The exact center frequency fm is obtained by the following equation.

fm= G^x/3 ＊1000
G =10^3/10 =1.99526
x is any positive, negative, or zero integer.

Example

x=-10　 fm =  1.99526^-10/3 ＊1000 = 100
x=-1　　fm =  1.99526^-1/3 ＊1000= 794.33
x=０　　fm =  1.99526^0/3 ＊1000 = 1000
x=1　   fm =  1.99526^1/3 ＊ 1000 = 1258.9
x=5　  fm =  1.99526^5/3 ＊ 1000 = 3162.3
The lower range frequency of each band is obtained.  fL = fm/2^1/6　
The upper range frequency of each band is obtained.  fU = fm*2^1/6

fm=1000　fL = 890.9,　fU = 1122.46

Please refer to “What is sound level meter” in Ono Sokki’s Technical Report.
https://www.onosokki.co.jp/English/hp_e/whats_new/SV_rpt/SV_7/sv7_11.htm#mark11