Intermittent Vibration Research Articles

Nonlinear dynamic analysis and vibration reduction of two sandwich beams connected by a joint with clearance

The dynamics and vibration reduction characteristics of the clamped–clamped two sandwich beams jointed with clearance is studied theoretically and experimentally. A transverse and torsional spring system with clearance is used to equivalent the joint model. The homogenization method is used to equivalent the core layer and Rayleigh-Ritz method is utilized to derive the mode function of the interconnected sandwich beam by using a sequence of orthogonal polynomials. The nonlinear motion equation of the two jointed sandwich beam structure with clearance is derived by the application of the Hamilton principle and then solved using an improved Newmark integration approach. In order to validate the accuracy of the natural frequency and vibration mode, the finite element model is established. This paper examines the impact of clearance on the amplitude frequency response and vibration transmission of the two jointed sandwich beam structure, it is found the jointed sandwich beams show obvious nonlinear characteristics and intermittent vibration transmission phenomenon due to the clearance. Moreover, the vibration transmission analysis reveals that the existed clearance demonstrates significant vibration reduction effect, for which an experiment is conducted to validate the results. In general, this work proposes a novel approach for modeling sandwich structures with clearance with improved vibration reduction performance.

Determination of riding comfort on cycleways using a smartphone application

Well maintained cycleways will encourage more people to cycle, as the condition of cycleways is important for the safety, accessibility and riding comfort of cyclists. Despite that, only a few models used to describe the quality of service for cyclists take the surface condition into account. Objective measuring methods are needed to enable reliable and effective assessment of surface conditions, and measurable performance criteria related to the needs of cyclists should be developed. The purpose of this study has been to test the reliability and validity of using accelerometers in smartphones to assess the riding comfort on cycleways. A smartphone application converting three-dimensional accelerometer measurements into a single indicator for cycleways has been used to assess road surfaces in two field studies, in Sweden and Norway, respectively. Both studies assessed test sections of varying quality. To relate the measurements to subjective riding comfort assessments by cyclists, recruited cyclists collected quantitative data using the app, whilst also rating their perceived riding comfort by completing a survey. Measurements were also related to standard road surface condition indicators, generated from a road surface tester equipped with 19 laser sensors: international roughness index (IRI), mega- and macrotexture. The results show that it is possible to describe the unevenness of a cycleway using the technology present in smartphones. A software application can be used to collect and analyse data from the acceleration sensors in the phone, which can then be used to describe the riding comfort of cyclists. It is mainly the unevenness in the 50–1000 mm size-range that create the greatest discomfort for cyclists, and intermittent vibrations are perceived as more uncomfortable than more evenly distributed vibrations. Therefore, IRI is not a relevant measurement for describing the riding comfort of cyclists.

Experimental study on flow-induced vibrations of an equilateral triangular prism with a high mass ratio

The mass ratio exerts a significant influence on the vibration responses exhibited by a bluff body in cross flows. In this investigation, the flow-induced vibration (FIV) of a transversely oscillating equilateral triangular prism, characterized by a high mass ratio (m* = 23.15), is experimentally examined to enhance our comprehension of these influences at elevated m*. Various angles of attack (AoA), ranging from α = 0°–60° with 5° increment, where α = 0° and 60° correspond to scenarios of one vertex facing upstream and downstream, respectively. The reduced velocity ranged from Ur = 3.0 to 31.0. The vibration responses are categorized into four regimes according to amplitudes and spectral characteristics: no vibration (α = 0°–20°), intermittent galloping (α = 25°), separated vortex-induced vibration (VIV) and galloping (α = 30°–35°), and galloping (α = 40°–60°). The implications of high m* are profound in the intermittent galloping regime, characterized by random and intermittent vibration responses, which is uniquely observed in the FIV of a triangular prism with a high mass ratio. Additionally, for FIV at high m*, the onset of galloping occurs at a notably lower Ur, and the restart of the prism's vibration in separated VIV and galloping regime is initiated by lower harmonic synchronization. Hard galloping is discerned exclusively at α = 60°, and the distinctions from soft galloping are deliberated.

