// Mutes-Unmutes the sound of this transfor each time the user presses space.    

function Update() {
     if(Input.GetKeyDown(KeyCode.Space)) {
         if(audio.mute)
            audio.mute = false;
        else
            audio.mute = true;
    } 
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Update() {
        if (Input.GetKeyDown(KeyCode.Space))
            if (audio.mute)
                audio.mute = false;
            else
                audio.mute = true;
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Update():
        if Input.GetKeyDown(KeyCode.Space):
            if audio.mute:
                audio.mute = false
            else:
                audio.mute = true