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At least 19 recordsLinked to original sources
PubMed2004

Picosecond IR-UV pump-probe spectroscopic study of the dynamics of the vibrational relaxation of jet-cooled phenol. I. Intramolecular vibrational energy redistribution of the OH and CH stretching vibrations of bare phenol.

The intramolecular vibrational energy redistribution (IVR) of the OH stretching vibration of jet-cooled phenol-h6 (C6H8OH) and phenol-d8 (C6D8OH) in the electronic ground state has been investigated by picosecond time-resolved IR-UV pump-probe spectroscopy. The OH stretching vibration of phenol was excited with a picosecond IR laser pulse, and the subsequent temporal evolutions of the initially excited level and the redistributed ones due to the IVR were observed by multiphoton ionization detection with a picosecond UV pulse. The IVR lifetime for the OH stretch vibration of phenol-h6 was determined to be 14 ps, while that of the OH stretch for phenol-d8 was found to be 80 ps. This remarkable change of the IVR rate constant upon the dueteration of the CH groups strongly suggests that the "doorway states" for the IVR from the OH level would be the vibrational states involving the CH stretching modes. We also investigated the IVR rate of the CH stretching vibration for phenol-h6. It was found that the IVR lifetime of the CH stretch is less than 5 ps. The fast IVR is described by the strong anharmonic resonance of the CH stretch with many other combinations or overtone bands.

Journal Article↗
PubMed2004

Picosecond IR-UV pump-probe spectroscopic study of the dynamics of the vibrational relaxation of jet-cooled phenol. II. Intracluster vibrational energy redistribution of the OH stretching vibration of hydrogen-bonded clusters.

A picosecond time-resolved IR-UV pump-probe spectroscopic study has been carried out for investigating the intracluster vibrational energy redistribution (IVR) and subsequent dissociation of hydrogen-bonded clusters of phenol (C6H5OH) and partially deuterated phenol (C6D5OH, phenol-d5) with various solvent molecules. The H-bonded OH stretching vibration was pumped by a picosecond IR pulse, and the transient S1-S0 UV spectra from the pumped level as well as the redistributed levels were observed with a picosecond UV laser. Two types of hydrogen-bonded clusters were investigated with respect to the effect of the H-bonding strength on the energy flow process: the first is of a strong "sigma-type H-bond" such as phenol-(dimethyl ether)(n=1) and phenol dimer, and the second is phenol-(ethylene)(n=1) having a weak "pi-type H-bond." It was found that the population of the IR-pumped OH level exhibits a single-exponential decay, whose rate increases with the H-bond strength. On the other hand, the transient UV spectrum due to the redistributed levels showed a different time evolutions at different monitoring UV frequency. From an analysis of the time profiles of the transient UV spectra, the following three-step scheme has been proposed for describing the energy flow starting from the IVR of the initially excited H-bonded OH stretching level to the dissociation of the H bond. (1) The intramolecular vibrational energy redistribution takes place within the phenolic site, preparing a hot phenol. (2) The energy flows from the hot phenol to the intermolecular vibrational modes of the cluster. (3) Finally, the hydrogen bond dissociates. Among the three steps, the rate constant of the first step was strongly dependent on the H-bond strength, while the rate constants of the other two steps were almost independent of the H-bond strength. For the dissociation of the hydrogen bond, the observed rate constants were compared with those calculated by the Rice, Ramsperger, Kassel, and Marcus model. The result suggests that dissociation of the hydrogen bond takes place much faster than complete energy randomization within the clusters.

Journal Article↗
PubMed2000

Analysis of the "Unusual" Vibrational Components of Triply Degenerate Vibrational Mode nu(6) of Mo(CO)(6) Based on the Classical Interpretation of the Effective Rotation-Vibration Hamiltonian.

