Clicking noise problem while combining 2 sounds in Unity

Hey,

I have 2 sounds in my game that are played one after another (making a fireball fly and then explode). The thing is that the transition from one to another may be possible in various timespans (e.g. fireball explodes right after start or one second later). Exploding right after start causes audio "clicking" which makes strange noise at certain frequency.

I've tried to recreate this exact transition in my DAW but there was no such "clicking noise". You can hear the difference in following link (just play sound on zippyshare - you don't have to download it) where first set of sounds are from in game (with "clicking noise") and second set is recorded directly from DAW (where there is no bug):

LINK

Also, I've tried different Compression Format combinations when importing to Unity but it didn't work.

Let me know if you have any suggestions how to resolve this problem :)

Thanks!