40 dB sounds twice as loud as 30 dB and 8 times as loud as 10 dB (10 to 20 to 30 to 40 = 2 x 2 x 2 = 8). Normal hearing ranges from 0 to 20 dB in all frequencies. From here on, the assumption is that you have a sensorineural hearing loss (that you have nerve damage to the inner ear)