Sensitivity of Seated Subjects to Low Frequency Random Vibrations in the Vertical Direction. Subjective Approach Using Vibrations Representative of Earthmoving Machines

1984 ◽  
Vol 3 (1) ◽  
pp. 18-27 ◽  
Author(s):  
P. Mistrot ◽  
D.G. Roley ◽  
P. Donati ◽  
L. Roure
Keyword(s):  
Low Frequency ◽  
Vertical Direction ◽  
Vertical Axis ◽  
Whole Body ◽  
Reference Stimulus ◽  
Random Vibrations ◽  
Body Sensation ◽  
Frequency Weighting ◽  
Iso 2631 ◽  
Earthmoving Machines

A study was conducted to compare various methods for evaluating complex vibrations. The two methods recommended by the Standard ISO 2631 were tested. A subjective equalization technique was used in which 10 seated subjects were asked to adjust the intensity of a test stimulus until they perceived a whole body sensation equivalent to a reference stimulus. The vibration stimuli were low frequency motions along the vertical axis and they were representative of earthmoving machines. They were compared to each other and to sinusoidal and third octave band random vibrations centred at the same frequencies. The results obtained indicate that the overall frequency weighting methods are the most appropriate for the evaluation of complex vibrations. The vertical weighting curve recommended by the Standard ISO 2631 produces suitable results.

Recovery of vestibulo-ocular reflex-function in subjects with an acute unilateral peripheral vestibular deficit

1999 ◽  
Vol 9 (2) ◽  
pp. 135-144 ◽  
Author(s):  
J.H.J. Allum ◽  
T. Ledin
Keyword(s):  
Low Frequency ◽  
Vestibular Function ◽  
Vertical Axis ◽  
Whole Body ◽  
Horizontal Semicircular Canal ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Central Compensation ◽  
Head Rotations ◽  
Vestibular Deficit

The centrally controlled compensation for a reduced horizontal vestibulo-ocular reflex (VOR) gain caused by a unilateral afferent deficit is usually studied following a selective surgical procedure which completely lesions the vestibular nerve or blocks the horizontal semicircular canal. The more common, unilateral, vestibular deficit encountered clinically, is a partial loss of peripheral vestibular function, following which peripheral recovery and/or central compensation may occur. We investigated changes of the VOR gain in response to a sudden, idiopathic, unilateral vestibular deficit in 64 subjects by examining the responses to low-frequency, whole-body, rotations about an earth vertical axis with different accelerations (5, 20 and 40 deg / sec 2 ) during in- and out-patient visits separated by 4 months in an attempt to identify changes brought about by peripheral recovery and by central compensation processes. Peripheral function was assumed to be measured by the response to caloric irrigation. It improved some 30% between the two visits. VOR responses for rotations towards the deficit side also improved between the two visits. Most improvement occurred for 20 deg / sec 2 accelerations. However, the correlation coefficient between rotation and caloric responses was always less than 0.6. Unlike caloric responses which improved over time, responses for rotations to the intact side did not change between the visits. For this reason, the majority of observed VOR rotation responses were nearly symmetrical at the time of the second visit, despite being below normal levels. These findings suggest that both peripheral recovery and central compensation processes help restore symmetrical VOR function for head rotations after a partial unilateral vestibular deficit. However the improvement of VOR response symmetry, particularly to slow ( < 40 deg / sec 2 ) accelerations, is largely independent of the recovery of peripheral sensitivity.

Anterior canal neurons in cat vestibular nuclei have large phase leads during low frequency vertical axis pitch

2007 ◽  
Vol 16 (6) ◽  
pp. 245-256
Author(s):  
Sandra C. Brettler ◽  
James F. Baker
Keyword(s):  
Low Frequency ◽  
Vertical Axis ◽  
Vestibular Nuclei ◽  
Whole Body ◽  
Posterior Canal ◽  
Spatial Sensitivity ◽  
Ocular Reflex ◽  
Vestibular Afferents ◽  
Vestibulo Ocular Reflex ◽  
Anterior Canal

