If you look at the typhoon and the Oscar two things stand out
Typhoon has a tongue between the propellers and her propellers are also shrouded, this makes her quiet and solves one issue the Oscar has.
The Oscar doesn't have these things which creates a resonance sound between the screws and an area of disturbed water which make the Oscar louder and more distinct thus easier to detect.
Apparently the Oscar is quite easy to detect and classify when at speed as the sound is so unique.
As for who pays if they get it wrong I'm sure Putin has his ways and means
|