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Many researchers have suggested that birds may use natural infrasound sources for navigation and hazard avoidance. However, there is a need to define the sound levels and frequencies to characterize potential infrasound sources. This paper summarizes new measurements from Niagara Falls which define a stable, powerful infrasound source that could be detected by birds on a regional scale of over 400 km. Measurements made in the vicinity of Niagara Falls show that exceptional infrasonic pressure levels can occur in the regions of large waterfalls (> 100 Pa at a range of about 500 m). This paper reviews investigator assessments of avian use of infrasound. A review of the results of Cornell researchers on pigeon hearing provides a basis for estimating avian detection ranges of waterfalls. It is possible that migrating birds use sounds from waterfalls as beacons- a component of their “navigation toolbox” as well as infrasound for hazard avoidance.

Exposure to low-frequency vibration is harmful to human lumbar health. However, the dynamic mechanical properties of lumbar spines with varying degrees of degeneration during time-dependent vibration remain incompletely understood. In this study, four poroelastic finite element models of human L2-L3 spinal motion segments, including the non-degeneration and the mild, moderate, and serious degeneration, were established. One-hour low-frequency vibrations with different frequencies were applied. Then, the dynamic mechanical properties of different degenerated lumbar models under the same vibration and the same lumbar model under vibrations at different frequencies were investigated. The results indicated and implied that the negative influences of 1-h vibration on the dynamic mechanical properties of the non-degenerated and mildly degenerated models were similar, but became obvious for the moderately and seriously degenerated models with time. Therefore, the damage caused by low-frequency vibration on the degenerated spinal motion segments was more serious compared with that on the healthy one. Meanwhile, the dynamic mechanical properties of the same lumbar model under vibrations at different frequencies expressed the negligible differences when the vibration frequency was not close to the lumbar natural frequency. Thus, the effects of the 1-h vibrations at different frequencies on one spinal motion segment were similar. Vibration frequency sensitivity analysis on the dynamic characteristics of human L2-L3 spinal motion segments with different degrees of degeneration.

Increasing demands call for the burr-free workpiece in precision manufacturing. Low-frequency vibration-assisted drilling (LFVAD) has been applied to improve the fabrication process. Prediction and minimization of burr size are one of the major research topics in precision machining. In this paper, an LFVAD parameters optimization model was proposed including harmony search (HS) algorithm and a modified LFVAD burr height analytical model. The burr height model of LFVAD was developed using existing analytical burr height model for conventional drilling (CD) and vibration-assisted drilling (VAD). The developed burr height models were then employed with HS algorithm, which is a new meta-heuristic optimization method based on the imitation of music improvisation process, to determine the optimal machining parameters for a given twist drill that results in minimum exit burr height. Experimental results show that the burr height of the optimized LFVAD decreased by 52.75% compared with the CD, and decreased by 17.59% compared with the un-optimized LFVAD. The simulation and experimental results demonstrate that under suitable LFVAD parameters, the burr height could be reduced.

In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom (2DOF) low frequency dynamic vibration absorber (DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density (PSD) and ride quality of the car body are calculated based on the pseudo excitation method (PEM) and covariance algorithm, respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness (HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.

A bistable state of a reaction system was theoretically shown to be possible for a multistage chemical reaction in the case of reagent association. The conditions for the bistability origin with a possible substantial change in the rate of reaction product formation were determined. The conditions for the appearance of oscillations of intermediate concentrations and the possibility for the origination of the corresponding acoustic frequencies were studied. The action of external vibrations with the frequency coinciding with that of intrinsic intermediate concentration oscillations can increase the reaction rate of reaction product formation.

A micro hole is a basic feature in micro manufacturing. Micro electrical discharge machining (EDM) is one of the key techniques for machining micro holes in metallic materials. Since debris is accumulated in the discharging gap between the tool electrode and the workpiece, it becomes increasingly very difficult to machine a micro hole as the chosen diameter is progressively decreased or the depth increased. The use of vibration in micro EDM drilling can improve machining efficiency by refreshing dielectric fluids and flushing out the debris from the gap. Although ultrasonic vibration over a few kHz has been introduced in many applications of micro EDM, it is difficult to apply to a workpiece of a very large size or mass. In this study, the effect of very-low-frequency vibration was investigated to improve the efficiency of micro EDM. Low-frequency vibration in the range of 10 to 70 Hz was applied to single-hole machining, to reverse EDM, and to multiple-hole machining. The machining efficiency was investigated while varying the vibration frequency and amplitude.

