bluuebunny/crossref_metadata_2025 huggingface dataset:
An Antisense Oligonucleotide Against H1 Inhibits the Classical Sodium Current but not ICa(TTX) in Rat Ventricular Cells
Authors: Sha Qun , Robinson Shawn W. , McCulle Stacey L. , Shorofsky Stephen R. , Welling Paul A. , Goldman L. , Balke C. William
Published: March 2003

I
Ca(TTX) is a sodium current component, functionally distinct from the main body of sodium current, seen in cardiac and other cells. To determine if ICa(TTX) channels are a separate isoform from the classical cardiac sodium channels, we exposed rat ventricular cells in primary culture to an antisense oligonucleotide (AON) directed against rH1 (rNav1.5): 5′‐CTCCTCATACCCTCT‐3′. The homologous human sequence has been identified (and confirmed by us on HEK 293 cells) as effective against hH1 expressed heterologously. Scrambled sequence (5′‐CCCCCCTTATCTACT‐3′) controls were also included. The AON (10 μm; day 2 of exposure) reduced the classical sodium current by 69.6 % compared to untreated and 60.8 % compared to scrambled sequence (10 μm; day 2 of exposure) controls (mean ±s.e.m. maximum peak inward current density of −8.23 ± 0.60 pA pF−1, 18 cells, for untreated; −6.37 ± 0.79 pA pF−1, 16 cells, for scrambled sequence; and −2.50 ± 0.31 pA pF−1, 18 cells, for AON‐treated cells). The two control groups are not significantly different from each other, but are both significantly different from the AON‐treated group (P < 0.001). The inhibition was specific for sodium channels, with no significant AON effect on the L‐type calcium current. This confirms that H1 generates the classical cardiac sodium current. This same AON at the same concentration and time of exposure had no significant effect on ICa(TTX) (mean of −4.72 ± 0.55, 15 cells; −5.47 ± 0.53, 13 cells; and −5.04 ± 0.63 pA pF−1, 15 cells, for untreated controls, scrambled controls and AON treated, respectively). Hence, ICa(TTX), which is functionally distinct from the classical cardiac sodium current, is encoded by a distinct gene.
The Smooth Muscle Myosin Seven Amino Acid Heavy Chain Insert's Kinetic Role in the Crossbridge Cycle for Mouse Bladder
Authors: Karagiannis Peter , Babu Gopal J. , Periasamy Muthu , Brozovich Frank V.
Published: March 2003

The seven amino acid insert in the smooth muscle myosin heavy chain is thought to regulate the kinetics of contraction, contributing to the differences between fast and slow smooth muscle. The effects of this insert on force and stiffness were determined in bladder tissue of a transgenic mouse line expressing the insert SMB at one of three levels: an SMB wild type (+/+), an SMA homozygous type (−/−) and a heterozygous type (+/−). For skinned muscle, an increase in MgADP or inorganic phosphate (Pi) should shift the distribution of crossbridges in the actomyosin ATPase (AMATPase) to increase the relative population of the crossbridge state prior to ADP release and Pi release, respectively. Exogenous ADP increased force and stiffness in a manner consistent with increasing the Ca2+ concentration in both the +/+ and +/− mouse types. However, the −/− type showed a significantly greater increase in force than in stiffness suggesting that immediately prior to ADP release, the AMATPase either has an additional force producing isomerization state or a slower ADP dissociation rate for the −/− type compared to the +/+ or +/− types. Exogenous Pi led to a significantly greater decrease in stiffness than in force for all three mouse types suggesting that there is a force producing state prior to Pi release. In addition, the increase in Pi showed similar changes in the +/+ and −/− types whereas in the +/− type the decreases in both force and stiffness were greater than the other two mouse types indicating that the insert can affect the cooperativity between myosin heads. In conclusion, the seven amino acid insert modulates the kinetics and/or states of the AMATPase, which could lead to differences in the kinetics of contraction between fast and slow smooth muscle.
Metabolic Regulation of Ca2+ Release in Permeabilized Mammalian Skeletal Muscle Fibres
Authors: Isaevaand Elena V. , Shirokova Natalia
Published: March 2003

In the present study, the link between cellular metabolism and Ca2+ signalling was investigated in permeabilized mammalian skeletal muscle. Spontaneous events of Ca2+ release from the sarcoplasmic reticulum were detected with fluo‐3 and confocal scanning microscopy. Mitochondrial functions were monitored by measuring local changes in mitochondrial membrane potential (with the potential‐sensitive dye tetramethylrhodamine ethyl ester) and in mitochondrial [Ca2+] (with the Ca2+ indicator mag‐rhod‐2). Digital fluorescence imaging microscopy was used to quantify changes in the mitochondrial autofluorescence of NAD(P)H. When fibres were immersed in a solution without mitochondrial substrates, Ca2+ release events were readily observed. The addition of l‐glutamate or pyruvate reversibly decreased the frequency of Ca2+ release events and increased mitochondrial membrane potential and NAD(P)H production. Application of various mitochondrial inhibitors led to the loss of mitochondrial [Ca2+] and promoted spontaneous Ca2+ release from the sarcoplasmic reticulum. In many cases, the increase in the frequency of Ca2+ release events was not accompanied by a rise in global [Ca2+]i. Our results suggest that mitochondria exert a negative control over Ca2+ signalling in skeletal muscle by buffering Ca2+ near Ca2+ release channels.
β‐Oxidation of 5‐hydroxydecanoate, a Putative Blocker of Mitochondrial ATP‐Sensitive Potassium Channels
Authors: Hanley Peter J. , Gopalan K. V. , Lareau Rachel A. , Srivastava D. K. , von Meltzer Martin , Daut Jürgen
Published: March 2003

