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

many experiments with non-steady-state noise have shown that the level of annoyance caused by fluctuating noise is greater than that of steady-state noise of equal energy, and is related to the change rate and average intensity of noise exposure. experiments have proven that adding a quantity indicating the amplitude of noise change to 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

in the formula:

k——constant, the value is 2.56 for traffic and aircraft noise;

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

in the formula: leq is the equivalent sound level; σ is the standard deviation.

if the noise obeys gaussian distribution, then lnp=l50+d+d^2/60

in the formula: d=l10-l90; l10 is the a sound level that occurs more than 10% of the time or times within the measurement time, and so on.

noise pollution level (lnp)

noise pollution level (lnp) calculation = l₅₀+L₁₀－L₉₀+（L₁₀－

L₉₀)²/60

here

npl = noise pollution level

L₁₀ = 10% above sound level a time

L₅₀ = more than 50% of a sound level time

L₉₀ = more than 90% of a sound level time