From May’s Rally de Portugal, the sport’s top-tier cars will all be fitted with the device – a decision that follows a meeting of the FIA’s World Motor Sport Council last Friday.

Members ruled that this should be positioned one metre from the ground and must produce a minimum of 80dB of noise spanning a two-metre area at the front and rear of the vehicle.

It will switch on at speeds no greater than 18.6mph, it has been agrred, and once the car exceeds this speed in electric-mode, the device goes silent.

As part of the new regulations first introduced last year, Rally1 cars marry a 1,600cc forced induction petrol engine tcarried across from the previous World Rally Car era with a 100kW electric unit that is securely mounted in the boot.

It is the latter part of this system that allows these Rally1 cars to run solely on electric propulsion on road sections, in the service park and through what are known as HEV (Hybrid Electric Vehicle) zones. When traversing the latter, cars must do so without the engine running.

The hybrid technology is intended to make the current crop of machines from M-Sport Ford, Hyundai Motorsport and Toyota Gazoo Racing clearner and more relevant at a time when hybridisation forms a large chunk of new registrations for automakers.

The sound module is another crossover, with these already in operation on passenger vehicles. Under rules set out by the European Union, those hybrid models that reverse park in electric mode must have this fitted to alert pedestrians to their presence given the absence of engine noise.

“When the cars are in full electric mode, they are silent and when they are in a busy service park with lots of people – team members, other drivers, marshals, etc – it is very easy to miss seeing a car coming towards you as you are used to hearing the noise of the car which simply is not there,” said M-Sport Ford’s Richard Millener.

“We need to be sensible and safe, so adding a sound module will help for service areas to be a safer place,” he added.