The equivalent noise levels, Leq can also be calculated as (5)
Leq = L50 + (L10 - L90)2 / 60
Noise Climate (NC): It is the range over which the sound levels are fluctuating in an
interval of time (5)
NC = L10 - L90
Hence, Leq in the above example is -
Leq = 69 + (76 - 64)2 /60 = 71.4 dB.
and noise climate, NC = 76 - 64 = 12 dB/sampling time.