5‐Hydroxydecanoate (5‐HD) inhibits ischaemic and pharmacological preconditioning of the heart. Since 5‐HD is thought to inhibit specifically the putative mitochondrial ATP‐sensitive K+ (KATP) channel, this channel has been inferred to be a mediator of preconditioning. However, it has recently been shown that 5‐HD is a substrate for acyl‐CoA synthetase, the mitochondrial enzyme which ‘activates’ fatty acids. Here, we tested whether activated 5‐HD, 5‐hydroxydecanoyl‐CoA (5‐HD‐CoA), is a substrate for medium‐chain acyl‐CoA dehydrogenase (MCAD), the committed step of the mitochondrial β‐oxidation pathway. Using a molecular model, we predicted that the hydroxyl group on the acyl tail of 5‐HD‐CoA would not sterically hinder the active site of MCAD. Indeed, we found that 5‐HD‐CoA was a substrate for purified human liver MCAD with a Km of 12.8 ± 0.6 μm and a kcat of 14.1 s−1. For comparison, with decanoyl‐CoA (Km∼3 μm) as substrate, kcat was 6.4 s−1. 5‐HD‐CoA was also a substrate for purified pig kidney MCAD. We next tested whether the reaction product, 5‐hydroxydecenoyl‐CoA (5‐HD‐enoyl‐CoA), was a substrate for enoyl‐CoA hydratase, the second enzyme of the β‐oxidation pathway. Similar to decenoyl‐CoA, purified 5‐HD‐enoyl‐CoA was also a substrate for the hydratase reaction. In conclusion, we have shown that 5‐HD is metabolised at least as far as the third enzyme of the β‐oxidation pathway. Our results open the possibility that β‐oxidation of 5‐HD or metabolic intermediates of 5‐HD may be responsible for the inhibitory effects of 5‐HD on preconditioning of the heart.
Pulsatile control of the human masticatory muscles
Authors: Jaberzadeh Shapour , Brodin Pål , Flavel Stanley C. , O'Dwyer Nicholas J. , Nordstrom Michael A. , Miles Timothy S.
Published: March 2003

Spectral analysis of jaw acceleration confirmed that the human mandible ‘trembles’ at a peak frequency around 6 Hz when held in its rest position and at other stationary jaw openings. The 6 Hz tremor increased during very slow movements of the mandible, but other lower‐frequency peaks became prominent during more rapid jaw movements. These lower‐frequency peaks are likely to be the result of asymmetries in the underlying, voluntarily produced, ‘saw‐tooth’ movements. In comparison, finger tremor at rest and during slow voluntary movements had a mean peak frequency of about 8 Hz: this frequency did not change during rhythmical finger flexion and extension movements, but the power of the tremor increased non‐linearly with the speed of the movement. The resting jaw tremor was weakly coherent with the activity of the masseter and digastric muscles at the tremor frequency in about half the subjects, but was more strongly coherent during voluntary movements in all subjects. The masseter activity was at least 150 deg out of phase with the digastric activity at the tremor frequency (and at all frequencies from 2.5–15 Hz). The alternating pattern of activity in antagonistic muscles at rest and during slow voluntary movements supports the idea that the masticatory system is subject to pulsatile control in a manner analogous to that seen in the finger.
Effects of Electrical Stimulation and Insulin on Na+–K+‐ATPase ([3H]Ouabain Binding) in Rat Skeletal Muscle
Authors: McKenna Michael J. , Gissel Hanne , Clausen Torben
Published: March 2003

