2012-03-01 12:00 - Messages

Whole-body vibration : Typical postures of the drivers result in enhanced spinal forces compared with the upright sitting posture

Typically drivers of container-bridge cranes are forced to sit with a forward bent upper trunk to control the position and motion of the container. Fork-lift truck drivers incline the upper trunk to the side to look forward or they twist to one side during reversing. The forces transmitted in the lumbar spine were assessed by means of a biomechanical model. Under realistic vibration stress the bent postures result in an increase of the compressive and the shear forces. The increase of the spine forces is the result of the increased muscle forces stabilizing the inclined trunk. On container bridge cranes or fork-lift trucks the typical postures of the drivers result in enhanced spinal forces compared with the upright sitting posture. This effect must be considered in the risk analysis of workplaces with whole-body vibration.

Source : Fritz, M., Schäfer, K. Influence of the Posture of the Trunk on the Spine Forces During Whole-Body Vibration. Low Frequency Noise, Vibration and Active Control, Volume 30, Number 4 / December 2011, 277-290. DOI : 10.1260/0263-0923.30.4.277


The bi-sound signal to be mandatory for track work (IFA): the perceptibility of the signals have been tested under working noise conditions

Warning signal generators are used at points where track work is being carried out in order to warn workers of approaching trains on neighbour-ing lines, electroacoustic signal generators are generally employed. Harmonization of the warning signals would simplify instruction at the work site. In addition, the signal generators fitted on track-laying machines would not repeatedly have to be set to whichever warning signal is emitted by the signalling devices on the track being worked on.

In order to determine the perceptibility of the signals under working noise conditions, hearing tests were conducted on test subjects in the IFA's laboratory in conjunction with the responsible German Social Accident Insurance Institutions (those for the building trade and for the railway services), and with Deutsche Bahn AG. The comparison of signal pairs above the masked threshold revealed a clear preference for the Minimel signal at all signal levels. This result is also confirmed by the hearing tests performed with hearing protection worn. In a direct comparison, the Minimel signal can therefore be considered more suitable for track work than the Autoprowa signal. The products of both manufacturers are capable of producing this signal. DB Netz AG will issue a technical bulletin shortly announcing harmonization of the warning signals and a deadline for withdrawal of CO2 signal horns. This bulletin will make use of the bi-sound signal mandatory after 31 December 2013.

Source : Harmonized warning signal for track work. IFA 0334; Edition 12/2011; 617.0-IFA:638.21





Study on the impact of exposure to noise in professional snipers

Facing an increasing violence level and higher firepower in the hands of criminal organizations (especially those related to drug trafficking), the Military Police of Pernambuco has created, in 1989, the “1a Companhia Independente de Operações Especiais” (1st Independent Company of Special Operations), as a tactical last resort of the Police to be used on special, complex situations. The CIOE progressively makes use of Negotiation measures, of less-than-lethal maneuvers, of Precision Shots and Tactical Assaults. When all possibilities are drained, the Precision Shot will bring the crisis perpetrator down. This study had as an objective to assess the level of impact noise suffered by the elite snipers of the 1st CIOE-PE in their training. The working conditions of the snipers were evaluated through the use of a semi-structured questionnaire. Noise measuring was done on four (4) .308 IMBEL AGLC (with ammo from the same lot) rifles. Six (6) shots were fired off each gun, separated by a 30-second pause. In the end, it has been concluded that the noise level the 1st CIOE snipers are submitted to is considered to be normal by Brazilian legislation.

Source : Barkokebas Junior B, Lago E, Vasconcelos B, Oliveira E. Work 2012. 41, p. 3269-3276.

“Hearing Conservation Programs” are not an adequate substitute for engineering and administrative controls.

Noise induced hearing loss is still too prevalent in American workplaces as the attempts at “hearing conservation programs” have proven inadequate. The author explains that the American workers have been the subjects in what has been largely a failed experiment for 28 years. Hearing protection devices are neither an efficient nor a humane replacement for eliminating the noise hazard and should once again be allotted their proper place in the control hierarchy. Several studies have found widespread and serious gaps in compliance with requirements such as audiometric testing, training, record keeping, and exposure measurement. These failures are particularly prevalent among small companies. Although opponents of requirements for engineering controls maintain that they are particularly difficult for small companies to implement, the per-worker costs of hearing conservation requirements for small companies are much greater than for large companies, and the use of engineering and administrative controls is likely to be more cost-effective than hearing protection devices (HPDs) for small businesses.

