bluuebunny/crossref_metadata_2025 huggingface dataset:
A two-dimensional model of a directional microphone: Calculation of the normal force and moment on the diaphragm
Authors: Homentcovschi Dorel , Aubrey Matthew J. , Miles Ronald N.
Published: February 2006

It has been shown that the parasitoid fly Ormia Ochracea exhibits exceptional sound localization ability achieved through the mechanical coupling of its eardrums [R. N. Miles et al., J. Acoust. Soc. Am. 98, 3059–3070 (1995)]. Based on this biological system a new directional microphone has been designed, having as a basic element a special diaphragm undergoing a rocking motion. This paper considers a 2D model of the microphone in which the diaphragm is considered as a 2D plate having slits on the sides. The slits lead to a backing volume limited by an infinite rigid wall parallel to the diaphragm in its neutral position. The reflection and diffraction of an incoming plane wave by this system are studied to determine the resultant force and resultant moment of pressure upon the diaphragm. The results show that such a microphone will be driven better in the case of narrow slits and deep cavities.
Material identification of real impact sounds: Effects of size variation in steel, glass, wood, and plexiglass plates
Authors: Giordano Bruno L. , McAdams Stephen
Published: February 2006

Identification of the material of struck objects of variable size was investigated. Previous studies on this issue assumed recognition to be based on acoustical measures of damping. This assumption was tested, comparing the power of a damping measure in explaining identification data with that of several other acoustical descriptors. Listeners’ performance was perfect with respect to gross material categories (steel-glass and wood-plexiglass) comprising materials of vastly different mechanical properties. Impaired performance was observed for materials within the same gross category, identification being based on the size of the objects alone. The damping descriptor accounted for the identification of the gross categories. However other descriptors such as signal duration explained the results equally well. Materials within the same gross category were identified mainly on the basis of signal frequency. Overall poor support for the relevance of damping to material perception was found. An analysis of the acoustical support for perfect material identification was carried out. Sufficient acoustical information for perfect performance was found. Thus, procedural biases for the origin of the effects of size could be discarded, pointing toward their cognitive, rather than methodological nature. Identification performance was explained in terms of the regularities of the everyday acoustical environment.
Acoustic detection and quantification of benthic egg beds of the squid Loligo opalescens in Monterey Bay, California
Authors: Foote Kenneth G. , Hanlon Roger T. , Iampietro Pat J. , Kvitek Rikk G.
Published: February 2006

The squid Loligo opalescens is a key species in the nearshore pelagic community of California, supporting the most valuable state marine fishery, yet the stock biomass is unknown. In southern Monterey Bay, extensive beds occur on a flat, sandy bottom, water depths 20–60m, thus sidescan sonar is a prima-facie candidate for use in rapid, synoptic, and noninvasive surveying. The present study describes development of an acoustic method to detect, identify, and quantify squid egg beds by means of high-frequency sidescan-sonar imagery. Verification of the method has been undertaken with a video camera carried on a remotely operated vehicle. It has been established that sidescan sonar images can be used to predict the presence or absence of squid egg beds. The lower size limit of detectability of an isolated egg bed is about 0.5m with a 400-kHz sidescan sonar used with a 50-m range when towed at 3 knots. It is possible to estimate the abundance of eggs in a region of interest by computing the cumulative area covered by the egg beds according to the sidescan sonar image. In a selected quadrat one arc second on each side, the estimated number of eggs was 36.5 million.
On the perception of voicing in syllable-initial plosives in noise
Authors: Jiang Jintao , Chen Marcia , Alwan Abeer
Published: February 2006

Previous studies [Lisker, J. Acoust. Soc. Am. 57, 1547–1551 (1975); Summerfield and Haggard, J. Acoust. Soc. Am. 62, 435–448 (1977)] have shown that voice onset time (VOT) and the onset frequency of the first formant are important perceptual cues of voicing in syllable-initial plosives. Most prior work, however, has focused on speech perception in quiet environments. The present study seeks to determine which cues are important for the perception of voicing in syllable-initial plosives in the presence of noise. Perceptual experiments were conducted using stimuli consisting of naturally spoken consonant-vowel syllables by four talkers in various levels of additive white Gaussian noise. Plosives sharing the same place of articulation and vowel context (e.g., ∕pa,ba∕) were presented to subjects in two alternate forced choice identification tasks, and a threshold signal-to-noise-ratio (SNR) value (corresponding to the 79% correct classification score) was estimated for each voiced/voiceless pair. The threshold SNR values were then correlated with several acoustic measurements of the speech tokens. Results indicate that the onset frequency of the first formant is critical in perceiving voicing in syllable-initial plosives in additive white Gaussian noise, while the VOT duration is not.
A numerically accurate and robust expression for bistatic scattering from a plane triangular facet
Authors: Wendelboe Gorm , Jacobsen Finn , Bell Judith M.
Published: February 2006