Exercise has been reported to increase the Na+–K+‐ATPase (Na+–K+ pump) α2 isoform in the plasma membrane 1.2‐ to 1.9‐fold, purportedly reflecting Na+–K+ pump translocation from an undefined intracellular pool. We examined whether Na+–K+ pump stimulation, elicited by muscle contraction or insulin, increases the plasma membrane Na+–K+ pump content ([3H]ouabain binding) in muscles from young rats. Stimulation of isolated soleus muscle for 10 s at 120 Hz caused a rapid rise in intracellular Na+ content, followed by an 18‐fold increase in the Na+ re‐extrusion rate (80 % of theoretical maximum). Muscles frozen immediately or 120 s after 10–120 s stimulation showed 10–22 % decrease in [3H]ouabain binding expressed per gram wet weight, but with no significant change expressed per gram dry weight. In soleus muscles from adult rats, [3H]ouabain binding was unaltered after 10 s stimulation at 120 Hz. Extensor digitorum longus (EDL) muscles stimulated for 10–60 s at 120 Hz showed no significant change in [3H]ouabain binding. Insulin (100 mU ml−1) decreased intracellular Na+ content by 27 % and increased 86Rb uptake by 23 % soleus muscles, but [3H]ouabain binding was unchanged. After stimulation for 30 s at 60 Hz soleus muscle showed a 30% decrease in intracellular Na+ content, demonstrating increased Na+–K+ pump activity, but [3H]ouabain binding measured 5 to 120 min after stimulation was unchanged. Stimulation of soleus or EDL muscles for 120–240 min at 1 Hz (continuously) or 10 Hz (intermittently) produced no change in [3H]ouabain binding per gram dry weight. In conclusion, the stimulating effects of electrical stimulation or insulin on active Na+, K+‐transport in rat skeletal muscle could not be even partially accounted for by an acute increase in the content of functional Na+–K+ pumps in the plasma membrane.
Molecular Basis of the Effect of Potassium on Heterologously Expressed Pacemaker (HCN) Channels
Authors: Azene Ezana , Xue Tian , Li Ronald A.
Published: March 2003

Hyperpolarization‐activated cyclic‐nucleotide‐gated (HCN) channels modulate the firing rates of neuronal and cardiac pacemaker cells. HCN channels resemble voltage‐gated K+ channels structurally, but much less is known about their structure‐function correlation. Although modulation of K+ channel gating by external K+ is a well‐known phenomenon, such a link has not been established for HCN channels. Here we examined the effects of external permeant (K+, Na+ and Li+) and non‐permeant (NMG+) ions on HCN1 and HCN2 gating. Substituting 64 of 96 mm external K+ with Na+, Li+ or NMG+ positively shifted steady‐state activation (∼13 mV), and preferentially slowed activation of HCN1. Mutating the pore variant C‐terminal to the GYG motif in HCN1, A352, to the analogous conserved Asp in K+ channels or Arg in HCN2 produced a significant hyperpolarizing activation shift (by 5–15 mV), slowed gating kinetics (up to 6‐fold), and abolished or attenuated gating responses to external K+. Whereas Na+, Li+ and NMG+ substitutions produced depolarizing activation shifts of HCN2 similar to those of HCN1, deactivation but not activation of HCN2 was exclusively decelerated. We conclude that gating and permeation of HCN channels are coupled, and that modulation of this ‘pore‐to‐gate’ coupling by external K+ is isoform‐specific.
Continuation of acoustic near-fields
Authors: Williams Earl G.
Published: March 2003

This paper deals with the analytic continuation of a coherent pressure field specified on a finite sheet located close to and conformal to the surface of a vibrator. This analytic continuation is an extension or extrapolation of the given (measured) field into a region outside and tangential to the original finite sheet, and is based on the Green’s function (the transfer function) relating acoustic quantities on the two conformal surfaces. The continuation of the measured pressure field is an inverse problem that requires the use or regularization theory, especially when noise is present in the data. An iteration algorithm is presented that is successful in continuing the pressure field into the tangential sheet. The results are accurate close to the original boundary and taper (decay) toward zero with distance away from it. The algorithm is tested on numerical and experimental data from a point-driven rectangular plate. Results show the successful extrapolation (continuation) of this data into an area nearly double that of the original pressure field. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces.
Effects of harmonic phase on nonlinear surface acoustic waves in the (111) plane of cubic crystals
Authors: Kumon R. E. , Hamilton M. F.
Published: March 2003

Spectral evolution equations are used to perform numerical studies of nonlinear surface acoustic waves in the (111) plane of several nonpiezoelectric cubic crystals. Nonlinearity matrix elements which describe the coupling of harmonic interactions are used to characterize velocity waveform distortion. In contrast to isotropic solids and the (001) plane of cubic crystals, the nonlinearity matrix elements usually cannot be written in a real-valued form. As a result, the harmonic components are not necessarily in phase, and dramatic variations in waveforms and propagation curves can be observed. Simulations are performed for initially monofrequency surface waves. In some directions the waveforms distort in a manner similar to nonlinear Rayleigh waves, while in other directions the velocity waveforms distort asymmetrically and the formation of shocks and cusped peaks is less distinct. In some cases, oscillations occur near the shocks and peaks because of phase differences between harmonics. A mathematical transformation based on the phase of the matrix elements is shown to provide a reasonable approximation of asymmetric waveform distortion in cases where the matrix elements have similar phase.
Improvement in matched field processing using the CLEAN algorithm
Authors: Song H. C. , de Rosny J. , Kuperman W. A.
Published: March 2003

Adaptive matched field processing such as the minimum variance distortionless processor (MV) provides excellent sidelobe (or ambiguity) suppression capability in source localization given a perfect knowledge of the ocean environment. Unfortunately, this processing is very sensitive to sources of mismatch and robust adaptive algorithms are then employed such as a white noise constraint (WNC) often at the expense of insufficient sidelobe control. The CLEAN algorithm was introduced in radio astronomy [Astron. Astrophys. Suppl. Ser. 15, 417–426 (1974)] to produce a high quality image of the sky by reducing sidelobe-induced artifacts. In this paper, the CLEAN concept is extended to matched field processing. Numerical simulations and experimental data demonstrate that matched field processing combined with the CLEAN algorithm can improve performance, especially when a weak source is masked by sidelobes from a much stronger source.
Measurement of acoustical characteristics of mosques in Saudi Arabia
Authors: Abdou Adel A.
Published: March 2003