Experience in remote vibration diagnostics of steam-turbine equipment using its regular vibration monitoring system is described, the features of the software of the vibration monitoring system in determining low-frequency vibrations are considered, and the mechanism by which the auxiliary equipment acts on the vibration state of the turbine equipment is indicated.

Formulas for calculating the dimensions of a dynamic low-frequency vibration damper are derived. The damper is designed as a circularly curved thin-walled plate. Bench tests demonstrated that the damper effectively reduces the amplitude of vibrations of the bearing of a high-power turbine-generator set in two directions simultaneously.

The original version of this article unfortunately contained a mistake. Reference #38 is incorrect. The correct reference is given below.

New experimental results present the effects of low-frequency vibrations in a vertical heat pipe. The thermal resistance was investigated under different heat transfer rates, filling ratios and frequencies, increase of which improved the thermal performance. The vibrations were effective 33.83 % on the performance, and the best performance was estimated using the L16 array of Taguchi method, and it was achieved with the thermal resistance 0.064 K/W in the frequency 30 Hz.

The appropriateness of using honeycomb seals in steam turbines is examined and the effective efficiency of using them is evaluated. It is shown that using honeycomb seals in the regulated stages and, in some cases, in the first unregulated stages, for the pressure in the high pressure cylinder, may be accompanied by losses of stability of the unit and the appearance of low frequency vibrations. Some examples of designs for seals in steam turbines with long lifetimes and enhanced antivibration properties proposed by leading foreign companies are discussed.

Body vibrations training has become popular in sports training, fitness activity, it is still a rare form of physical rehabilitation.. Vibrations are transmitted onto the whole body or some body parts of an exercising person via a vibration platform subjected to mechanical vertical vibrations. During the training session a participant has to maintain his body position or do exercises that engage specific muscles whilst vibrations of the platform are transmitted onto the person's body. This paper is the continuation of the earlier study covering the effects of low-frequency vibrations on selected physiological parameters of the human body. The experiments were conducted to find the answer to the question if vibration exposure (total duration of training sessions 6 hours 20 min) should produce any changes in hepatic profile of blood. Therefore a research program was undertaken at the University of Science and Technology AGH – UST to investigate the effects of low-frequency vibration on selected parameters of hepatic profile of human blood. Cyclic fluctuations of bone loading were induced by the applied harmonic vibration 3.5 Hz and amplitude 0.004 m. The experiments utilizing two vibrating platforms were performed in the Laboratory of Structural Acoustics and Biomedical Engineering AGH-UST. The applied vibrations were harmless and not annoying, in accordance with the standard PN-EN ISO 130901-1, 1998. 23 women volunteers had 19 sessions on subsequent working days, at the same time of day. during the tests the participants remained in the standing position, passive. The main hypothesis has it that short-term low-frequency vibration exposure might bring about the changes of the hepatic profile of blood, including: bilirubin (BILIRUBIN), alkaline phosphatase (Alp), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and albumin (ALBUMIN) levels. Research data indicate the low-frequency vibrations exposure produces statistically significant decrease of bilirubin level [umol/l] in blood serum from 14.05 to 9.70 for 82% of participants, the probability level being p = 0.000041.

In order to make clear the effects of mirror grinding conditions on the ground surfaces in the surface mirror grinding of sintered carbide adopting an in-process electrolytic dressing method, experiments are conducted to measure the vibration signals of the workpiece during grinding and the profile of the ground surface. It is found that components with low frequency vibration signals have a very close relation to the undulation of a ground surface and components with high frequencies to the surface roughness .

Low-frequency vibration spectra, structure, and biological activity of azolidons with the NH ... X (X = S, N, O) intermolecular hydrogen bond and of dimers with nonrigid structure and in the crystalline state are investigated both experimentally and theoretically. The principal moments of inertia, the force constants for vibration-rotation spectra of molecules and dimers, and their frequencies νr are calculated. The mechanism of generating particles and fields by the hydrogen bond ring is elucidated, and the non-spectral parameters of heterosubstituted compounds that possess a biological activity are determined.

Multi-parametric experimental and computer analyses has shown that unsteady low energy thermal control actions “thermal waves”, induced by periodic variations of heater temperature, changes of crystal and crucible rotation speeds and low frequency vibrations, are able to eliminate temperature fluctuations at the crystallization front and can be used as potential tools for the growth of crystals with high homogeneity.

Spectral energy transformation is one of the general properties of nonlinear systems. We examined the Frohlich vibration system as a model nonlinear system. Energy is transferred down towards low frequency vibration modes with considerable damping.

