2011-11-01 12:00 - Messages

A predictive discomfort measure of seated subjects is proposed to assess discomfort in complicated environments and to develop reliable biodynamic models.

A predictive discomfort measure considering the combined neck and trunk is introduced in this work and compared with the seat-to-head transmissibility and subjective reported discomfort due to fore-aft whole-body vibration of seated subjects under two sitting postures. The proposed discomfort quantifies whole-body musculoskeletal discomfort considering body posture, closeness of the joints to their limits, and severity of the angular acceleration at the joints. The proposed predictive discomfort captured the trend of the subjective reported discomfort and showed good potential to capture the effect of two seated postures: the unsupported- and supported-back conditions. With advances in computer modeling, the proposed predictive discomfort may provide efficient ways to assess discomfort in complicated environments and to develop reliable biodynamic models for design of equipment inside moving vehicles.


Source: Predictive discomfort and seat-to-head transmissibility in low-frequency fore-aft whole-body vibration.  DeShaw J. and Rahmatalla S.; Journal of low frequency noise, vibration and active control; Vol. 30 No. 2 2011, p. 185 – 195.







The Zwicker loudness calculation method, soon deleted from ISO standardization

A widely used metric, the Zwicker loudness calculation method, is currently being deleted from ISO standardization to be replaced with a new method. The Moore & Glasberg method behaves differently than Zwicker method with different signal bandwidths. National technical advisory group representatives to ISO TC43 will present each country's voting position. This issue is very important; there is a possibility of a significant shift in the use and industrial usefulness of psychoacoustic metrics. No «translation formula» may be applied universally to a result calculated with one method to make it equivalent to a result from the other method.  There is a bandwidth-related behavior difference and the amount of difference in loudness values seen with technical sounds suggest that the continuity and comparability of archived results needed by industrial users would be disrupted by suddenly eliminating the widely used method.


Source: Editorial- Help Wanted Now. Bray W. R.  Sound & vibration/September 2011, Dynamic testing reference issue.


Duration of noise exposure, a better predictor than noise exposure levels

In this retrospective study, medical records of periodic occupational health examinations of 29,644 construction workers are analysed. Pure-tone audiometric thresholds of noise-exposed workers are compared to a non-exposed control group and to ISO-1999 predictions. Regression analyses are conducted to explore the relationship between hearing loss and noise intensity, noise exposure time and the use of hearing protection. For the first decade, the population medians show poorer hearing than predicted by ISO-1999. Duration of noise exposure was a better predictor than noise exposure levels, probably because of the limitations in noise exposure estimations. In this population, noise-induced hearing loss was already present at the beginning of employment and increased at the same rate as is predicted for longer exposure durations.

Source: A retrospective analysis of noise-induced hearing loss in the Dutch construction industry. Leensen MC, van Duivenbooden JC, Dreschler WA. Int Arch Occup Environ Health. 2011 Jun; 84(5):577-90.



Repeated measurements of Hand-Arm Vibrations are crucial for good dose precision

This study was to assess hand–arm vibration (HAV) exposure during different grinding operations, in order to obtain estimates of the variance components and to evaluate the effect of work postures. In the wheel wear test, the equivalent hand–arm-weighted accelerations for Grinder 1 during the first and second grinding minutes were 3.4 and 2.9 m s−2, respectively, and for Grinder 2, they were 3.1 and 2.9 m s−2, respectively. For Grinder 1, the equivalent hand–arm-weighted acceleration during the first grinding minute was significantly higher (P = 0.04) than during the second minute. The authors concluded that work posture during grinding operations does not appear to affect the level of HAV. Grinding wheels explained much of the variability in this study, but almost 40% of the variance remained unexplained. The considerable variability in the equivalent hand–arm-weighted acceleration has an impact on the risk assessment at both the group and the individual level.

Source: Variability in Hand–Arm Vibration during Grinding Operations. Liljelind I., Wahlström J., Nilsson L., Toomingas A. and Burström L. Ann Occup Hyg (2011) 55 (3): 296-304.


Construction workers followed for 10 years had a substantial potential risk of NIHL

Estimates were developed including work duration, trade-mean (TM)-equivalent continuous exposure level (LEQ), task-based (TB) LEQ, a hybrid LEQcombining TB and subjective information, and an estimate of noise exposure ‘peakiness'. Hybrid and TB exposure estimates demonstrated much greater variability than TM estimates. Work duration and estimates of exposure peakiness showed poor agreement with average exposures, suggesting that these metrics evaluate different aspects of exposure and may have different predictive value for estimating NIHL. Construction workers in the cohort had subject-interval and study-average exposures which present a substantial potential risk of NIHL.


Source: Longitudinal Assessment of Noise Exposure in a Cohort of Construction Workers. Neitzel R.L., Stover, B. and Seixas, N.S.Annals of Occupational Hygiene (2011) First published online: August 8, 2011



Communiquer sans entendre le bruit ambiant

Des casques supercommunicants et antibruit permettront une meilleure communication entre opérateurs en milieu industriel. Les fabricants d'EPI se penchent sur les solutions Bluetooth adaptées à l'environnement industriel. «Les prochaines générations de ces appareils devraient permettre de communiquer avec un plus grand nombre de personnes et sur des portées plus grandes.» Des détecteurs sans fil mesureront l'exposition du travailleur et des logiciels performants donneront «avec précision combien d'heures ou de mois un employé a été exposé à des substances nocives... (telles) les vibrations.»

Source : L'ouvrier du futur, ce superhéros. Chandès C. Enquête-innovations, L'usine nouvelle, 22 septembre 2011.



Hearing risk during worship in Brazil.

Worship in Protestant churches in Brazil is very noisy. Thus, this practice may pose a hearing risk. An analysis was carried out in 5 churches located in the city of São José dos Campos, Brazil. The priest’s noise exposure was over the recommended limits. The normalized exposure level varied between 95.4 to 99.5 dB (A). In 2 of the churches, the noise exposure registered, with values of 85.3 and 86.5 dB (A), may also pose risk to the worshippers. The authors conclude that worship in the churches generated sound pressure levels that imply health risk, especially to priests, so hearing conservation programs with adequate acoustical sanitation measures must be implemented there.


Source: Noise Exposure Levels of Priests and Worshippers in Protestant Churches. Silva L.F., Cabral R. Int J Occup Saf Ergon 2011; 17(1):79-86.

Whole body vibration as a potential cause of Parkinson’s disease

In the largest case-control study of Parkinson's disease conducted in Canada to date, Parkinson’s disease showed u-shaped pattern of risk for whole body vibration: increased risk among those with no exposure, and among those with exposure, increasing risk with increasing intensity of exposure. Among those with exposure, there were increasing odds of Parkinson’s disease with increasing intensity of exposure and with increasing censoring of exposure in the years prior to diagnosis. The odds ratio was statistically significant in the second highest intensity category, for exposures up to 10 years prior to diagnosis. Duration and dose of whole body vibration exposure were not associated with Parkinson’s disease. We found no other studies that have examined this exposure. Whole body vibration as a potential cause of Parkinson’s disease is worthy of continued investigation.

Source: Parkinson’s disease: Workplace Risk Factors. Teschke, K et al.; Final Report to WorkSafeBC, September 2011




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