Blasting Noise and Vibration

Many lime kiln installations incorporate a screen to remove fines produced by breakage before charging the limestone into the kiln. When the particle size of the stone is large, a metal screen deck can produce high sound levels. Use of rubber decking reduces the problem. 

Guidance for rating industrial noise and assessing the likelihood of complaint is given in [33.10]. Pure tones cease to be noticeable when they are 10 dB or more below the general sound level. 

The emission of noise from primary blasting is best limited by good blasting practices (see section 4.3.4). The use of down-the-hole initiation coupled with adequate stemming, helps to contain the gases produced by the explosion and to reduce sound levels. TTie use of unconfined explosive, or explosive cord, should be avoided wherever possible. 

The sound level experienced at a distance from an explosion can be heavily depended on transient atmospheric conditions (e.g. temperature inversions, wind shear, and even gusts of wind). The low frequency air pressure from a blast can cause vibration in buildings, in addition to its startle effect. Such vibration can give rise to concern about possible building damage at relatively low over-pressure levels. The subject has been investigated in depth by the United States Bureau of Mines, whose conclusions are summarised in [33.11]. 

Guidance has also been published relating to human response to vibration in buildings [33.12]. 

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