Sonar research refers to the scientific study and development of sonar (Sound Navigation and Ranging) systems and technologies. It involves investigating how sound waves travel through water (or other media), how they interact with objects, and how those sound signals can be interpreted to detect, locate, and identify objects such as submarines, marine life, or underwater terrain. This research can include improving sonar hardware, signal processing methods, and applications in fields like oceanography, naval defense, and underwater robotics.