Vestibulo-ocular and second-order neurons in medial and superior vestibular nuclei of alert cats were identified by antidromic and orthodromic electrical stimulation, and their responses to whole body rotations were recorded in the dark. Neurons that had spatial sensitivity most closely aligned with the anterior canal (anterior canal neurons) were compared with neurons that had spatial sensitivity most closely aligned with the posterior canal (posterior canal neurons). Responses were recorded during low frequency earth-horizontal axis pitch rotations in the normal upright posture, and during earth-vertical axis pitch with the head and body lying on the left side. During upright pitch, response phases of anterior canal neurons slightly lagged those of posterior canal neurons or primary vestibular afferents, as previously reported. During on-side pitch, anterior canal neurons showed far greater phase leads with respect to head velocity than posterior canal neurons, primary vestibular afferents, or previously reported vestibulo-ocular reflex eye movements. These results provide challenges for vestibulo-ocular reflex models to incorporate central mechanisms for phase leads among the inputs to anterior canal neurons and to explain how the anterior canal neuron signals reported here combine with other signals to produce observed vestibulo-ocular reflex behavior.

EVALUATION OF FREQUENCY WEIGHTING (ISO 2631-1) FOR ACUTE EFFECTS OF WHOLE-BODY VIBRATION ON GASTRIC MOTILITY

2002 ◽  
Vol 253 (1) ◽  
pp. 31-36 ◽  
Author(s):  
T. ISHITAKE ◽  
Y. MIYAZAKI ◽  
R. NOGUCHI ◽  
H. ANDO ◽  
T. MATOBA
Keyword(s):  
Gastric Motility ◽  
Whole Body Vibration ◽  
Whole Body ◽  
Acute Effects ◽  
Body Vibration ◽  
Frequency Weighting ◽  
Iso 2631

scholarly journals The Evaluation of Horizontal Whole-Body Vibration in the Low Frequency Range

2002 ◽  
Vol 21 (1) ◽  
pp. 29-36
Author(s):  
Masashi Uchikune
Keyword(s):  
Nervous System ◽  
Parasympathetic Nervous System ◽  
Whole Body Vibration ◽  
Low Frequency ◽  
Psychological Effects ◽  
Whole Body ◽  
Frequency Range ◽  
Horizontal Vibration ◽  
Public Transport System ◽  
Iso 2631

International Standard ISO 2631 gives the reaction to horizontal vibration for the occupant of a building, a public transport system, the oscillations of the ocean and so on. These effects have not yet been evaluated by physiological methods as the criterion curves in the Standard are based on psychological evaluations of comfort and discomfort, rather than physiological investigations. Physiological and psychological effects of low frequency horizontal vibration on the whole-body were as follows: Changes in the autonomic nervous system were observed, in which the system tended to change from the state of predominance of the parasympathetic nervous system to that of the sympathetic nervous system, when the frequency exceeded the range 0.2 to 0.4Hz, typically around 0.3Hz.

Body Sensation of Low Frequency Noise of Ordinary Persons and Profoundly Deaf Persons

1983 ◽  
Vol 2 (3) ◽  
pp. 32-36 ◽  
Author(s):  
S. Yamada ◽  
M. Ikuji ◽  
S. Fujikata ◽  
T. Watanabe ◽  
T. Kosaka
Keyword(s):  
Low Frequency ◽  
Semicircular Canals ◽  
Normal Hearing ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Body Sensation ◽  
Deaf Persons

Comparison of the thresholds of body sensation of profoundly deaf subjects and those of normal hearing, when exposed to intense low frequency noise, showed similar trends. Since the deaf subjects were judged to have normal balance mechanisms, it was concluded that the semicircular canals are not sensitive to low frequency noise at its normal levels in the environment.