Rotational structure of the triply degenerate vibrational state nu(6)(F(1u)) of the octahedral molecule Mo(CO)(6) is analyzed qualitatively on the basis of classical mechanics. We show that the energy level redistribution between the vibrational components of nu(6)(F(1u)) occurs due to rotational excitation and is related to the formation of singular points of classical rotational energy surfaces. The singularity is stable under small variations of parameters of the effective rovibrational Hamiltonian. Parameters responsible for the persistence of this phenomenon are specified. Comparison with quantum calculations demonstrates the high qualitative and quantitative accuracy of our classical analysis. Copyright 2000 Academic Press.

Journal Article↗
PubMed1996

Vibrotactile TTS of fingertip vibratory sensation from hand-transmitted vibration having the same equal equivalent tool vibration levels according to the JIS B 4900 determination method.

The purpose of this paper is to clarify the temporary threshold shifts in fingertip vibratory sensation produced by hand-transmitted vibrations that have the same equivalent tool vibration levels according to the JIS B 4900 determination method. The JIS B 4900 standard is based on vibration exposure dose values. Therefore, even though the vibration exposure pattern is varied, the severity of vibration at the end of vibration exposure has a same value if the equivalent tool vibration level is unchanged. The experiment was conducted by using four kinds of hand-transmitted vibration patterns as stimuli. As a result, although the vibration transmitted to the hand by steady continuous vibration, intermittent vibration with short pauses, intermittent vibration with long pauses and repeated single bursts of vibration all have the same equivalent tool vibration levels (equal vibration exposure dose value) according to the JIS B 4900 determination method, the TTS after vibration exposure did not produce the same value. Therefore, these results suggest that the determination methods of the JIS B 4900 standard are not adequate for describing the vibration exposure dose value.

Adult↗
PubMed1997

Proposal for hand-arm vibration exposure limits adopted for Japanese workers operating hand-held vibration tools.

On the basis of data presented in our previous, reports, the current study was undertaken to estimate frequency-weighted hand-arm vibration exposure limits for various daily exposure times. The procedures for the present study were as follows. (1) The prevalence of vibration-induced white finger (VWF) as well as the vibration exposure were investigated in various groups of workers operating hand-held vibrating tools. The vibration magnitude of various tools was measured and the results were presented as the energy-equivalent frequency-weighted root-mean-square (m/s2 rms) acceleration. There was a statistically significant positive correlation between the prevalence of VWF and the measured vibration magnitude (R2 = 0.5, P < 0.05). Hence, it was concluded that in decisions concerning quantitative recommendations for vibration exposure, the prevalence of VWF should be considered. (2) By a careful selection of available publications which contain useful information on duration of vibration exposure of < or = 2 h/day and the occurrence of VWF, a significant correlation between the prevalence of VWF and the vibration magnitude could be observed. The regression equation was estimated as: y = -18.5 + 4.6 (x), R2 = 0.8. On the basis of this equation, it was speculated that the prevalence of VWF in workers using vibrating tools might be restricted to the prevalence of Raynaud's phenomenon in the Japanese general population if the 2-h daily vibration exposure is about 4.5 m/s2 rms. (3) Regarding this speculation, the equation provided in the documentation of ISO 5349 was used and modified as: [alpha h,w)eq,t = (alpha h,w)eq,2(2/t)1/2 (m/s2 rms)] and then the vibration limit values for daily exposure of 1 min to 8 h were calculated. (4) In order to achieve compatibility with standards of other countries, and to formulate an easy method for using the recommended values presented here, the daily exposure time of 8, 4, 2, 1 and 0.5 h were selected. The correspondence vibration magnitudes were in the range 22-9.0 m/s2 rms, and the lower limit (2.2 m/s2 rms) was assumed as the permissible vibration exposure limit for an 8-h working period. The proposed daily vibration limits were then compared with those recommended by other institutions.

Adult↗
PubMed1991

Factors influencing vibration sense thresholds used to assess occupational exposures to hand transmitted vibration.

