If we take a alarm watch in a vacuum glass box where its sound will gone when we open it?

if we take alarm clock in a vacuum place (a glass box ). obiously we will not hear the sound of it. after stopping the alarm we open the glass box and hears no sound where the sound which was created by the alarm clock gone. or where will be its sound energy gone. when sound energy created it should be there in the box.and also please explain me why sounds comes to our ears through the air.