The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.
Phase change measurement, and speed of sound and attenuation determination, from underwater acoustic panel tests
Authors: Piquette Jean C. , Paolero Anthony E.
Published: March 2003

A technique for measuring the change in phase produced by the insertion of a panel between a projector and receiver is described. Presented also is a procedure for determining the phase speed and attenuation of the panel material. Although the methods were developed over the frequency decade 10–100 kHz, they are not limited to that band. It was observed that a “settling time” of approximately 20 min is required to obtain reproducible phase measurements if the experiment is disturbed even slightly. For example, rotating the panel 10 degrees, then immediately returning to the original position, causes the observed phases to differ by up to 10 deg from those obtained prior to the disturbance. These differences are distributed randomly across frequency. Temperature stabilization within the medium as well as the material is also required before measurements can take place. After the stated 20 min settling time, however, the phases return to the values obtained prior to rotation, or after temperature stabilization, to within ±12 deg. The sound speed and attenuation determination technique employs least-squares fitting of a causal model to the measurements. Four (or fewer) adjusted parameters accommodate the measurements over the stated frequency decade, even for samples that exhibit significant dispersion. The sound speed is typically determined to an accuracy of ±30 m/s, as judged from a propagation-of-error calculation. This model assumes single-layered panels.
Quantitative evaluation of lexical status, word frequency, and neighborhood density as context effects in spoken word recognition
Authors: Benkı́ José R.
Published: March 2003

Listeners identified a phonetically balanced set of consonant–vowel–consonant (CVC) words and nonsense syllables in noise at four signal-to-noise ratios. The identification scores for phonemes and syllables were analyzed using the j-factor model [Boothroyd and Nittrouer, J. Acoust. Soc. Am. 84, 101–114 (1988)], which measures the perceptual independence of the parts of a whole. Results indicate that nonsense CVC syllables are perceived as having three independent phonemes, while words show j=2.34 independent units. Among the words, high-frequency words are perceived as having significantly fewer independent units than low-frequency words. Words with dense phonetic neighborhoods are perceived as having 0.5 more independent units than words with sparse neighborhoods. The neighborhood effect in these data is due almost entirely to density as determined by the initial consonant and vowel, demonstrated in analyses by subjects and items, and correlation analyses of syllable recognition with the neighborhood activation model [Luce and Pisoni, Ear Hear. 19, 1–36 (1998)]. The j factors are interpreted as measuring increased efficiency of the perception of word-final consonants of words in sparse neighborhoods during spoken word recognition.
Beam intensity striations and applications
Authors: Yang T. C.
Published: March 2003

The single-element spectrogram for a continuous broadband signal, plotted as a function of range, has been shown to exhibit striated bands of intensity maxima and minima. The slope of the striations is an invariant of the modal interference and is described by a waveguide invariant parameter “beta.” The striation pattern is analyzed and modeled in this paper for the beam outputs of a horizontal line array obtained by conventional beamforming. Array beamforming makes it possible to measure the waveguide invariant parameter for weak signals due to the enhancement of signal levels by the array gain over that of a single element. It is shown that the signal beam spectrogram as a function of range exhibits the same striation pattern as that (predicted) for a single element. Specifically, for a broadside signal, the beam striation is identical to that of a single-element plus a constant signal gain. For a nonbroadside target, the signal beam intensity will be modified by a frequency-bearing dependent signal gain due to the signal spread over multiple beams, nevertheless the beam spectrogram retains the same striation pattern (slope) as for a single element. The sidelobe beams (outside the canonical cones containing the signal arrivals) exhibit an entirely different striation pattern as a function of frequency and range. For array processing, it is shown that a fast range-rate, close range target and a distant, slow range-rate interference source will have a different striation pattern (slope) in the corresponding beam spectrograms as a function of time, assuming no prior knowledge of the source ranges. The difference in the striations between the beam spectrograms can be used in array processing to suppress the interference contribution. A 5–7 dB interference suppression is demonstrated using simulated data.
A second, low-frequency mode of vibration in the intact mammalian cochlea
Authors: Lukashkin Andrei N. , Russell Ian J.
Published: March 2003

The mammalian cochlea is a structure comprising a number of components connected by elastic elements. A mechanical system of this kind is expected to have multiple normal modes of oscillation and associated resonances. The guinea pig cochlear mechanics was probed using distortion components generated in the cochlea close to the place of overlap between two tones presented simultaneously. Otoacoustic emissions at frequencies of the distortion components were recorded in the ear canal. The phase behavior of the emissions reveals the presence of a nonlinear resonance at a frequency about a half octave below that of the high-frequency primary tone. The location of the resonance is level dependent and the resonance shifts to lower frequencies with increasing stimulus intensity. This resonance is thought to be associated with the tectorial membrane. The resonance tends to minimize input to the cochlear receptor cells at frequencies below the high-frequency primary and increases the dynamic load to the stereocilia of the receptor cells at the primary frequency when the tectorial membrane and reticular lamina move in counterphase.
Impedance measurements around grazing incidence for nonlocally reacting thin porous layers
Authors: Allard Jean-François , Henry Michel , Gareton Vincent , Jansens Gert , Lauriks Walter
Published: March 2003

