according to speedweek http://www.speedweek.com/formel1/news/4 ... chenk.html
"In Monza it came out that neither Renault's and Mercedes' layout nor the sound of their test engines are near the real ones that gonna be raced and first tested in January 2014. Ferrari therefore prefers to show the "real" engine before christmas. The Italian believe at this time it is too late for the competitors (Renault and Mercedes) to copy some smart things."
So it seems Renault and Mercedes were/are sandbagging with their soundclips and published pictures.