrays. The ability to deduce ground impedance using random sounds incident on a three-dimensional array would increase, for example, the accuracy of estimated elevation angles. The methods described by the American National Standards Institute Method for Determining the Acoustic Impedance of Ground Surfaces are extended to simulate deducing ground impedance by a three-dimensional array. Ground parameters indicative of grassland are successfully determined using a simulated three-dimensional array.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4826149
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
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  • 6
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    A study of the acoustic behavior of a plastic, blast-hardened, antitank landmine
    Acoustical Society of America (ASA) ; 2005
    In:  The Journal of the Acoustical Society of America Vol. 118, No. 3_Supplement ( 2005-09-01), p. 2022-2022
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 118, No. 3_Supplement ( 2005-09-01), p. 2022-2022
    Abstract: Mechanical resonances in landmines are often exploited by some acoustic-to-seismic detection schemes. As such, a study of an acoustically active landmine has been performed. Measurements of the mechanical resonances of the pressure plate reveal seven modes below 1.6 kHz and a large frequency shift of the first symmetric mode of the pressure plate, such that it occurs higher in frequency than the first asymmetric mode. The pressure plate is considered to act as an elastically supported thin plate, and the observed perturbation of the first symmetric mode is believed to be caused by the landmine’s blast-hardening mechanism. This is confirmed by a lumped acoustic element model of the system of pressure plate and blast-hardening mechanism. Mass-loading experiments in water show a decrease in resonance frequency with increasing depth that saturates at shallow depths as predicted by Velea et al. [J. Acoust. Soc. Am. 115, 1993 (2004)]. Similar mass-loading measurements in sand reveal an interesting phenomenon; flush burial of the landmine effectively removes the effect of the blast-hardening mechanism on the pressure plate. A qualitative theoretical model of this phenomenon will be presented.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4785756
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2005
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  • 7
    Online Resource
    Online Resource
    Association of impulsive infrasonic events at medium ranges
    Acoustical Society of America (ASA) ; 2017
    In:  The Journal of the Acoustical Society of America Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3568-3568
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3568-3568
    Abstract: Multiple, widely spaced, infrasonic arrays are routinely used to detect and localize impulsive events of unknown origin at medium ranges ( & lt;100 km). Event data are subsequently processed to yield line of bearing (LOB) information and localization is accomplished manually. This method of analysis could significantly benefit from automatic association and localization. Because infrasound arrays are often separated by many tens of kilometers and signals reaching the arrays can be significantly altered along the propagation path, the task of associating signals is difficult and time consuming. Further, confidence in an event association is difficult to assign to a signal due to arrival timing and local interferers. By using beamforming methods and coherence between signals, it is possible to automatically associate a given recorded event. At each array, a delay and sum beamformer is used to calculate the LOB to an unknown source. The delayed and summed beam at each array is then used to calculate the pairwise coherence between all beams. Impulsive events due to sources recorded by widely spaced infrasound arrays often exhibit high coherence at many of the frequencies in the signal. Examples of successful associations between widely spaced arrays will be discussed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4987580
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2017
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  • 8
    Online Resource
    Online Resource
    Studying the mechanical behavior of a plastic, shock-resisting, antitank landmine
    Acoustical Society of America (ASA) ; 2006
    In:  The Journal of the Acoustical Society of America Vol. 120, No. 6 ( 2006-12-01), p. 3655-3663
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 120, No. 6 ( 2006-12-01), p. 3655-3663
    Abstract: Modal behavior in landmines has recently become a topic of interest for acoustic landmine detection. It is well known that landmines exhibit mechanical resonance behavior that enhances the soil velocity over a buried landmine. Recent experimental work by Zagrai et al. [A. Zagrai, D. Donskoy, and A. Ekimov, J. Acoust. Soc. Am. 118 (6), 3619–3628 (2005)] demonstrates the existence of structural modes in several landmines. The work reported herein parallels the work of Zagrai et al. in studying the structural modes of the pressure plate of a plastic, cylindrically symmetric, antitank landmine. The pressure plate is considered to act as an elastically supported thin elastic plate. An observed perturbation of the first symmetric mode of the pressure plate is caused by the landmine’s shock-resisting mechanism. This is validated by a lumped element model for the first symmetric mode coupled to the shock-resisting mechanism.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2357999
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2006
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  • 9
    Online Resource
    Online Resource
    Performance of Green’s function retrieval methods for various sound source distributions: Application to outdoor acoustic propagation
    Acoustical Society of America (ASA) ; 2017
    In:  The Journal of the Acoustical Society of America Vol. 142, No. 4_Supplement ( 2017-10-01), p. 2674-2674
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 142, No. 4_Supplement ( 2017-10-01), p. 2674-2674
    Abstract: In this work, Green’s function retrieval methods for an outdoor acoustic propagation channel are presented. Green’s function retrieval methods by multidimensional deconvolution and crosscorrelation are compared for different source distributions. Of particular interest is the accuracy of the retrieved Green’s function of an arbitrary sound source with that of an impulsive sound source. Also, the signal-to-noise ratio of both methods will be investigated. To this end, outdoor acoustic experiments are conducted in a clearing and wooded area in southern Maryland. Results will be obtained for various source-receiver ranges up to 400 m.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5014745
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2017
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  • 10
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    Online Resource
    Acoustic propagation in the vicinity of an isolated building
    Acoustical Society of America (ASA) ; 2007
    In:  The Journal of the Acoustical Society of America Vol. 121, No. 5_Supplement ( 2007-05-01), p. 3064-3064
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 121, No. 5_Supplement ( 2007-05-01), p. 3064-3064
    Abstract: The literature regarding urban acoustics has often been concerned with the propagation of sound through street canyons typical of residential areas in large cities, while sparsely built suburban areas have received little attention. As a fundamental case of acoustic propagation in suburban areas, the study of the influence that an isolated building has on propagating sound is a necessity in order to determine the processes (wall impedance, ground impedance, diffraction, diffusion, etc.) required to model the interaction of propagating acoustic waves with an isolated building. As such, an experimental and theoretical investigation of this fundamental case is currently being performed on isolated buildings of construction typical to North American suburban areas. Experimental results, using both continuous and impulsive excitation sources, for propagation near a single story, gabled roof building typical of some suburban areas will be presented.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4781840
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2007
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