JEREZ, Spain - The sound of Formula 1's new "power units" was a blast from the past for Nico Rosberg, son of 1982 champion Keke, but others were less sure after the 2014 cars made a quiet test debut here on January 28.The Mercedes driver said: "It reminds me a bit of when I used to look at the videos from the 1980s, the old turbos, and it's that same sound now - deep, with lots of power on the straight. It really gave me a flashback..."The sport in 2014 is undergoing a transformation with the screaming V8 engines replaced by a complicated turbocharged V6 with energy recovery systems. The sound has been a vexed question for many, some fearing the 1.6-litre engines could prove a turnoff for spectators accustomed to having their eardrums assaulted by a barrage of noise.HARD TO JUDGEThe sport's commercial supremo Bernie Ecclestone is no fan of the V6, introduced to help lend the sport a greener image and pioneer fuel-saving technology of relevance to ordinary-road users. With plenty of teething problems on Tuesday, it was a case of all quiet on the testing front with some teams even failing to get out of the garage and long periods of eerie silence - normally a sign of something amiss at a racetrack.The few cars that did put in laps did so mostly in isolation and it was hard to form a serious judgement of the sound from the evidence available.Mercedes motorsport head Toto Wolff assured reporters they would come to like what they heard. "You must not forget that what we are doing here is basically a system check and shakedown and once you hear a car on full revs and flat out and more cars I think in a couple of months nobody is going to really speak about the 'old engines' and 'old engine sound'."Others were yet to be convinced.Nico Hulkenberg's verdict: "A bit disappointing. It sounds a bit like a DTM (German Touring Car) championship car. It's not the same sound as a V8, it's a lot quieter. Let's see, maybe there's more to come... but it's not the old screaming V8 and high revs engine sound."Red Bull's quadruple champion Sebastian Vettel, a driver fascinated by the sport's history, was clearly in Hulkenberg's camp. "On the sound? I love V8's. I would have loved to go the other way, back to V10." Stay with Wheels24 for the 2014 F1 season – fresh reports every day.