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Arbete och Hälsa, Vetenskaplig Skriftserie
Journal of Sound and Vibration (1979) 63(4), 617-620
HUMAN RESPONSE TO VIBRATION
ABSTRACTS Prepared by M. J. Griffin and J. Griffin, Human Factors Research Unit, Institute of Sound and Vibration Research, University of Southampton, Southampton SO9 5NH, England G. F. Rowlands 1977 Royal Aircraft Establishment Technical Report 77068. The transmission of vertical vibration to the heads and shoulders of seated men. (115 pages, 40 figures, 8 tables, 49 references) Author’s Abstract. Modem forms of transportation can impose high levels of vibration upon occupants. These levels can cause discomfort to the passengers or loss of performance by pilots or drivers. To determine the effects of vibration, it is necessary to define the vibration levels experienced by such people. This definition should preferably quantify not only the input levels, but also those at the parts of the body most likely to be affected by the vibration. This report covers an investigation of the frequency response of the human body to vertical vibration, using six subjects on a rigid seat. The input used was a swept sine acceleration, where the frequency of the vibration varied linearly with time between an upper and lower value, at a fixed amplitude. The use of such an input facilitated measurements of amplitude ratio and phase angle plots of the ratio of head and shoulder acceleration to seat acceleration against frequency, to be made for various postures and limb positions. Resting the back against the seat and putting the legs forward, were both found to have a major effect on transmission. Attempts are made to model these response curves so that by simply monitoring floor vibration in vehicles and assuming the seat response is known one can predict the range of vibrations present at the head and shoulders. Theoretical analysis is used to demonstrate that the response of cushions is directly related to the human frequency response. Topics: Biodynamics (Transmissibility, Models). J.-E. Hansson and B.-O. Wikstrijm 1976 Arbete och Halsa, Vetenskaplig Skrtftserie 1976:14. Exposure to whole-body vibrations among forest machines. (27 pages, 12 figures, 3 tables, 11 references) (in Swedish) English Abstract. This report summarizes measurements, made according to IS0 2631, of wholc-body vibration. to which drivers of forest machines are exposed. The studies have been conducted during the years 1973-76. Vibration characteristics of altogether 66 working sites have been studied. The studies show that drivers of slashers and cutters are exposed to vibrations only to a small extent. Heavy vibrations occur in forwarders, skidders, loaders, trimmers and on certain occasions in processors. For these machines vibrations are of such a magnitude, related to IS0 standard 2631, that fatigue and work-proficiency are influenced during a working day of 8 hours. In 4 out of 66 machines studied, vibrations constituted a health hazard according to the above mentioned standard for an exposure time of more than 8 hours. The greatest energy content of the vibrations lies for horizontal directions in the frequency regions of 1-3 Hz, and for the vertical direction in the frequency region of 1.5-6 Hz. Comparison between l/3 octave band analysis and narrow band analysis shows 617
618
HUMAN
RESPONSE
TO VIBRATION
that the former is narrow enough for the resonances to show up in the analysis. Vibrations in horizontal directions are usually more critical to the driver than those in the vertical direction. The heaviest vibration load is represented in forwarders and skidders when driving without load. A lower driving-speed will give a considerable reduction of the vibrdtion load on the driver. The extent to which the seat reduces the vibration load on the driver has been studied. Of 16 seats studied only 2 reduced the vibration load according to IS0 2631. Topics: Vibration Measurements (Qff Road Vehicles) ; Seating. D. J. Martin, P. M. Nelson and R. C. Hill 1978 Transport and Road Research Laboratory Report 402. Measurement and analysis of traffic-induced vibration in buildings. (27 pages, 11 figures, 9 references) Authors’ Abstract. Techniques are described for the measurement and analysis of groundborne structural vibration and air-borne low frequency noise in buildings caused by road traffic. A measurement system comprising piezoelectric quartz crystal accelerometers and condenser microphones was used, and signals from these transducers were recorded on a magnetic tape recorder. Analysis of the recorded data was carried out using l/3 octave frequency bands over the range from 3.15 to 500 Hz. Long term statistical averages and single vehicle peak even frequency spectra were obtained from measurements taken in a terraced property adjacent to a busy city road. The results showed that at this site low frequency noise, (in the range 50 to 200 Hz) was responsible for most of the floor and window vibrations inside the house. Topics: Vibration Measurements (Buildings) : Combined Stress (Vibration ana’Noise). Supplementary