For locally reacting materials with a constant surface impedance, a classical method based on the work of Chien and Soroka [J. Sound Vib. 43, 9–20 (1975)] for measuring this impedance in situ around grazing incidence is currently used. A generalization of this work to include thin nonlocally reacting materials with a surface impedance noticeably dependent on the angle of incidence is performed. It is shown that the model by Chien and Soroka can be used, though the constant surface impedance must be replaced by the impedance at grazing incidence for the evaluation of the numerical distance. Measurements performed on a thin porous layer using this method are compared with measurements performed using the near-field acoustical holography method [M. Tamura, J. Acoust. Soc. Am. 88, 2259–2264 (1990)]. Other measurements performed on a fibrous layer are in good agreement with the predicted values of the impedance at grazing incidence.
Evaluation of array-processing algorithms for a headband hearing aid
Authors: Greenberg Julie E. , Desloge Joseph G. , Zurek Patrick M.
Published: March 2003

Several array-processing algorithms were implemented and evaluated with experienced hearing-aid users. The array consisted of four directional microphones mounted broadside on a headband worn on the top of the listener’s head. The algorithms included two adaptive array-processing algorithms, one fixed array-processing algorithm, and a reference condition consisting of binaural directional microphones. The algorithms were evaluated under conditions with both one and three independent noise sources. Performance metrics included quantitative speech reception thresholds and qualitative subject preference ratings for ease-of-listening measured using a paired-comparison procedure. On average, the fixed algorithm improved speech reception thresholds by 2 dB, while the adaptive algorithms provided 7–9-dB improvement over the reference condition. Subjects judging ease-of-listening generally preferred all array-processing algorithms over the reference condition. The results suggest that these adaptive algorithms should be evaluated further in more realistic acoustic environments.
A state feedback electro-acoustic transducer for active control of acoustic impedance
Authors: Samejima Toshiya
Published: March 2003

In this paper, a new control system in which the acoustic impedance of an electro-acoustic transducer diaphragm can be actively varied by modifying design parameters is presented and its effectiveness is theoretically investigated. The proposed control system is based on a state-space description of the control system derived from an electrical equivalent circuit of an electro-acoustic transducer to which a differentiating circuit is connected, and is designed using modern control theory. The optimal quadratic regulator is used in the control system design, with its quadratic performance index formulated for producing desired acoustic impedance. Computer simulations indicate that the acoustic impedance of the diaphragm can be significantly varied over a wide frequency range that includes the range below the resonance frequency of the electro-acoustic transducer. A computer model of the proposed control system is used to illustrate its application to semi-active noise control in a duct. It is demonstrated that the proposed control system provides substantial reductions in the noise radiating from the outlet of the duct, both in the stiffness control range and in the mass control range.
Long-lasting stable cavitation
Authors: Mestas Jean-Louis , Lenz Peter , Cathignol Dominique
Published: March 2003

Stable cavitation is produced on the surface of a special target, i.e., an abrasive foil with a grain size of about 15 μm, insonified by a 473 kHz focused beam. Cavitation bubbles are first created by a pressure of about 2 MPa. Progressive reduction of the pressure to about 100 kPa leads to a state of stable cavitation characterized by strong stable emission of the half-order subharmonic. This state can be maintained for five hours if the defining parameters (position and pressure) are optimized and constant to within a few percent. There is strong evidence for the presence of “latent” cavitation bubbles, which can persist for a few minutes without being excited.
Wall compliance and violin cavity modes
Authors: Bissinger George
Published: March 2003

Violin corpus wall compliance, which has a substantial effect on cavity mode frequencies, was added to Shaw’s two-degree-of-freedom (2DOF) network model for A0 (“main air”) and A1 (lowest length mode included in “main wood”) cavity modes. The 2DOF model predicts a V−0.25 volume dependence for A0 for rigid violin-shaped cavities, to which a semiempirical compliance correction term, V−xc (optimization parameter xc) consistent with cavity acoustical compliance and violin-based scaling was added. Optimizing xc over A0 and A1 frequencies measured for a Hutchins–Schelleng violin octet yielded xc≈0.08. This markedly improved A0 and A1 frequency predictions to within approximately ±10% of experiment over a range of about 4.5:1 in length, 10:1 in f-hole area, 3:1 in top plate thickness, and 128:1 in volume. Compliance is a plausible explanation for A1 falling close to the “main wood” resonance, not increasingly higher for the larger instruments, which were scaled successively shorter compared to the violin for ergonomic and practical reasons. Similarly incorporating compliance for A2 and A4 (lowest lower-/upper-bout modes, respectively) improves frequency predictions within ±20% over the octet.
Near-field calculations for a rigid spheroid with an arbitrary incident acoustic field
Authors: Barton John P. , Wolff Nicholas L. , Zhang Haifeng , Tarawneh Constantine
Published: March 2003

