Based on the classic B&K curve: https://www.bksv.com/media/doc/17-197.pdf
Hz  dB
20  0.00
31  0.50
63  0.75
125  0.40
250  -0.25
500  -1.00
1000  -1.75
2000  -2.50
4000  -3.40
8000  -4.45
16000  -5.45
20000  -5.80