For impulses with a peak sound-pressure level (SPL) under 140 dB, ISO1999 provides a standardized approach using total A-weighted energy. Some countries may use a small correction factor in addition. At the present time, most approaches for evaluating impulse noise above 140 dB use the peak sound-pressure level and some estimate of duration of the waveform. There is no recognized standard method for evaluating such impulses. Furthermore, the problem with this peak and duration method is that some waveforms with the same peak and duration parameters are far more hazardous than others. As will be discussed, each major country is using a slightly different approach. However, there is a NATO working group investigating a common approach. A part of this approach may be to use some type of weighted energy.