A general spheroidal coordinate separation-of-variables solution is developed for the determination of the acoustic pressure distribution near the surface of a rigid spheroid for a monofrequency incident acoustic field of arbitrary character. Calculations are presented, for both the prolate and oblate geometries, demonstrating the effects of incident field orientation and character (plane-wave, spherical wave, cylindrical wave, and focused beam) on the resultant acoustic pressure distribution.
Psychophysical evidence for auditory compression at low characteristic frequencies
Authors: Plack Christopher J. , Drga Vit
Published: March 2003

Psychophysical estimates of compression often assume that the basilar-membrane response to frequencies well below characteristic frequency (CF) is linear. Two techniques for estimating compression are described here that do not depend on this assumption at low CFs. In experiment 1, growth of forward masking was measured for both on- and off-frequency pure-tone maskers for pure-tone signals at 250, 500, and 4000 Hz. The on- and off-frequency masking functions at 250 and 500 Hz were just as shallow as the on-frequency masking function at 4000 Hz. In experiment 2, the forward masker level required to mask a fixed low-level signal was measured as a function of the masker–signal interval. The slopes of these functions did not differ between signal frequencies of 250 and 4000 Hz for the on-frequency maskers. At 250 Hz, the slope for the 150-Hz masker was almost as steep as that for the on-frequency masker, whereas at 4000 Hz the slope for the 2400-Hz masker was much shallower than that for the on-frequency masker. The results suggest that there is substantial compression, of around 0.2–0.3 dB/dB, at low CFs in the human auditory system. Furthermore, the results suggest that at low CFs compression does not vary greatly with stimulation frequency relative to CF.
Reverberation of rapid and slow trills: Implications for signal adaptations to long-range communication
Authors: Naguib Marc
Published: March 2003

Many acoustic signals in animals include trills, i.e., rapid repetitions of similar elements. Elements within these trills usually are frequency modulated and are degraded by reverberation during long-range transmission. Reverberation primarily affects consecutive elements with the same frequency characteristics and thus imposes a major constraint in the evolution of design and perception of long-range signals containing trills. Here transmission of frequency-unmodulated trills with different element repetition rates was studied. Trills were generated at different frequencies to assess frequency dependence of reverberation and then broadcast under three acoustic conditions—an open field and to assess seasonal changes in transmission properties, a deciduous forest before and after foliage had emerged. Reverberation was quantified at different positions within trills. The results show strong effects of vegetation density (season), transmission distance, frequency, element repetition rate, and element position within the trill on effects of reverberation. The experiments indicate that fast trills transmit less well than slow trills and thus are less effective in long-range communication. They show in particular that selection on trills should not act only on element repetition rate within trills but also on the trill duration as effects of reverberation increased with trill duration.
Nonlinear wave interactions in bubble layers
Authors: Karpov S. , Prosperetti A. , Ostrovsky L.
Published: March 2003

Due to the large compressibility of gas bubbles, layers of a bubbly liquid surrounded by pure liquid exhibit many resonances that can give rise to a strongly nonlinear behavior even for relatively low-level excitation. In an earlier paper [Druzhinin et al., J. Acoust. Soc. Am. 100, 3570 (1996)] it was pointed out that, by exciting the bubbly layer in correspondence of two resonant modes, so chosen that the difference frequency also corresponds to a resonant mode, it might be possible to achieve an efficient parametric generation of a low-frequency signal. The earlier work made use of a simplified model for the bubbly liquid that ignored the dissipation and dispersion introduced by the bubbles. Here a more realistic description of the bubble behavior is used to study the nonlinear oscillations of a bubble layer under both single- and dual-frequency excitation. It is found that a difference-frequency power of the order of 1% can be generated with incident pressure amplitudes of the order of 50 kPa or so. It appears that similar phenomena would occur in other systems, such as porous waterlike or rubberlike media.
Speech perception, localization, and lateralization with bilateral cochlear implants
Authors: van Hoesel Richard J. M. , Tyler Richard S.
Published: March 2003

