2011-09-01 12:00 - Messages

Un système de climatisation qui déplace de gros volumes d’air, mais lentement, si bien qu’on n’entend rien.

M.Tateo Nakajima, associé de la firme d'acoustique Artec parle de la nouvelle salle de concert de l'Orchestre symphonique de Montréal. Les qualités acoustiques de la nouvelle salle résultent avant tout du respect d'une exigence primordiale chez Artec concernant les bruits extérieurs: l'isolation phonique. Jack Diamond, membre du cabinet d'architectes Diamond-Schmitt, a trouvé le moyen de l'obtenir en faisant reposer la salle sur des coussins acoustiques en caoutchouc formant une enveloppe distincte des fondations extérieures.

Dans une grande salle, la distance que parcourt le son est plus grande et si la réverbération est trop forte, elle fera écho. L'ajustement des réflecteurs fait en sorte que le son initial atteint le public plus rapidement et qu'on peut moduler la quantité d'énergie sonore dirigée vers la partie supérieure du plafond. Le son se fond, revient, et l'auditeur le perçoit comme un son unique.»

L'architecte a eu une trouvaille pour éliminer le bruit provoqué par la climatisation. «Nous avons fait sortir l'air par des bouches rondes placées à la base de chaque fauteuil, fait observer M. Diamond. Ce système déplace de gros volumes d'air, mais lentement, si bien qu'on n'entend ou ne sent rien.» … «En d'autres termes, il faut que la salle suscite l'intérêt, qu'elle dégage une force sereine qui vous enveloppe.»

 

Source : La démocratie acoustique : Une nouvelle maison pour l'OSM. Wah Keung Chan,  La Scena Musicale - Vol. 17, No. 1 septembre 2011.

http://www.scena.org/lsm/sm17-1/sm17-1_front_FR.html

Calculation of cumulative hours across all vibrating tools used is a more powerful predictor of HAVS than the use of simple years of exposure.

Assessing past cumulative vibration exposure is part of assessing the risk of hand-arm vibration syndrome (HAVS) in workers exposed to hand-arm vibration and invariably forms part of a medical assessment of such workers. This study investigates the strength of relationships between the presence and severity of HAVS and different cumulative exposure metrics obtained from a self-reporting questionnaire.

Use of simple years of exposure is a weak predictor of HAVS or its increasing severity. The calculation of cumulative hours across all vibrating tools used is a more powerful predictor. More complex calculations based on involving likely acceleration data for specific classes of tools, either frequency weighted or not, did not offer a clear further advantage in this dataset.

The study concludes that assessing years of exposure or 'latency' in a worker should be replaced by cumulative hours of tool use. This can be readily obtained using a tool-pictogram-based self-reporting questionnaire and a simple spreadsheet calculation.

 

Source: Exposure assessment in health assessments for hand-arm vibration syndrome. Mason HJ, Poole K, Young C; Occup Med (Lond). 2011 Aug;61(5):374-6.

www.ncbi.nlm.nih.gov/pubmed/21831830

Less overall comfort of insert earplugs is associated with an increase in attenuation.

Noise-induced hearing loss is almost always preventable if properly fitted hearing protectors are worn to reduce exposure. Many individuals choose not to wear hearing protection because it may interfere with effective communication in the workplace or it may be uncomfortable. Hearing protector comfort has not received the same amount of attention as noise reduction capability. The present study was conducted to evaluate the comfort level of two different types of insert earplugs as well as the attenuation levels achieved by the earplugs. Attenuation levels were obtained with a commercially available earplug fit-test system, and the comfort ratings were obtained by questionnaire. The primary research objective was to determine whether hearing protector comfort was related to measured attenuation values. A linear mixed effects model provided evidence for an inverse relationship between comfort and attenuation. A standardized, valid, reliable, and easy-to-use multi-dimensional comfort assessment tool such as the one used in this study would benefit the hearing conservation community.

Source: Relationship between comfort and attenuation measurements for two types of earplugs. David C Byrne et al. , Noise Health 2011;13:86-92.

http://www.noiseandhealth.org/text.asp?2011/13/51/86/77193

L’indicateur tardif audio-sonométrique (ITAS) permet de suivre la perte auditive de groupes de travailleurs exposés à des bruits impulsifs.

Ce modèle exponentiel considère qu’une exposition quotidienne à des bruits impulsifs est plus nocive pour l’audition que celle à un bruit continu. En effet, certains bruits impulsifs peuvent causer des dommages irréversibles instantanément et un facteur de correction doit être ajouté au niveau moyen mesuré.

L’indicateur s’applique au suivi audiologique de travailleurs dans la cinquantaine et tient compte, entre autres, des résultats du groupe (HEG, Homogeneous Exposure Groups). Une surveillance audiométrique occasionnelle pourrait être proposée à des travailleurs exposés à des bruits impulsifs dangereux, par exemple si les valeurs médiane et moyenne de l’ITAS devenaient inférieures à 20 pour les hommes et à 23 pour les femmes (valeurs seuils indicatives, en lien avec l’état auditif d’une population de travailleurs non exposés à l’âge de la retraite).

Source: Assessment of mean auditory hazard incurred by occupational exposure to impulse noise. Forget, P. European Annals of Otorhinolaryngology, Head and Neck Diseases, Volume 128, Issue 1, January 2011, Pages 14-17. doi:10.1016/j.aforl.2010.11.003 

 

http://www.ncbi.nlm.nih.gov/pubmed/21185251

http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6KC9-51SDKTW-2-1&_cdi=461&_user=4494765&_pii=S1879729610001225&_origin=browse&_zone=rslt_list_item&_coverDate=01%2F31%2F2011&_sk=998719998&wchp=dGLbVzW-zSkWl&md5=729dba69c4868c57b17e86d0ff077ccd&ie=/sdarticle.pdf

“Speaker’s comfort and voice health in classrooms” project shows speakers adjust their voices to other acoustic cues than only loudness.

