Discussion about the noise rating number

The evaluation methodology of Noise Rating Curve in ISO is analyzed.The calculation of Noi-se Rating Number(NR) is programmed utilizing Visual Basic and the constant a,together with b,is ex-panded to 31.5Hz(a=55.4,b=0.681).Two methods of calculation the NR are proposed.One of them is to seek the maximum of each NR which is calculated in each band separately,and this method takes shorter time to make evalustion.To meet the requirement of improving accuracy,the use of octave is no longer satisfied.So the constants a,together with b,for every 1/3 octave wihtin 31.5Hz and 8000Hz are expanded too.And the noise rating curver are simulated by numerical analysis method.