Recreational activities that can put you at risk for NIHL include target shooting and hunting, snowmobile riding, listening to MP3 players at high volume through earbuds or headphones, playing in a band, and attending loud concerts. Harmful noises at home may come from sources including lawnmowers, leaf blowers, and woodworking tools.
Big Room Tools Vol 2 Noise Factory
In 1981, OSHA implemented new requirements to protect all workers in general industry (e.g. the manufacturing and the service sectors) for employers to implement a Hearing Conservation Program where workers are exposed to a time weighted average noise level of 85 dBA or higher over an 8 hour work shift. Hearing Conservation Programs require employers to measure noise levels, provide free annual hearing exams and free hearing protection, provide training, and conduct evaluations of the adequacy of the hearing protectors in use unless changes to tools, equipment and schedules are made so that they are less noisy and worker exposure to noise is less than the 85 dBA.
Far from the noise source--unless the boundaries are very absorbing--the reflected sound dominates. This region is called the reverberant field. If the sound pressure levels in a reverberant field are uniform throughout the room, and the sound waves travel in all directions with equal probability, the sound is said to be diffuse.
Impulsive/impact noise is typically generated by the rapid release of compressed gases (impulse) or the collision of solid objects (impact) and is defined as the instantaneous change in sound pressure over a short period of time. Examples may include the impact of two metal objects, or the shooting of a firearm. The standard states that exposure to impulsive or impact noise should not exceed a 140-dB peak sound pressure level. Impulsive or impact noises are considered to be much more harmful to hearing than continuous noises. In construction, most of the 500,000 workers who are exposed to hazardous noise levels are also exposed to impulsive and impact noise sources on worksites. Impulsive and impact noise is typified by a sound that rapidly rises to a sharp peak and then quickly fades. Both are transient noises of brief duration and high intensity. The sound may or may not have a "ringing" quality (such as a striking a hammer on a metal plate or a gunshot in a reverberant room). Impulsive noise can be repetitive or a single event (like a sonic boom); if impulses occur in very rapid succession (such as with some jack hammers), it is not described as impulsive or impact noise.
The hierarchy of controls for noise can be summarized as: 1) eliminate or minimize noise exposure by installing equipment that produces less noise (e.g., buy-quiet programs), 2) prevent or contain the escape of noise at its source (engineering controls), 3) control exposure by changing work schedules to reduce the amount of time any one worker spends in the high noise area (administrative controls) or by changing practices such as distancing from noise-producing equipment (work practice controls), and 4) control the exposure with hearing protection. This hierarchy highlights the principle that the best prevention strategy is to eliminate exposure to hazards that can lead to hearing loss. Corporations that have started buy-quiet programs are moving toward workplaces where no harmful noise will exist. Many companies are automating equipment or setting up procedures that can be managed by workers from a quiet control room free from harmful noise. When it is not possible to eliminate the noise hazard or relocate the worker to a safe area, the worker must be protected with PPE.
For compressed air systems that perform a service or specific task, such as ejecting parts or blowing off debris, a number of devices are available for retrofit at the point of discharge. Another typical application for compressed air is in blow-off guns or air wands. These tools come in a variety of sizes and shapes, and depending on the velocity of the air and the surface area they contact, can generate noise levels of 90 dBA to 115 dBA, depending on the velocity of the air and the surface area they contact. It is recommended that the Noise and Vibration Control Product Manufacturer Guide be consulted for a list of available suppliers. Usually, the manufacturer websites provide sufficient information and self-help guidance to enable selection of the most appropriate device for retrofit.
Assuming that all available options for controlling noise at the source have been exhausted, the next step in the noise-control hierarchy is to determine ways to treat the sound transmission path. Typical path treatments include adding sound-absorption materials to the room or equipment surfaces, installing sound transmission loss materials between the source and receiver(s), using acoustical enclosures or barriers, or any combination of these treatments. A description of each treatment option follows.
