Use this mode when you want to lower the volume of your sound over the distance.

	// Sets the rolloff of the audio source attached to
	// this script to linear.
	@script RequireComponent(AudioSource)
	function Start() {
		audio.rolloffMode = AudioRolloffMode.Linear;
	}

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(AudioSource))]
public class Example : MonoBehaviour {
    void Start() {
        audio.rolloffMode = AudioRolloffMode.Linear;
    }
}

import UnityEngine
import System.Collections

[RequireComponent(typeof(AudioSource))]
public class Example(MonoBehaviour):

	def Start() as void:
		audio.rolloffMode = AudioRolloffMode.Linear