The effects of various conditions, including temporary threshold shifts (TTS) induced by exposure to vibration on vibration sense thresholds, have been investigated. The vibration sense thresholds of five subjects were measured on the middle fingertip of the left hand. A contactor with a diameter of 7 mm was surrounded by three alternative plates with holes of different sizes. The contact force was controlled at either 1 N, 2 N, or 3 N. For the TTS test, the left hand was exposed to vibration at 20 ms-2 rms for five minutes. The frequencies of both the exposure to vibration and the vibration threshold test were in the range 16 Hz to 500 Hz. Using a surround around the contactor greatly reduced the vibration sense threshold at 16 Hz and 31.5 Hz but increased the threshold at 125 Hz, 250 Hz, and 500 Hz. An effect of contact force was seen only at the higher frequencies; larger contact forces led to lower thresholds at 125 Hz, 250 Hz, and 500 Hz. As temperature of the finger skin decreased, the vibration thresholds increased, with the changes at higher frequencies greater than those at lower frequencies. The TTS at 16 Hz and 31.5 Hz measured 0.5 minutes after exposure to vibration (TTS0.5) were highest after exposures to vibration at lower frequencies. The TTS0.5 at 63 Hz was similar after exposure to all frequencies. The TTS0.5 values at 125 Hz, 250 Hz, and 500 Hz were highest after exposures to vibration at 125 Hz and 250 Hz. It was apparent that the physiological characteristics of vibration sensation at low and high frequencies differed significantly. These findings suggest that two representative frequencies can be used when evaluation the neurological effects of occupational exposures to vibration by means of vibration sense thresholds.

Adult↗
PubMed1981

Response of soleus Ia afferents to vibration in the presence of the tonic vibration reflex in the decerebrate cat.

1. Micro-electrode recordings were made from single Ia afferents in the intact nerve to the soleus muscle in the decerebrate cat while the muscle was developing a tonic vibration reflex. This was done in order to test how effectively the afferents were excited by the vibration, and to see if any insecurity in driving might be related to tremor.2. When the amplitude of vibration was 50 mum, and the tonic vibration reflex was reasonably well developed (> 1 N of active tension) all but one of forty-four Ia afferents were driven 1:1 by the vibration. Most were still driven by 30 mum vibration. The vibration, consisting of a train of discrete pulses at 150 Hz, was applied longitudinally in combination with a stretch of 1 mm to make the muscle taut.3. If the reflex was poorly developed (active tension < 1 N) the driving was on average less secure. However, fourteen of eighteen afferents then studied were still driven 1:1 by 50 mum vibration. The lower level of excitation by vibration was thought to be due to a deficiency of spontaneous fusimotor activity, because stroking the cat's tail or other similar gentle manipulation led each of the three misbehaving afferents so tested to be driven securely by 50 mum vibration; at the same time the reflex tension increased.4. Additional, indirect evidence favouring widespread security of Ia driving by 50 mum vibration in the presence of the reflex was obtained by modulating the amplitude of the 150 Hz vibration with a 7-10 Hz square wave and detecting any tension fluctuations at that frequency by spectral analysis. Small degrees of modulation (e.g. < 10%) produced little if any effect, although larger depths of modulation had a powerful action.5. When the amplitude of vibration was reduced to permit insecure driving but still to elicit a reflex response, the fluctuations in Ia firing pattern were unlike those previously seen in the de-efferented muscle. Spectral analysis showed that these firing fluctuations bore a general similarity to the tremor in the same preparation, but measurement of coherence demonstrated that the tremor and Ia firing were not well related. This was probably because individual Ia afferents were primarily influenced by local factors, and provides further evidence against the tremor of this preparation being attributable to the action of the stretch reflex.

Action Potentials↗
PubMedDate not supplied

Quantitative exposure assessment for shipyard workers exposed to hand-transmitted vibration from a variety of vibration tools.