A Methodology for the Test Design and Evaluation of Human Whole-Body Vibration in Ground Vehicle Systems

1989 ◽  
Vol 33 (18) ◽  
pp. 1192-1196
Author(s):  
Ellen C. Haas
Keyword(s):  
Whole Body Vibration ◽  
International Standards ◽  
Whole Body ◽  
Test Design ◽  
Exposure Limits ◽  
Ground Vehicle ◽  
Body Vibration ◽  
Exposure Limit ◽  
Vehicle Systems ◽  
Iso 2631

To date, testing and evaluation of whole-body vibration in ground vehicle systems have not always fully utilized appropriate experimental design methodology, applicable statistical tests, or relevant criteria. A test design and evaluation methodology was developed to eliminate these oversights. This methodology uses inferential statistics, questionnaires, and a comparison of vibration data with representative mission scenarios. The methodology was employed in the evaluation of two alternative tracked ground vehicle designs. The independent variables were track type, terrain, vehicle speed, and crew position. The dependent variables were International Standards Organization (ISO) 2631 whole-body vibration exposure limit times at the lateral, transverse, and vertical axes. Two different multivariate analyses of variance (MANOVAs) performed on the exposure limit data indicated that all main effects, as well as several interactions, were significant (p < .01). A comparison of exposure limits to a representative mission scenario indicated that both track types would exceed ISO 2631 exposure, comfort, and fatigue limits during expected travel over cross-country terrain. Crew questionnaires also indicated crew discomfort when exposed to this type of terrain. The experiment demonstrated that the procedure was useful in helping to determine the extent that vehicle vibration permits the performance of the vehicle mission, within limits dictated by safety, efficiency, and comfort.

Torsional vestibulo-ocular reflex during whole-body oscillation in the upright and the supine position: II. Responses in patients after vestibular neuritis

2004 ◽  
Vol 14 (4) ◽  
pp. 353-359
Author(s):  
A. Schmid-Priscoveanu ◽  
A.A. Kori ◽  
D. Straumann
Keyword(s):  
Supine Position ◽  
Semicircular Canal ◽  
Low Frequency ◽  
Phase Changes ◽  
Vestibular Neuritis ◽  
Whole Body ◽  
Healthy Human ◽  
Phase Lead ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex

In a recent study we demonstrated that otolith input modifies the torsional angular vestibulo-ocular reflex (torVOR) of healthy human subjects: Compared to turntable oscillations in supine position, oscillations in upright position increased the gain of torVOR by 0.1 and cancelled the phase lead originating from low-frequency semicircular canal signals. We asked whether these otolith-related changes of torVOR are still present in patients after vestibular neuritis (VN). Eight patients were sinusoidally oscillated about their naso-occipital axis in supine (canal-only stimulation) and upright (canal-and-otolith stimulation) position. Three-dimensional eye movements were recorded with dual search coils. The patients showed similar otolith-related gain and phase changes of the torVOR as healthy subjects: the gain increased by about 0.1 (p < 0.05) and the low-frequency phase lead from semicircular canal signals was abolished. These results indicate that otolith function after VN is still sufficient to interact with semicircular canal signals to optimize torsional gaze stabilization when the head is upright.

scholarly journals Whole Body Vibration Analysis of Baby Hammock

2018 ◽  
Vol 217 ◽  
pp. 01005
Author(s):  
Ying Hao Ko ◽  
Chia Sin Geh
Keyword(s):  
High Speed ◽  
Whole Body Vibration ◽  
Whole Body ◽  
Asian Countries ◽  
Body Vibration ◽  
Limit Value ◽  
Exposure Limit ◽  
Rocking Motion ◽  
Action Value ◽  
Iso 2631

Studies have been carried on the effect of rocking on a baby and concluded that baby sleeps easier while being rocked. In Malaysia, as in many Southeast Asian Countries, it is common to put babies to sleep in a baby hammock. the vertical rocking motion generated by baby hammock has exposed babies to whole-body vibration (WBV). It has been shown by ISO2631 (1997) that WBV may lead the discomfort and adverse effect on health. Standards have been set by ISO 2631 (1997) concerning the WBV for people in a recumbent position and consider weighted vibrations of more than 2 m/s2 to be extremely uncomfortable. However, standards concerning the allowable amount vibrations a baby in a baby hammock can safety endure are currently lacking. WBV analysis of the baby hammock with the weight ranged from 3kg to 14kg is conducted. For each measurement, four conditions are considered: manual rocking, auto rocking with low, medium and high speed. In this study, average root-mean-square values for the acceleration were found to be at a maximum of 2.46 m/s2, and to be above the extremely uncomfortable level. This study develops a baseline exposure time for the baby hammock before it reaches the safety values of exposure action value (EAV) and exposure limit value (ELV) set by ISO 2631(1997).

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