Experimental investigation on vortex-induced vibration of a flexible pipe in combined uniform and oscillatory flow

Vortex-induced vibrations (VIV) induced by ocean currents can cause severe fatigue damage to marine risers. The background current and oscillatory flow caused by the motion of the floating platform form a combined flow field, which complicates the VIV of risers. In this paper, a series of model tests were conducted in a towing tank to investigate the VIV characteristics of a flexible pipe in combined uniform and oscillatory flow. Effects of oscillating amplitude, oscillating period and uniform flow velocity on VIV of the pipe were investigated and discussed based on the experimental results. VIV fatigue damage of the pipe was also calculated. Intermittent vibration, hysteresis and mode transition were observed in combined flow. Large oscillating amplitude and short oscillating period tend to enlarge the fatigue damage. But when the uniform flow velocity is too high, small oscillating amplitude and long oscillating period tend to enlarge the fatigue damage. Critical short period and combined ratio threshold are discovered in the VIV of the pipe in combined flow. VIV characteristics in different types of flows are also compared. VIV in combined flow may cause severe fatigue damage, which should be given enough attention.

Coupling effect of time-varying axial tension and combined unsteady flow on vortex-induced vibration of flexible risers

The surge and heave motions of the floating platform have a non-negligible effect on vortex-induced vibration (VIV) of marine risers, which generates time-varying axial tension of risers, i.e., parametric excitation, and unsteady flow and complicates the prediction of VIV. A semi-empirical model is improved to simulate the VIV of flexible risers with parametric excitation under combined unsteady flow. Both the flow velocity and the stiffness matrix are updated with time. Fifty-five cases are simulated to investigate the separate and coupling effects of parametric excitation and combined unsteady flow on VIV. The phenomena such as sum and difference frequencies, Mathieu-type resonance, intermittent vibration and frequency fluctuation are observed. The effects of parameters such as excitation amplitude dT, excitation frequency fp, combined ratio r and oscillation period P on VIV are discussed in detail. Some interesting conclusions are drawn: VIV may be significantly suppressed when transition-low-frequency parametric excitation and short-period combined unsteady flow act together. Larger r makes the effect of combined unsteady flow more significant. VIV is mainly dominated by the parametric excitation when fp is twice the natural frequency of the riser corresponding to the dominant mode.

Adding Intermittent Vibration to Varied-intensity Work Intervals: No Extra Benefit.

Varied-intensity work intervals have been shown to induce higher fractions of maximal oxygen uptake during high-intensity interval training compared with constant-intensity work intervals. We assessed whether varied-intensity work intervals combined with intermittent vibration could further increase cyclists' fraction of maximal oxygen uptake to potentially optimise adaptive stimulus. Thirteen cyclists (V̇O2max: 69.7±7.1 ml·kg-1·min-1) underwent a performance assessment and two high-intensity interval training sessions. Both comprised six 5-minute varied-intensity work intervals within which the work rate was alternated between 100% (3×30-second blocks, with or without vibration) and 77% of maximal aerobic power (always without vibration). Adding vibration to varied-intensity work intervals did not elicit a longer time above ninety percent of maximal oxygen uptake (415±221 versus 399±209 seconds, P=0.69). Heart rate- and perceptual-based training-load metrics were also not affected (all P≥0.59). When considering individual work intervals, no between-condition differences were found (fraction of maximal oxygen uptake, P=0.34; total oxygen uptake, P=0.053; mean minute ventilation, P=0.079; mean heart rate, P=0.88; blood lactate concentration, P=0.53; ratings of perceived exertion, P=0.29). Adding intermittent vibration to varied-intensity work intervals does not increase the fraction of maximal oxygen uptake elicited. Whether intermittent exposure to vibration can enhance cyclists' adaptive stimulus triggered by high-intensity interval training remains to be determined.

Adding Vibration During Varied-Intensity Work Intervals Increases Time Spent Near Maximal Oxygen Uptake in Well-Trained Cyclists.