This work is related to modeling of synthetic sonar images of naval mines or other objects. Considered here is the computation of high frequency scattering from the surface of a rigid 3D-object numerically represented by plane triangular facets. The far field scattered pressure from each facet is found by application of the Kirchhoff approximation. Fawcett [J. Acoust. Soc. Am. 109, 1319–1320 (2001)] derived a time domain expression for the backscattered pressure from a triangular facet, but the expression encountered numerical problems at certain angles, and therefore, the effective ensonified area was applied instead. The effective ensonified area solution is exact at normal incidence, but at other angles, where singularities also exist, the scattered pressure will be incorrect. This paper presents a frequency domain expression generalized to bistatic scattering written in terms of sinc functions; it is shown that the expression improves the computational accuracy without loss of robustness.
Hybrid vibration isolator: Single axis control study
Authors: Herdic Peter C. , Corsaro Robert D. , Houston Brian H. , Baden Robert M.
Published: February 2006

Results are presented for a laboratory study of a compact, single-axis hybrid (active-passive) vibration isolator. The passive system component demonstrates a very high level of vibration isolation at frequencies roughly a factor of 3 above the fundamental system resonance. The active component complements the system by significantly reducing the transmitted vibration levels at lower frequencies, where the passive-only system is ineffective. The device consists of three basic components, a passive compliant spring, force and velocity sensing, and a piezoelectric actuation layer. The experimental system is typically excited at 50Hz with response characteristics measured over the band from ∼10 to 2000Hz. The isolation performance is evaluated for an optimized passive stage as well as for all relevant hybrid layer configurations. The optimal physical control law is determined by identifying positions in the device stack where actuation and sensing are most effective at minimizing the downstream base velocity and power flow through the mount. Local force and velocity minimization are implemented via a least mean squared adaptive control filter. The role of harmonic distortion and actuator nonlinearity is examined by comparing the system performance and out-of-band enhancement obtained using PZT-4, PZT-5H, and single-crystal PMN-PT actuator materials.
A comparison of the underwater acoustic performance of single crystal versus piezoelectric ceramic-based “cymbal” projectors
Authors: Tressler James F. , Howarth Thomas R. , Huang Dehua
Published: February 2006

For nearly 50years, piezoelectric ceramics (primarily from the PZT family) have been the materials of choice as the active elements in underwater electroacoustic sound projectors. There is currently great interest in the materials science community for the consideration of newly discovered single crystal relaxor ferroelectric compositions as a potential replacement in applications that utilize piezoelectric ceramics. One of the salient features of single crystal ferroelectrics is piezoelectric coefficients that are three to seven times greater than those found in PZT. Most of the single crystal data reported in the open literature, however, are for near static drive conditions. This paper reports on the acoustic performance of prototype underwater sound projectors built from single crystal materials and driven at high drive levels over the frequency range of 500Hz to 25kHz. It is shown that the single crystal-based projectors exhibit at least a 4dB higher source level as compared to identical PZT-based units. In addition, the volt-amp product required to produce 1W of acoustic output is approximately one-third as much. It has also been demonstrated that when driving either the PZT-based or single crystal projectors for 1–2h under high drive, no significant degradation in acoustic performance occurs.
Optimally sensitive and efficient compact loudspeakers
Authors: Aarts Ronald M.
Published: February 2006

In conventional loudspeaker system design, the force factor Bl is chosen in relation to enclosure volume, cone diameter, and moving mass to yield a flat response over a specified frequency range. For small-cabinet loudspeakers such a design is quite inefficient. This is shown by calculating the efficiency and voltage sensitivity. The frequency response is manipulated electronically in a strong nonlinear fashion, which has consequences for the sound quality, but it then turns out that systems using much lower force factors can provide greater usable efficiency, at least over a limited frequency range. For these low-force-factor loudspeakers, a practically relevant and analytically tractable optimality criterion, involving the loudspeaker parameters, will be defined. This can be especially valuable in designing very compact loudspeaker systems. An experimental example of such a design is described. This new, optimal design has a much higher power efficiency as well as a higher voltage sensitivity than current bass drivers, while the cabinet can be much smaller.
Causal analysis of transient viscoelastic wave propagation
Authors: Moura André
Published: February 2006

Dispersion due to internal frictions as wave propagates is a consequence of the second principle of thermodynamics. When the wavelengths are several times higher than the mesoscopic inhomogeneities, internal diffractions can be ignored and the propagation medium can then be considered as a continuum at the scale of these wavelengths. Here, we consider the dissipation mechanism due to viscosity only. By mean of Laplace transforms both on time and space, a causal analysis leads us to a closed-form solution, which we think is the simplest analytical form. This is illustrated by searching the viscoelastic Green’s function associated with the horizontal shear wave generated by a uniform impulsive line source in an infinite homogeneous medium, whose example is almost mathematically equivalent to the study of the scalar wave generated in viscous fluid. The described method is thus restricted to one-wave propagation problems and is probably not generally applicable when the source generates several waves. In the course to obtain a transient analytical expression of pulsed wave through a dispersive medium, this study proposes a method for transient cylindrical waves, while most previous methods concern plane waves.
Comodulation detection differences for fixed-frequency and roved-frequency maskers
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: February 2006

