Audio alert sound files for Xastir.
The "sounds" subdirectory here should be copied to the Xastir share directory into which other Xastir data has been installed. This depends on your system, but may be /usr/share/xastir, /usr/local/share/xastir, or some other variant depending on how you built the code.
Xastir will look in /sounds for any sound files it needs to play for its audio alerts feature (enabled under File->Configure->Audio Alerts).