Previous research suggests that the percentage of maximal oxygen uptake attained and the time it is sustained close to maximal oxygen uptake (eg,>90%) can serve as a good criterion to judge the effectiveness of a training stimulus. The aim of this study was to investigate the acute effects of adding vibration during varied high-intensity interval training (HIIT) sessions on physiological and neuromuscular responses. Twelve well-trained cyclists completed a counterbalanced crossover protocol, wherein 2 identical varied HIIT cycling sessions were performed with and without intermittent vibration to the lower-intensity workloads of the work intervals (6 × 5-min work intervals and 2.5-min active recovery). Each 5-minute work interval consisted of 3 blocks of 40seconds performed at 100% of maximal aerobic power interspersed with 60-second workload performed at a lower power output, equal to the lactate threshold plus 20% of the difference between lactate threshold and maximal aerobic power. Oxygen uptake and electromyographic activity of lower and upper limbs were recorded during all 5-minute work intervals. Adding vibration induced a longer time ≥90% maximal oxygen uptake (11.14 [7.63] vs 8.82 [6.90] min, d = 0.64, P = .048) and an increase in electromyographic activity of lower and upper limbs during the lower-intensity workloads by 20% (16%) and 34% (43%) (d = 1.09 and 0.83; P = .03 and .015), respectively. Adding vibration during a varied HIIT session increases the physiological demand of the cardiovascular and neuromuscular systems, indicating that this approach can be used to optimize the training stimulus of well-trained cyclists.

A rotational vibration energy harvester for near-zero-energy applications in railway environment

The vibration in the railway environment contains a huge amount of available mechanical energy, which can be utilized as a practical power source for low-power independent distributed appliances. This paper proposed a rotational vibration energy harvester (RVEH) based on a linear cam mechanism for near-zero-energy applications in railway environment. The RVEH system mainly consists of a motion conversion mechanism (MCM) and electromagnetic generators. The motion conversion mechanism realizes the motion conversion from vibration to uni-directional rotation based on a linear cam and a one-way rectifier. The electromagnetic generators convert kinetic energy into electrical energy. The test shows that the electric outputs of the proposed RVEH is improved under vibration excitations compared with the conventional vibration energy harvester (VEH, the RVEH without a one-way rectifier). Also, the RVEH has a comparatively long duration of electric outputs after the vibration excitation, suitable for the intermittent vibration excitation input. And the RVEH can operate as a power supply, producing output characteristics of an average output power of 66 mW and a peak output power of 0.15 W, sufficient to power 155 LEDs in series or a thermometer. It is foreseeable that the RVEH is a promising self-powered solution for applications in railway environment.

Exploiting flocculation and membrane filtration synergies for highly energy-efficient, high-yield microalgae harvesting

High energy consumption during harvesting is one of the main bottlenecks for sustainable microalgae production. Membranes can efficiently separate microalgae from liquids with low energy consumption, but membrane fouling remains an important issue. Flocculation prior to membrane filtration can increase membrane fluxes and decrease fouling, thus offering a low-cost and efficient solution to harvest microalgae. Biobased cationic cellulose nanocrystals were successfully used as flocculants for microalgae and were effective over a wide pH-range and for both freshwater and marine microalgae. Such flocculation was for the first time combined with vibration-assisted filtration using a charged, surface patterned membrane, enabling operation at very high flux (95 L/m2 h) using a vibration frequency of only 1 Hz, and even under sub-optimal flocculation conditions. Intermittent vibration decreased energy consumption further while keeping excellent filtration performance to finally achieve a record-low energy consumption for the membrane filtration of only 6.7 Wh/m3, which is >25-times lower than that of normal membrane filtration. Interaction forces revealed that increasing particle size through flocculation prior to membrane filtration can significantly prevent microalgae attachment on the vibrating membrane surface. This work opens a new direction for sustainable microalgae harvesting with an ultra-low energy consumption, combined with a very high microalgae recovery, reduced use of chemicals, and lower membrane investment cost.

Aspect ratio-dependent hysteresis response of a heavy inverted flag

The bistable fluttering response of heavy inverted flags with different aspect ratios ( $AR$ ) is investigated to determine how the vortical structures affect the intermittent vibration response of the flag. A heavy inverted flag in a uniform flow may exhibit several response modes; amongst them are three major modes that occur over an extended velocity range: stationary, large-scale periodic oscillation and one-sided deflected modes. Significant hysteretic bistability is observed at the transition between these modes for all $AR$ , which is notably different from the conventional flag vibration with a fixed leading edge and free trailing edge where no hysteresis is observed at the lower $AR$ limit ( $AR<1$ ). The difference is associated with the distinct roles of vortices around the flag. Experiments with flags made of spring steel are conducted in a wind tunnel, where the flow speed is steadily increased and later decreased to obtain different oscillatory modes of the heavy inverted flags. The experimental results are used to validate the numerical model of the same problem. It is found that different critical velocities exist for increasing and decreasing flow velocities, and there is a sustained hysteresis for all $AR$ controlled by the initiation threshold and growth of the leading-edge and side-edge vortices. The effect of the vortices in the bistable oscillation regime is quantified by formulating a modal force partitioning approach. It is shown that $AR$ can significantly alter the static and dynamic vortex interaction with the flexible plate, thereby changing the flag's hysteresis behaviour and bistable response.

