Chinese researchers have developed a novel phased-array sonar. Using a semiconductor amplifier to generate signals at higher power levels allows the device to be made much more compact, compared to previous phased-array systems.

By superimposing the sonar waves and focusing them, researchers produced sound waves over 238 decibels, akin to the sound volume of the Saturn V rocket used in the Apollo missions. At these frequencies, the beams would penetrate the hulls of submarines, resulting in nausea, blurred vision, and tissue damage to sub crews.

Applications of this technology would largely be non-military, however. China is developing fleets of unmanned submersible vehicles to survey the ocean floors, and to extract raw materials from the seabeds beneath. These missions, too, require the most powerful sonar systems.

Resources and links:

China's new high-power sonar can penetrate outer shells of submarines
https://interestingengineering.com/in...

Low-cost, technologically advanced SONAR system could give China maritime power edge over US unmanned smart weapons
https://www.scmp.com/news/china/scien...

CBO: Navy’s Next Nuclear Attack Submarine Could Cost $5.5B a Hull
https://news.usni.org/2019/10/10/cbo-...