Well, you may still hear “th” and “s”.
In laymen terms, normal hearing from (zero to 120 dB) for a total of 120 dB is compressed and relocated to where you can hear it even with your hearing loss. It gets compressed and amplified into the new range where you can hear, in this example the target range of (20 to 105) or 85dB in total.
So, you can still hear “th” and “s” because it will be amplified/louder. Though the downside is, you won't have the full range (0 to 120 dB) anymore because it has been cut down to a range of (20 to 105 dB) or 85dB in total.
A bigger downside (for someone with really profound hearing loss) is that you may run out of space to accept the new hearing range because the top of the target range is limited and not infinite.
