The audio in the nine MP3 files is just as it seems: nothing but silence of various lengths. Downloading the files and examining the metadata, however, gives these nine albums:

1. Golden Road by Keith Urban
2. Labour of Love III by UB40
3. Slow Motion Daydream by Everclear
4. Sawdust by The Killers
5. Nevermind by Nirvana
6. The Road to Ensenada by Lyle Lovett
7. Mutations by Beck
8. Off the Deep End by "Weird Al" Yankovic
9. Karma and Effect by Seether

All of these albums have a hidden track that follows a period of silence. These are (along with the length in seconds of the corresponding MP3):

1. One Chord Song (5)
2. Brahm's Lullaby (8)
3. White Noise (9)
4. Questions with the Captain (13)
5. Endless Nameless (10)
6. The Girl in the Corner (14)
7. Diamond Bollocks (6)
8. Bite Me (4)
9. Kom Saam Met My (12)

Indexing into these songs' names gives the answer HUSH MONEY.