Enhancement of high-frequency acoustic cavitation effects by a low-frequency stimulation

The cavitation effects given by a high-frequency pulsed ultrasound field are studied with and without the stimulation of a low-frequency field. Sonoluminescence intensity and subharmonic one-half intensity of the high-frequency field are measured. The stimulation gives a sharp rise of both subharmonic and sonoluminescence intensities.     

On acoustic stimulation of atmospheric precipitation

Stimulation of atmospheric precipitation by acoustic waves is considered. The interaction of acoustic waves with fog particles and the acoustic coagulation phenomenon are analyzed. It is proposed that the effect of amplification of sound in a weakly ionized gas be used to prevent sound decay away from the source in a foggy environment.     

Ultrasound effects on miniature end plate potential discharge frequency are contingent upon acoustic environment

The effects of low level ultrasonic stimulation (250 mW cm-2; 1.5 MHz; continuous wave) on the frequency of miniature end-plate potential (MEPP) production, at the frog neuromuscular junction, have been examined in two situations. In a simple exposure environment, where the muscle was immersed in Ringer solution and stretched over a polyurethane resin base at room temperature, the ultrasound stimulus produced a marked increase in the MEPP discharge rate, with only a small concomitant rise (1.0-1.6 degrees C) in local temperature. Control temperature increases of a similar magnitude produced only small changes in the rate of MEPP production. The experiment was repeated in an environment with better defined field conditions. The muscle was suspended in a chamber sealed at the base with an acoustically transparent polycarbonate material, 0.05 mm thick, and contained in a thermostatically controlled bath lined with an acoustically absorbent material. In this situation, no increase in MEPP frequency was observed in response to ultrasonication, although the local measured temperature increase was similar in both magnitude and time course. It is suggested that these results may depend upon differences between standing wave conditions and free field progression of the beam through the sample.     

Dynamics of peptidergic secretory granule transport are regulated by neuronal stimulation

Background  

Peptidergic neurons store and secrete the contents of large dense core vesicles (LDCVs) from axon terminals and from dendrites. Secretion of peptides requires a highly regulated exocytotic mechanism, plus coordinated synthesis and transport of LDCVs to their sites of release. Although these trafficking events are critical to function, little is known regarding the dynamic behavior of LDCVs and the mechanisms by which their transport is regulated. Sensory neurons also package opiate receptors in peptide-containing LDCVs, which is thought to be important in pain sensation. Since peptide granules cannot be refilled locally after their contents are secreted, it is particularly important to understand how neurons support regulated release of peptides.     

Adult-child differences in acoustic cue weighting are influenced by segmental context: children are not always perceptually biased toward transitions

It has been proposed that young children may have a perceptual preference for transitional cues [Nittrouer, S. (2002). J. Acoust. Soc. Am. 112, 711-719]. According to this proposal, this preference can manifest itself either as heavier weighting of transitional cues by children than by adults, or as heavier weighting of transitional cues than of other, more static, cues by children. This study tested this hypothesis by examining adults' and children's cue weighting for the contrasts /saI/-/integral of aI/, /de/-/be/, /ta/-/da/, and /ti/-/di/. Children were found to weight transitions more heavily than did adults for the fricative contrast /saI/-/integral aI/, and were found to weight transitional cues more heavily than nontransitional cues for the voice-onset-time contrast /ta/-/da/. However, these two patterns of cue weighting were not found to hold for the contrasts /de/-/be/ and /ti/-/di/. Consistent with several studies in the literature, results suggest that children do not always show a bias towards vowel-formant transitions, but that cue weighting can differ according to segmental context, and possibly the physical distinctiveness of available acoustic cues.     

Locus equations are an acoustic expression of articulator synergy

The study investigated the articulatory basis of locus equations, regression lines relating F2 at the start of a Consonant-Vowel (CV) transition to F2 at the middle of the vowel, with C fixed and V varying. Several studies have shown that consonants of different places of articulation have locus equation slopes that descend from labial to velar to alveolar, and intercept magnitudes that increase in the opposite order. Using formulas from the theory of bivariate regression that express regression slopes and intercepts in terms of standard deviations and averages of the variables, it is shown that the slope directly encodes a well-established measure of coarticulation resistance. It is also shown that intercepts are directly related to the degree to which the tongue body assists the formation of the constriction for the consonant. Moreover, it is shown that the linearity of locus equations and the linear relation between locus equation slopes and intercepts originates in linearity in articulation between the horizontal position of the tongue dorsum in the consonant and to that in the vowel. It is concluded that slopes and intercepts of acoustic locus equations are measures of articulator synergy.     

