Alfa Romeo has teamed up with acoustic experts Sandy Brown to develop a ‘Sound Tunnel Index’ of the UK’s best tunnels. The Stelvio Quadrifoglio, with its 510hp 2.9-litre V6 Bi-Turbo engine and four tip exhaust system was used to benchmark each tunnel on the index 


The Alfa Romeo ‘Sound Tunnel Index’ lists the top 10 tunnels for motorists across the UK, with each tunnel ranked on the recorded vehicle sound, consisting of a combination of engine and exhaust sound, tyre/road noise and wind noise. The recordings of each drive were then ranked subjectively by Sandy Brown - one of the UK’s leading acoustic consultancies -  and the results combined to create the final ‘Sound Tunnel Index’ results.


With a one-way traffic to each side of the tunnel, 70mph speed limit, an excellent road surface, and a U-shaped profile, the Penmaencbach tunnel in North Wales was found to provide the best acoustic environment to enjoy a car’s engine sounds. The Saltash tunnel in Cornwall and Beaminster tunnel in Dorset were found to offer the second and third best environments for drivers. 


To experience the sounds of the top 4 tunnels, click on the carousel below.


Alfa Romeo began narrowing down the list by asking its fanbase, the Alfisti, to share their own suggestions on which UK tunnels they love to drive through most notably because they make the most of the sound generated by their car. From these suggestions, the top 10 were shared with Sandy Brown.


Sandy Brown experts then visited each tunnel in turn, and driving the Stelvio Quadrifoglio in Dynamic mode, which gives the car a sharper throttle response and produces a greater sound, recorded a number of trips through each tunnel.


A sound level meter was used to record each drive, with audio recorded from the passenger seat. The passenger window was down during all measurements, to ensure the full effect of the engine and exhaust was captured for analysis.


The vehicle sound is composed of three separate components; engine sound, tyre/road noise and wind noise. As each operate at different frequency ranges, with engine sound being a low frequency component, the best sounding tunnels subjectively have good low frequency noise without having very high tyre and wind noise.




Full ranking and reasoning below:




1.      Penmaenbach, North Wales, 658m 

A cylindrical bore tunnel with a U shaped profile which, when paired with a good road surface and system that allows one way traffic in each tunnel, scored it the highest in both the vehicle noise analysis and subjective review by the Sandy Brown team.





2.       Saltash, Cornwall, 410m

Although this is another cylindrical bore tunnel and the speed limit is only 30mph, high speed tunnels are not necessarily better as the increased wind and tyre noise can drown out the noise of the car. Dropping down a gear and accelerating to the speed limit, the slower pace of the road means drivers can hear the growling from the exhaust very clearly. 





3.       Beaminster, Dorset, 105m

Similarly at Beaminster, a U shaped tunnel with a national speed limit of 60mph, the narrow design of the tunnel means that drivers can hear the engine sound really well. 





4.       Hindhead, Surrey, 1,830m

Another cylindrical bore tunnel with a good road surface with the potential to be higher up in the list, however, the lane control means acceleration of any kind is limited and therefore, drivers would struggle to hear the maximum effect from the engine exhaust. 





5.       Holmesdale, Enfield, 600m

The Holmesdale tunnel is a slight outlier in the top five as it is a rectangular tunnel with four lanes moving at 70mph. The advantages of this is that, when traffic is moving quickly, there is room for acceleration at higher speeds to really experience the roar of the V6 Bi-Turbo in the Stelvio Quadrifoglio.





6.       Queensway, Cheshire, 2,010m

Despite being a lengthy tunnel with a good road surface, the profiling to the tunnel walls resulted in a ticking effect, which impacted the results. The narrow lanes and bumpy road markers also created more noise that distracted from the noise of the car.





7.       Dartford, Kent Thurrock, Essex, 1,430m

The upward slope in the Dartford tunnel produced a good sound as the engine needs to be engaged to maintain speed, however the tunnel itself is prone to high wind noise and the tar joints on the road surface are very audible when crossing.





8.       Hatfield, Hertfordshire, 1,200m

The current road surface produces a really loud noise, cancelling out any engine or exhaust growls. Hatfield tunnel does appear to be undergoing road resurfacing works, so might rank higher once completed.





9.       Limehouse, Poplar, 1,100m

Limehouse tunnel ranked almost last on the initial Index as the amount of traffic driving through is typically high at all times, even late at night. With side tunnel merging this can also impact driving style and cause more congestion with drivers switching lanes.





10.    Tyne, Durham, Northumberland, 1,700m

The Tyne tunnel ranked as the least audibly pleasing in both the vehicle noise analysis and subjective comparison. Lane restrictions and its proneness to traffic resulted in it placing last on the Index.





Richard King, Associate at Sandy Brown, says “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 car like the Stelvio Quadrifoglio, where the combination of the engine and exhaust sound add to the excitement of driving it, so this index will help petrolheads and car lovers across the UK make the most of their drives.”




The award-winning Alfa Romeo Stelvio Quadrifoglio has a 2.9-litre V6 Bi-Turbo petrol engine, which generates 510hp and launches the car from a standing start to 62mph in 3.8 seconds and onto a top speed of 176mph. This responsive engine is coupled with Alfa™ Active Suspension, Alfa™ D.N.A. Pro, with Race mode, Brembo® high-performance braking system, Alfa™ Q4 four-wheel drive and 50/50 weight distribution for a class leading driving experience.



About Sandy Brown


Sandy Brown is the largest independent acoustic consultancy in the UK.


Founded in 1969 by our pioneering namesake - the renowned jazz musician, architect and acoustician Sandy Brown – we have been instrumental in driving the development of building acoustics, both in the UK and internationally. Today, our strong heritage and reputation is supported by a contemporary approach, sophisticated modelling and auralisation capabilities and a commitment to achieving acoustic excellence on every project.




Richard King has worked in the acoustic industry for around 20 years, including 6 years at Sandy Brown. He has undertaken extensive testing and analysis of vehicle noise whilst working at the Transport Research Laboratory and worked for an automotive manufacturer for a number of years.