For your reference:  The higher the number of decibels (dBs), the greater the shielding effectiveness:
10 dB = blocks 90 %
20 dB = blocks 99 %
30 dB = blocks 99.9 %
40 dB = blocks 99.99 %
50 dB = blocks 99.999 %
60 dB = blocks 99.9999%