The quantitative exposure to vibration for shipyard workers who have used several kinds of vibratory tools was studied. The dose-response relationship between lifetime exposure dose and hand-arm vibration syndrome also was studied. The study included 344 workers who were exposed to vibration in one shipyard and 53 unexposed workers in the same company. Vibration measurements were made on several vibratory tools according to the international standard, ISO 5349. The actual exposure times for the vibratory tools were measured. Questionnaires for demographics, exposure to vibration, and confounding factors were completed. A lifetime vibration dose was calculated for each worker using job categories, usage pattern of vibratory tools, and the measured vibration acceleration magnitude. Each worker was asked about vascular and neurological symptoms, and symptoms were classified according to the Stockholm workshop scale. The prevalence of vascular and sensorineural symptoms for workers exposed to vibration was 22.7 and 78.2%, which were significantly higher than 0 and 34.0% obtained in the nonexposed workers, respectively. The prevalence and severity of the hand-arm vibration syndrome was increased with an increased lifetime vibration dose. The lifetime vibration dose showed a significant association with both vascular and sensorineural symptoms. In conclusion, the lifetime vibration dose was a useful parameter for quantitative exposure assessment and showed a dose-response relationship between exposure and symptoms when adjusted for confounding factors.

Adult↗
PubMed1983

Vibration syndrome and vibration in pedestal grinding.

At one Finnish foundry all the workers had typical symptoms of vibration induced white finger (VWF) after they began using a new type of pedestal grinding machine. The objectives of this study were to establish the severity of the symptoms and the difference in vibration exposure between the new and the old machines. Vibration detection thresholds and grip forces were measured, as well as the vibration in the casting and in the wrist simultaneously. The mean latency for VWF among the grinders was 10.3 months after the change of pedestal grinding machines. All the grinders had numbness in their hands. The vibration detection threshold was significantly higher for the grinders than for their referents. At the same circle speed, the new wheels caused vibration levels up to 12 dB more than the old wheels. The circle speed had a slight influence on the vibration. The vibration levels of light (0.5 kg) casting were up to 25 dB higher than the heavy (5 kg) casting. The use of a pneumatic pressing device decreased the vibration levels in the wrist by 5-10 dB. The increase in vibration, which occurred when the new wheels were taken into use, was too small to explain such a dramatic outbreak of VWF. This led to the conclusion that some other feature such as the impulse character of the vibration also contributed to the effects of vibration.

Adult↗
PubMed1994

Hand-arm vibration syndrome and dose-response relation for vibration induced white finger among quarry drillers and stonecarvers. Italian Study Group on Physical Hazards in the Stone Industry.

OBJECTIVES: To investigate the occurrence of disorders associated with the hand arm vibration syndrome in a large population of stone workers in Italy. The dose-response relation for vibration induced white finger (VWF) was also studied. METHODS: The study population consisted of 570 quarry drillers and stonecarvers exposed to vibration and 258 control stone workers who performed only manual activity. Each subject was interviewed with health and workplace assessment questionnaires. Sensorineural and VWF disorders were staged according to the Stockholm workshop scales. Vibration was measured on a representative sample of percussive and rotary tools. The 8 h energy equivalent frequency weighted acceleration (A (8)) and lifetime vibration doses were calculated for each of the exposed stone workers. RESULTS: Sensorineural and musculoskeletal symptoms occurred more frequently in the workers exposed to vibration than in the controls, but trend statistics did not show a linear exposure-response relation for these disorders. The prevalence of VWF was found to be 30.2% in the entire group exposed to vibration. Raynaud's phenomenon was discovered in 4.3% of the controls. VWF was strongly associated with exposure to vibration and a monotonic dose-response relation was found. According to the exposure data of this study, the expected percentage of stone workers affected with VWF tends to increase roughly in proportion to the square root of A(8) (for a particular exposure period) or in proportion to the square root of the duration of exposure (for a constant magnitude of vibration). CONCLUSION: Even although limited to a specific work situation, the dose-response relation for VWF estimated in this study suggests a time dependency such that halving the years of exposure allows a doubling of the energy equivalent vibration. According to these findings, the vibration exposure levels currently under discussion within the European Community seem to represent reasonable exposure limits for the protection of workers against the harmful effects of hand transmitted vibration.