Influence of the intermittent vibration ratio on the electro-osmotic consolidation of dredged sludge

During electroosmosis experiments, the electrical interface resistance between electrodes increases with soil cracking, which hinders the further improvement of electroosmosis efficiency. To improve the effectiveness of later stage electroosmosis, the consolidation effect of dredged sludge was studied using electroosmosis combined with excitation loading. In this study, a series of experimental tests were used to analyze the influence of the intermittent vibration ratio on the consolidation effect of sludge. The electric current, effective potential, drainage, surface settlement, water content and undrained shear strength were monitored during sludge improvement. After testing, it was concluded that compared with the pure electro-osmotic method, the consolidation effect of the electro-osmotic method combined with the excitation loading method had significant performance improvements on the soil. In addition, the optimal intermittent vibration ratio was obtained, which could provide a design basis for engineering practice.

ACUTE EFFECTS OF SLING EXERCISE RECOVERY WITH WHOLE-BODY VIBRATION RESTING MUSCLE FUNCTION AND BLOOD OF LACTATE

The purpose of this study was to investigate an effective recovery method on muscle function and blood of lactate level after maximal isotonic exercise. This study was conducted in 36 adult males. The group was divided into three groups. Sling therapy group (SG, [Formula: see text]), sling therapy group with whole body vibration continuous (SAVG, [Formula: see text]) and sling therapy group with whole body vibration in intermittent (SIVG, [Formula: see text]) were randomly composed. Sling exercise therapy using supine position and whole-body vibration of 10[Formula: see text]Hz, 5[Formula: see text]mm were performed. Lactate level and muscle function during the rest, fatigue and recovery period were measured and then maximal exercise using back extension was performed to induce fatigue. After 15[Formula: see text]min, sling with whole body vibration was conducted in two groups, respectively. Blood lactate was measured a few hours before and after of vibration. Also, muscle function between only sling exercise therapy condition, sling with whole body vibration condition in all time and sling with whole body vibration condition in intermittent time were analyzed. Lactate level was recorded by lactate measurement device. Isokinetic of lumber joint extension and flexion Peak torque/body weight, total work (J), average power (W) and acceleration time (m/s2) were measured using isokinetic dynamometer. The recovery method of sling with whole body vibration showed positive changes in physical characteristics. Isokinetic contraction of peak torque/body weight (N[Formula: see text]m), average power (Watts) and total work (J) were significantly increased in the recovery step for SIVG. Lactate level was significantly decreased for SIVG as compared with SG and SAVG. This study demonstrated that sling exercise therapy with intermittent time whole body vibration could provide a positive effect on the efficient recovery of muscle function and higher reduction of lactate after maximal isotonic exercise.

Experimental Measurement of Large-Amplitude Intermittent Vibrations of an Inclined Bendable Riser Transporting Unsteady Multiphase Flows

Marine risers transporting unsteady multiphase flows may experience internal flow-induced vibrations depending on several flow-structure parameters. This study presents an experimental investigation of large-amplitude intermittent vibrations of an inclined bendable riser transporting an air-water flow that exhibits an unsteady slug flow pattern. The riser has an initial catenary profile with a length over an internal diameter of about 320. By using a non-intrusive measurement with a high-speed motion capture camera, new insights into the riser dynamic features and slug flow-riser interaction phenomena are presented and discussed in the case of varying gas-to-liquid flow rate ratio (RGL). Pressure signals are also recorded at the riser inlet and outlet, measuring the pressure fluctuation caused by the hydrostatic change, flow-induced momentum and frictional forces. For a given liquid flow rate or superficial velocity, the inclined bendable riser experiences a modified mean drift of the equilibrium configuration and a greater vibration amplitude when increasing RGL or the superficial gas velocity. The most critical case has a spatially maximum amplitude of greater than six diameters of the riser pipe. Experimental results of the space-time varying responses and frequencies of the riser are analysed in relation to the associated slug flow features including the slug unit length, translational velocity, frequency and pressure fluctuations. Owing to a coupled slug flow-riser interaction, the liquid slugs and elongated gas bubbles vary spatially and temporally. This entails the highly modulated responses and frequencies, intermittently switching the riser multimodal response, especially when RGL is greater than two. The amplified bending stresses in the riser are reported, highlighting the critical hydrodynamic effect of unsteady multiphase flow. The characteristic slug frequencies associated with the flexible inclined riser dynamics are also evaluated and compared with those predicted by several empirical correlations in the literature based on stationary, straight and rigid pipes. Overall, experimental observations and data are useful for a numerical model development and comparison towards a practical analysis and design of flexible curved/sagged risers transporting multiphase flows.

