calling www to get audio.clip multiple times causes memory problems

I download a wav sound then load it with www. Then if I download another the memory is still being used by the first one (this is on the iphone -- I'm watching the memory profile of the app)

How do I clear the memory or variables (delete? destroy) to free up the memory each time I download a new sound? What are the general rules for deleting things in variables if they are going to be used multiple times?

Thanks,

Here's the code that I call multiple times which causes the memory accumulation.

 function getAudio1(){
     
  var mp3WWW = new WWW(path_to_sound_file);
  display="loading clip";
     yield mp3WWW;
     
 var myclip=mp3WWW.GetAudioClip(false);
 audio.clip=myclip;
 audio.ignoreListenerVolume =true; 
 audio.pitch=1;
 audio.Play();    
 display="loaded";
 
 }