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PubMed2004

Chaotic vibrations of a vocal fold model with a unilateral polyp.

A nonlinear model was proposed to study chaotic vibrations of vocal folds with a unilateral vocal polyp. The model study found that the vocal polyp affected glottal closure and caused aperiodic vocal fold vibrations. Using nonlinear dynamic methods, aperiodic vibrations of the vocal fold model with a polyp were attributed to low-dimensional chaos. Bifurcation diagrams showed that vocal polyp size, stiffness, and damping had important effects on vocal fold vibrations. An increase in polyp size tended to induce subharmonic patterns and chaos. This study provides a theoretical basis to model aperiodic vibrations of vocal folds with a laryngeal mass.

Humans↗
PubMed1978

Human response to house vibrations caused by sonic booms or air blasts.

Descriptions of the effects of sonic booms of air blasts by observers in buildings have included such statements as "noticeable vibrations" in addition to phrases such as "the house rattles," "the windows rattle," or "bric-à-brac rattles." Analysis of studies of human response to vibrations, vibration complaints in the Toronto area, special tests by Kryter at Edwards Air Force Base, and laboratory studies of human response to sonic booms show that perceived vibration is not normally a factor that contributes significantly to human response to airborne, large-amplitude impulse noise. Rather, human response is solely the result of the impulse noise itself and of audible noise due to induced radiation from vibrating surfaces.

Affect↗
PubMed1980

The interaction of whole body vibration and impulse noise.

Three groups of chinchillas, each consisting of five monaural animals, were exposed to one of three conditions: 1 h of sinusoidal, 30-Hz vibration at 1 g rms; 50 noise impulses at 155 dB, 1.5-m A duration, at the rate of 1/min; or a combination of the vibration and the impulse noise. Before exposure, and at various times after exposure, each animal's auditory evoked responses (AER) were measured at seven frequencies between 0.5 and 8.0 kHz. Thirty days after the exposure all animals were sacrificed for cochlear surface preparation histology. Chinchillas exposed to the vibration alone showed no significant temporary or permanent change in AER thresholds. The group exposed to impulse noise showed a maximum median TTS of from 34 dB at 0.5 kHz to 72 dB at 2 kHz and a flat PTS of 15-20 dB between 1 and 2.8 kHz. The combination group at all test times and frequencies showed a greater TTS and PTS than did the groups exposed to noise or vibration alone. The cochleograms are related in a variety of ways with hearing thresholds. The data from all three groups of experimental animals are consistent and demonstrate a potentiating effect of vibration on an impulse noise exposure.

Animals↗
PubMed1984

Predicting the subjective response to nonsteady vibration based on the summation of subjective magnitude.

A purpose of this study was to determine the values of exponents of psychophysical functions for the discomfort produced by whole-body vertical vibration. In addition, the applicability of a method of predicting the average stimulus intensity of a stimulus the intensity of which varies with time was investigated. The first experiment investigated the effect on discomfort of the duration of vibration (for durations of 2, 5, 10, 20, and 50 s) and of the vibration acceleration magnitude [for 0.5, 0.75, 1.11, 1.67, and 2.5 ms-2 (rms) at 8 Hz]. The magnitude estimation method was used. The results show that the logarithm of the magnitude estimates is in linear proportion to both the logarithm of the acceleration and the logarithm of the duration. The values of exponents for acceleration and duration were 0.96 and 0.56, respectively. In the second experiment, the point of subjective equality of each of 16 nonsteady vibrations was measured and compared with the stimulus intensity predicted by means of the method proposed by the authors. Good agreement was found between the measured and predicted stimulus intensity and it was confirmed that the predicting method could be applied to vibration as well as to noise.

Adult↗
PubMed1988

Biological effects of the hand-arm vibration syndrome: historical perspective and current research.

The objective of this paper is to highlight gaps of information regarding mechanisms of vascular, neurological, and musculo-skeletal damage caused by vibration. Also addressed is evidence that high noise level may act synergistically to the development of vibration syndrome of the hand and arm. Areas of research currently active in psychophysical and neurophysiological investigations to increase our understanding of tactile and spatial discrimination are discussed. Although the importance of sensory loss or "fine touch" is understood, there is neither a proven objective scientific test with which the syndrome can be diagnosed nor is there a scale of damage assessment. Determining the exact role of the central nervous system in assessing damage from vibration is difficult in view of nonspecific symptoms reported from eastern Europe and from Japan. To complicate matters still further, there is the possibility that repeated, rapid mechanical movements of the hand and arm associated with handling heavy tools produce carpal tunnel syndrome but that the injury is not directly attributed to vibration. Therefore, it follows that there could exist an element of carpal tunnel syndrome in many vibration syndrome cases.

