So do they not have propellers? I believe that props may give away a little acoustic signature even with cruciform vortex dissipaters.
I mean no Gyroscope?? No bearings in the gyro?
Define very very quiet.
Information on the noise level of submarines is mostly secret.
So quiet that they’ve been undetectable by US and Russian subs.
So quiet that the Russian navy has ceased encroaching in Norwegian littoral waters.
So quiet that the US has contracted one of these subs to provide OPFOR and training.
So quiet that the US Navy has considered buying one of these subs for evaluation and littoral work.
THAT quiet.
Especially compared to a nuclear sub.