Does object speed affect audio.PlayOneShot? How can I make my audio sound normal?

So at first I thought it was because I was playing the audio in an update which is constantly being called but even with the 1 second pause it doesn’t seem to work. Let me know if you guys need any more information as this is my first time posting a question here.

void FixedUpdate()

	{
		speedDisplay.guiText.text = "MPH: " + 10 * (int)rigidbody.velocity.z;
		if (rigidbody.velocity.z > 10.0f && transform.position.y >= 0.6f) {
					audio.pitch = 1;	
					audio.PlayOneShot (cowa, 0.90f);
					letAudioPlay();
				}
	}

	IEnumerator letAudioPlay()
	{
				yield return new WaitForSeconds (1.0f);
		}

No, object speed does not affect it.
Try:

audioPlaying = false;

 if (!audioPlaying && rigidbody.velocity.z > 10.0f && transform.position.y >= 0.6f) {
audio.pitch = 1;
audio.PlayOneShot (cowa, 0.90f);
audioPlaying=true;
letAudioPlay();

 IEnumerator letAudioPlay()
{
yield return new WaitForSeconds (1.0f);
audioPlaying=false;
}