分层砂底对浅海信道声传播影响的研究

推导有指向性脉冲声源在海底是分层结构的浅海中声场的积分表达式;分别仿真了爆炸声源和指向性脉冲源在浅海信道中传播的信号波形,其中假设了海底的沉积层和基底分别由水浸泡的砂和固态介质构成,砂底的参数数值用孔隙介质理论和实测相结合的方法进行选择;此外,在用砂和玻璃珠分别模拟砂层海底的水池内,观测了指向性脉冲源在不同接收点的信号的波形;结果表明:仿真波形的包络得到实验的印证。从而证明本文建立的指向性脉冲源在具有砂层海底的浅海中声场模型是可行的,可用于预报海洋环境参数对接收波形的影响,为水下通信、声呐信号设计与处理提供参考信息。     

Improved speech recognition in noise in simulated binaurally combined acoustic and electric stimulation

Speech recognition in noise improves with combined acoustic and electric stimulation compared to electric stimulation alone [Kong et al., J. Acoust. Soc. Am. 117, 1351-1361 (2005)]. Here the contribution of fundamental frequency (F0) and low-frequency phonetic cues to speech recognition in combined hearing was investigated. Normal-hearing listeners heard vocoded speech in one ear and low-pass (LP) filtered speech in the other. Three listening conditions (vocode-alone, LP-alone, combined) were investigated. Target speech (average F0=120 Hz) was mixed with a time-reversed masker (average F0=172 Hz) at three signal-to-noise ratios (SNRs). LP speech aided performance at all SNRs. Low-frequency phonetic cues were then removed by replacing the LP speech with a LP equal-amplitude harmonic complex, frequency and amplitude modulated by the F0 and temporal envelope of voiced segments of the target. The combined hearing advantage disappeared at 10 and 15 dB SNR, but persisted at 5 dB SNR. A similar finding occurred when, additionally, F0 contour cues were removed. These results are consistent with a role for low-frequency phonetic cues, but not with a combination of F0 information between the two ears. The enhanced performance at 5 dB SNR with F0 contour cues absent suggests that voicing or glimpsing cues may be responsible for the combined hearing benefit.     

用信号处理技术及传播理论还原雷声频谱

以往关于雷声的研究都限于观测点雷声频域范围的探讨, 由于噪音和衰减因素的影响, 观测点的雷声频谱有很大失真. 针对在兰州地区观测的一次雷暴过程中的雷声信号, 利用数字信号处理技术,由观测点处的雷声音频信号得到频率谱,并对雷声频谱进行噪音分析; 然后结合声音在大气中传播的衰减理论, 分析了不同大气环境对声吸收的影响, 并推算出了声源附近的雷声频率谱. 关键词： 雷声频谱 信号处理 传播理论 峰值频率     

Visualization of acoustic wavefronts by means of acoustic stroboscopy

The amplitude and phase distributions of a progressive acoustic wave are visualized simultaneously by means of acoustic stroboscopy. Two methods are described: (i) modulation of a laser beam by a progressive acoustic wave; (ii) modulation by a stationary wave. Spatial filtering of diffracted orders enables the progressive wavefronts to be seen as if they were stationary.     

A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation

Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.     

Experimental study of nonlinear acoustic effects in a granular medium

Results of a series of experimental studies of nonlinear acoustic effects in a granular medium are presented. Different effects observed in the experiments simultaneously testify that the nonlinearity of granular media is governed by the weakest intergrain contacts. The behavior of the observed dependences suggests that the distribution function of contact forces strongly increases in the range of forces much smaller than the mean force value, which is inaccessible for conventional experimental measuring techniques. For shear waves in a granular medium, the effects of demodulation and second harmonic generation with conversion to longitudinal waves are studied. These effects are caused by the nonlinear dilatancy of the medium, i.e., by the nonlinear law of its volume variation in the shear stress field. With the use of shear waves of different polarizations, the anisotropy of the nonlinearity of the medium is demonstrated. The observation of the cross-modulation effect shows that the nonlinearity-induced modulation components of the probe wave are much more sensitive to weak nonstationary perturbations of the medium, as compared to the linearly propagating fundamental harmonic. The nonlinear effects under study offer promise for diagnostic applications in laboratory measurements and in seismic monitoring systems.     

