My Mac Pro has started irregularly making a strange sound, like an error chord or something. I've no clue what it is or which application is doing it. Console displays this line when it happens: Code: 7/28/16 16:53:16.520 com.apple.WebKit.WebContent: [16:53:16.520] FigAgglomeratorSetObjectForKey signalled err=-16020 (kFigStringConformerError_ParamErr) (NULL key) at /Library/Caches/com.apple.xbs/Sources/CoreMedia/CoreMedia-1731.15.206/Prototypes/LegibleOutput/FigAgglomerator.c line 92 It's just done it about eight times in the last few minutes, but has been silent for several hours before that. It does it a few times a day, with no fixed time or pattern. The sound is coming from the connected speakers, no the internal speaker.