Sound on pause it doesn't works.

Hello I want to play a sound on pause but it doesn't work like I want. When I press P it pause but sound is not playing, and when I press R it sound but if it isn't paused and you press R it sounds too.

I want that when you press P and pause play the sound and when you press R unpause and play the sound, and when is unpaused and press R that sound don't play.

Here's my code fragment of my code.

 void update ()
 {
 
 if (Input.GetKeyDown (KeyCode.P))
         {
                     Time.timeScale = 0; 
                     EfectosDeSonido.Instancia.ReproducirSonidoPause ();
                 }
 
 
         if (Input.GetKeyDown (KeyCode.R))
             {
                     Time.timeScale = 1;
                     EfectosDeSonido.Instancia.ReproducirSonidoPause ();
             }
 }