Unity jumping sound, help.

So I’m trying to make a sidescroller in Unity using 2D. I want my character to make a sound when he jumps. But if I press the jump button again in the air the sound will play but hes not jumping, I don’t want this.

Here’s my code…

#pragma strict

var jump : AudioClip;

function Update () {
	if(Input.GetButtonDown("Jump")){
		if(!audio.isPlaying){
	
			audio.Play();
				
		}	
	}	
}

use CharacterController.isGrounded