Based on the classic B&K curve: https://www.bksv.com/media/doc/17-197.pdf
Hz  dB
20  0.00
25  0.25
32  0.50
40  0.63
50  0.75
63  0.75
80  0.70
100  0.60
125  0.40
160  0.20
200  0.00
250  -0.25
315  -0.50
400  -0.75
500  -1.00
630  -1.25
800  -1.50
1000  -1.75
1250  -2.00
1600  -2.25
2000  -2.50
2500  -2.80
3150  -3.10
4000  -3.40
5000  -3.75
6300  -4.10
8000  -4.45
10000  -4.80
12500  -5.13
16000  -5.45
20000  -5.80