// Play a sound when we hit an object with a big velocity
function OnCollisionEnter(collision : Collision) {
if (collision.relativeVelocity.magnitude > 2)
audio.Play();
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void OnCollisionEnter(Collision collision) {
if (collision.relativeVelocity.magnitude > 2)
audio.Play();

}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def OnCollisionEnter(collision as Collision):
if collision.relativeVelocity.magnitude > 2:
audio.Play()