This study investigated comodulation detection differences (CDD) for fixed- and roved-frequency maskers. The objective was to determine whether CDD could be accounted for better in terms of energetic masking or in terms of perceptual fusion/segregation related to comodulation. Roved-frequency maskers were used in order to minimize the role of energetic masking, allowing possible effects related to perceptual fusion/segregation to be revealed. The signals and maskers were composed of 30-Hz-wide noise bands. The signal was either comodulated with the masker (A/A condition) or had a temporal envelope that was independent (A/B condition). The masker was either gated synchronously with the signal or had a leading temporal fringe of 200ms. In the fixed-frequency masker conditions, listeners with low A/A thresholds showed little masking release due to masker temporal fringe and had CDDs that could be accounted for by energetic masking. Listeners with higher A/A thresholds in the fixed-frequency masker conditions showed relatively large CDDs and large masking release due to a masker temporal fringe. The CDDs of these listeners may have arisen, at least in part, from processes related to perceptual segregation. Some listeners in the roved masker conditions also had large CDDs that appeared to be related to perceptual segregation.
Probe-corrected near-field measurements on a truncated cylinder
Authors: Hansen Thorkild B.
Published: February 2006

A probe-corrected theory is presented for computing the acoustic far fields of transducers and scatterers from measurements of near fields on a cylindrical surface. The near-field data is truncated at the top, bottom, and angular edges of the scan cylinder. These truncation edges can cause inaccuracies in the computed far fields. Correction techniques are developed for the top and bottom truncation edges. The cylindrical wave expansions automatically apply an angular taper to the near-field data that reduces the effect of the angular truncation edges. The taper function depends on the probe and the angular sample spacing. The theory is validated through numerical examples involving a point source and a baffled piston transducer probe.
Preliminary evidence for the use of microseismic cues for navigation by the Namib golden mole
Authors: Lewis Edwin R. , Narins Peter M. , Jarvis Jennifer U. M. , Bronner Gary , Mason Matthew J.
Published: February 2006

Insect prey of the Namib golden mole congregate beneath clumps of grass scattered among the sand dunes of the Namib Desert. In the presence of the light winds that typically blow over the Namib Desert, these grass clumps emit low-amplitude vibrations that are transmitted through the sand. While foraging in the sand-swimming mode (a few centimeters below the surface of the sand), some moles apparently were attracted toward manmade sources emitting vibrations matching those recorded from the grass clumps. This is the first direct evidence that these desert mammals use seismic cues for navigation.
An inversion of Freedman’s “image pulse” model in air
Authors: Tsakiris Janos , McKerrow Phillip
Published: February 2006

In recent years, research into object classification based on ultrasonic sensing has shown that sonar is a rich source of data suitable for robust classification for specific classes of objects. However, these systems lack generality, precision, and are often slow as they need to collect and integrate multiple scans. The objective was the development of more efficient techniques for ultrasonic based object recognition through an inversion of the extended form of Freedman’s “image pulse” model. Earlier work extended this model, originally developed for a fluid medium with coincident transmitter/receiver configurations, to noncoincident configurations in air. This extended model was inverted, producing one that would calculate the geometry of a scattering body from an analysis of echoes received after insonification of the body with ultrasonic pulses. Quantitative verification of this model with various scattering bodies proved elusive, with low correlation between experiment and theory due to matrix instability and difficulties in obtaining data of sufficient accuracy. However, qualitative trends in the data indicate the model is essentially correct, though very sensitive to measurement precision and media characteristics, and there is reason to believe that further work under more controlled laboratory conditions and/or a different medium would verify the model’s validity quantitatively.
Individual differences in auditory discrimination of spectral shape and speech-identification performance among elderly listeners
Authors: Shrivastav Mini N. , Humes Larry E. , Kewley-Port Diane
Published: February 2006

Speech-understanding difficulties observed in elderly hearing-impaired listeners are predominantly errors in the recognition of consonants, particularly within consonants that share the same manner of articulation. Spectral shape is an important acoustic cue that serves to distinguish such consonants. The present study examined whether individual differences in speech understanding among elderly hearing-impaired listeners could be explained by individual differences in spectral-shape discrimination ability. This study included a group of 20 elderly hearing-impaired listeners, as well as a group of young normal-hearing adults for comparison purposes. All subjects were tested on speech-identification tasks, with natural and computer-synthesized speech stimuli, and on a series of spectral-shape discrimination tasks. As expected, the young normal-hearing adults performed better than the elderly listeners on many of the identification tasks and on all but two discrimination tasks. Regression analyses of the data from the elderly listeners revealed moderate predictive relationships between some of the spectral-shape discrimination thresholds and speech-identification performance. The results indicated that when all stimuli were at least minimally audible, some of the individual differences in the identification of natural and synthetic speech tokens by elderly hearing-impaired listeners were associated with corresponding differences in their spectral-shape discrimination abilities for similar sounds.
A four particle velocity sensor device
Authors: Yntema D. R. , Druyvesteyn W. F. , Elwenspoek M.
Published: February 2006

