Zikkick plainly said use his ability mimic any sound (think of the black guy from police academy series). Zikkick replays a past battle which occurred in near by canyon outside the base. Zikkick screwed over Reese's more sensitive and accurate sensors so he cannot get 'clear reading' but Zikkick also created static which makes briefly flash sometimes that there is dozen of bugs after small unit of humans.<br/><br/>Also Zikkick signaled that the near by normal soldier bugs make attacks on the armored Reese, to add more genuine feel to the bluff that there is battle going outside.