If you want to get certain sounds back you can delete any of the sounds in the \World of Warcraft\Data\Sound\Ambience\Creature\Gyrocopter folder.
Enjoy!
1.3
Added a few more sounds to silence that I missed.
1.2
Checked for 3.3 compatability. Still seems to work just fine. Also changed the file path so extracting it into your DATA folder actually works. Though I already fixed that.
1.1
Fixed a file path error. Thanks to littlebuddha79 for doing the testing.