Viewpoint
Tom Lee, Senior Engineer at MIRA, explains how automobile manufacturers are tuning the sounds produced by the vehicles, both inside and outside the cabin.
To help their products stand out from the competition in an increasingly competitive marketplace, global vehicle manufacturers are using Noise, Vibration and Harshness (NVH) engineering to enhance the appeal of their vehicles to their target audience.
By using specialist NVH facilities to analyse and develop specific acoustic attributes of vehicles, Original Equipment Manufacturers (OEMs) are able to create a signature ‘audio brand’ for either a specific vehicle, or for their range as a whole. For example Rolls Royce cars are famed for their quietness – a key characteristic that their clientele demand. This is summed up by David Ogilvy’s famous Rolls Royce advert which claims that “At 60 miles an hour the loudest noise in this new Rolls Royce comes from the ticking of its electric clock.” In this case, NVH engineering has been applied to analyse and suppress sound sources and provide the passenger with a relaxing journey.
Sports car companies on the other hand often use NVH engineering to analyse and enhance the ‘sportier’ acoustic characteristics of their vehicles, such as the exhaust note or engine noise. For example a British sports car manufacturer carried out extensive NVH work on one of its new high performance cars during development in an effort to enhance the appeal of their product over its main Italian competitors.
Today NVH has become a key focus for OEMs. This is drastically different to how vehicle manufacturers used to operate in the 1960s and 1970s, where NVH was primarily focused around making products more driveable than desirable. Back then engineering effort would be directed towards reducing the structure borne issues in the vehicle by reengineering the acoustic and vibration transfer paths through the structure, as well as reducing the airborne noise with soundpacks. OEMs started to pay more attention to the characterisation of vehicle acoustics with the introduction of V8 and V12 sports cars however, with more effort being applied to exhaust and intake tuning, as well as tuning the firing frequency of the engine.
This approach to NVH was subsequently restricted following the tightening of drive-by noise legislation in 1970, which put a level cap on the amount of noise that a vehicle could generate. This led vehicle manufacturers to focus on sound quality, rather than just volume, which is now a key feature in sports cars as well as premium and luxury vehicles. As a result marketing teams are now often leading their engineering counterparts in the development of NVH; specifying what a vehicle should sound like in order to uniquely position their vehicles in the marketplace and get one up on the competition.
As a result of this, there have been great engineering advances in NVH over the past decade. Electronic Control Unit (ECU) tuning, advances in Computer Aided Engineering (CAE) and intake and exhaust tuning have all become key parts of NVH development. Active noise is another field of NVH that OEMs are tapping into. The use of sound symposers is becoming more widespread, with vehicle manufacturers feeding desirable sounds into the cabin whilst blocking out other undesirable noises. Active exhausts, vibration neutralisers (which change the path of structure borne noise), road noise cancellation devices and active engine mounts are all NVH development techniques currently being used by OEMs. To make matters even more complicated, some companies now design vehicles to be quiet when being driven in ‘economy mode’, but come to life when driven in a more spirited fashion. All of this is leading to further advances in NVH development.
To date, developing sound quality has mainly been focused around internal combustion engines (ICE). However the introduction of hybrid and electric vehicles has caused OEMs to drastically rethink how these types of vehicles should sound.
Generally speaking, hybrid vehicles currently focus on the noise quality of the internal combustion engine, and less attention is paid to the sound of the electric motor at lower speeds. This has created a potential gap in the marketplace for OEMs to exploit.
Fully electric vehicles (EVs) on the other hand do not make any noise, other than wind and tyre noise and the ‘whine’ of the motor currently seen in many of the EVs on our roads. Although this has been the norm until now, NVH experts are able to significantly reduce the EV sound if required. This in turn has raised a number of questions in the automotive industry. Many people would welcome the introduction of silent EVs in densely populated areas as this would significantly reduce sound pollution. However safety campaigners argue that this would be a potentially dangerous decision, as pedestrians would no longer be able to hear the vehicles approaching.
Another EV NVH characteristic currently being considered by OEMs is the passenger’s expectation of sound inside the vehicle. Over time, customer perception for how an ICE vehicle should sound when driven sportily or in a refined manner has gradually evolved. For EVs however, interior sound quality norm is still to be established. In order to achieve this, the marketing teams of different OEMs are currently trying to define the expectations of vehicle occupants for different classes and types of EVs.