Adult↗
PubMed1995

Temperature and vibration perception thresholds in workers exposed to hand-arm vibration.

Exposure to hand-arm vibration causes damage in the peripheral nerves of the upper extremities, and a method for early detection of neuropathy induced by vibration is needed. The thin nerve fibres seem to be the most sensitive to vibration and may be damaged first. In the present study, vibration and thermal thresholds in workers exposed to hand-arm vibration were compared in a case-control study. Previously, both vibration perception and temperature sense have been impaired in workers exposed to hand-arm vibration. The study population consisted of 15 workers exposed to hand-arm vibration (mean age 37.1 yrs) and 15 controls matched for age (mean age 36.1 yrs). The vibration perception thresholds (VPT) were measured with modified Bruel & Kjaer's equipment with the limits technique method. Thermal sense was measured by the Marstock method with a thermostimulator, in which the Peltier element controls the temperature of a thin metal plate (surface 35 x 40 mm) in contact with the skin. The lumberjacks had lower cold thresholds and wider neutral zones of temperature sensation in the hands and slightly higher VPTs at the high frequencies (125-500 Hz) than the controls. The results for the matched pairs showed 80-87% of the lumberjacks to have wider neutral zones, but only 53-66% of them had higher VPTs than the controls. In an intraindividual comparison of the lumberjacks (the newly scaled results with the mean and standard deviation of the controls), the temperature sense was often (66-73%) deteriorated more than the VPTs at 125-500 Hz. In addition, the newly scaled results showed the width of the neutral zone to be significantly more deteriorated than the VPTs at 125 and 250 Hz in the fingers. This indicates that measurement of the temperature sense is useful in the prevention of nerve damage caused by vibration and might be more sensitive to vibration than vibration perception.

Adult↗
PubMed2000

Vibration-induced multifocal neuropathy in forestry workers: electrophysiological findings in relation to vibration exposure and finger circulation.

OBJECTIVES: To investigate neural conduction in the upper limbs of symptomatic forestry workers with and without exposure to hand-transmitted vibration. A further aim was to assess the possible relationships between vibration exposure, nerve conduction and finger circulation in the forestry workers who used chain saws. METHODS: A detailed neurophysiological investigation was performed on the upper extremities of 20 chain saw workers, 20 forestry operators with heavy manual work but without vibration exposure, and 20 healthy male controls. All subjects were screened to exclude polyneuropathy. Measurements of sensory and motor nerve conduction (velocity and amplitude) were obtained bilaterally from the median, ulnar and radial nerves. To assess peripheral vascular function, the forestry workers underwent a cold test with plethysmographic measurement of finger systolic blood pressure (FSBP). In the chain saw operators, vibration exposure was evaluated according to the International Standard ISO 5349. Indices of daily vibration exposure and lifetime cumulative vibration dose were estimated for each chain saw operator. RESULTS: Sensory nerve conduction in several segments of the median and radial nerves was significantly reduced in the chain saw operators compared with that in the workers doing heavy manual work and the controls. The neurophysiological pattern more frequently observed in the chain saw operators was a multifocal nerve conduction impairment to several neural segments with predominant involvement of sensory rather than motor fibres. Sensory nerve conduction velocities in the hands of the chain saw operators were inversely related to both daily and lifetime cumulative vibration exposures. In the vibration-exposed forestry workers, neither were sensori-motor complaints associated with vascular symptoms (finger whiteness) nor were electrophysiological data related to cold-induced changes in FSBP. CONCLUSIONS: Exposure to hand-transmitted vibration, in addition to ergonomic stress factors, can contribute to peripheral nerve disorders occurring in forestry workers who operate chain saws. The findings of this study suggest the existence of an exposure-effect relationship for vibration-induced neuropathy. Different underlying mechanisms are likely to be involved in the pathogenesis of the neurological and vascular components of the hand-arm vibration syndrome.