Source: Alice H. Suter. Engineering Controls for Occupational Noise Exposure- The Best Way to Save Hearing. Sound and Vibration, January 2012 – 45th Anniversary Issue


Improvements in education, technical support, and regulatory enforcement reduce barriers to implementation of engineered noise control

The most effective intervention—engineered noise controls (ENC) —is rarely implemented; a qualitative study was designed to investigate barriers to the implementation of ENC. Many factors emerged as possible barriers to the implementation of engineered noise control, including: poor knowledge of relevant regulations, noise reduction options and the health impacts of noise; weak technical skills and experience; low ranking of noise as a hazard by stakeholders; issues around job insecurity, weak language skills; lack of ‘quiet’ machine options and information from equipment manufacturers; poor employer-regulator relationships; barriers to employee-employer reporting; informal valuation of ENC costs; and feasibility issues. Many barriers could be addressed by a more rigorous application of existing HCP regulation and improvements in education, technical support, and regulatory enforcement.

Source : Davies, H.W., Louie, A., Nahid, M., Shoveller, J. Potential barriers to engineered noise control in food and beverage manufacturing in British Columbia, Canada: A qualitative study. International Journal of Audiology; February 2012, Vol. 51, No. S1, Pages S43-S50 (doi:10.3109/14992027.2011.633936)


Patients and staff in intensive care units are exposed to high noise levels

In intensive care units, the main noise sources are hospital staff on duty and medical equipment, which generates both operating noise and acoustic alarms. Results of a survey of hospital staff are presented, as well as measurements in two German hospital wards: a standard two-bed room and a special intermediate care unit (IMC-Unit), each in a different intensive care unit (ICU). An analysis of the survey and the measured data, together with a comparison of thresholds of national and international regulations and standards describe the acoustic situation and its likely noise effects on staff and patients.

Source : Noise in an intensive care unit. Salandin, A. Arnold, J., Kornadt, O. Acoust. Soc. Am. Volume 130, Issue 6, pp. 3754-3760 (2011); (7 pages)


Syllabus of the NEBOSH National Diploma «Physical agents»

This article explain that vibration injury is typical of the «slow accidents» that build through continued exposure to the so-called physical agents, which also include noise and radiation... damages many lives. It presents the syllabus of the NEBOSH National Diploma «Physical agents» and resumes information on Whole-body vibration and Hand-arm vibration.

In his series for NEBOSH National Diploma students, Lawrence Bamber details the risks posed by vibration, its effects on the individual and assessment and control of exposure.

Source : Bad Vibes. Bamber, L. Health and Safety at Work, dec.2011


One way transmission system for sound waves

Mechanisms to truly control the direction of sound waves are still in their infancy but researchers at the California Institute of Technology have created the first tunable acoustic diode, a device that allows acoustic waves to travel only in one direction, at controllable frequencies. "We exploited a physical mechanism that causes a sharp transition between transmitting and nontransmitting states of the diode," says Chiara Daraio, professor of aeronautics and applied physics at Caltech and lead author on the study. "Using experiments, simulations, and analytical predictions, we demonstrated the one-way transmission of sound in an audible frequency range for the first time. We may be able to scavenge sound energy from undesired structural vibrations in machinery by controlling the flow of sound waves away from the machinery and into a transducer. The transducer would then convert the sound waves into electricity.’’ These systems may be applicable to a range of technologies including biomedical ultrasound devices and advanced noise control.

Source : http://www.physorg.com/news/2011-07-one-way-transmission.html

Voir aussi : Bifurcation-based acoustic switching and rectification. Boechler, N., Theocharis, G., Daraio, C. Nature Materials Volume: 10, Pages: 665–668 Year published: (2011). DOI: doi:10.1038/nmat3072


Abonnement courriel

Messages récents


Mots-Clés (Tags)