Calling myfunction from update function

i need to call my function if player score 10 but i need to use update function to know player's score, it works okey but my function plays sound when its called so because of the update function audio clip sounds bugged

little part of my code

 function OnGUI()
 {
 
 GUI.skin= customSkin;
    if(guienabled == true)
    
    {
      GUI.Label (Rect (52,163,261,939), "SPEED UP !");
      audio.clip = speedup;
      audio.Play(); 
    }
 
 }
 
 function guic(){
  
   guienabled = true;
   yield WaitForSeconds(1);
   guienabled = false;
 
 
 }
 
 
 function Update (){
 
 if (ScoreHolder.score >= 10)
 {
   Time.timeScale = 1.1;
   guic();
 }