The audio files can be found in the RadControls installation directory. Basically, if you download the RadControls for ASP.NET AJAX package, you will need to navigate to:
C:\Program Files (x86)\Telerik\RadControls for ASP.NET AJAX Q3 2012\App_Data\RadCaptcha
( the path may vary based on your OS and version of Controls package installed )
to find all the audio files. Then you will need to configure the RadCaptcha control as per the documentation of the RadControls:
Since we ship the controls with Sitefinity, we have the controls, but all related files to extend their functionality ( such as the audio files ) are provided by the RadControls installation package.
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