Diesel-electric submarines are generally quieter than nuclear...

Diesel-electric submarines are generally quieter than nuclear submarines when running on battery power.[1][2] This is because nuclear submarines require systems like pumps and coolant to operate the nuclear reactor, which generates noise.[1] In contrast, diesel-electric submarines running on batteries have minimal noise from components like shaft bearings and the propeller.[1]

While nuclear submarines are very quiet overall, they cannot match the extreme stealth of modern diesel-electric submarines, especially air-independent propulsion (AIP) submarines that can stay submerged for weeks without snorkeling.[2] The ability of AIP submarines to operate almost silently has allowed them to "sink" nuclear submarines and surface ships in exercises on multiple occasions.[1][3]

However, nuclear submarines have significantly greater endurance and speed compared to diesel-electric boats.[2][4] So while diesel-electric submarines are stealthier for coastal operations, nuclear propulsion provides critical advantages for long-range deployments and high speeds.[4][5]

Sources
[1] There's a Case for Diesels | Proceedings - U.S. Naval Institute https://www.usni.org/magazines/proceedings/2018/june/theres-case-diesels
[2] Did Sweden Make America's Nuclear Submarines Obsolete? https://nationalinterest.org/blog/t...ke-americas-nuclear-submarines-obsolete-18908
[3] Are Diesel-Powered Submarines Better Than America's Nuclear ... https://observer.com/2019/10/diesel-powered-submarines-vs-american-nuclear-fleet/
[4] Diesel-Electric vs Nuclear : r/submarines - Reddit https://www.reddit.com/r/submarines/comments/a5tah4/dieselelectric_vs_nuclear/
[5] Nuclear versus diesel-electric: the case for conventional submarines ... https://www.aspistrategist.org.au/nuclear-versus-diesel-electric-case-conventional-submarines-ran/