sound doesnt work well on a voice channel with 3 or more people

Hi, when i am connected to a channel on any server with 3 or more people on it, I have big problems with sound. I cant hear or they cant hear me sometimes, even cant hear the music bot. Sometimes the sound gets broken for few seconds and sometimes when others speak i cant hear the whole sentence. The sound just stop playing. In real life i am in a room with other guy, but i have similar problems even when i am alone.