The indirect auditory feedback from one's own voice arises from sound reflections at the room boundaries or from sound reinforcement systems. The relative variations of indirect auditory feedback are quantified through room acoustic parameters such as the room gain and the voice support, rather than the reverberation time. Variation in voice level is induced by the acoustic environment as a consequence of the sidetone compensation or Lombard effect. In the range of typical rooms for speech, the variations in overall voice level that result in a constant autophonic level are on the order of 2 dB, and more than 3 dB in the 4 kHz octave band. By comparison of these curves with previous studies, it is shown that talkers use acoustic cues other than loudness to adjust their voices when speaking in different rooms. This research has been partially funded by the Swedish organization AFA Försäkring as a part of the project “Speaker's comfort and voice health in classrooms. 

Source: Equal autophonic level curves under different room acoustics conditions. David, Pelegrín-García, Oier Fuentes-Mendizábal, Jonas Brunskog, and Cheol-Ho Jeong; J.Acoust.Soc.Am., Volume 130, Issue 1, pp. 228-238 (2011); (11 pages). 

http://asadl.org/jasa/resource/1/jasman/v130/i1/p228_s1?isAuthorized=no

The standard test defined for vibration emission values of drills must be improved for usability and reproducibility.

This report assesses the standard test defined in BS EN 60745-2-1:2003 (incorporating amendment no. 1 [2007]) for usability and reproducibility. Drills, impact drills and diamond core drills were used. Test specifications for drilling into metal and impact drilling into concrete were usable. However, the standard lacked clarity about how the machines should be used when diamond core drilling. The test code appears to have good usability but poor reproducibility for drilling into metal; good usability and good reproducibility for impact drilling into concrete; and poor usability and poor reproducibility for diamond core drilling.

The test code offers potential for estimating workplace vibration and subsequent estimation of workplace vibration exposures if usability and reproducibility can be improved.

Source: RR879 - Evaluation of EN 60745 test codes: BS EN 60745-2-1 2003 (inc. amendment no.1), Particular requirements for drills and impact drills. Health and Safety Laboratory for HSE, 2011, 116 p.

http://www.hse.gov.uk/research/rrhtm/rr879.htm

http://www.hse.gov.uk/research/rrpdf/rr879.pdf

Drummers are being evaluated with signs of hand and arm vibration exposure.

The health effects of vibration exposure in drummers can result from extended periods of contact between a drummer and the vibrating surface they are exposed too. Drummers particularly are at risk since they can be exposed to vibration through multiple body parts such as the hands-stick-drum head, feet-pedals-base drum head and or hi hat or from the buttocks-seat-floor interfaces. Drummers can develop symptoms including back pain, diminished sensation and dexterity in the hands or feet, decreased grip strength, vascular injury resulting in finger blanching or “white fingers”, tendonitis or a variety of nerve entrapment neuropathies such as carpal tunnel syndrome.

Whole-body vibration levels can often be reduced by using vibration isolation or by utilizing suspension systems between the drummer and the vibrating source such as using a cushioned drum throne. Drumsticks have also evolved over the last few years with manufacturers experimenting with different stick shapes, materials as well as dipped or coating sticks for better grip. 

Source: Feeling the Vibe! Dr. Podesta; POSMI- Podesta Orthopedic and Sports Medicine Institute, March 17, 2011. 

http://podestasportsmedicine.com/articles/feeling-the-vibe/

How much noise will cause hearing loss over a lifetime?

For many years, those working in the field of industrial noise control have struggled to educate people about how much noise will cause hearing loss over a lifetime. Part of the difficulty is a result of the logarithmic nature of decibel scaling. The concept of expressing noise exposure in industrial environments without decibels is the focus of this paper. Eldred (“Sound Exposure without Decibels,” Inter-Noise 86) discusses this approach for community noise.39 ANSI Standard S3.44-1996 defines sound exposure; the units are Pascals squared seconds, or PASQUES, as noted by Eldred. This article proposes that a safe value for lifetime occupational exposure to noise be expressed in terms of PASQUES. The authors discuss the pros and cons of such an approach and offer 11.5 million PASQUES as the upper limit for a safe lifetime exposure to occupational noise. Noise exposure of workers in the industry should be expressed in PASQUES to facilitate the easy calculation of the lifetime occupational noise exposure.

 

Source: Safe Lifetime Occupational Noise Exposure – 1 LONE. Robert D. Bruce, Arno S. Bommer, Noel W. Hart, and Kimberly A. Riegel, , Sound and Vibration, June 2011.

http://www.sandv.com/downloads/1106bruc.pdf

The London 2012 Olympic and Paralympic Games: practical solutions to significantly reduce the hand arm vibration and noise hazards.

The Olympic Stadium contains 80,000 seats secured by four bolts to the concrete terrace. This work involved a lengthy and repeatable process of drilling into the concrete.A wheeled jig was developed for holding two drills originally designed to be hand held. This significantly reduced the hand arm vibration and noise hazards.The time required to complete the job was reduced as longer “trigger periods” (hours rather than minutes) were permitted and two holes were drilled simultaneously. The operator was further away from the noise source so the potential noise hazard was reduced. The wheeled jig also helped to reduce the need for lifting and carrying.

Source: The London 2012 Olympic and Paralympic Games: The health and safety learning legacy. HSE, April 15th.

 

http://www.hse.gov.uk/aboutus/london-2012-games/casestudies/three-risks-reduced.htm

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