I frequently record Keynote presentations I give using my Mac (using ProfCast). Typically I use a wireless lapel mic and have my sound preferences pane set to record from Line In. However, on occasion I forget to turn on my mic, or the battery is dead, and so I get nothing but silence. In these instances, I'd like to be able to use my PowerBook's internal mic as a backup, so I set about finding a method using AppleScript to accomplish this.I eventually got something working with the help of a freeware program called AudioLeak that monitors the RMS sound level of the selected input source. Together with a little GUI scripting, I can have my Mac try to connect to Line In, but switch to the internal mic if the line is dead. Here's the final script. I have this script embed...

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