[MadMike]

A certain three letter agency has declassified sound signatures for a wide range of Soviet submarines. Original date of the document is 1969.

Operating levels considered "quiet" were 30-35 decibels in the low frequency band, and 20-25 db in the sonar band.

For the Victor class, these levels were-

Low freq, at 5 knots- 55-60db. At 14 knots- 65db

Sonar band, at 5 knots- 16db. At 14 knots- 22 db.

Yours, Mike