Mute/unmute issue

I want to perform mute /unmute For that i am using following code

               public function audioMuteUnMute(state:String):void{
                           
                if (state=="Mute"){
                    ns.attachAudio(null);
                    ns.receiveAudio(false);
                   
                }
                else  
                {
                   
                    ns.attachAudio(microphone);
                    ns.receiveAudio(true);
                   
                }
            }

Give errror at ns = new NetStream(nc);

firstly i mute then press for unmute then it gives folloeing error.

Error #2044: Unhandled NetStatusEvent:. level=error, code=NetStream.Seek.Failed
    at com.controller::BroadcastPod/connectStream()
    at com.controller::BroadcastPod/init()
    at com.controller::BroadcastPod/___BroadcastPod_Canvas1_creationComplete()
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at mx.core::UIComponent/dispatchEvent()
    at mx.core::UIComponent/set initialized()
    at mx.managers::LayoutManager/doPhasedInstantiation()
    at Function/http://adobe.com/AS3/2006/builtin::apply()
    at mx.core::UIComponent/callLaterDispatcher2()
    at mx.core::UIComponent/callLaterDispatcher()