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At least 37 records · Page 2Linked to original sources
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↗
PubMed2007

Application of 2 vibrators salvages ejaculatory failures to 1 vibrator during penile vibratory stimulation in men with spinal cord injuries.

PURPOSE: Penile vibratory stimulation is the treatment of first choice for anejaculation in men with spinal cord injury. Nonresponders to penile vibratory stimulation are usually referred for electroejaculation or surgical sperm retrieval. Compared to penile vibratory stimulation these methods are invasive and usually yield lower total motile sperm, potentially limiting options for assisted reproductive technologies. To avoid these less than ideal options a simple method to salvage penile vibratory stimulation failures would be of benefit to spinal cord injured patients. We investigated the recovery rate when 2 vibrators were used to salvage ejaculatory failures to 1 vibrator in men with spinal cord injury. MATERIALS AND METHODS: A retrospective chart review was performed in 297 spinal cord injured men who underwent a total of 965 trials of penile vibratory stimulation at our center between 1991 and 2006. Only trials with high amplitude vibrators were examined. All men underwent 2 or more penile vibratory stimulation trials using 1 vibrator applied to the dorsum or frenulum of the glans penis. Men failing to ejaculate with 1 vibrator received 1 or more trials in which the glans penis was then sandwiched between 2 vibrators. RESULTS: Of all men 49% and 57% of those whose level of injury was T10 or above responded to penile vibratory stimulation with 1 vibrator. Of failures with 1 vibrator 22% responded to penile vibratory stimulation with 2 vibrators. CONCLUSIONS: Application of 2 vibrators salvaged ejaculatory failures to 1 vibrator during penile vibratory stimulation procedures in men with spinal cord injury. This simple penile vibratory stimulation sandwich method is recommended before referring patients for electroejaculation or surgical sperm retrieval.

Adolescent↗
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↗
PubMed2006

Hand-arm vibration syndrome with use of anti-vibration chain saws: 19-year follow-up study of forestry workers.

OBJECTIVES: Hand-arm vibration syndrome (HAVS) consists of vascular and neurological component. Musculoskeletal component has not been delineated yet. In the present follow-up study, we evaluated the prevalence of HAVS and the cumulative exposure to vibration among a cohort of forestry workers. Special interest was given to numbness and musculoskeletal disorders of upper extremity and neck in forestry workers. METHODS: A follow-up study starting from 1976 was conducted among forestry workers in Suomussalmi in Finland. Total exposure of hand-arm vibration was recorded during 11 cross-sectional surveys. The last study was carried out in 1995. The lifetime dose of vibration energy was calculated. A cohort of 52 forest workers participated to all 11 cross-sectional surveys 1976-1995. HAVS and musculoskeletal disorders were evaluated. RESULTS: The prevalence of active vibration white finger (VWF) decreased from 13 to 4% in the cross-sectional study. In the cohort VWF decreased from 17 to 8% and numbness increased from 23 to 40%. Rotator cuff syndrome (P=0.034) and epicondylitis (P=0.004) associated with numbness. Regional neck pain was diagnosed in 38% of workers and associated with low back pain. In modeling VWF, the lifelong vibration energy (OR 1.03, CI 1.01-1.05), and smoking (OR 7.36, CI 1.07-50.76) were significant. Numbness was modeled by pain in upper extremities (OR 12.43, CI 2.42-63.80) and neck pain (5.97, CI 1.25-28.39), not by lifelong vibration energy. Right rotator cuff syndrome was modeled by age (OR 2.58, CI 1.04-6.41) and lifelong vibration energy (OR 1.04, CI 1.00-1.07). CONCLUSIONS: The prevalence of VWF constantly decreased. Numbness did not follow the vibration exposure profile. Numbness also associated with upper extremity musculoskeletal disorders. Hand-arm vibration associated with the right rotator cuff syndrome in forestry workers.

Cohort Studies↗
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↗
PubMed1995

Operating vibrating tools and prevalence of subjective complaints in vibration syndrome.

