What are DB-15 connectors on a sound card typically used for?

DB-15 connectors found on sound cards are typically used for MIDI (Musical Instrument Digital Interface) connections. This type of connection allows electronic musical instruments, computers, and other audio devices to communicate with each other, facilitating the transmission of music performance data. MIDI is crucial in digital music production, and the use of DB-15 connectors provides a standard and reliable interface for connecting various MIDI-compatible devices.

The other options, while they might refer to different types of connections or peripherals, do not accurately describe the primary use of DB-15 connectors on a sound card. Network connections would typically use RJ-45 connectors, while external storage devices use USB or eSATA connections, and loudspeakers are connected via different audio output connectors such as 1/4-inch or RCA plugs.