Arm Injuries↗
PubMed2000

Vibration characteristics of pipe organ reed tongues and the effect of the shallot, resonator, and reed curvature.

Pipe organ reed pipes sound when a fixed-free curved brass reed mounted on a shallot connected to a resonator is forced to vibrate by an impressed static air pressure. Five sets of experiments were performed in order to investigate the influence of the most important parameters which could affect the tone of a reed pipe. First, the phase difference between the pressure variation in the shallot and the boot, and its relationship to the motion of the reed tongue were analyzed to compare their phases and their spectra. Next, the frequency dependence of the reed on three basic parameters (reed thickness, its vibrating length, and the imposed static air pressure) was investigated in an attempt to determine an empirical equation for the frequency. For each trial, two of the variables were kept constant while the third was altered in order to construct an equation giving frequency as a function of the three variables. Third, experiments were conducted using three different types of shallots: the American (or English) style, the French style, and the German style. The results show that for each shallot, the frequency increases linearly with thickness and linearly with air pressure (over the normal operating range of the reed). For each of the shallots, frequency varies inversely with length when the other variables are held constant. The effect on the reed spectrum of using the three different types of shallot was also investigated, as was the effect of reducing the interior volume of each type. Progressively filling the shallot interior generally decreases the frequency of the vibrating reed. The effect of the resonators on frequency and spectrum was studied because the resonator is an integral part of the resulting tone; virtually every reed stop has some type of resonator. The resonator tends to raise the Q of the impedance peaks and reduce the fundamental frequency. Finally, the influence of the type and degree of curvature on reed vibration was briefly examined; increasing the reed curvature tends to decrease the vibration frequency and increase the sound intensity by creating a richer spectrum.

Acoustics↗
PubMed2005

Abnormal vibration induced illusion of movement in essential tremor: evidence for abnormal muscle spindle afferent function.

OBJECTIVES: Vibration induced illusion of movement (VIIM) is abnormal in patients with idiopathic focal dystonia, an abnormality which corrects with fatigue of the vibrated muscle. Since dystonia and essential tremor sometimes coexist in families, we investigated the perception of VIIM and the effect of fatigue on VIIM in patients with essential tremor. METHODS: VIIM in 18 patients with essential tremor was compared with VIIM in 18 healthy control participants before and after volitional fatigue of the vibrated muscles. RESULTS: Vibration of the immobilised biceps produced a subnormal VIIM in patients with essential tremor (12.81 degrees (SEM 2.15)) compared with healthy control subjects (28.55 degrees (1.66)). The perception increased following volitional fatigue of the vibrated arm in patients with essential tremor (16.23 degrees (2.50)) but not in healthy controls (27.55 degrees (1.66)). No difference was observed in patients with alcohol or non-alcohol responsive tremor. CONCLUSIONS: The VIIM decreased with increasing age in healthy control subjects. Abnormal VIIM implies abnormal sensorimotor processing in patients with essential tremor, similar to that found in idiopathic focal dystonia, and the change of the perception with age could explain the age related onset of the disorder.

Afferent Pathways↗
PubMed1975

Studies on the receptor responsible for vibration induced inhibition of monosynaptic reflexes in man.

A further attempt has been made to define the receptor responsible for the inhibition of monosynaptic reflexes by vibration in man. Vibration of the tendo Achillis will produce inhibition of the H reflex even when the muscles of the anterior compartment of the leg are denervated or blocked with local anaesthetic, implying that there are receptors in the posterior compartment capable of producing this effect. However, there is evidence that vibration spreads through the limb. The inhibition is greater when the anterior compartment is innervated indicating that there is a contribution from receptors in this compartment. Stretching the muscles of the posterior compartment alone, or the muscles of the anterior and posterior compartments reciprocally does not influence the inhibition of the monosynaptic reflex by vibration. These observations support the contention that the reduction of the monosynaptic reflex by vibration in man is due to presynaptic inhibition resulting from activation of primary spindle endings.

Adult↗
PubMed1975

Evidence for a monosynaptic mechanism in the tonic vibration reflex of the human masseter muscle.

Vibration of the masseter and temporalis muscles in normal human adult subjects elicits a tonic vibration reflex with unexpected features. The electromyographic response is not asynchronous as in the limb muscles, but involves well-defined spikes with a one-to-one temporal relation to the vibration cycles. The effect of various parameters such as muscle stretch, vibration frequency or amplitude, etc, has been investigated. The small latency fluctuation of the vibration-induced spikes is compatible with a monosynaptic reflex mechanism which is considered to be assisted by a polysynaptic facilitatory background of proprioceptive origin.

