The noise pollution level (LNP) is an evaluation of noise given by combining the influence of both the energy average and the variation characteristics (expressed as standard deviation). The noise pollution level (LNP) is an evaluation of noise given by combining the influence of both the energy average and the variation characteristics (expressed as standard deviation).

Many practices of non-steady-state noise have shown that the degree of annoyance caused by fluctuating noise is greater than that of steady-state noise of equal energy, and is related to the rate of change of noise exposure and the average intensity. Experiments have shown that adding a quantity representing the amplitude of noise change on the basis of the equivalent continuous sound level can better reflect the actual degree of pollution. It is more appropriate to use this noise pollution level to evaluate aviation or road traffic noise. Therefore, the noise pollution level (LNP) formula is:

LNP = Leq + Kσ

Where:

K is a constant, which is 2.56 for traffic and aircraft noise;

σ —— standard deviation of instantaneous sound level during the measurement process.

Where: Leq is the equivalent sound level; σ is the standard deviation.

If the noise follows a Gaussian distribution, then LNP=L50+d+d^2/60

In the formula: d=L10-L90; L10 is the sound level A that occurs more than 10% of the time or frequency during the measurement time, and the rest are similar.

Noise Pollution Level (LNP)

Noise Pollution Level (LNP) Calculation = L₅₀+L₁₀－L₉₀+（L₁₀－

L₉₀)²/60

here

NPL = Noise Pollution Level

L₁₀ = 10% of the time above sound level A

L₅₀ = A sound level time above 50%

L₉₀ = A sound level time above 90%