Adult↗
PubMed1992

A study on the vibration-dose limit for Japanese workers exposed to hand-arm vibration.

To obtain a vibration-dose limit for Japanese workers exposed to hand-arm vibration, the prevalences of vibration-induced white finger (VWF) and numbness of the hand were studied in 5 different groups of workers exposed to segmental vibration. In addition, the prevalence of primary Raynaud's phenomenon (PRP) in the general population without occupational vibration exposure was computed. The vibration levels in the exposed groups (except chain saw operators) ranged from 124.1-129.2 dB (reference value, 10(-6) m/s2). The prevalence of VWF in these groups was 2.2-4.8%. This value was not statistically significant (p greater than 0.05) when compared to the prevalence of PRP in the general Japanese population (2.7-2.9% in our study and 0.5-4.6% in other surveys in Japan). Although the prevalence of numbness of the hands fluctuated among the groups, no significant differences could be demonstrated. Our results were then compared to those of previous reports by literature study [319 papers on hand-arm vibration syndrome (HAVS) and 25 reports on PRP]. At a glance the Japanese population showed a lower prevalence for PRP compared to other countries, which suggested that exposure to cold and biological abilities should also be considered to assess vibration syndrome. A comparison of the vibration characteristics of different tools and the occurrence of VWF in the hands of workers in the literature with those of our data suggested that a daily hand-arm vibration exposure at a level lower than 2.5 m/s2 (128 dB, reference value 10(-6) m/s2) could possibly decrease the risk of VWF among workers exposed to segmental vibration.

Adult↗
PubMed1989

[Experimental study of vibration analysis in middle ear models by holographic interferometry. Effects of the cross-sectioned area of aditus on the vibration of tympanic membrane].

To aid in the establishment of optimum conditions for postoperative function of the tympanic membrane, a model of the middle ear was experimentally prepared, the cross-sectioned area of aditus ad antrum was altered and the effects on the tympanic membrane vibrational characteristics were observed using the holographic interference method. The following results were obtained. 1) At the low frequencies below 2 kHz, the vibration mode of tympanic membrane was concentric on the whole, but the vibration pattern became fractionated at 4 kHz and above. The frequency of onset of the fractionated vibration pattern was changed only by the conditions of the membrane itself and was not affected much by the sound pressure, the volume of the middle ear cavity and the cross-sectioned area of aditus ad antrum. 2) There were resonance and anti-resonance points in the tympanic vibration pattern. These resonance and anti-resonance frequencies became higher as the diameter of aditus increased until eventually a constant value was reached. At diameters in excess of this constant value, the resonance frequency tended to fall and the anti-resonance frequency tended to rise. 3) The tympanic vibration in the middle ear cavity was not influenced very much by the diameter of aditus at 250Hz. Vibration decreased when aditus was blocked at 500Hz and the opening diameter had a major influence at 1kHz. Vibration was maximum at a diameter of about 2mm and a minimum when aditus was blocked. At 2 to 3kHz, the effects on vibration increased when aditus was blocked. 4) When aditus ad antrum was blocked, the vibration frequency characteristics of tympanic membrane deteriorated at under 1kHz and improved at 2 to 3kHz. When a comparison was made between the case with opened aditus, (which was considered to be equivalent to the closed method of tympano-plasty), and the case with closed aditus, (considered to be equivalent to the open method), the vibration frequency characteristics of the tympanic membrane improved in the low sound region up to 2kHz when the diameter was 4mm.

