Noise indication (xx.x dB) of submarines

[Knightpawn]

Can someone please explain what this indication denotes? Is it dBs measured at the point of the sound source? Is it an absolute number or is dBs above the ocean's ambient noise? I am trying to understand how is this indication related to the Signature Type mentioned on the unit details of each submarine

[blu3s]

It is source level; dB is never an absolute number, since by definition it is a ratio that compares one level to another (in the case of sound pressure level (SPL) in water, referred to 1 µPa).

If I remember correctly, the signature type in the database refers to the submarine operating at maximum speed.