[Freeswitch-dev] silence on a native recording

Hi, I am getting the warnings in the freeswitch.org , saying... [WARNING] switch_ivr_play_say.c:567 Can't detect silence on a native recording. This is thrown each time I am calling session:recordFile in my lua scripts. I am not specifying any extensions, thus relaying on the encoding type chosen by freeswitch. So the files are given extensions .PCMU. I've been told that this is a harmful warning. However, we need an ability to detect the silence in the following scenario. In a voicemail, while the caller is leaving a message, he can mute his phone. The application may kick up the event, saying that silence is detected, so we would pause the recording and play the prompt "Are you still there?" to the caller. Thanks.