The calculated noise level based on sampling the varying noise climate and expressing the result as a percentage of time above the chosen statistical level. For example, the LN10% is the noise level exceeded for 10% of the measured time interval. The samples of the noise are sorted into a distribution table at fixed dB intervals and the statistics are calculated from the cumulative distribution curve that is produced. The LN90% is often used to describe the background noise level in noise measurements. The LN50% describes the median noise level with half the samples being above and half the samples being below this level. Because of the logarithmic nature of noise measurements with the decibel scale the LN50% is not the same as the average noise level.