Adult↗
PubMed1998

Measuring vibration threshold with a graduated tuning fork in normal aging and in patients with polyneuropathy. European Inflammatory Neuropathy Cause and Treatment (INCAT) group.

OBJECTIVE: To provide clinically useful vibration threshold normal values. METHODS: The graduated Rydel-Seiffer tuning fork was evaluated in 198 healthy controls and 59 patients with a polyneuropathy. The measures were done in triplicate at four locations: the distal interphalangeal joint of the index finger, ulnar styloid process, interphalangeal joint of the hallux, and internal malleolus. The values obtained with this tuning fork in healthy controls and patients with polyneuropathy were compared with the values of an electronic device, the Vibrameter. RESULTS: Vibration sense was better perceived in the arms compared with the legs. There was a significant age related decline of vibration sense at all locations. The values from the Rydel-Seiffer tuning fork and the Vibrameter were significantly correlated in both groups. The sensitivity of these two instruments for the four sites examined in the polyneuropathy group ranged from 29-76% and 31-73%, respectively and was the highest at the hallux for both instruments. CONCLUSION: This study provides clinical useful normal values of vibration threshold for the Rydel-Seiffer tuning fork. This is a simple and easily applicable instrument that assesses vibration sense semiquantitatively and should therefore have a place in routine neurological examination.

Age Factors↗
PubMed2005

A follow up study of vibration induced white finger in compensation claimants.

AIMS: To follow up vibration induced white finger (VWF) in a selected group of 73 vibration exposed workers who claimed unsuccessfully for VWF compensation at a first examination. METHODS: The VWF claimants were sent to our unit by the National Insurance Institute. The basic compensatory criteria included a positive history of VWF and abnormal cold response of the digital arteries. Following the first unsuccessful examination, over a mean time period of 4.1 (range 1-11) years the National Insurance Institute requested a second examination for all 73 claimants and a third examination for 29. During the follow up period, all subjects continued to work with vibratory tools. RESULTS: There were 14 new cases who reported white finger during the follow up period. In the new VWF cases, finger blanching attacks became visible after about 3.5 years since the first examination. All incident cases of anamnestic VWF showed an abnormal cold response in the digital arteries and obtained compensation according to the basic compensatory criteria. In the entire sample of VWF claimants, there was a discrepancy between positive history of VWF symptoms at medical interview (55%) and abnormal cold provocation outcomes (19%). Digital arterial hyperresponsiveness to cold was associated with both VWF symptoms and the duration of vibration exposure since the first examination. Over the follow up period, a significant increase in the vasoconstrictor response to cold was observed in the vibration exposed workers with no symptoms of finger whiteness. Abnormal cold response was not associated with either age or smoking habit. CONCLUSIONS: Cold test measuring finger systolic blood pressure may be considered a useful laboratory method to confirm objectively VWF symptoms and to disclose abnormal cold induced vasoconstrictor response in vibration exposed workers with a negative history of VWF. Medical interview outcomes should be interpreted with caution in medicolegal situations involving VWF claimants.

Adult↗
PubMed1984

Symptoms of vibration syndrome and radiographic findings in the wrists of lumberjacks.

In a cross sectional study 279 lumberjacks exposed to chain saw vibration and a reference group of 178 peat bog workers were examined. The mean ages of the two groups were 34.6 and 33.1 years, respectively. The lumberjacks' mean duration of exposure to vibration was 10.4 years. The study consisted of a questionnaire and a clinical examination, including radiographs of the wrists. The prevalence of reported white finger symptoms was 18% for the lumberjacks and 3% for the referents, whereas that of numbness in the upper extremities was 51% and 22%, respectively. Among lumberjacks the occurrence of white finger symptoms increased significantly with the duration of exposure to vibration but was not associated with age or smoking. The prevalence of the numbing of the upper extremities increased linearly with age in both groups, but it was not associated with duration of exposure after adjustment for age. Among lumberjacks there was a significant association between the numbing symptom and the white finger symptom, but not among the referents. A high prevalence of numbing in the upper extremities among the lumberjacks could be at least partly explained by occupational factors other than vibration--work posture, for example. Radiographically, cysts were found in the wrist bones of 8-9% of both groups. The exposure to chain saw vibration no longer seems to be a determinant in the development of vacuoles in the carpal bones.