Exploration and verification of the feasibility of sulfur-based autotrophic denitrification process coupled with vibration method in a modified anaerobic baffled reactor for wastewater treatment

As an effective nitrate removal process with lower sludge production, sulfur-based autotrophic denitrification (SAD) has attracted extensive attention in recent years. This study investigated a modified anaerobic baffled reactor coupled with a vibration frame (MV-ABR) for the SAD process to treat nitrate contaminated water. The nitrate removal rate (NRR) of 0.34 kg NO3−-N·m−3·d−1 was obtained under an ambient temperature. With adding oyster shells in two steps, the maximum NRR can be further increased from 0.34 kg NO3−-N·m−3·d−1 to 0.37 kg NO3−-N·m−3·d−1. The MV-ABR also achieved a strong impact resistance and robustness nitrogen removal performance under transient shocks. In addition, coupling the anaerobic baffled reactor (ABR) with the vibration method demonstrated that vibration could improve the denitrification performance, even under low temperatures (10 °C–15 °C). Under a suitable intermittent vibration intensity (level 1 (5–60)), the average NRR increased from 0.26 kg NO3−-N·m−3·d−1 to 0.35 kg NO3−-N·m−3·d−1, which suggests this is an economic and effective method for the SAD process. Overall, these results suggest that the MV-ABR could boost the SAD treatment performance, and present a stable nitrate removal performance even under a lower temperature environment (<15 °C) or transient shocks.

Intermittent vibrational stimulation enhances mobility during stair navigation in patients with knee pain

BackgroundReduced quadriceps function and proprioception can cause decreased mobility during stair navigation in patients with knee pain. Patients can benefit from interventions to mitigate pain and restore quadriceps function. Activating the somatosensory system via intermittent vibrational stimulation has the potential to improve stair navigation mobility in patients with knee pain by moderating quadriceps inhibition and enhancing proprioception. Research questionWhat are the effects of intermittent vibrational stimulus synchronized to stair ambulation on muscle activity, kinematics, kinetics, and pain using a randomized controlled clinical trial design. MethodsThirty-eight patients with knee pain were enrolled into a blinded cross-over study, and twenty-nine patients completed all assessments and analyses. Subjects were randomly assigned sequentially to both an active Treatment A (active) and passive Treatment B (passive) worn at the knee during ambulation for 4 weeks with a 2-week washout period between treatments. ResultsKnee pain during stair navigation was significantly reduced only with Treatment A (P = 0.007). During ascent, Treatment A (active) significantly increased vastus lateralis activation (P = 0.01), increased knee flexion moment (P = 0.04) and decreased trunk flexion angles (P = 0.015) between baseline and 4-week follow-up. After using passive Treatment B, there were no significant differences in pain (P = 0.19), knee flexion moment (P = 0.09), and trunk flexion angles (P = 0.23). Changes in muscle function correlated significantly with changes in knee flexion moment and trunk flexion with Treatment A (P < 0.015).Descending differed from ascending in response to Treatment A with significantly decreased knee flexion moment(P = 0.04), hip(P = 0.02) and ankle(P = 0.04) flexion angles. Treatment B significantly reduced hip flexion angles (P = 0.005) but not knee flexion moment (P = 0.85). SignificanceThe results of this study suggest that intermittent vibration can improve joint motion and loading during stair navigation by enhancing quadriceps function during stair ascent and improving movement control during stair descent by modifying an adaptive flexed movement pattern in the lower limb.

The effects of vibration on efficiency in off-road cyclists.

