@tan9890

Hi, i collect some acoustic's too and i even mix them to suit my needs. Same as you, i like to know about producing / modifying acoustic too. I'm very interested at it.
I think:
play.zapf files have something related to the sound played from file manager and media player / walkman player and audio from video file too.
call.zapf's handle the sound when you have a call.
ring.zapf's is for ringtone's sound.
Now,
Farfield's is for the backspeaker's, so for example farfield_play controls the backspeaker sound when you hear audio file played from file manager or media player/walkman player.
Farfield_ring controls sound when the phone rings from the backspeaker.
Its the same with phf's file, phf_play controls sound coming from handsfree when you play audio files from file manager or built in player.
I guess they work that way.
Oh, handset0_call responsible for the sound that comes from the handset's earpiece.
That's all I know, hope it helps you a bit my friend.
Sorry 4 my english.
Cheers from Indonesia :-)