The aim of this paper is to evaluate the prevalence of subjective symptoms and signs related to vibration syndrome in various groups of subjects exposed to hand-arm vibration (HAV). In 9 groups of subjects occupationally exposed to HAV, one group of subjects previously exposed to HAV, one control group, and 2 groups of general population (males and females), the prevalence of finger blanching, numbness in the hands, stiffness in the hands, and pain in the hands were investigated. The age of subjects ranged from 25 to 59 years. In subjects exposed to HAV, hand-transmitted vibration levels (HTVLs) were measured by means of vibration dosimeters, and the frequency-weighted acceleration levels [(Lh,w)eq,t] were determined as the vibration levels. The prevalence of vibration-induced white finger (VWF) in the exposed subjects was in the range of 0.0-9.6%, and that in subjects who were previously exposed to HAV was 4.1%. The prevalence rates of finger blanching in males and females of the general population were 2.7 and 3.4%, respectively. The highest prevalence rate of VWF was observed among subjects exposed to HTVLs of 2.7-5.1 m/s2. The prevalence of numbness of the hands fluctuated among the groups; i.e., in the exposed groups: in the range of 6.5-30.4%; in those previously exposed to HAV: 16.4%; and was 13.4% in males and 29.5% in females of the general population. The prevalence rates of stiffness in the hands were in the range of 7.6-65.2% in the exposed workers, 13.7% in those previously exposed to HAV, and was 5.5% in males and 20.9% in females of the general population. The prevalence of pain in the hands was between 7.4 and 17.4% in the exposed groups, 1.4% in those who stopped exposure to vibration, and 1.2% in subjects without segmental vibration exposure. Among the subjective symptoms, only VWF showed a significant positive correlation with the measured vibration acceleration; Y = -0.9 + 1.9 X, r = 0.8, P = 0.01. It was concluded that VWF is the most appropriate signs in decisions concerning quantitative recommendations for segmental vibration exposure.

Adult↗
PubMed1990

Physical characteristics of vibration in relation to vibration-induced white finger.

Predicted and observed prevalences and latency periods of vibration-induced white finger (VWF) were examined among workers exposed to hand-arm vibration. The different physical characteristics of vibration--spectra and impulsiveness--were measured. The following groups of workers were included in the study: forest workers (n = 199), pedestal grinders (n = 12), stone workers (n = 16), shipyard workers (n = 171), and platers (n = 5). The exposure to vibration was measured according to the ISO 5349 method. The impulsiveness of vibration was defined as the difference between peak levels and RMS levels. A good agreement was observed between the predicted and observed data for prevalence and latency of VWF in the forest workers. For the tools with high impulsiveness used in grinding, stone works, and shipyard assembly hall, the results were nonconfirmative; and there was a poor correlation between vibration and VWF. The ISO 5349 standard does not consider the high peak values of the vibration signal which may comprise high-frequency components and cause short transients in the underlying tissue of the worker's hand. These characteristics in vibration may be hazardous in the genesis of VWF and cannot be predicted when measuring vibration by the present standard method.

Cross-Sectional Studies↗
PubMed1995

Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.

OBJECTIVES: 31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). METHODS: Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. RESULTS: Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. CONCLUSION: There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration.

Adult↗
PubMed2006

Optimal vibration stimulation to the neck extensor muscles using hydraulic vibrators to shorten saccadic reaction time.

