Calling sound once in update

I have a sound for a car and I am using this script

  public AudioSource carsound;    
  public float pitch;    
  Private bool play;    
  void Update ()
     pitch = speed/currentspeed;    
     carsound.pitch = pitch;    
     play = false;  

It plays my sound once my car start but after few seconds my sound stops playing
Can anyone solve this ? ;_;

Hello, You have the function PlayOneShot() and the properties isPlaying.
Learn more here: Unity - Scripting API: AudioSource