In a sound field disturbance of pressure, particle velocity, density, temperature, and energy occur. In this paper acoustic disturbances in air are considered. In the majority of papers on acoustics only changes in the sound pressure are reported while in this paper results on the particle velocity are reported. Since particle velocity is a vector, while the pressure is a scalar, more information can be obtained when using a particle velocity sensor instead of a pressure sensor (microphone). Four particle velocity sensors are combined to one (small) device. In a reverberant room the four autospectra and the six cross spectra are determined. Interpretation of the measured results gives information of the free field (sound field without a contribution of reflections) as well as of the reverberant field.
Technique for “tuning” vocal tract area functions based on acoustic sensitivity functions
Authors: Story Brad H.
Published: February 2006

A technique for modifying vocal tract area functions is developed by using sum and difference combinations of acoustic sensitivity functions to perturb an initial vocal tract configuration. First, sensitivity functions [e.g., Fant and Pauli, Proc. Speech Comm. Sem. 74, 1975] are calculated for a given area function, at its specific formant frequencies. The sensitivity functions are then multiplied by scaling coefficients that are determined from the difference between a desired set of formant frequencies and those supported by the current area function. The scaled sensitivity functions are then summed together to generate a perturbation of the area function. This produces a new area function whose associated formant frequencies are closer to the desired values than the previous one. This process is repeated iteratively until the coefficients are equal to zero or are below a threshold value.
The spatial context of free-ranging Hawaiian spinner dolphins (Stenella longirostris) producing acoustic signals
Authors: Lammers Marc O. , Schotten Michiel , Au Whitlow W. L.
Published: February 2006

To improve our understanding of how dolphins use acoustic signals in the wild, a three-hydrophone towed array was used to investigate the spatial occurrence of Hawaiian spinner dolphins (Stenella longirostris) relative to each other as they produced whistles, burst pulses, and echolocation clicks. Groups of approximately 30 to 60 animals were recorded while they traveled and socialized in nearshore waters off Oahu, Hawaii. Signaling animals were localized using time of arrival difference cues on the three channels. Sequences of whistles occurred between dolphins separated by significantly greater distances than animals producing burst pulses. Whistles typically originated from dolphins spaced widely apart (median = 23m), supporting the hypothesis that whistles play a role in maintaining contact between animals in a dispersed group. Burst pulses, on the other hand, usually came from animals spaced closer to one another (median = 14m), suggesting they function as a more intimate form of signaling between adjacent individuals. The spacing between echolocating animals was more variable and exhibited a bimodal distribution. Three quarters of echolocating animals were separated by 10m or more, suggesting that the task of vigilance in a pod may not be shared equally by all members at all times.
Perception and production of English vowels by Mandarin speakers: Age-related differences vary with amount of L2 exposure
Authors: Jia Gisela , Strange Winifred , Wu Yanhong , Collado Julissa , Guan Qi
Published: February 2006

In this study we assessed age-related differences in the perception and production of American English (AE) vowels by native Mandarin speakers as a function of the amount of exposure to the target language. Participants included three groups of native Mandarin speakers: 87 children, adolescents and young adults living in China, 77 recent arrivals who had lived in the U.S. for two years or less, and 54 past arrivals who had lived in the U.S. between three and five years. The latter two groups arrived in the U.S. between the ages of 7 and 44 years. Discrimination of six AE vowel pairs ∕i-ɪ∕, ∕i-eɪ∕, ∕ϵ-æ∕, ∕æ-α∕, ∕α-Λ∕, and ∕u-α∕ was assessed with a categorial AXB task. Production of the eight vowels ∕i, ɪ, eɪ, ϵ, æ, Λ, α, u∕ was assessed with an immediate imitation task. Age-related differences in performance accuracy changed from an older-learner advantage among participants in China, to no age differences among recent arrivals, and to a younger-learner advantage among past arrivals. Performance on individual vowels and vowel contrasts indicated the influence of the Mandarin phonetic/phonological system. These findings support a combined environmental and L1 interference/transfer theory as an explanation of the long-term younger-learner advantage in mastering L2 phonology.
Characterizing glottal jet turbulence
Authors: Alipour Fariborz , Scherer Ronald C.
Published: February 2006

