Sound play on keydown and continue playing

I want to have a car horn on my car. I thought it'd be bast to use this script:

function Update () {
if (Input.GetKey(KeyCode.H)) {
audio.Play();
} else {
audio.Stop();
}
}

But it doesn't work; the audio just stutters. How can i get it that when you press and hold the key, the sound continues, rather that restarting itself?

Just check if it's already playing, and make sure it's set to be looped:

function Update () {
  if (Input.GetKey(KeyCode.H)) {
    if(!audio.isPlaying) {
      audio.loop = true;
      audio.Play();
    }
  } else {
    audio.Stop();
  }
}