Adult↗
PubMed1988

Aesthesiometric threshold changes over the course of a workshift in miners exposed to hand-arm vibration.

The objective of this study was to investigate whether aesthesiometric threshold changes occur over the course of a workshift in vibration exposed hard rock miners relative to workers unexposed to vibration during the shift. The subjects were 99 miners and 40 smelter workers; four subjects declined to participate and nine were excluded from the analysis because of apparent failure to comprehend the testing procedure. Two point discrimination and depth sense aesthesiometry were conducted at the beginning and at the end of the workshift in all digits of both hands excluding the thumbs. In addition to the use of a vibrating tool during the shift, age, digital temperature, signs of arm injury, presence of fingertip callus, and handedness were documented. In the analysis the difference between postshift and preshift readings was studied in relation to these variables, particularly exposure to the jackleg drill during the shift. With the exception of exposure of the jackleg drill, no associations were observed between these variables and change over the workshift in aesthesiometric results, on both unadjusted comparison of means and backward elimination regression analysis. A statistically significant association, however, was found between the use of a jackleg drill and change in two point discrimination and in depth sense aesthesiometric results over the course of the shift, for the right hand. Evidence of the occurrence of a learning effect, particularly for two point discrimination aesthesiometry, was observed. The occurrence of an effect in the right, but not the left, hand reflects dominant handedness and relatively greater vibration exposure in the right hand in our subjects. This study supports the incorporation of an exposure free interval before aesthesiometric testing of vibration exposed workers.

Fingers↗
PubMed1992

A cross sectional epidemiological survey of shipyard workers exposed to hand-arm vibration.

The hand-arm vibration syndrome, widely known as vibration white finger, is a disorder of nerves and blood vessels that occurs in workers exposed to segmental vibration. A cross sectional symptom survey was performed on a sample of workers employed by a large shipyard in the north eastern United States. Random samples were drawn from departments composed of full time dedicated pneumatic grinders, workers with part time exposure to vibration, and other workers not exposed to vibratory tools. Of the 375 workers sampled, 79% responded. The prevalence of white finger symptoms was 71%, 33%, and 6% among the three exposure groups respectively. Similarly, the prevalence of numbness and tingling in the hands and fingers in the three exposure groups was 84%, 50%, and 17%. Workers were classified according to the Stockholm Workshop staging systems for vascular and sensorineural symptom severity. Exposure-response analyses of both vascular and sensorineural stage showed monotonically increasing prevalence of higher disease stages with increasing duration of exposure. Logistic regression analysis, performed to control for potential confounding factors including age and current smoking state, produced highly significant (p less than 0.001) associations between cumulative duration of exposure and prevalence of symptoms. In these analyses smoking state was significantly related to vascular and sensorineural symptoms and age was not. Average latency to onset of symptoms was less than five years of full time equivalent work with vibratory tools. Logistic regression analyses were performed to assess the effect of use of particular work practices on reported symptoms. Further study of this workforce with objective, quantitative measures of peripheral neurological and vascular function is required to characterise the clinical and subclinical effects of vibration exposure.

Cross-Sectional Studies↗
PubMed1992

Radiographic osteoarthrosis in the acromioclavicular joint resulting from manual work or exposure to vibration.

The hypothesis that manual work and exposure to vibration are antecedents to the development of osteoarthrosis was assessed employing a cross sectional study design. The frequency of osteoarthrosis in the acromioclavicular joint was studied in three groups of workers in the construction industry. Two groups were manual workers (54 bricklayers and 55 rock blasters); the third group consisted of 98 foremen. The radiographic appearance of the right and left acromioclavicular joints was classified into one of five grades of osteoarthrosis. A protocol was developed to assess exposure on the basis of job title, years of manual work, total weight lifted during working life, and total hours of exposure to vibrating tools. Odds ratios for job titles (manual worker v foreman) and for years of manual work as indicators of exposure were of similar magnitude of around 2.5. Construction workers who had lifted more than 709 tonnes had an increased risk of developing severe osteoarthrosis of the right acromioclavicular joint, odds ratio: 2.62 (95% confidence interval (95% CI), 1.13-6.06). The odds ratio for the left side was 7.67 (95% CI, 2.76-21.34). In the analysis of vibration exposure, workers who had been highly exposed to vibration had an odds ratio of 1.99 (95% CI, 1.00-3.92) on the right side and 2.20 (95% CI, 1.07-4.56) on the left. This effect almost disappeared after simultaneous adjustment for manual work. Occupational and ergonomic factors, such as the sum of lifted tonnes during working life, job title, and the sum of years of manual work seem to be risk factors for osteoarthrosis of the acromioclavicular joint, whereas vibration alone was a weaker risk factor.