Keep in mind that adding sound absorption to decrease the reflected or reverberant noise in a room will do nothing to reduce the acoustical energy propagating by direct line of sight from the source. Therefore, it is helpful for the user to estimate what portion of a worker's noise exposure comes from the direct sound field and what percentage results from reverberant sound. When reverberant noise is a major contributor to a worker's daily noise exposure, then adding sound-absorbing materials may be beneficial.
A user must understand and apply the principles of room acoustics when adding sound-absorbing materials to the walls and ceiling to reduce the noise levels throughout the room. If a user installs sound absorption in a room without putting any science behind the decision, then the likelihood of success will be tenuous at best.
Sound TL materials are used to block or attenuate noise propagating through a structure, such as the walls of an enclosure or room. These materials are typically heavy and dense, with poor sound transmission properties. Common applications include barriers, enclosure panels, windows, doors, and building materials for room construction.
Enclosures, or personnel shelters, can provide a cost-effective means for lowering worker noise exposure instead of lowering equipment noise levels. Control booths or rooms are commercially available from a number of manufacturers, many of which are listed in the Noise and Vibration Control Product Manufacturer Guide (see Section VII-Resources). The cost for these units typically ranges from $5,000 to $35,000 depending on the size and sophistication of their design and their need for electronic controls, video monitoring, number of observation windows, and other features. Any of the vendors listed in the manufacturer's guide can provide a cost estimate upon request. As a minimum requirement, all control rooms should maintain an interior sound level lower than 80 dBA, which will minimize worker noise exposure. Should there be a need to communicate with workers inside a control room, however, then a better design criterion would be to limit sound levels to 60 dBA or less.
Another administrative control involves redesigning workers' work schedules to reduce the amount of time that any one worker is located in the hazard area. To increase the effectiveness of this control, employers can also ensure that noise exposure is kept to a minimum in nonproduction areas frequented by workers. Select quiet areas to use as lunch rooms and work break rooms. If these areas must be near the production line, they should be acoustically treated (as describe elsewhere in this section) to minimize background noise levels. Employers can also increase the distance between workers and the noise source. This can be accomplished in many ways. For example, television monitors allow the worker to monitor a job or process at a safe distance from the noise-producing area; a boom-mounted drill increases the distance from the noise source to the worker. Additionally, noisy jobs on construction sites might be scheduled when other trades will not be affected.
HPDs are rated to indicate the extent to which they reduce worker noise exposure. New technologies have been developed to test the effectiveness of earplugs and could eventually change the way hearing protection is rated. Although not required by the OSHA noise standard, several tools are available to employers that allow fit testing of HPDs, similar to respirator fit testing. HPD fit-testing enables employers to determine how well individual HPDs actually protect, and is also especially useful when workers have experienced an STS. See Appendix F for information on NRR methods, ratings, and requirements.
OSHA's CTC is qualified to perform periodic (annual) calibration for the noise-monitoring instruments and acoustical calibrators commonly issued to CSHOs. CTC also coordinates periodic factory calibration of any OSHA-owned noise-monitoring instruments that it does not service directly.
Other types of SLMs also exist but do not meet ANSI requirements for the Type 2 or Type 1 designation. These meters, which are often modestly priced, can be useful pre-screening tools for employers seeking to identify noisy locations and track improvements during noise reduction efforts. They cannot, however, be used to document compliance with OSHA standards; only properly calibrated Type 2 or Type 1 meters can serve that purpose. For example, SLM applications are available for some smartphones. Such an application can give a rough estimate of the noise level in a particular location but may not be used to document compliance with OSHA standards.
The HRT maintains multipurpose Type I sound level meters and octave band analyzers, which can also be operated as sound intensity analyzers for identifying noise sources and determining engineering controls. In addition, this equipment includes a building acoustics system for measuring noise decay and determining the reverberation characteristics for a given room. Based on the noise decay data, calculations can be performed to estimate potential noise reduction if absorptive materials are applied to room surfaces, such as the walls and ceiling. 2ff7e9595c
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