Noise peak action level

The third defined level is a peak action level of 140dB(A) or 200 Pa of pressure which is likely to be linked to the use of cartridge-operated tools, shooting guns or similar loud explosive noises. This action level is likely to be most important where workers are subjected to a small number of loud impulses during an otherwise quiet day. 

New regulations introduced in 2006 reduce the first action level to 80dB(A) and the second level to 85dB(A) with a peak action level of 98dB(A) or 140 Pa of pressure. Every employer must make a noise assessment and provide workers with information about the risks to hearing if the noise level approaches the first action level. They must do all that is reasonably practicable to control the noise exposure of their employees and clearly mark ear protection zones. Employees must wear personal ear protection while in such a zone. 

The exposure criterion used in these Regulations is the equivalent noise level over the working day or shift (Lep ci). Three actions levels are identified, the first action level is an lEP,d of 85 dB(A) when an employee has to be provided with hearing protection on request (Reg. 8(1)), the second action level is an exposure of 90dB(A) or more when hearing protection must be provided and worn (Reg. 8(2)) and the third level is the peak action level when a peak sound pressure level of 200 pascals occurs when hearing protection must, again, be provided and worn. 

Regulation 4 requires that every employer shall, when any of his employees is likely to be exposed to the first action level or above, or to the peak action level or above, ensure that a competent person makes a noise assessment which is adequate for the purposes ... 

Where the noise exposure exceeds the second action level or the peak action level, employers must in addition to the requirements detailed above ... 

The source of noise and vibration on demolition sites will normally be caused by the use of plant and equipment, falling debris and/or explosives. Compressors, pneumatic hand-held tools, front end loaders, excavators and other equipment can create noise levels of more than the lower exposure action level of 80dB(A) and may at times create peak noise levels of more than 137 dB(C) the lower peak sound pressure action value. A noise assessment will be required and workers given ear defenders. 

When the noise levels on the positive peaks exceed a specified design level, Hmiting action is produced by driving the FET out of the active region into saturation. To help ensure saturation, the supply voltage is... 

If upper and lower action values, for daily or weekly exposure levels or sound pressure peak, are reached or exceeded, appropriate preventive measures should be adopted in order to reduce noise levels and enhance the safety of workers. 

These relations can be seen in action Fig. 13 below, where the band-passed peak velocity amplitudes of earthquakes are compared to the clip level and noise floor of a seismometer. 

---