Optimal vibration stimulation to the neck extensor muscles using hydraulic vibrators to shorten the saccadic reaction time was examined. Subjects were 14 healthy young adults. Visual targets (LEDs) were located 10 degrees left and right of a central point. The targets were alternately lit for random durations of 2-4 seconds in a resting neck condition and various vibration conditions, and saccadic reaction times were measured. Vibration amplitude was 0.5 mm in every condition. The upper trapezius muscles were vibrated at 40, 60, 80, and 100 Hz in a sub-maximum stretch condition in which the muscles were stretched at 70% of maximum stretch. In addition, the muscles were vibrated at 60 Hz with the muscles maximally stretched, with 70% vertical pressure without stretching, and with vibration applied to the skin in the same area as the muscle vibration. At 60, 80, and 100 Hz at 70% maximum stretch, saccadic reaction time shortened significantly compared with the resting neck condition. However, no significant difference in the reaction time was observed among the frequencies. The saccadic reaction times in the maximum stretch condition, muscle pressure condition, and skin contact condition did not differ significantly from that in the resting neck condition. Vibration stimulation to the trapezius with 60-100 Hz frequencies at 0.5 mm amplitude in the sub-maximum stretch condition was effective for shortening saccadic reaction time. The main mechanism appears to be Ia information originating from the muscle spindle.

Adult↗
PubMed1975

Vertical vibration of seated subjects: effects of posture, vibration level, and frequency.

The transmissibility of 12 seated subjects to sinusoidal vertical vibration was measured at 12 frequencies in the range of 7 to 75 Hz. Transmissibility, the ratio of seat vibration to vertical head vibration measured on a bite-bar, was determined at each of six levels of vibration (0.2 to 4.0 m/s2 r.m.s.) in two body postures. The postures were defined by the body positions that maximised and minimised the sensation of vibration at the subjects' heads. Measurements of the fore-and-aft (ax), lateral (ay), and pitch motions of the head were measured on three subgroups. Posture was found to have a very large effect on the vibration of the head with an approximate 6:1 difference in the mean vertical head vibration of the subjects between the two postures in the range 35 to 50 Hz. In both postures the mean transmissibility of the subjects decreased as frequency increased from 7 to 75 Hz and there were statistically significant reductions in transmissibility with increasing levels of vibration. Some results from individuals are presented to illustrate the large differences between subjects. The reactions of the subjects to the vibration are outlined and some implications of the results are discussed.

Adult↗
PubMed1996

Comparison of different methods for vibration measurements on hand-held vibrating tools.

Vibration measurements have been done on hand-held tools in a group of 48 platers by evaluating the individual vibration acceleration and absorption of vibration energy. The measurement of acceleration has been done frequency-weighted and frequency-unweighted in accordance with ISO 5349 and NIOSH (USA) recommendations for hand-arm vibration standards, respectively. The acceleration and the energy absorption have been measured simultaneously in the three orthogonal directions, the latter by using a specially designed adapter. The exposure time has been determined by both subjective rating and objective measurements. Individual energy-equivalent accelerations and vibration dosages have been calculated from these data. The outcome shows that the type of tool was critical to vibration load when the different measures for determining vibration levels were used. Of the methods used, the evaluation specified by ISO 5349 makes most consideration of low frequencies of vibration (< 50 Hz), absorption of vibration energy middle frequencies (50-200 Hz) and NIOSH of high frequencies (> 200 Hz). The results show a poor correlation between the three methods used. Close agreement between mean subjective rating and objective measurement of the average exposure time was found. Further studies of the relation between results presented here and generated disturbance will be conducted, which may clarify any exposure-response relationship.

Acceleration↗
PubMed1990

Measuring method for vibration perception threshold of fingers and its application to vibration exposed workers.

A measuring method for the vibration perception threshold (VPT) of fingers has been developed. The VPTs of 118 and 149 professional forest workers were measured during a compulsory annual health examination in 1979 and 1983, respectively. Also the VPTs of eight pedestal grinders, who were suffering vibration-induced white finger (VWF), were measured in 1979 and 1983. The control group consisted of 20 research workers who had no vibration exposure in the past and no symptoms in their hands. The measuring system for VPT gave repeatable results. The frequency of the most sensitive VPT of vibration exposed workers alternated between 63 and 125 Hz instead of 125 Hz of subjects without vibration exposure. The VPT of the pedestal grinders and forest workers with decreased hand grip force and with vibration-induced white finger were significantly higher than those of the controls. The VPTs of the forest workers decreased slightly and that of the grinders increased from 1979 to 1983. In spite of long vibration exposure in the past and continuing lower level vibration exposure, the increased VPT of forest workers does not seem to be permanent.