Five bilateral cochlear implant users were tested for their localization abilities and speech understanding in noise, for both monaural and binaural listening conditions. They also participated in lateralization tasks to assess the impact of variations in interaural time delays (ITDs) and interaural level differences (ILDs) for electrical pulse trains under direct computer control. The localization task used pink noise bursts presented from an eight-loudspeaker array spanning an arc of approximately 108° in front of the listeners at ear level (0-degree elevation). Subjects showed large benefits from bilateral device use compared to either side alone. Typical root-mean-square (rms) averaged errors across all eight loudspeakers in the array were about 10° for bilateral device use and ranged from 20° to 60° using either ear alone. Speech reception thresholds (SRTs) were measured for sentences presented from directly in front of the listeners (0°) in spectrally matching speech-weighted noise at either 0°, +90° or −90° for four subjects out of five tested who could perform the task. For noise to either side, bilateral device use showed a substantial benefit over unilateral device use when noise was ipsilateral to the unilateral device. This was primarily because of monaural head-shadow effects, which resulted in robust SRT improvements (P<0.001) of about 4 to 5 dB when ipsilateral and contralateral noise positions were compared. The additional benefit of using both ears compared to the shadowed ear (i.e., binaural unmasking) was only 1 or 2 dB and less robust (P=0.04). Results from the lateralization studies showed consistently good sensitivity to ILDs; better than the smallest level adjustment available in the implants (0.17 dB) for some subjects. Sensitivity to ITDs was moderate on the other hand, typically of the order of 100 μs. ITD sensitivity deteriorated rapidly when stimulation rates for unmodulated pulse-trains increased above a few hundred Hz but at 800 pps showed sensitivity comparable to 50-pps pulse-trains when a 50-Hz modulation was applied. In our opinion, these results clearly demonstrate important benefits are available from bilateral implantation, both for localizing sounds (in quiet) and for listening in noise when signal and noise sources are spatially separated. The data do indicate, however, that effects of interaural timing cues are weaker than those from interaural level cues and according to our psychophysical findings rely on the availability of low-rate information below a few hundred Hz.
Lamb wave reflection at the free edge of a plate
Authors: Morvan Bruno , Wilkie-Chancellier Nicolas , Duflo Hugues , Tinel Alain , Duclos Jean
Published: March 2003

This study concentrates on the reflection of Lamb waves at the free end of a plate. The conversion phenomena are examined in detail over a large frequency range and the energy conversion coefficients are obtained by three different ways: theoretically, numerically (finite element method) and experimentally. The experimental energy determination is obtained from the measurement of the plate normal displacements, by mean of a laser interferometer. All results are in relatively good agreement and the energy balance between incident and reflected waves is discussed in each case.
Green’s function estimation using secondary sources in a shallow water environment
Authors: Roux Philippe , Fink Mathias
Published: March 2003

This work provides a new way to measure the Green’s function between two points in an acoustic channel without emitting a pulse by any of the two points. The Green’s function between A and B is obtained from a set of secondary sources in the guide by averaging either the correlation or the convolution of the signals received in A and B. A theoretical approach based on mode propagation in a monochromatic regime is presented. Results are then extended to the time domain. Estimation of the Green’s function is performed numerically in a range-independent and a range-dependent environment. Application to discreet acoustic communications is discussed.
Analysis of a compliantly suspended acoustic velocity sensor
Authors: McConnell James A.
Published: March 2003

The dynamics of a compliantly suspended acoustic velocity sensor having a spherical geometry are analyzed using theory and experiment. The analysis starts with a review of the motion associated with an unconstrained solid sphere when subjected to an acoustic plane wave in an unbounded inviscid fluid medium. The theory is then modified to account for the inclusion of an inertial sensor and an external suspension system. Accordingly, the open-circuit receiving response of a geophone-based and accelerometer-based device is derived. Density variations associated with the sphere and the surrounding fluid medium are assessed along with the effects fluid viscosity. Wave effects in the sphere and the suspension system are also analyzed.
Acoustic scattering from a thermally driven buoyant plume revisited
Authors: Oeschger John , Goodman Louis
Published: March 2003

Far-field weak scattering theory is applied to the case of high-frequency broad-bandwidth acoustic scattering from a thermally generated buoyant plume in a controlled laboratory environment. To first order, the dominant scattering mechanism is thermally driven sound-speed variations that are related to temperature deviations from ambient. As a result, the received complex acoustic scattering is a measure of the one-component three-dimensional Fourier transform of the temperature difference field measured at the Bragg wave number. The Bragg wave number vector is the difference between the scattered and incident wave vectors. Solving for its magnitude yields the Bragg scattering condition; this is the Fourier component of the plume variability that produces scattering. Results are presented for multistatic scattering from unstable and turbulent plumes using a parallel scattering geometry. The data justify application of the far-field weak scattering theory to the present case of a thermal plume. As a consequence, quantitative results on medium variability can be inferred using high-frequency broad-bandwidth acoustic scattering. Particular attention is given to the role of anisotropy of the variability of the scattering field in determining the validity of far-field Bragg scattering.
Absolute measurements of total target strength from reverberation in a cavity
Authors: Demer David A. , Conti Stephane G. , De Rosny Julien , Roux Philippe
Published: March 2003

