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Optimal suspension characteristics for the reduction of the vibrations transmitted by a small pneumatic hammer.
This paper describes a systematic approach for optimizing suspension systems to reduce the vibrations transmitted to workers by hand-held power tools. The optimization is based on modeling tool-operator interactions using a mobility scheme. The tool is modeled as a vibration generator, and its internal impedance is included. A hand–arm impedance matrix is used to model the operator upper limbs. The mobility model is used to identify the optimal suspension characteristics, which in our study were the set of parameters that minimizes the frequency-weighted acceleration at the hand–tool...
A bit isolator and a chuck isolator reduce the noise radiated by the drill steel and chuck
Among underground coal miners, hearing loss remains one of the most common occupational illnesses. In response to this problem, the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) conducts research to reduce the noise emission of underground coal-mining equipment, an example of which is a roof bolting machine. Field studies show that, on average, drilling noise is the most significant contributor to a roof bolting machine operator’s noise exposure. NIOSH OMSHR has determined that the drill steel and chuck are the dominant sources...
Models of the substructures of the hand-arm system can be used to help design and analyze palm and orbital sanders
Prolonged, intensive exposure to vibrations from palm and orbital sanders could cause finger disorders. They are associated with the biodynamic responses of the fingers. This study confirmed that the distributed hand responses generally varied with locations on each finger, vibration frequencies, and applied hand force. This study enhanced the understanding of the biodynamic responses of the fingers and hand exposed to vibrations on a contact surface with a large effective radius such as that found on palm and orbital sanders. These results are useful for developing hand and finger models required...
Pneumatic nail guns produce loud “impulse” noise peaks in a range from 109 to 136 dBA.
Pneumatic nail guns produce short (less than a tenth of a second in du­ration) but loud “impulse” noise peaks: one from driving the nail and one from exhausting the air. Most nail gun manufacturers recommend that users wear hearing protection when operating a nailer. Available information indicates that nail gun noise can vary depending on the gun, the work piece, air pressure, and the work setting. The type of trigger system does not appear to affect the noise level. Peak noise emission levels for several nailers ranged from 109 to 136 dBA. These loud short bursts can contribute...
A variety of problem-solving noise and vibration tools are at the engineer’s disposal to improve the product development process for noise and vibration
This article captures the strategies involved in addressing a system-level sound and vibration concern late in the design cycle . A noise and vibration problem often shows itself very late in the design cycle or even after the product has been released. Noise and vibration issues can generally be separated into two categories: a problem caused by lack of compliance to a regulation or specification; or the product does not perform adequately in-situ , causing sound or vibration quality (SVQ) concerns. Measurements must be made on the product during the appropriate operating conditions, and focus...

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