The best road tunnels in the UK for motorists to enjoy the sound of their cars have been revealed in the new Alfa Romeo ‘Sound Tunnel Index’.

The 658-metre long Penmaenbach tunnel in North Wales topped the Alfa Romeo rankings, after being judged to provide the best acoustic environment to fully appreciate a car’s engine and exhaust sounds.

The Alfa Romeo ‘Sound Tunnel Index’ ranks the top 10 tunnels for motorists across the UK, with each location rated based on a sound recording of the Stelvio Quadrifoglio performance SUV driving through each tunnel. The sound, captured from inside the vehicle, was then assessed by Sandy Brown – one of the UK’s leading acoustic consultancies.

Its experts – who led acoustic improvements to the iconic Royal Albert Hall – measured the engine and exhaust sound, plus tyre, road and wind noise, to help rank  the findings. Following the objective analysis, Sandy Brown experts then provided a subjective score for each tunnel, with both scores combined to help create the definitive ‘Sound Tunnel Index’.

With a one-way traffic to each of the tunnel’s twin bores, an excellent road surface, and a distinctive U-shaped profile, the Penmaenbach tunnel in North Wales provided the best acoustic environment to enjoy a car’s engine sounds.

The Saltash tunnel in Cornwall and Beaminster tunnel in Dorset finished second and third in the ranking respectively.

Alfa Romeo began by asking its Alfisti fanbase to nominate the UK tunnels that provide the best acoustics. The top 10 were shared with Sandy Brown, whose experts visited each tunnel.

The Stelvio Quadrifoglio, which is powered by a 510hp 2.9-litre V6 Bi-Turbo engine, was driven through each tunnel in Dynamic mode, giving the performance SUV a sharper throttle response and enhanced exhaust sound, while a sound metre recorded each drive from the passenger seat.

Richard King, Associate at Sandy Brown, said: “The shape and size of tunnels, their length, the speed of the road, background sounds such as other cars, airflow and tyre noise, all have an impact on the sound you hear while driving through it. This is heightened in a performance SUV like the Stelvio Quadrifoglio, where the combination of the V6 Bi-Turbo engine and exhaust sound add to the excitement, so this index will help petrolheads and car lovers across the UK make the most of their drives.”

The passenger window was down during all measurements to ensure the full effect of the engine and exhaust was captured for analysis.