Yes it can, Meap (Ex-submariner here
. Mind you I know more about the electronics then anything else
.).
More then just the machinery or prop design of the submarine goes into its "noise" though. The echoes made by the submarines wave-generation against the local topography (underwater mountains, trenches, etc.), the presence of natural emitters (sea life, geological movements) and, the ocean's temperature or the water's depth, the "noise" a particular item makes will vary depending on the relevance or presence of a number of factors.
Each of these emitters can also alter the EM signature of a submarine and make magnetic detection more difficult. I touched on this in a different thread:
https://defence.pk/threads/so-you-want-to-detect-a-submarine.362636/
As for what you can do with that acoustic signature... identification is the most common use. If you know it's "noise" for a given set of parameters, a submarine operating in the straight of Horuz (where we can accurately ascertain the relevant metrics of the local waters - such as a lack of undersea features, depth and average temp) can be easily identified based on store metrics, including acoustic, but also including magnetic, size and possible EM signatures (the latter dissipates quickly in water as does IR). We'd know an Iranian Fateh class from a Pakistani Agosta90 b and that from one of our Virginia's saying hello to regional undersea metallic fauna in a cylindrical shape and emitting EM signals... cables for short
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Based mostly around their noise for a given set of parameters, which will change as the submarines operates in different areas and waters.
Can you also use this data to help a weapon discriminate against background noise too? Say upload it to a torpedo to have it guide itself towards an enemy based on their emissions? Yes, but cable guidance is still the preferred option for submarine launched torpedoes as it's low-probability of intercept.
Quick strike torpedoes, often referred to as light weight, typically will use active sonar or acoustic homing.
One such system that uses noise to distinguish between hostile targets and friendlies, and only attack those matching a given signature, is the US Navy's Mark 60 CAPTOR mine:
The Mark 60 CAPTOR is a fancy piece of kit known as an Encapsulated Torpedo that houses one of the Mk 46 torpedoes in the above photo (two above actually).
It uses passive sonar and discrimination software to identify the noise signature of passing vessels. When it detects something that isn't friendly, the Mk 46 torpedo is launched to attack the target. It quickly switches into active sonar to be able to trace a moving, possibly evading target.
Sonar emits or receives sound waves and maps an area based on the return:
Acoustic homing relies on microphones to sweep for "unnatural noises" or noises of interest. If a certain noise profile is uploaded, a torpedo, as shown with the CAPTOR mine, will attempt to locate and track it by using a collection of microphones to ascertain where the noise is noisiest.
Active Acoustic Homing is also known as active sonar, so there's a bit of an overlap too between the two types of guidance. Active homing does not require you to know the target's signature, it'll find it itself.
So in short, you can register their "noise" but more then just the sound the submarine's machinery, or people or operations make matters. So to do natural causes, like ocean depth or temperature or man-made disturbances such as underwater cables or surface ships, all of which will mask or alter the submarine's noise emissions.
Once you have that info for a given area (one where you know the depth, average temp, underwater topography, etc.) you can use that info for identification or attack, depending on your inclination.
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Any questions?
They're still a credible threat in their given area. They are not to be mocked except by the ignorant or arrogant.
Besides, Iran also has a few Kilos and no one dares mock their credibility.
Iran doesn't have the flashiest or most modern (or largest) navy in the world and the IRGC adds only a bit to its overall capabilities, but having outdated designs doesn't mean they can't do damage. We, the USN (I work for them so, yes, we) respect what the Iranian Navy has.
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