In the Hentai_Milf.SWF file, there are two audio clips, 3081: sfxHeld2 & 3083: sfxHeld4, that have a sound like that of clinking/dropping metal chains at the beginning of their playback. The two audio clips can be previewed by opening the .SWF file with the FFDec program.
This already excellent mod would be improved further if the aforementioned audio clips could be cleaned up to remove the sound of the clinking/dropping metal chains.