Ferrari driver Sebastian Vettel says off-season exhaust changes mean 2016 cars "sound a bit more like Formula 1".
The sound and volume of the current power units has been a constant criticism since the platform's introduction two years ago.
All cars now have separate exhaust pipes for the turbine and wastegates following a regulation change, with the previous set-up deemed to have had a silencing effect.
One of the more vocal critics in early 2014, Vettel says he has noticed a difference during this week's Barcelona test.
"About the engine, I can say it is nice to have a bit more sound coming back," he said.
"It is still not as loud as it could or should be but it is a lot better than it was, now sounds a bit more like Formula 1."
Mercedes' technical team says that the revised exhaust layout equates to an additional 4dB of volume on its dyno.
While that differs in the environment of a grand prix circuit, Mercedes driver Nico Rosberg agreed with Vettel that some progress has been made.
"The engines are a little bit louder now," he said.
"Of course it's not perfect, perfect would be a little more noise, but we've got this and we have to accept it."
Ben Anderson, Grand Prix Editor (@BenAndersonAuto)
From trackside, it is difficult to be certain that the engines sound louder in themselves, though it is apparent that the individual notes produced by the respective engine manufacturers are naturally converging.
While the engines don't necessarily sound louder, they certainly sound better.
The Ferrari sounds much closer to the Mercedes, which last year was arguably the cleanest and loudest of the different V6 configurations.
Renault - which last year emitted a very muted engine note - sounds closer to these other two than before.
Ditto the Honda, which retains its distinctive guttural roughness off-throttle and under full load through the long right-hander of Turn 3, but otherwise sounds more conventional this year.
This quality may well improve further as McLaren discovers how to properly map the new power unit during the remainder of pre-season.
Williams technical chief Pat Symonds estimated the engines would sound approximately 12 per cent louder this season, thanks to these revisions, and the natural improvement that comes from engine developers discovering more power from what remains relatively immature technology.
Mercedes technical supremo Paddy Lowe has also revealed that his team measured 124dB on the dyno with the old exhaust, and the current specification at 128dB. The old V8s came in at 129.5dB.
So, objectively speaking, the cars are definitely producing more sound energy than they were last season.