Ear, Middle↗
PubMed1993

Internal vibrations of a molecule consisting of rigid segments. I. Non-interacting internal vibrations.

For molecular crystals, a procedure is proposed for interpreting experimentally determined atomic mean square anisotropic displacement parameters (ADPs) in terms of the overall molecular vibration together with internal vibrations with the assumption that the molecule consists of a set of linked rigid segments. The internal librations (molecular torsional or bending modes) are described using the variable internal coordinates of the segmented body. In paper I of this two-part report, it is assumed as a zero-order approximation that the internal vibrations about the linkage axes between pairs of segments are uncorrelated with each other and with the overall molecular rigid-body vibrations. As a first-order approximation, the possibility that each internal vibration can be correlated with the external vibrations is also considered. An important feature of this approach is that the internal librations are required to give zero contribution to the overall momentum of the molecule at all times, so the internal coordinates must be orthogonal to the external ones. Also, each of the internal librations involves the motion of all atoms in the molecule. The resulting internal vibrational parameters are invariant to the choice of reference segment. With this procedure, the experimental ADPs obtained from crystal structure determinations involving six small molecules (sym-trinitrobenzene, adenosine, tetra-cyanoquinodimethane, benzamide, alpha-cyanoacetic acid hydrazide and N-acetyl-L-tryptophan methylamide) have been analyzed. As a consequence, vibrational corrections to the bond lengths and angles of the molecule are calculated as well as the frequencies and force constants (with e.s.d.'s) for each internal torsional or bending vibration. Compared with other models used for describing internal vibrations, there are differences in how the total ADP is partitioned between the internal and overall molecular vibrations.

Adenosine↗
PubMed1979

Psychophysical assessment of angular vibration: comparison of vertical and roll vibrations.

A psychophysical matching experiment was conducted to compare the perceived intensity of roll vibration with the perceived intensity of Z-axis translational vibration. Seated subjects matched their perceptions of the intensity of Z-axis vibrations by adjusting the intensity of roll vibrations of the same frequency. The Z-axis stimuli were administered at seven frequencies (from 2.5 to 10 Hz) at each of three intensity levels: the 25-min Fatigue-Decreased Proficiency (FDP) level, the 1-hr FDP level, and the 2.5-hr FDP level, as defined in ISO Standard 2631-1974. The results showed that the acceleration of the roll matching response increased significantly as a function of both the intensity and the frequency of the stimulus vibrations. Since the stimuli were chosen from existing Z-axis equal intensity contours, the mean matching responses define equivalent contours of equal intensity for roll vibration. These results provide information on the relationship between Z-axis vibrations measured in translational acceleration units of G and roll vibrations measured in angular acceleration units of rad/s2. The determination of such relationships is essential for the development of improved vibration exposure criteria applicable to complex vibration environments.

Environmental Exposure↗
PubMed1984

Subjective effects of combined-axis vibration: comparison of Y-axis and Y-plus-roll vibrations.

A psychophysical matching experiment was conducted to compare the perceived intensity of Y-axis and Y-plus-roll vibrations. Seated subjects matched their perceptions of the intensity of single-axis stimulus vibrations in the Y-axis, or combined-axis stimulus vibrations made up of Y-axis and roll motions, by adjusting the intensity of a sinusoidal, 5 Hz, Z-axis response vibration. Stimulus vibrations were sinusoidal at 3.15, 4, 5, 6.3, and 8 Hz. For each frequency, both types of stimulus vibrations were presented at three acceleration levels related to three axis-to-seat distances for the roll vibrations. The results showed that as frequency increased the acceleration of the Z-axis matching response decreased for both types of stimuli. In addition, as stimulus acceleration (axis-to-seat distance) increased, response acceleration showed substantial increases at every frequency. However, the matching responses showed only minor differences due to vibration type, indicating that the effects of roll vibrations can be accounted for in terms of the Y-axis translational vibrations produced at the subject's seat.

Acceleration↗