Air pressure associated with airflow from the lungs drives the vocal folds into oscillation and allows the air to exit the glottis as a turbulent jet, even though laminar flow may enter the glottis from the trachea. The separation of the turbulence from the deterministic portion of the glottal jet was investigated in the excised canine larynx model. The present study is methodological in that the main goal was to examine three methods of obtaining reasonable representations of both the deterministic signal and the residual turbulence portion: (a) smoothing, (b) wavelet denoising, and (c) ensemble averaging. Ensemble averaging resulted in a deterministic signal that disregarded gross cyclic alterations while exaggerating the turbulence intensity. Wavelet denoising can perform an excellent analysis and synthesis of the glottal velocity, but was problematic in determining which levels of analysis to choose to represent both the deterministic and turbulence appropriately. Smoothing appeared to be the most appropriate for phonation velocities because it preserved gross cyclic variations important to perturbations and modulations, while extracting turbulence at what appears to be reasonable levels.
Measurement of temporal changes in vocal tract area function from 3D cine-MRI data
Authors: Takemoto Hironori , Honda Kiyoshi , Masaki Shinobu , Shimada Yasuhiro , Fujimoto Ichiro
Published: February 2006

A 3D cine-MRI technique was developed based on a synchronized sampling method [Masaki et al., J. Acoust. Soc. Jpn. E 20, 375–379 (1999)] to measure the temporal changes in the vocal tract area function during a short utterance /aiueo/ in Japanese. A time series of head-neck volumes was obtained after 640 repetitions of the utterance produced by a male speaker, from which area functions were extracted frame-by-frame. A region-based analysis showed that the volumes of the front and back cavities tend to change reciprocally and that the areas near the larynx and posterior edge of the hard palate were almost constant throughout the utterance. The lower four formants were calculated from all the area functions and compared with those of natural speech sounds. The mean absolute percent error between calculated and measured formants among all the frames was 4.5%. The comparison of vocal tract shapes for the five vowels with those from the static MRI method suggested a problem of MRI observation of the vocal tract: data from static MRI tend to result in a deviation from natural vocal tract geometry because of the gravity effect.
Predicting perceived sharpness of broadband noise from multiple moments of the specific loudness distribution
Authors: Marui Atsushi , Martens William L.
Published: February 2006

Equal sharpness contours for broadband noise were generated through matches made between a standard reference noise and comparison noise stimuli varying in spectral envelope. Based upon the results of the sharpness matching task, a set of 20 percussive broadband noise stimuli was constructed and presented to three subjects in a sharpness rating experiment using white noise as a standard stimulus. Predicting obtained sharpness ratings for these percussive broadband noise stimuli from first and second moments of the stimulus specific loudness distribution was more successful than conventional prediction based only upon the weighted first moment.
Description and measurement of the acoustic characteristics of two-tailpipe mufflers
Authors: Torregrosa A. J. , Broatch A. , Fernández T. , Denia F. D.
Published: February 2006

Two-tailpipe mufflers have become a usual solution for flow noise abatement in turbocharged Diesel engines, since the mean flow velocity at the exhaust outlet may be reduced without increasing the tailpipe diameter, which would give rise to an increase of noise associated with engine orders. In this communication, the acoustic characteristics of mufflers with two tailpipes are studied. First, a global representation of the muffler acoustics in terms of three reflection coefficients and six transmission coefficients is presented, and a procedure to obtain, from such representation, a conventional two-port transfer matrix by setting the reflection coefficient at one of the outlet pipes is provided. A procedure based on the extension of the impulse method as applied to single inlet-single outlet mufflers was devised for the experimental determination of the transmission and reflection coefficients, and experiments on a nonsymmetric oval expansion chamber allowed one to check the suitability of the representation. The results indicate that nonsymmetries in the location of the tailpipes may be relevant for the design of realistic mufflers, as they may affect the source located at each tailpipe outlet and thus the resulting exhaust noise radiated.
Separation of thermoviscous losses in CelcorTM ceramic
Authors: Liu Jin , Garrett Steven L. , Long Gregory S. , Sen Ayusman
Published: February 2006

A series of three papers by Sabatier and coauthors reported successive improvements to both the theory and measurement of excess attenuation due to the wall porosity of CelcorTM. We report an independent measurement of excess attenuation due to wall porosity of Celcor conducted to study the attenuation due to viscous and thermal effects separately for a thermoacoustic refrigeration application. A 38-mm-long sample was placed at the center of a 700-mm-long electrodynamically driven plane wave resonator. The location of the Celcor within the standing wave would select different contributions from viscosity and thermal conductivity. As per the technique described by Moldover et al. [Modern Acoustical Techniques for the Measurement of Mechanical Properties (Academic, San Diego, 2001)], the quality factors Q were measured between 230Hz and 1.6kHz in air at atmospheric pressure on a pristine sample. Wall pores were then blocked by an in situ polymerization sealing process. There was no observed decrease in attenuation of even modes (dominated by thermal loss) for the coated sample below 1.0kHz. The volume exclusion due to pore sealing was inferred by the increase in even mode resonance frequencies in good agreement with other determinations of wall porosity. Thermoviscous losses were computed with DELTAE and compared to measured losses.
Noninvasive generation and measurement of propagating waves in arterial walls
Authors: Zhang Xiaoming , Greenleaf James F.
Published: February 2006

