A closed audio circuit is disclosed with function of eavesdropping prevention and audio clarity enhancement. The closed audio circuit includes a plurality of user equipment (UEs) and an audio signal combiner for a group audio communication session. The UEs and the audio signal combiner form a closed audio circuit allowing a user to target another user to create a private conversation to prevent eavesdropping. The UEs receive user audio input signals and send the audio input signals to the audio signal combiner. The audio signal combiner receives the audio input signals from each UE and transfer desired mixed audio output signals to each of the UE.