D. J. Martin 1978 Transport and Road Research Laboratory Supplementary Report 429. Low frequency traffic noise and building vibration. (18 pages, 11 figures, 2 tables, 11 references) Author’s Abstract. Building vibrations caused by heavy traffic close to buildings in urban areas were investigated at four sites where a high degree of vibration bother had been demonstrated or was expected. It was found that low frequency acoustic excitation was responsible for floor vibrations at all sites. Floor vibrations were generated in two frequency ranges. These were 63-125 Hz which corresponded with the excitation frequencies in exhaust emissions, and at lo-25 Hz which corresponded with the natural frequencies of the upper freely-suspended floors at the sites. The use of vibration perception thresholds to describe criteria for bother is discussed. It is suggested that the mechanism of vibration disturbance may be a complex combination involving structural vibration and low frequency sound which may be either heard or felt as body vibration. Topics: Vibration Measurements (Buildings); Combined Stress (Vibration and Noise) ; Vibration Sense (Thresholds).
R. A. Shryock, J. W. Klahs and D. A. Dietrich 1977 2nd International Conference on Vehicle U.S.A., 18-20 April, Paper 770594. System modeling techniques to improve the ride and vibration isolation characteristics of heavy equipment. (13 pages, 18 figures, 29 references) Authors’ Abstract. Much attention has been devoted to the importance of vehicle dynamics relative to human response ride criteria. The present work extends this effort by providing a practical computerized design approach in which the vehicle designer selects a representative terrain input, either sinusoidal or power spectral density, to excite a vehicle model constructed by the modal Building Block method. To evaluate vehicle ride the resulting system response. accounting for human dynamic characteristics, is compared to accepted Structural Mechanics, Southfield, Michigan,
HUMAN RESPONSE TO VIBRATION
ABSTRACTS Prepared by M. J. Griffin and J. Griffin, Human Factors Research Unit, Institute of Sound and Vibration Research, University of Southampton, Southampton SO9 5NH, England G. F. Rowlands 1977 Royal Aircraft Establishment Technical Report 77068. The transmission of vertical vibration to the heads and shoulders of seated men. (115 pages, 40 figures, 8 tables, 49 references) Author’s Abstract. Modem forms of transportation can impose high levels of vibration upon occupants. These levels can cause discomfort to the passengers or loss of performance by pilots or drivers. To determine the effects of vibration, it is necessary to define the vibration levels experienced by such people. This definition should preferably quantify not only the input levels, but also those at the parts of the body most likely to be affected by the vibration. This report covers an investigation of the frequency response of the human body to vertical vibration, using six subjects on a rigid seat. The input used was a swept sine acceleration, where the frequency of the vibration varied linearly with time between an upper and lower value, at a fixed amplitude. The use of such an input facilitated measurements of amplitude ratio and phase angle plots of the ratio of head and shoulder acceleration to seat acceleration against frequency, to be made for various postures and limb positions. Resting the back against the seat and putting the legs forward, were both found to have a major effect on transmission. Attempts are made to model these response curves so that by simply monitoring floor vibration in vehicles and assuming the seat response is known one can predict the range of vibrations present at the head and shoulders. Theoretical analysis is used to demonstrate that the response of cushions is directly related to the human frequency response. Topics: Biodynamics (Transmissibility, Models). J.-E. Hansson and B.