Arterial wall stiffness can be associated with various diseases. Arteriosclerosis involves the buildup of plaques within artery walls that stiffen the arteries. The stiffness of an artery can be assessed by measurement of the pulse wave velocity (PWV). Usually, PWV is estimated using the foot-to-foot method. However, the foot of the pressure wave is not very clear due to reflected waves. Also, the blood pressure wave generated by the heart is normally a low frequency wave, hence the time resolution is low. PWV is an average indicator of artery stiffness between the two measuring positions, and therefore cannot easily identify local stiffness. In this paper a force on the arterial wall is generated noninvasively by the radiation force of ultrasound. Techniques for measuring the propagating wave due to this localized force are studied. The excitation force can be either a very short pulse or a modulated cw signal of a few hundred hertz. The temporal resolution of this method, which is in the range of microseconds, is much higher than the conventional pressure PWV method, and therefore allows the wave velocity to be measured accurately over short distances of a few millimeters.
Obtaining the complex pressure field at the hologram surface for use in near-field acoustical holography when pressure and in-plane velocities are measured
Authors: Harris Michael C. , Blotter Jonathan D. , Sommerfeldt Scott D.
Published: February 2006

Acoustical-based imaging techniques have found merit in determining the behavior of vibrating structures. These techniques are commonly used in numerous applications to obtain detailed noise source information and energy distributions on source surfaces. Source reconstructions using near-field acoustical holography (NAH) are reliant upon accurate measurement of the pressure field at the hologram surface. For complex acoustic fields this requires fine spatial resolution and therefore demands large microphone arrays. In this paper, an interpolation method is developed for obtaining the complex pressure field at the hologram surface from pressure and velocity measurements. Because particle velocity measurements provide directional information, a more accurate characterization of the pressure field with fewer measurement locations is obtained. The processing technique presented does not relate directly to the holographic reconstruction itself. However, the interpolation scheme presented serves as a preprocessing step before a NAH algorithm is applied. The presentation and validation of the interpolation scheme is the major focus of the paper. An analytical comparison of NAH reconstructions from traditional pressure measurements to reconstructions using the preprocessed pressure and velocity measurements is presented. A vibrating plate and cylinder are considered as test cases to validate the analytical results.
Invariance principles for cochlear mechanics: Hearing phases
Authors: Reimann H. M.
Published: February 2006

A functional model of the cochlea is devised on the basis of the results from classical experiments. The basilar membrane filter is investigated in detail. Its phase is close to linear in the region around the peak of the amplification. On one side this has consequences for the time analysis and on the other side this has led to a prediction on phase perception for very simple combinations of tones, a prediction which is now confirmed by experiments. Equivariance under the dilation group permits one to describe the model by a wavelet transform [Daubechies, Ten Lectures on Wavelets (SIAM, Philadelphia, 1992)]. The wavelet is discussed in reference to the phase analysis of the basilar membrane filter.
Resolution in azimuth sound localization in the Mongolian gerbil (Meriones unguiculatus)
Authors: Maier Julia K. , Klump Georg M.
Published: February 2006

Minimum resolvable angles (MRAs) for sound localization in azimuth in the gerbil were determined in a behavioral study using tones, 300-Hz bands of noise centered at frequencies between 500Hz and 8kHz and broad-band noise of on average 60dB SPL overall level. Using the method of constant stimuli, seven gerbils were trained in a two-alternative-forced-choice procedure to indicate if sounds were presented to them from the left or from the right by choosing the left or right arm of a Y-shaped cage. The MRA is the minimum angle between two loudspeaker locations that the gerbils discriminated. Animals were either stimulated from the front (N=4) or from the back (N=3). The MRA for broad-band noise randomly varying in level by ±6dB was 23° and 45° for gerbils stimulated from the front or back, respectively. Generally a gerbil’s MRA for tones declined up to 2kHz reaching 20° and 31° for gerbils stimulated from the front or back, respectively, and the MRA was generally increased above this frequency. Results for narrow-band noise stimuli were similar. Results are discussed with respect to the available interaural cues and physiological mechanisms of sound localization in the gerbil.
Induced loudness reduction as a function of exposure time and signal frequency
Authors: Wagner Eva , Scharf Bertram
Published: February 2006

Induced loudness reduction (ILR) is the decline in the loudness of a weaker tone induced by a preceding stronger tone. In this study we investigate how ILR depends on exposure time and signal frequency. For 12 listeners, successive magnitude estimation was used to measure the loudness of 70-dB-SPL test tones, presented with and without preceding 80-dB-SPL inducer tones at the same frequency. Experiment 1 measured the evolution of ILR over time at 0.5kHz. The results suggest that ILR may begin after a single inducer presentation, and increases over at least 2 to 3min as the inducer and test tones are repeated every few seconds. Following the cessation of the inducer, the recovery of loudness is slow and still incomplete after 1min. Experiment 2 extended the measurements to additional signal frequencies. The results show that the amount of ILR and its evolution over time are approximately the same at frequencies from 0.5 to 8kHz. Similarly, loudness matching showed no effect of frequency on ILR, which averaged 8.2dB. These findings, together with previously noted similarities among ILR, ipsilaterally induced loudness adaptation, and temporary loudness shift, indicate that loudness reduction induced by stronger sounds is a very common phenomenon.
Hearing sensitivity and critical ratios of hooded crows (Corvus corone cornix)
Authors: Jensen Kenneth K. , Klokker Signe
Published: February 2006

