If you save your QR picture as an icon (depends on the dimensions you need), you could then change the icon for the embedded audio file to that. This approach would avoid the need to have separate QR pictures and audio files.

An alternative would be to save your QR picture as an image, select the embedded audio file and the Edit|Object option (working from a PC here) to change its fill effects to use the QR picture for the fill, then apply either a transparent icon or a 1-pixel icon to the embedded audio file.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]