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Nov 1988

Volume 84, Issue S1, pp. S2-S224

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back to top Session C. Bioresponse to Vibration I: Hand‐arm Vibration
Invited Papers
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Hand‐arm vibration: New perspectives (A)

Robert L. Brubaker

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S3-S3 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Signs and symptoms of the hand‐arm vibration syndrome (HAVS) will be described followed by recent research developments. Much attention has been focused on elucidating the pathophysiological basis of vibration‐induced injury to vascular, neural, muscular, and skeletal tissues in the hand and arm. New information suggests that chronic neural damage is less reversible after long‐term cessation of vibration exposure than vascular damage. If confirmed, current hand‐arm vibration standards (based mainly on prevention of onset of finger blanching symptoms) should be re‐evaluated to also preclude onset of chronic neurologic deficits. Progress has been made in designing and validating new objective measures of peripheral somatosensory dysfunction, as well as improving and testing existing methods for assessing neural and vascular pathology. The Stockholm Workshop symptom scale (revised Taylor‐Pelmear scale) for assessing the vascular component of HAVS will be described as well as a suggested new scale for evaluating neural damage.
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System for monitoring peripheral circulation in the diagnosis of vibration hazards (A)

Seiichi Nohara and Hideki Nakamura

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S3-S3 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Peripheral circulatory disorders such as Raynaud's phenomenon are thought to be basal symptoms of vibration hazards. The elucidation of their pathogenesis and their diagnosis between attacks is regarded as important. A system for monitoring the body surface circulation noninvasively and continuously has been developed, which enables the quantitative dynamic assessment of skin blood flow. This apparatus is based on the thermal diffusion method and uses a probe incorporating a Peltier stack. After fundamental studies on this system, the peripheral circulatory functions of workers using vibrating tools were studied. The workers were divided into three groups: group A, without any symptoms; group B, with numbness and/or pain but without Raynaud's phenomenon; and group C, with Raynaud's phenomenon. The finger blood flow (FBF) of group C at rest was significantly lower than that of group A (p < 0.01). In a handgrip test and with exposure to local vibration (60 Hz, 50 m/s2), the FBF of group A significantly changed compared to its value at rest, but that of group C showed no significant change.
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Vibrotactile perception thresholds in hands occupationally exposed to vibration: Interpretation of sensorineural loss (A)

J. E. Piercy, A. J. Brammer, H. Nakamura, S. Nohara, P. L. Auger, and A. T. Haines

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S3-S3 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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The tactile performance of the hand is now known to be critically dependent on neural activity in one population of slow‐adapting (SAI) and two populations of fast‐adapting (FAI, FAII) mechanoreceptors. A technique has recently been developed to establish the sensitivity of these receptor populations at the fingertip from vibrational perception thresholds determined psychophysically with sinusoidal stimulation [A. J. Brammer et al., J. Hand Surg. 12A, 870–875 (1987)]. A comparison of data from 98 vibration‐exposed and 34 normal hands, all screened to exclude confounding factors, has revealed two patterns of abnormal threshold elevation. The first, involving similarly elevated thresholds at all frequencies (2–200 Hz), is indicative of sensorineural losses of similar magnitude in each type of receptor‐nerve system, and so is suggestive of peripheral nerve degeneration. The second pattern involves elevated thresholds at frequencies mediated only by one or sometimes two receptor types (commonly SAI and/or FAII). A mechanoreceptor‐specific mechanism is unlikely to occur within a nerve trunk, and so this frequency‐dependent pattern is suggestive of selective damage to the nerve endings.
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A study on the setting position of vibration pickups for the measurement of hand‐arm transmitted vibration (A)

Yasuo Tokita, Atushi Oda, and Tunenobu Ohkuma

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S4-S4 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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In order to reduce hand‐arm vibration disease, it is important to know the amount of vibration transmitted from a hand‐held vibration tool to the hand‐arm system. There are many problems in determining the amount of exposure in practice. For example, (1) the handle vibration does not always correspond to the vibration disease. (2) If the vibration pickup is set between the handle and palm, this system will not be usable for a long time, because the vibration pickup will become an obstacle for the worker. In this study, Leq8 (8 h of equivalent hand‐arm vibration level according to ISO 5349) is used to evaluate the transmitted vibration, and the back side of the hand is recommended for the placement of the vibration pickup to measure the amount of transmitted vibration without disturbing the worker during the long‐time use of the measuring device. The reasons for this proposal are indicated by the results of field measurements of actual hand‐held vibration tools (chain saw, breaker, etc.) and by the analytical results of the model experiment. [Work supported by Ministry of Labor of Japan.]
Contributed Papers
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Errors in the measurement of power tool handle vibration from excess accelerometer weight (A)

S. E. Keith and A. J. Brammer

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S4-S4 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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ISO 7505 (Forest Machinery—Chain Saws—Measurement of hand‐transmitted vibration. International Oragnization for Standardization, Geneva, 1986) specifies for the measurement of frequency‐weighted handle acceleration a maximum permissible accelerometer weight of 50 g, which is comparable to that of most chain saw handles. To explore the magnitude of errors so introduced, a series of difference measurements has been conducted with a variable mass accelerometer mount. With this device the effective accelerometer weight can be cycled between 6 and 25, 50, or 100 g, in a time in which other parameters affecting handle vibration during saw operation with no load (viz: engine speed and hand grip) usually vary little. Reductions in frequency‐weighted acceleration from the minimum resolvable (± 5%) to 50% were recorded when changing accelerometer weight from 6 to 50 g, depending on handle design and material. Investigation of the vibration spectra (6–1250 Hz) and transmissibility (30–700 Hz) of one handle suggests that the data are consistent with a localized mass loading, introduced by the accelerometer, reducing the amplitude of one or more flexural modes of handle vibration.
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Materials performance evaluation for hand‐arm vibration isolation (A)

Gary A. Hampel

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S4-S4 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Materials performance affecting the level of surface vibration ordinarily in direct contact with the hand under specified conditions will be reported. The intent of this study was to develop a method by which elastic materials can be evaluated for isolation properties relating to test surface vibration using nonrigid loading. The hand and arm, as a complex system, are used in place of the more traditional and simpler rigid mass load. This research and the scope of these findings report performance as a more realistic means for determining isolation, i.e., vibration reduction caused by an intervening material. The findings reported use this method to identify materials that exhibit isolation and display this positive effect, if it occurs, by graphic means over the frequency range of 1 to 800 Hz. The Z‐axis (basicentric) hand‐arm apparent mass, evaluated while grasping a 3.81‐cm‐diam handle with 4.5‐Newton total grip force accelerated at 4 m/s2, will be used as the reference load to determine material isolation effectiveness, reported as transmissibility.
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