The hearing threshold and critical ratios were estimated psycho-acoustically for captive wild-caught hooded crows by a yes/no procedure and the method of constant stimuli. Human subjects were tested in the same setup for direct comparison and to check for experimental artifacts. The hooded crows were found to have excellent low-frequency hearing capabilities compared to other passerine birds. Their hearing sensitivity is very close to that of humans at and below 5.6kHz. The distribution of the critical ratios differed from that of the average bird and humans in being rather constant with frequency and not increasing monotonically. It furthermore showed a middle region of 5–6dB lower critical ratio values between 500Hz and 2kHz. It is suggested that this improved range for hearing in noise is an adaptation to long distance communication. Human critical ratios gave the expected values and were between 3 and 6dB lower than those of the crows.
A constitutive model of the human vocal fold cover for fundamental frequency regulation
Authors: Zhang Kai , Siegmund Thomas , Chan Roger W.
Published: February 2006

The elastic as well as time-dependent mechanical response of the vocal fold cover (epithelium and superficial layer of the lamina propria) under tension is one key variable in regulating the fundamental frequency. This study examines the hyperelastic and time-dependent tensile deformation behavior of a group of human vocal fold cover specimens (six male and five female). The primary goal is to formulate a constitutive model that could describe empirical trends in speaking fundamental frequency with reasonable confidence. The constitutive model for the tissue mechanical behavior consists of a hyperelastic equilibrium network in parallel with an inelastic, time-dependent network and is combined with the ideal string model for phonation. Results showed that hyperelastic and time-dependent parameters of the constitutive model can be related to observed age-related and gender-related differences in speaking fundamental frequency. The implications of these findings on fundamental frequency regulation are described. Limitations of the current constitutive model are discussed.
Model for vocalization by a bird with distensible vocal cavity and open beak
Authors: Fletcher Neville H. , Riede Tobias , Suthers Roderick A.
Published: February 2006

Some birds make use of a distensible oral cavity to produce nearly pure-tone song. Songbirds such as the Northern cardinal (Cardinalis cardinalis) have a muscularly distended oropharyngeal-esophageal cavity between the top of the trachea and the open beak. The present paper analyzes the acoustics of this vocal system. It is shown that the resonance of the oropharyngeal-esophageal cavity, vented through the beak, introduces a dominant peak in the radiation efficiency, the frequency of which can be adjusted by varying the volume of the cavity, the beak gape, and perhaps the position of the tongue in the mouth. To produce nearly pure-tone song, the bird adjusts the frequency of this peak to coincide with the fundamental of the syringeal oscillation. The present paper provides the acoustical analysis underlying this behavior.
Directionality of sperm whale sonar clicks and its relation to piston radiation theory
Authors: Beedholm Kristian , Møhl Bertel
Published: February 2006

This paper investigates the applicability to sperm whales of the theory of sound radiating from a piston. The theory is applied to a physical model and to a series of sperm whale clicks. Results show that wave forms of off-axis signals can be reproduced by convolving an on-axis signal with the spatial impulse response of a piston. The angle of a recorded click can be estimated as the angle producing the spatial impulse response that gives the best match with the observation when convolved with the on-axis wave form. It is concluded that piston theory applies to sperm whale sonar click emission.
Acoustic impedance matching for axial wave radiation from cylindrical polyvinylidene fluoride film air ultrasonic transducer mounted inside of concentric hollow cylinder
Authors: Toda Mionoru
Published: February 2006

It is well known that radial vibration of cylindrical polyvinylidene fluoride (PVDF) film excites acoustic waves towards radial direction in 360-deg range. When the length of cylindrical film is equal to or less than half the wavelength, the excited wave towards the axial direction becomes stronger than the radial wave. In this work, a cylindrical PVDF transducer was concentrically mounted inside of a hollow cylinder, and it was observed that the smaller the gap between film surface and inner wall surface of the pipe, the more the axial wave was excited. In order to explain this phenomenon, radiation impedance for axial wave excitation was calculated, and it was found that (1) radiation impedance increases with decreasing gap; (2) energy flow from transducer to axial wave increases with decreasing gap and becomes maximum at impedance matched condition; and (3) for the radiation impedance larger than optimum matched condition, the output decreases with increasing radiation impedance (decreasing gap) and the resonance frequency of cylindrical transducer shifts to the higher side due to loading of imaginary part of too high radiation impedance. All these results were successfully observed by experiments at 85-kHz burst mode. This principle can be applied to a new class of ultrasonic air transducer.
Acoustic microscopy inspection of layered structures
Authors: Du Jikai , Tittmann Benhard R.
Published: February 2006

