Equipping and unequipping a (Xang Xi small port) Storm Radar Extender triggers the sound effect for 'out of ammo'.

When flying around, the equipment icon shows the ammo indicator with a '0'.

(After logging off and logging on again, I was unable to reproduce the anomaly.)

The default VO client doesn't have an "out of ammo" sound effect. Are you using the Sound Alert Suite plug-in?

SAS doesn't do anything that would add a '0' ammo indicator to your equipment icons, so there may be multiple factors at play here.

Ah, I've been using SAS for so long, I didn't realize the sound effect was not part of the core game.