Objectives The aim of this study was to investigate whether vibration significantly affected the efficiency of off-road cyclists. Patients and methods Eight male mountain cyclists (mean age 21.1±1 years; range, 19 to 22 years) between August 2017 and November 2017 were included. The experimental protocol included four testing sessions with a one-day interval between testing sessions: a familiarization session; performance of submaximal tests; performance of maximal graded exercise test; and a 30-min mountain bike trial performed with vibration or without vibration. Physiological measures including volume of oxygen uptake (VO2), volume of 2), VO2, VCO2, heart rate, respiratory exchange ratio, rating of perceived exertion, and gross efficiency (GE) were compared between the trials performed with vibration or without vibration. Results There was a significant increase in the GE with the addition of intermittent vibration, particularly over the last 15 min of the cycling trial (p<0.05). There were no significant effects of vibration on other parameters. Conclusion This study demonstrates that addition of intermittent vibration may provide positive benefits in improving GE during a 30-min submaximal cycling trial.

Analysis of Intermittent Vibration and Its Emergency Treatment Measures

Intermittent vibration is a major unstable factor in the safe operation of unit. Based on the working experiences of dealing with the intermittent vibration of steam turbine, this paper is to analyze the reasons for the intermittent vibration and the corresponding measures, which can provide reference for the unit for which such a phenomenon may appear.

Permeability characteristics of bedrock fissures under disturbance conditions based on neural network

During different periods of rock fracture engineering, the surrounding rock is subject to intermittent and periodic vibration disturbances of different degrees. This disturbance has a great influence on the permeability characteristics of bedrock fissures. The permeability characteristics of bedrock fissure permeability are the most important hydrogeological element of underground water-containing medium, and determining the stratum permeability is an important link to evaluate the hydrogeological conditions of the mining area. Therefore, this paper studies the permeability characteristics of bedrock fissures based on the disturbance of neural network. First, use the basic structure of the neural network to understand the method applied to the study of permeability characteristics of bedrock cracks; secondly, put forward the rock permeability model driven by coal mining to help the subsequent experimental design of various relevant factors after the bedrock cracks Finally, the stress intensity factor method at the tip of the fracture is used to calculate the permeability of the bedrock fracture. The experimental data shows that the infiltration rate tested in the first minute of the experiment is 5.5 * 10−4 cm/s, which is equivalent to 12 times the stable infiltration rate. At 50 min after the start of the test, the infiltration rate dropped to 4.6 * 10−4 cm/s, which was close to the stable infiltration rate. The experimental results show that under the disturbance condition of neural network, the infiltration rate of bedrock fissures is accelerated and the permeability is increased.

How universal is the vibration-velocity controlled granular convection?

Recently, a number of articles have reported that granular convection induced by continuous vibration is controlled by vibration velocity, in contrast with some previous studies. We have reported such an example for the Brazil nut effect when the vibration is given discontinuously, using a one-layer granular bed in a cell with down-facing side walls. Here, we report the effect of vibration phase and wall friction using the same experimental system, to confirm rising motion of an intruder induced by granular convection is again governed by vibration velocity. We compare two different cases of vibration phase for giving intermittent vibration cycles, and found one, in which granular packing is well established before grains start to lose contacts due to vibration, provides distinctly high reproducibility. We further control the side wall friction using a microfabrication technique, and found that significantly high reproducibility is attained in a cell with vertical side walls when a millimeter texture is introduced on the side walls. Our results indicate that the granular convection is universally controlled by vibration velocity. The present study opens a way to conduct highly reproducible experiments on granular dynamics, which is indispensable for deep physical understanding of granular flow and segregation.

Sleep Induction by Mechanosensory Stimulation in Drosophila

SUMMARYPeople tend to fall asleep when gently rocked or vibrated. Experimental studies have shown that rocking promotes sleep in humans and mice. However, the mechanisms underlying the phenomenon are not well understood. A habituation model proposes that habituation, a form of non-associative learning, mediates sleep induction by monotonous stimulation. Here, we show that gentle vibration promotes sleep in Drosophila in part through habituation. Vibration-induced sleep (VIS) leads to increased homeostatic sleep credit and reduced arousability, and can be suppressed by heightened arousal or reduced GABA signaling. Multiple mechanosensory organs mediate VIS, and the magnitude of VIS depends on vibration frequency and genetic background. Sleep induction improves over successive blocks of vibration. Furthermore, training with continuous vibration does not generalize to intermittent vibration, demonstrating stimulus specificity, a characteristic of habituation. Our findings suggest that habituation plays a significant role in sleep induction by vibration.