Thin films are widely applied in a variety of fields and, for example, are utilized in semiconductor devices, biological measurements, optical components, and micro-electro-mechanical-structures (MEMS). Thin films can serve for conductive and capacitive effects, tissue elastic properties evaluation, and control of optical properties. Therefore, the evaluation of thin film integrity is necessary and important. A thin film component is a layered structure and usually referred to as a film-substrate system. Acoustic microscopy is a nondestructive technique, which can generate surface acoustic waves (SAWs) in the thin film/substrate system. The energy of these SAWs is confined to the system surface and thus suitable for the evaluation of film properties. In our research, theoretical modeling of wave propagation in soft thin film/substrate system with different material properties and bond strength is established. A relationship between dispersive wave propagation and film integrity is discussed. A new experimental system is reported for measuring dispersion curves up to 1 GHz. Preliminary data are presented and compared to the theory. Good agreement was observed.
Industrial noise control engineering principles and standard practices applicable to engineers and industrial hygienists
Authors: Anderson Robert R.
Published: February 2006

Industrial organizations have accepted the notion that noise control is no longer 100% of one person’s responsibility, but a collaborative effort among engineers and industrial hygiene professionals. Proven noise control measures exist and are commercially available for many industrial noise sources. There are also noise control concepts and techniques that can be adopted by maintenance and other personnel as standard practices. Awareness of the elements of noise control engineering can offer benefit in areas such as equipment procurement, workplace risk assessment, and manufacturing program planning. The focus of this presentation is to discuss the elements of noise control engineering that manufacturing engineers and industrial hygiene professionals would need to apply out of their university education into practice, and the benefits that would be derived from this information.
Characteristics of phonation in women who produce voiced versus voiceless /h/
Authors: Koenig Laura L.
Published: February 2006

Production of the consonant /h/ typically involves a vocal-fold abduction gesture. Although /h/ is traditionally described as voiceless in English, voiced allophones also occur. Our recent work has described the phonatory behavior of women who produce a mixture of voiced and voiceless /h/; our results suggested speaker-specific patterns of the factors that lead to devoicing. This study characterizes the behavior of normal women who produce exclusively voiced /h/ and compares it to those who produced both voiced and voiceless /h/. Measures of baseline (dc) airflow are used as an index of abduction degree; peak intraoral pressures during adjacent /p/ closures provide a measure of subglottal pressure; and pulse-by-pulse measures are made of f0 and pulse amplitude (ac flow) around the /h/ abduction gesture. Multidimensional analyses are carried out within speakers to determine how these vocal parameters are related. We expect that women who produce only voiced /h/ will differ from those who devoice some /h/ productions in the parameters that facilitate phonation, such as higher subglottal pressures, smaller abduction degrees, and reduced vocal-fold tension as reflected in f0 measures. Based on our previous findings, however, we also expect individual variation in the phonatory settings that produce voiced /h/. [Work supported by NIH.]
Simulation of B-mode image synthesis with the fast near-field method and time-space decomposition
Authors: Kelly James F. , McGough Robert J.
Published: February 2006

Rapid calculations of scattered and pulse-echo acoustic fields are required for simulations of ultrasonic imaging systems. Due to the large computational grids, broadband pulses, and complex scattering geometries, these simulations are computationally intensive with traditional tools. A new computational framework, based on the fast near-field method and a time-space decomposition technique, is developed for transient acoustic scattering problems. By analytically decomposing the temporal and spatial dependence of the pulse-echo field, this time-space decomposition method computes the first-order scattered field in an efficient and flexible manner. Due to the bandlimited nature of the time-space decomposition approach, sampling frequencies commensurate with the bandwidth of the excitation pulse are used in the scattering simulations. B-mode imaging is simulated by computing the scattered fields due to a collection of scatterers for multiple steering angles. The pulse echo field generated by a 128-element phased array of rectangular elements is derived and numerically evaluated. The computed transient fields are validated and compared with the FIELD II software in terms of computation time. Preliminary results show that the combination of the fast near-field method and time-space decomposition is significantly faster than FIELD II for numerical simulations of diagnostic imaging systems.
Toxic Potential of Materials at the Nanolevel
Authors: Nel Andre , Xia Tian , Mädler Lutz , Li Ning
Published: February 2006

Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. These materials are increasingly being used for commercial purposes such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and drug carriers. Materials in this size range may approach the length scale at which some specific physical or chemical interactions with their environment can occur. As a result, their properties differ substantially from those bulk materials of the same composition, allowing them to perform exceptional feats of conductivity, reactivity, and optical sensitivity. Possible undesirable results of these capabilities are harmful interactions with biological systems and the environment, with the potential to generate toxicity. The establishment of principles and test procedures to ensure safe manufacture and use of nanomaterials in the marketplace is urgently required and achievable.