Calculation of turbulence effects on acoustic remote-sensing system

Summary A mathematical tool for the calculation of the effects of turbulence on acoustic remote-sensing systems is described. The systems taken into account are sodar, which operates in air, and underwater acoustic Doppler current profilers (ADCP). Included in the modelling are echo spectrum broadening and the contribution of turbulence to the scattering cross-section. A method for the measurement of the transverse velocity with a single beam is also suggested.     

Search for acoustic effects from extensive atmospheric showers in Baikal

The search for acoustic effects from showers by means of hydrophones was realized in a trigger scheme of recording sound files when atmospheric showers were detected by the scintillation installation. A method of peaks and noncoincidences was proposed to search for weak sound sources. The algorithm of the method is amplitude independent. Processing of a great body of data (obtained for different geometries, different noise background during three expeditions to Baikal) allows one to indicate the closely analogous phenomena at the instant of time of expected sound signals from showers. In spite of their low power, the effects appear in the different hydrophones and have similar time distributions, which points to the detection of the acoustic effects. The text was submitted by the authors in English.     

Wave effects in acoustic media with a negative refractive index

A method for analyzing media with a negative refractive index in acoustics has been proposed. An analog of the Lippmann-Schwinger equation is derived from the initial hydrodynamical equation and a theory of wave scattering by inhomogeneities of a medium with an arbitrarily specified value and sign of density and compressibility is constructed. Numerical simulation of the effects related to negative refraction is performed.     

Nonlinear acoustic effects in a resonator with saturation of hysteretic loss

Nonlinear wave processes in an acoustic rod resonator with hysteretic nonlinearity under harmonic excitation are studied. The characteristics of longitudinal nonlinear modes of the resonator with hard and soft boundaries (amplitude-dependent loss, shifts of resonance frequencies, and amplitudes of the second and third harmonics) are determined. The comparison of the theoretical and experimental dependences of nonlinear acoustic effects in a resonator that is made of annealed polycrystalline copper is used to determine the parameters of the hysteretic nonlinearity.     

Oblique collisional effects of dust acoustic waves in unmagnetized dusty plasma

Effects of oblique collisions of the dust acoustic(DA)waves in dusty plasma are studied by considering unmagnetized fully ionized plasma.The plasma consists of inertial warm negatively charged massive dusts,positively charged dusts,superthermal kappa distributed electrons,and isothermal ions.The extended Poincaré–Lighthill–Kuo(e PLK)method is employed for the drivation of two-sided Korteweg–de Vries(KdV)equations(KdVEs).The Kd V soliton solutions are derived by using the hyperbolic secant method.The effects of superthermality index of electrons,temperature ratio of isothermal ion to electron,and the density ratio of isothermal ions to negatively charged massive dusts on nonlinear coefficients are investigated.The effects of oblique collision on amplitude,phase shift,and potential profile of right traveling solitons of DA waves are also studied.The study reveals that the new nonlinear wave structures are produced in the colliding region due to head-on collision of the two counter propagating DA waves.The nonlinearity is found to decrease with the increasing density ratio of ion to negative dust in the critical region.The phase shifts decrease(increase)with increasing the temperature ratio of ion to electron(κe).The hump(compressive,κeκec)and dipshaped(rarefactive,κeκec)solitons are produced depending on the angle(θ)of oblique collision between the two waves.     

Electrode effects on general modes in high-overtone bulk acoustic resonators

Generally, in theoretical calculations of high-overtone bulk acoustic resonators (HBAR), metal electrode effects were always ignored. However, the acoustical impedance, thickness and loss of the electrodes affect practically the performances of HBAR operating at high-frequency. For very high-frequency cases, the thickness of the metal electrode is always on the same order of that of the piezo-film and the electrode effects on modes cannot be negligible. In this paper, based on the resonance frequency spectra and Butterworth Van Dyke equivalent circuit of HBAR, the effects of the material, loss, and thickness of the electrodes on the figure of merit, effective electromechanical coupling factor, quality factor, etc. are analyzed. It is demonstrated that the performance of HBAR can also be optimized by using the electrodes with proper impedance, loss and thickness.