Is it possible to trigger the built-in Trash sound effect via AppleScript?
How about this one:

do shell script "afplay '/System/Library/Components/CoreAudio.component/Contents/SharedSupport/SystemSounds/dock/drag to trash.aif'"




Update:

To address your comment, this is covered in Technical Note TN2065 - do shell script in AppleScript under Other Concerns where it says:


  "... how do I make do shell script not wait until the command completes?" 
  
  Use do shell script \"command &amp;&gt; file_path &amp;\". do shell script will return immediately with no result and your AppleScript script will be running in parallel with your shell script. The shell script’s output will go into file_path; if you don’t care about the output, use /dev/null.


Example:

do shell script "afplay '/System/Library/Components/CoreAudio.component/Contents/SharedSupport/SystemSounds/dock/drag to trash.aif' &amp;&gt; /dev/null &amp;"