Sonobuoys that transmit an acoustic pulse and detect a resulting echo are classified as what type of sonobuoy?

The classification of sonobuoys that transmit an acoustic pulse and detect the resulting echo falls under active sonobuoys. Active sonobuoys work by emitting a sound signal into the water and then listening for any echoes that return after interacting with underwater objects, such as submarines or other marine life. This method allows for the detection and identification of objects based on the return time and characteristics of the echoes, thus providing critical information for anti-submarine warfare and other naval operations.

In contrast, passive sonobuoys do not transmit sound; instead, they only listen for sounds produced by submarines or other underwater sources without generating their own signals. Telemetry sonobuoys are designed to transmit data regarding their status or environmental conditions rather than engage in echolocation. Reconnaissance sonobuoys serve a different function as well, often focused on surveillance over acoustic gathering. Therefore, the defining characteristic of transmitting a pulse and detecting echoes categorizes the sonobuoys as active.