Community noise levels

The Environmental Protection Act 1990 provides general legislation for limiting community noise as well as other pollutants. No specific limits are set but, in sections 80 and 81, the Act empowers the local authority to require a reduction in noise emission and impose conditions for noisy operations, e.g. specify a level of noise emission for a particular operation which must not be exceeded at certain given times. In certain instances they may not only set the limits but specify how they are to be met or how equipment is to be operated, referring to the relevant British Standard. 

Criteria that can be used to assess the reasonableness of complaints and for seffing noise limits for design purposes are contained in a British Standard 4142 1997 which in itself does not recommend specific limits, but predicts the likelihood of complaints. These predictions are based on measured or predicted noise levels, corrections for the noise characteristic and measured or notional backgrmmd noise levels. 

The following procedure is t)qjical for evaluating the existing neighbourhood noise situation  

1 Identify critical areas outside the factory by taking measurements over a reference period, as defined in the standard. 

2 Note which equipment in the factory is operating during the measurement period to help evaluate the major sources. 

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The actual noise levels produced by HVAC systems can var) considerably, and it is not possible to generalize the problems that may be encountered. From a safety point of view, it is advisable to start hearing conservation programs for workers. Permanent hearing damage will result when the noise levels exceed 80 dB(A) for a given time period. Whenever possible, it is desirable to control noise pressure levels to meet the requirements of speech communication in this case noise should not exceed 65-70 dB(A). 

Noise—with the assessment of permissible noise levels lor communication and warning signals and the development of technology for noise abatement and control. Developments have included an audio dosimeter to replace conventional sound-level meters, discriminating earmuffs, and a noise control muffler system to reduce pneumatic drill noise. 

There are three places noise can be reduced at the source, in the path between the source and personnel, and on the persormel [16]. The ideal place to stop noise is at the source. There are several techniques used in the flare and burner industry to reduce the noise at the source, however, these techniques are limited. Ear protection can reduce noise relative to the personnel using it, unfortunately a plant operator cannot ask a surrounding community or workers within a nearby office building to wear ear protection when the noise levels become a problem. The most common method for reducing noise is in fhe pafh befween the source and personnel using silencers, plenums, and mufflers. The purpose of fhis section is to discuss fhe most common and effective noise abatement techniques utilized in the flare and burner industry. 

Noise is unwanted sound. It is a form of vibration conducted through solids, liquids, or gases. Noise can startle, annoy, and disrupt concentration, sleep, or relaxation. It can interrupt communication and interfere with job performance and safety, and it can lead to hearing loss and circulatory problems. Noise levels greater than 90 dBA should be avoided. Workers must wear hearing protection if workplace noise levels are greater than 90 dBA. 

Instead of employing a single electrode, an array of electrodes [67] or an inter-digitated electrode [68] may be used to study electrochemical systems. Similar to advantages achieved by variations in electrode geometry, the use of several communicating electrodes poised at the same or different potentials opens up new possibilities for the study of the properties or the kinetics of chemical systems. An interesting development is the random assemblies of microelectrodes (RAM) (see Fig. II. 1.14), which promises the experimental timescale of microelectrodes but with considerably improved current-to-noise levels [69]. 

An established noise level that is intended to permit adequate speech communications for a given area and is also used to minimize human annoyance. 

The National Institute of Occupational Safety and Health (NIOSH) estimates that 90 percent of noise-exposed workers in the United States are exposed to 95 dB of TWA (time-weighted average), meaning they need only 10 dB of protection or attenuation. Workers who are overprotected from the noise exposure may feel they may not hear communications properly and might not be safe. There are no U.S. standards for overprotection for noise exposure however, European guidance, EN 458, states that workers attenuated noise levels should be no lower than 75-84 dB for ideal communication in noise (Table N.2). 

Noise measurement can be based on either sound power level or sound pressure level . Sound power level is the total sound power emitted from a body and is used in measurement of community noise, whereas sound pressure level is the level of noise at the point of measurement and is the more common measurement of noise level at work. 

Research demonstrates that construction workers are regularly overexposed to noise. The National Institute for Occupational Safety and Health (NIOSH) estimates that 421,000 construction workers are exposed to noise above 85 dBA. According to NIOSH, 15 percent of workers exposed to noise levels of 85 dBA or higher will develop a hearing impairment. In addition to hearing loss, other risks of noise exposure include impaired balance and falls, h5 er-tension, elevated blood pressure, reduced communication and effectiveness of audible warning devices (such as vehicle back-up alarms). 

Spills and/or fumes have high impact on equipment, people or services High noise levels make communication difficult... 

The first four sections of this chapter explain what noise is, how it is defined and the theory and practice behind the measurement of noise levels. The rest outlines the way the ear works and the damage that can occur to cause noise-induced hearing loss. Some of the problems created by vibrations are considered. Reference is made to the guidelines, recommendations and legislation that exist and which are aimed at limiting the harmful effects of noise in the workplace, and the nuisance effect on the community. 

The sound power level is used to calculate the reverberant and pressure level and community noise. 

In general the noise level in the community or inside a factory will vary with time. The equivalent noise level is defined as the notional steady noise level which, over a given period of time, would deliver the same amount of sound energy as the fluctuating level. Thus to maintain the Leg when SPL is doubled, exposure time must be halved (Table 20.2). The equivalent noise level concept forms the basis of the exposure criteria used in the Noise at Work Regulations 1989 which calls it daily personal noise exposure (Lep,ci). Where the fluctuation is not well defined the calculations can be done electronically using a dosimeter or statistical analyser. Transient noises also require statistical analysis and those measurements often required are ... 

Noise is commonly defined as any unwanted sound. Noise literally surrounds us every day and is with us just about everywhere we go however, the noise we are concerned with here is that produced by industrial processes. Excessive amounts of noise in the work environment (and outside of it) cause many problems for workers, including increased stress levels, interference with communication, disrupted concentration, and, most importantly, varying degrees of hearing loss. Exposure to high noise levels also adversely affects job performance and increases accident rates. 

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