A command operator of fire and rescue units needs to pay attention to several simultaneous streams of radio voices to optimize information gathering for the coordination of simultaneous emergency missions. An experiment investigated command operator ability to discern stereo and 3D-audio call-signs presented in background noise of added voice sources. Each of 10 command operators listened to 1 to 4 call-signs combined with 2 to 4 background voices with the primary task to identify the speaker of each call-sign. A secondary visual and manual-response task was used to induce an overall heightened mental workload situation. 3D-audio presentation resulted in a slightly increased number of correctly indicated locations of call-signs. Four background voices reduced correctness compared to sets of 1 and 2 call-signs, respectively. The results are discussed in relation to the potential for improving 3D-audio presentation and intelligibility, and its possible impact on operator effectiveness.