While Russia and China have made significant progress in creating low-noise submarines, the United States is trying to compensate for the lagging behind by developing new means of detecting them.
For example, in the framework of the DARPA-funded PALS program - Persistent Aquatic Living Sensors, research is underway to adapt shrimp clicks to detect enemy submarines.
As project manager Alison Laferrier of defense contractor Raytheon BBN Technologies said in an interview with Discover Magazine:
The idea is to use our sensors to record the sounds emitted by shrimp after they are reflected from underwater objects.
Among the marine fauna, shrimp are considered one of the noisiest - they are able to click their claws, making sounds with a volume of up to 190 decibels. Since these animals are very common, it becomes possible to use their clicks as a living sound generator to detect enemy submarines and underwater drones.
To create a full-fledged detection system, DARPA specialists will have to create a network of listening devices capable of identifying reflected signals. They are supposed to be installed on special drones plying in areas where submarines can be found.
If successful in the first phase of the program, PALS will be sent to the Virgin Islands later this year to record and analyze ocean noise.