Formula 1 is continuing to nudge up the volume of its controversial 'power units'.

In 2011, in the midst of the screaming V8 era, a German newspaper clocked the leading Mercedes engine at 128 decibels - beyond the human pain threshold.

Then in 2015, for the second season of the much quieter V6 turbo 'hybrid' era, a Spanish publication found that the Ferrari was just 102 decibels.

"The pain threshold," said a correspondent, "is around 120 decibels, a figure that none of the current cars are close to."

Now, Italy's La Gazzetta dello Sport has recorded the Mercedes and Ferrari 'power units' at between 109 and 110 decibels during recent Barcelona testing.

The sports newspaper said that is just six decibels louder than at the start of the new engine era in 2014.

The 2017 Renault is just 105 decibels, the report added, with 1997 world champion Jacques Villeneuve declaring: "The sound of these (F1) cars is still not good."

The 2017 championship commences on March 26 with the Australian Grand Prix.