A new method was developed to acoustically measure the density and total scattering cross-section (σt) or total target strength [TTS=10 log10(σt/4π)] of objects in motion in a highly reflective cavity [J. De Rosny and P. Roux, J. Acoust. Soc. Am. 109, 2587–2597 (2001)]. From an ensemble of pulse-echo recordings, the average contribution of the scatterer(s) to the reverberation within the cavity provides a measurement of the scattering mean free path. The latter was shown through theory and experiment to be proportional to the volume of the cavity and inversely proportional the product of the mean σt and number of scatterers. Here, the TTS measurement uncertainty is characterized using standard metal spheres as references. Theoretical TTS was calculated for multiple copper and tungsten carbide standard spheres (Cu: 60.0 30.05 and 23 mm and WC: 38.1 and 33.4 mm diameters, respectively), using well-described theory for scattering from elastic spheres and the optical theorem. Measurements of TTS were made over a wide bandwidth (30–120 kHz) and compared to their theoretical values. Measurements were made in a corrugated, cylindrical, galvanized-steel tank with 25 or 50 l of fresh water at a temperature of 21±1 °C. The results indicate the method can provide TTS measurements that are accurate to at least 0.4 dB with an average precision of ±0.7 dB (95% confidence interval). Discussed are the requisite cavity volumes and signal-to-noise ratios for quality measurements of TTS, tank volume, and/or numerical abundance of mobile targets. Also discussed are multiple potential applications of this technique in bioacoustical oceanography.
Modeling signal loss in surficial marine sediments containing occluded gas
Authors: Gardner Trevor
Published: March 2003

The presence of occluded gas in inland lakes, harbor muds, and surficial marine sediments is well documented. Surficial gassy sediments cause underlying beds to be acoustically impenetrable to seismic surveys; therefore, the modeling of signal loss arising from mudline reflection and transmission absorption is of particular interest. The Anderson and Hampton [J. Acoust. Soc. Am. 67, 1890–1903 (1980)] model for attenuation in gassy sediments was evaluated against the physical and acoustical properties of eight laboratory silty clay soils containing different amounts of occluded gas in bubbles of 0.2- to 1.8-mm diameter. The model was shown to give good agreement with measured data over the lower frequencies of bubble resonance and above resonance. It did not agree with measured data at frequencies below resonance, for which the model did not simulate the bulk properties of the gassy soils. The Mackenzie [J. Acoust. Soc. Am. 32, 221–231 (1960)] model for reflection loss was also examined for the gassy soils. The maximum reflection losses of 6 dB, at a grazing angle of 40°, does not wholly support speculation by Levin [Geophysics 27, 35–47 (1962)] of highly reflective pressure-release boundaries arising from substantial reflection and absorption losses in gassy sediments. It was found that mudlines formed from sediments with significant occluded gas may be successfully penetrated, although the substantial absorption loss arising from signal transmission through the sediment prevents penetration of the surficial layers to much beyond a meter in depth.
An experimental study on antipersonnel landmine detection using acoustic-to-seismic coupling
Authors: Xiang Ning , Sabatier James M.
Published: March 2003

An acoustic-to-seismic system to detect buried antipersonnel mines exploits airborne acoustic waves penetrating the surface of the ground. Acoustic waves radiating from a sound source above the ground excite Biot type I and II compressional waves in the porous soil. The type I wave and type II waves refract toward the normal and cause air and soil particle motion. If a landmine is buried below the surface of the insonified area, these waves are scattered or reflected by the target, resulting in distinct changes to the acoustically coupled ground motion. A scanning laser Doppler vibrometer measures the motion of the ground surface. In the past, this technique has been employed with remarkable success in locating antitank mines during blind field tests [Sabatier and Xiang, IEEE Trans. Geosci. Remote Sens. 39, 1146–1154 (2001)]. The humanitarian demining mission requires an ability to locate antipersonnel mines, requiring a surmounting of additional challenges due to a plethora of shapes and smaller sizes. This paper describes an experimental study on the methods used to locate antipersonnel landmines in recent field measurements.
New modeling method and mechanism analyses for active control of interior noise in an irregular enclosure using piezoelectric actuators
Authors: Geng Hou C. , Rao Zhu S. , Han Zu S.
Published: March 2003

A new modeling method is developed in this paper for the active minimization of noise within a three-dimensional irregular enclosure using distributed lead zirconate titanate piezoelectric (PZT) actuators, and the control mechanisms for irregular enclosure are analyzed. The irregular enclosure is modeled with four rigid walls and two simply supported flexible panels, and PZT actuators are bound to one of the flexible panels. The process of the new modeling method is as follows. First, the modal coupling method is used to establish the motion equations, which contain important coefficients such as modal masses and modal coupling coefficients, etc., of acoustic–structural–piezoelectric coupling system. Then, the acoustic modes and the modal masses of irregular enclosure are calculated by numerical methods. Last, the modal coupling coefficients in motion equations are calculated according to the numerical results of the acoustic modes of irregular enclosure and the modes of two panels. The validity of this modeling method is verified by a regular hexahedron enclosure. Two cost functions are applied to this model. With the two cost functions, good results are obtained in minimizing the sound-pressure level (SPL) within irregular enclosure according to numerical investigations. By comparing the results obtained under controlled and uncontrolled states, the control mechanisms of the system are discussed. It is found that the control mechanisms vary with disturbance frequencies. At most disturbance frequencies, the SPL within enclosure is reduced by restructuring the modes of two panels simultaneously. When the disturbance frequency comes close to one of the natural frequencies of panel a, the dominant mode of panel a is suppressed, while the modes of panel b are reconstructed. While the disturbance frequency is near one of the natural frequencies of panel b, the modes of two panels are restructured at the same time.