This research could lead to greater variety in OEM brands’ sounds in the future. Some may opt to tailor the sound to a traditional IC engine, whilst some may play on the signature of the electronic sound of the vehicle or construct a purely synthetic sound.
OEMs are increasingly turning to NVH experts such as those at MIRA for help in defining how their ICE, EV and hybrid vehicles should sound in the future. By using specialist NVH equipment such as NVH simulators – devices which enable engineers to alter the NVH characteristics of vehicles at the touch of a button – engineering consultants are helping OEMs to research and define their own acoustic brand, and in turn increase their competitiveness in the marketplace.
Could we please have buses that sound like buses when they are approaching (cyclists especially) i.e. from their front. At present, nearly silent.
This is because most busses have rear engines.
Since traditional sound of a bus is Diesel engine sound I would propose a more pleasant sound be generated that identifies approaching bus.
Each city could even have its own sound.
Good example is Annecy in France that has busses with a cow bell sound
I can’t believe that people are so fix minded that they expect electric vehicles to sound like ICE ones!! If this were true then why weren’t ICE cars fitted with a horn that made a horse neigh sound? Shouldn’t electric trains chuff chuff like the steam powered ones?? What nonsense.
Personally I think cars should be made quieter. Our cities our filled with the noise of ICE, diesels are the worsed offender, especially at low speed. If all vehicles are quiet EV ones then you could still hear the sound of one approaching, it is just that at the moment there is so much noise for other vehicles. Also I have noticed that certain ICE powered cars such as Lexus and Jaguar are already so quiet that you cannot hear the engine at low speed anyway all you hear is tyre noise. I for one would welcome quite cities and towns. I don’t accept the arguments about the need for noise makers to warn pedestrians, and I find it rediculous that drivers might insist on a vroom vroom noise on an EV vehicle. People will quickly adapt once EV vehicles become the norm, and adaptation to the sound will be as fast as EV vehicles are introduced.
The reason ICE vehicles dont sound like a horse is that people like the sound of engines. The reason they want an EV to sound like an ICE is that they still like the sound of engines !!
I want my car to sound like a Rolls Royce Merlin complete with supercharger whine.
Thank you for all your comments.
I would like to elaborate upon some of your comments as best I can.
To jg – It can often be difficult to hear buses approaching as their sound is masked, due to the engine being placed at the rear of the vehicle.
As mentioned by Bill Frame, one potential solution that is currently being investigated by OEMs is to design vehicles in such a way that certain sounds can be emitted directionally. For example the bus might emit an audible warning in a forward direction, meaning that only pedestrians crossing the road in front will be alerted to the oncoming vehicle. This advanced form of NVH development could help to reduce vehicle borne noise pollution in the future.
To Chris Longbottom – This debate is currently being played out in the automotive industry as it can be seen from both points of view, however you have certainly put forward a valid point for discussion. OEMs are in a difficult position as they must ensure that their customers are comfortable with the products they are driving. Some people find it difficult to adjust to change so they might be reluctant to buy an EV if it sounds totally different to what they’re used to.
One idea currently being considered to make this transition smoother is the introduction of downloadable apps. These could be used to change the sound of a vehicle to something more familiar, or to something totally different altogether e.g. making a small petrol powered hatchback sound like it has a V12 engine under the bonnet.
As a long in the tooth petrol head I agree with Chris Longbottom.
The age of the ICE is dying/dead. People used to like clippty cloppy smelly nags, but no one attached hooves and a poo dispenser to cars, just a rattly ole’ engine and a smelly, noisy exhaust.
I used to love the sound of my MG Midgets and MGB’s but the 70’s was a different era and the roads weren’t completely clogged with cars. It’s no fun to go for a run just for the sake of it in the SE of England.
The idea of an app playing to the self obsessed boy/girl racer whilst he/she’s driving their 500cc turbo/hybrid city car around in virtual silence suits me. It is after all only a progression of illusion our youff seem to enjoy these days……providing they can’t attach Boom Boom speakers to them that can be heard half a mile away.