For multispan beams of periodic structure with constant characteristics between supports we obtain closed-form expressions for the monodromy matrix and the characteristic equations for its eigenvalues. In the low-frequency approximation we establish bounds on the first zone of instability of parametric vibrations of a homogeneous multispan beam. Bibliography: 4 titles.

The action of continuous low-frequency vibration on rats for 1 month caused no changes in the total adenine nucleotides of the brain but led to a marked decrease in the ATP content and total adenine nucleotides in the limb muscles. After exposure to vibration for 3 months considerable exhaustion of the total adenine nucleotides of both muscles and brain was found. In the case of interrupted exposure to vibration the state of the adenine-nucleotide system depended on the duration of the pauses between periods of continuous exposure to vibration. During vibration with the shortest pauses (4 min) between successive periods of 30 min of vibration no changes were observed in the energy metabolism of the muscles and brain. Vibration with pauses of 8 and 15 min was found to be unfavorable for the adenine nucleotides of the muscles and vibration with a pause of 8 min for the brain.

The role of low-frequency vibrations in altering line shapes of Raman excitation profiles is investigated with particular reference to the scattering of nontotally symmetric modes and vibronically active totally symmetric modes.

In 46 isolated and 4in situ preparations of perioral skin, afferent impulse patterns, leading from cutaneous mechanoreceptors and responding to orthogonal square as well as sine-wave stimuli, were investigated in selachians (Scyliorhinus canicula). 1. Two distinct classes of specific mechanoreceptors could be differentiated: pressure- and tension-sensitive units, excited only in either the pressure or the tension phase of standard steps. Both populations yielded PD-transfer functions with predominating D-components and slow adaptation. The pressure units (majority of trigeminal skin afferents) usually revealed lower thresholds than the tension type. 2. Receptive areas (with a considerable portion of overlapping) and local discrimination thresholds were determined. A comparison with values of the dorsolateral region showed a twofold higher sensitivity in perioral skin. Several response parameters, such as overshoot and latency, were proved to be a function of the distance between focus and stimulus, as well as of the hydromechanical pressure bias of the skin. 3. Under biologically relevant conditions, the focal transformation characteristics and amplitude-frequency responses of 78 cutaneous afferents were measured for low-frequency vibration. Increasing skin pressure resulted in a significant amplitude and frequency shift of different synchronization thresholds. 4. In addition to specific responses, afferent discharges of unspecific units, sensitive to touch as well as cold, were also recorded. Most of these fibres revealed spontaneous activity, which could be modulated by superimposed mechanical stimulation.

The development of the low-frequency-vibration apparatus described in this report was done in response to a need to establish and verify vibration-pickup performance at infrasonic frequencies. The exciter design is an extension of the Dimoff type exciters1 and, in fact, many of its components are identical.

Rotational isomerism in model compounds of cis- and trans-1,4-polybutadienes was studied. Infrared spectra in the region 600–300 cm−1 were measured for cis- and trans-2-butenes, 1-butene, 1-pentene, 1-hexene, cis- and trans-2-pentenes, cis- and trans-4-methyl-2-pentenes, cis- and trans-3-hexene, cis-2-hexene, and 1,5-hexene. Normal frequencies were calculated for the low frequency vibrations of rotational isomers. From changes in the spectra in the gaseous, liquid, and solid states, it was concluded that the cis and skew conformations are stable for C–C bond neighbouring the trans C=C bond, and only the skew conformation is stable for the C–C bond neighbouring the cis C=C bond.The stable conformations of cis- and trans-1,4-polybutadiene chains are discussed, taking into account the infrared spectra of these polymers and the stable conformations of the model compound molecules.

THE low temperature specific heat of glasses and amorphous solids is characterised by an anomalous linear variation with temperature1–6. Of the proposed theoretical explanations (reviewed by Leadbetter7), the most favoured attributes this anomaly to localised two-level systems8,9 or to low frequency vibrations of single atoms or molecules trapped in cavities10,11. It is difficult, however, to conceive of a level-splitting mechanism that would be sufficiently general to explain the apparent universality of the anomaly. Moreover, several impurities that could have produced two-level systems have now been eliminated as possible candidates12,13. An explanation based on low frequency vibrations of atoms or molecules in cavities rests on two ad hoc assumptions about the size and distribution of the cavities, and Stephens et al.5 argue that to account for the experimental results, these assumptions seem to be physically implausible.