-O. Wikstrijm 1976 Arbete och Halsa, Vetenskaplig Skrtftserie 1976:14. Exposure to whole-body vibrations among forest machines. (27 pages, 12 figures, 3 tables, 11 references) (in Swedish) English Abstract. This report summarizes measurements, made according to IS0 2631, of wholc-body vibration. to which drivers of forest machines are exposed. The studies have been conducted during the years 1973-76. Vibration characteristics of altogether 66 working sites have been studied. The studies show that drivers of slashers and cutters are exposed to vibrations only to a small extent. Heavy vibrations occur in forwarders, skidders, loaders, trimmers and on certain occasions in processors. For these machines vibrations are of such a magnitude, related to IS0 standard 2631, that fatigue and work-proficiency are influenced during a working day of 8 hours. In 4 out of 66 machines studied, vibrations constituted a health hazard according to the above mentioned standard for an exposure time of more than 8 hours. The greatest energy content of the vibrations lies for horizontal directions in the frequency regions of 1-3 Hz, and for the vertical direction in the frequency region of 1.5-6 Hz. Comparison between l/3 octave band analysis and narrow band analysis shows 617
618
HUMAN
RESPONSE
TO VIBRATION
that the former is narrow enough for the resonances to show up in the analysis. Vibrations in horizontal directions are usually more critical to the driver than those in the vertical direction. The heaviest vibration load is represented in forwarders and skidders when driving without load. A lower driving-speed will give a considerable reduction of the vibrdtion load on the driver. The extent to which the seat reduces the vibration load on the driver has been studied. Of 16 seats studied only 2 reduced the vibration load according to IS0 2631. Topics: Vibration Measurements (Qff Road Vehicles) ; Seating. D. J. Martin, P. M. Nelson and R. C. Hill 1978 Transport and Road Research Laboratory Report 402. Measurement and analysis of traffic-induced vibration in buildings. (27 pages, 11 figures, 9 references) Authors’ Abstract. Techniques are described for the measurement and analysis of groundborne structural vibration and air-borne low frequency noise in buildings caused by road traffic. A measurement system comprising piezoelectric quartz crystal accelerometers and condenser microphones was used, and signals from these transducers were recorded on a magnetic tape recorder. Analysis of the recorded data was carried out using l/3 octave frequency bands over the range from 3.15 to 500 Hz. Long term statistical averages and single vehicle peak even frequency spectra were obtained from measurements taken in a terraced property adjacent to a busy city road. The results showed that at this site low frequency noise, (in the range 50 to 200 Hz) was responsible for most of the floor and window vibrations inside the house. Topics: Vibration Measurements (Buildings) : Combined Stress (Vibration ana’Noise). Supplementary
D. J. Martin 1978 Transport and Road Research Laboratory Supplementary Report 429. Low frequency traffic noise and building vibration. (18 pages, 11 figures, 2 tables, 11 references) Author’s Abstract. Building vibrations caused by heavy traffic close to buildings in urban areas were investigated at four sites where a high degree of vibration bother had been demonstrated or was expected. It was found that low frequency acoustic excitation was responsible for floor vibrations at all sites. Floor vibrations were generated in two frequency ranges. These were 63-125 Hz which corresponded with the excitation frequencies in exhaust emissions, and at lo-25 Hz which corresponded with the natural frequencies of the upper freely-suspended floors at the sites. The use of vibration perception thresholds to describe criteria for bother is discussed. It is suggested that the mechanism of vibration disturbance may be a complex combination involving structural vibration and low frequency sound which may be either heard or felt as body vibration. Topics: Vibration Measurements (Buildings); Combined Stress (Vibration and Noise) ; Vibration Sense (Thresholds).
R. A. Shryock, J. W. Klahs and D. A. Dietrich 1977 2nd International Conference on Vehicle U.S.A., 18-20 April, Paper 770594. System modeling techniques to improve the ride and vibration isolation characteristics of heavy equipment. (13 pages, 18 figures, 29 references) Authors’ Abstract. Much attention has been devoted to the importance of vehicle dynamics relative to human response ride criteria. The present work extends this effort by providing a practical computerized design approach in which the vehicle designer selects a representative terrain input, either sinusoidal or power spectral density, to excite a vehicle model constructed by the modal Building Block method. To evaluate vehicle ride the resulting system response. accounting for human dynamic characteristics, is compared to accepted Structural Mechanics, Southfield, Michigan,