[Freeswitch-users] Noise for dial out conference

Hello, I use below to realize call out conference: conference testconf bgdial {originate_timeout=30}sofia/default/1001@192.168.0.72 1234567890 FreeSWITCH_Conference" conference testconf bgdial {originate_timeout=30}sofia/default/1002@192.168.0.170 1234567890 FreeSWITCH_Conference" but when the second phone is connected. there are big noise in the phone, Can anyone help me to solve it? zhao xiaoqiang