Exactly. If the mission was set up such that the Kilo didn’t need to run on diesel during the engagement window, he’s potentially got an advantage.
To get some idea of how quiet a diesel-electric boat is when operating on batteries, go out to your garage, open your car’s hood, and listen to the battery.
The best new subs out there are the diesels being manufactured in Europe. Very, very quiet.
Or spend a couple of years as a Submarine Sonar Officer. ;-)
There is still the shaft turning, and ventilation, plus some other mechanical operations to maintain depth so it’s not quite that quiet.
Nonetheless, it’s all buried, oftentimes, under a thick rubber skin or some other soundproofing.
As you suggest, much more difficult to detect via noise.
It's not the batteries that make noise. Nuclear submarines have batteries too by the way. The battery bank on a nuclear submarine is about the size of a tractor trailer.
They can provide propulsion on battery power alone, just like a diesel submarine. You can shut down the reactor and steam plants, run off the batteries, and hell even go to snorkel depth to recharge the batteries with the diesel. But you're not going to be able to go very fast.
But the LA boats are old. I read that the follow up class of Seawolf boats were supposedly quieter at 20 knots than the LA boats were tied to the pier with the reactor shut down. Not sure if that's possible, but that's what I read. (They only made three Seawolf class subs and are now on the Virginia class.)
Another thing I read is that Ohio class SSBNs, which are only slightly less old than the LA class SSNs, are quieter than the background noise of the ocean. Supposedly they are found by looking for "holes" in the noise. Again, not sure if that's possible or a bunch of BS.