Adult↗
PubMed1992

Vibration perception thresholds in workers exposed to vibration.

The vibration perception thresholds (VPT) at six frequencies from 16 to 500 Hz were examined in 77 workers exposed to hand-arm vibration and in 77 controls using a limits procedure. A dose-response relationship between VPTs and exposure to vibration was found, and the age-adjusted VPTs at each frequency were higher in workers exposed to vibration than in controls. Carpal tunnel syndrome (at 250 Hz) and consumption of alcohol (at 125 Hz) significantly increased the VPT, but vibration-induced white finger was not correlated with VPT. Indices for low (16 and 32 Hz) and high (63-500 Hz) VPT frequencies were calculated to evaluate the entire vibrogram, which consisted of several frequencies with two numbers. The results showed that hand-arm vibration disturbs first the high frequencies, and that the disturbance spreads thereafter to the low frequencies. The characteristics of the VPT test regarding vibration exposure and the association between VPT and nerve symptoms in the hand support the view that VPT is a useful measure for vibration-induced sensory nerve damage.

Arm↗
PubMed1999

The effect of tennis racket string vibration dampers on racket handle vibrations and discomfort following impacts.

In this study, we evaluated the effect of the use of tennis racket string vibration dampers on racket handle vibrations, and perceptions of hand and arm discomfort experienced by tennis players owing to stationary racket impacts. Twenty tennis players (10 males, 10 females) aged 18-29 years volunteered for the study. Two different racket models were impacted at the geometric centre of the racket face and 100 mm distal to the centre both with and without string vibration dampers in place. The participants could neither see nor hear the impacts, and they indicated their discomfort immediately after each impact using a visual analogue scale. An analysis of variance (2 x 2 x 2 factorial) was performed on the scaled discomfort ratings with the factors damping condition, racket type and impact location. No significant differences in discomfort ratings between damped and undamped impacts or between the two racket types were found. Also, central impacts were found to be more comfortable than impacts 100 mm distal to the centre (P< 0.05). There were no significant interaction effects. Vibration traces from an accelerometer mounted on the racket handle revealed that string vibration dampers quickly absorbed high-frequency string vibration without attenuating the lower-frequency frame vibration. In conclusion, we found no evidence to support the contention that string vibration dampers reduce hand and arm impact discomfort.

Adolescent↗
PubMed1978

Mechanism of the vibration paradox: excitatory and inhibitory effects of tendon vibration on single soleus muscle motor units in man.

1. The parameters of presynaptic inhibition of the Ia spindle afferents from soleus muscle by vibration have been investigated. The inhibitory effects increase with the amplitude of vibration, but decrease when the vibration frequency is increased.2. The monosynaptic reflex threshold of twenty-one single soleus motor units activated in the H (Hoffmann) reflex by a single electrical stimulus to the posterior tibial nerve was estimated quantitatively and expressed in relation to the size of the simultaneously recorded H reflex.3. A parametric study of the effects of various Achilles tendon vibrations on the reflex threshold of the single soleus motor units indicated that their order of derecruitment is concordant with their rank order for activation in the phasic reflexes of the soleus. The last recruited motoneurones are the most susceptible to being silenced by steady vibration.4. Muscle vibration progressively recruits single motor units according to the motoneurone size principle through polysynaptic proprioceptive pathways. However the presynaptic inhibition of Ia spindle afferents simultaneously induced by the vibration works in reverse on the same rank order of motoneurones of the soleus spinal pool, thereby limiting the polysynaptic recruitment of units in the tonic vibration reflex while depressing the autogenic phasic proprioceptive reflexes. These mechanisms elucidate the so-called vibration paradox and extend the size principle of Henneman to presynaptic inhibitory effects.

Achilles Tendon↗