Acromioclavicular Joint↗
PubMed1995

Prognosis of vibration induced white finger: a follow up study.

OBJECTIVES--To follow up 102 patients with vibration induced white finger (VWF). METHODS--102 subjects with VWF were reexamined one to 13 years after the condition had first been diagnosed. Information about symptoms, occupation, vibration exposure, smoking habits, age, and the prevalence of other diseases was present in the medical records from the first examination and was collected by a questionnaire and an interview at the second examination. The decrease in systolic blood pressure in a finger during cold provocation (FSP%) was measured in the same finger at both examinations. RESULTS--At the second examination, 22% stated that the frequency of attacks had decreased. The improvement was most frequent in subjects with little or no exposure to vibration during the previous two years, in non-smokers, and in subjects without other circulatory diseases than VWF. 32% stated that the frequency of attacks had increased. The aggravation was most notable in smokers and subjects who also had circulatory diseases other than VWF. The number of finger phalanges that blanched on cooling averaged 15.8 at the first examination and 14.4 at the second examination. Working with high vibration hand held tools during the previous two years was related to an aggravation, with more finger phalanges affected at the second examination. Presence of other circulatory diseases had the same effect. In non-smokers the number of affected finger phalanges had decreased at the second examination. The FSP% had increased (improvement) in 43%, decreased (aggravation) in 12%, and was unchanged in 45%. The increase in FSP% was more pronounced in the older than in the younger subjects. The decrease of FSP% was more frequent among the younger subjects and subjects with a short follow up. CONCLUSION--As the FSP% in nearly half of the subjects had improved, it is concluded that VWF has a good prognosis in patients with mainly moderate to severe VWF after one to 13 years of observation. The improvement in FSP%, however, was not reflected in the subjective experience of the development of attacks of VWF. Continued work with high vibration hand held tools, smoking, other circulatory diseases, and low age at the time of diagnosis had an unfavourable influence on the prognosis.

Adult↗
PubMed1995

Neuropathy in female dental personnel exposed to high frequency vibrations.

OBJECTIVE: To evaluate early neuropathy in dental personnel exposed to high frequency vibrations. METHODS: 30 dentists and 30 dental hygienists who used low and high speed hand pieces and ultrasonic scalers were studied, and 30 dental assistants and 30 medical nurses not exposed to vibration (all women). Vibrotactile sensibility, strength, motor performance, sensorineural symptoms and signs, and vascular symptoms in the hands, as well as mercury concentrations in biological samples and cervicobrachial symptoms, were studied. RESULTS: The two groups exposed to vibration had significant impairments of vibrotactile sensibility, strength, and motor performance, as well as more frequent sensorineural symptoms. In the dentists there were significant associations between the vibrotactile sensibility and strength, motor performance, superficial sensibility, and sensorineural symptoms. There were no associations between these findings and cervicobrachial symptoms, mercury concentrations, or smoking. There was no increase of vascular symptoms of the hands in the groups exposed to vibration. CONCLUSION: Dental hygienists and dentists had a slight neuropathy, which may be associated with their exposure to high frequency vibrations, and which may be detrimental to their work performance. Thus, development of safer equipment is urgent.

Adult↗
PubMed1997

Structural nerve changes at wrist level in workers exposed to vibration.

OBJECTIVES: To analyse the character of morphological changes occurring in a well defined peripheral nerve in humans exposed to vibration from hand held tools. METHODS: Biopsies of the dorsal interosseus nerve just proximal to the wrist were taken from 10 men exposed to vibration and from 12 male age matched necropsy controls. The nerve was resected for pain relief either as the sole procedure or in conjunction with carpal tunnel release. All specimens were sectioned and examined by light microscopy in standard sections, thin epon sections, and teasing preparations. RESULTS: The combined results of the analyses showed pathological changes in all 10 patients dominated by breakdown of myelin and by interstitial and perineurial fibrosis. All but one of the 12 controls were normal. CONCLUSION: These findings often show severe nerve injury previously not described at this level. They indicate that demyelination may be the primary lesion in neuropathy induced by vibration followed by fibrosis associated with incomplete regeneration or with organisation of oedema. Vibration can induce structural changes in peripheral nerves just proximal to the wrist and such changes may constitute a structural component in carpal tunnel syndrome among people exposed to vibration. This may help to explain the poor results achieved by carpal tunnel release in these patients.

Adult↗