@mikefm
aec files are used to store your volume level if you have set different level, i mean other than default level which is 4 dots. It's the same with other volume setting. For example if you have set volume at 6 dots when you play your music through backspeaker then there will exist farfield play.aec or if you have set volume to max when you call then there will exist handset0 call.aec.
And it's save to erase this files cause your phone will just return the volume settings to the default one (4dots)
@keksler
You can try to google to find "apf to zapf converter", i have try it when i mod my acoustic and it worked beautifuly. I think there's a link for it at the other site. Just try to look for it using google, trust me. Happy modding my friend!
Sorry for my lousy English mate!