If you are a first-time visitor, I would like to wish you welcome to Elevating Sound – a site dedicated to the world of sound.
This is the first post in Elevating Sound’s newly launched Quiet Cars section – a section that will be dedicated to covering the ins and outs of quiet motoring and the quest to reduce cabin noise.
Quiet Cars – An Overlooked Need
Increasing numbers of car buyers are looking at noise as one of the key factors when looking for a new vehicle. Car manufacturers indeed have to take numerous aspects into consideration when designing a vehicle – safety, road handling etc – but it’s nevertheless astonishing that modern cars are not quieter than they currently are. The manufacturers have failed to recognize a sizable and growing market segment that highly values their car providing a quiet ride.
It seems to me that the automotive manufacturers and, even more so, the automotive journalists have put too much emphasis on sporty road handling, which have resulted in vehicles with stiffer chassis and suspension that deliver good handling when driving fast in steep curves, but as a downside, makes the cars too noisy.
The options are too few for drivers who love the idea of soft, smooth long-distance rides that make them feel fresh and relaxed upon arriving. Think the Bentley smoothness but in other price categories. There’s Lexus LS600h – perceived as the world’s quietest passenger vehicle – but it’s also out of reach to most people. Another quiet vehicle is the Mercedes-Benz S-Class.
There can be many different reasons for why someone has problems with too much noise inside the car. It can cause headaches, tiredness/fatigue, stress, irritation etc. And people with tinnitus, hyperacusis and other ear disorders may find driving a noisy car outright painful, forcing them to wear ear plugs or ear muffs to make it bearable.
When talking about noise in the cabin of the car, I am primarily referring to these three areas:
- Engine noise
- Road noise, i.e. the noise transferred into the car from the tires rolling on the road
- Wind noise
Besides these, you will have noise from other mechanical functions in the car, such as ventilation. And you may also hear different squeaks and rattles from the interior. But the focus here will be on engine, road and wind noise.
The subjectivity of noise
In order to assess the noise situation in the cabin, it is essential for you to test drive the cars you are interested. You need to get a feel for everything first hand, and not just listen to what others have said as to whether a car is noisy or not.
When it comes to sound and noise, it will be subjective in terms of how you actually experience it. The noise level in the cabin of the car can be measured in decibels (dB) which is an objective measurement of how loud it is.
But it will be insufficient for you to just look at the number of decibels, since that does not say anything about the frequencies of the noise at hand. People subjectively experience noise differently, since they react to high and low frequencies differently. When you test drive a car, you can both bring a decibel meter to measure the noise level (some meters will also include frequency) and you can, by listening with your own ears, conclude whether you react well to the nature of noise inside the car or not.
While there are no truly quiet cars below the luxury level, there are still a number of factors to take into consideration to help you out when seeking the quietest vehicle that meets your particular needs and budget.
The Essential Quiet Car Checklist
Do your own research on which car brands and models that are seen as quieter than others. As a general rule of thumb, larger vehicles are quieter than smaller. Some manufacturers will be attempting to position themselves as having quiet car models and you will be able to read about what noise-reducing measures they have taken in terms of the chassis, suspension, engines, windows, sound proofing in the doors etc.
The Car Platform
Many successful car models are long-lived and every so often, the model is overhauled through the launch of an entirely new platform/generation. In-between, throughout the lifecycle of a platform, there will be one or a few minor updates. The updates will in most cases have no impact on the noisiness in the cabin, but the noise level can vary considerably between different platforms/generations.
Hence, it is important to jot down the model year – and ideally also the platform name (or you can just ask about that at the car dealership) – if you read about a car being quiet so that you look at the right platform if you consider buying the car. As an example, the BMW 5 series has launched a new platform called F10 (Sedan) / F11 (Station Wagon) (2009-present), which is considered to be quieter than the previous platform, the E60/E61 (2003-2010).
The Car Type – Sedan vs. Station Wagon
As a general rule of thumb, Station Wagons are perceived as noisier than Sedans due to the acoustic resonance generated in the large open space at the back. However, most perceive the difference to be fairly small. If it’s important to you to bring down the noise as much as possible and you are ok with foregoing the extra space of a Station Wagon, then go for a test drive and see whether the Sedan is quieter.
The Car Type – SUVs, Trucks etc
SUVs, Trucks and other larger vehicles will – with their larger and higher surfaces – generate more wind noise. Depending on the type of windows and how well-isolated the doors are, you will get more or less of that wind noise transferred into the cabin.
Some vehicle models have a sportier configuration, often encompassing a sporty feel to the chassis by having it lowered. As a general rule of thumb, the sportier the vehicle is, the more road noise you will get inside the cabin. A stiffer, lowered chassis means more road noise when the road surface is a bit rough.
If you want a driving experience that is smooth with a car that does not transfer vibrations from the roughness of the road surface straight into the cabin, you should look for a softer suspension. Inquire about what kind of suspension is used and ask about its characteristics.
Again, it is important to test drive yourself. If you notice that road roughness is making the ride ‘hard’ and that almost none of it is ‘absorbed’ by the suspension, then it is probably quite stiff. Based on my experience, most modern cars seem to go with too stiff suspension. Maybe manufacturers believe that’s what consumers want, but I think it is sad that people who enjoy driving a car fast like a sports car down curvy roads have such an impact on the car market. There are lots of us who prefer an enjoyable motoring experience that is smooth and soft.
It goes without saying that the electric engines are the quietest. Then comes the hybrids – i.e. the mix between electric and gas/petrol.
Historically, the diesel engines used to be very loud but the modern ones are substantially quieter and they are even quieter than gas/petrol engines when driving at highway speeds due to the fact that diesel engines work at lower revs. However, when driving at lower speeds, diesel engines are still audibly noisier than petrol/gas.
Besides the actual engine, it is the degree and nature of sound proofing that will impact the engine noise in the cabin. Go for a test drive to hear it for yourself.
Some manufacturers offer laminated windows as standard or option. This feature constitutes layered glass in which the plastic laminate material provides an additional sound barrier, helping to reduce outside noise inside the cabin.
If you are unsure of the relative benefits of laminated windows, try test driving one car with and another without.
The choice of tires is incredibly important. Merely changing tires on a car can really change the driving experience dramatically in terms of the level of road noise.
As a general rule of thumb, you get less road noise…
…the narrower the tires are
…the smaller the wheels are, e.g. 16-inch wheels are quieter than 18-inch – the reason being that the thicker the tire is in terms of height of rubber rolling on the road, the less noise will be created. 16-inch wheels will leave more room for a thicker tire than the 18-inch ones.
I will be going into explaining car tire sizes in detail in a later post.
It is also essential to note that the noise level of different tires with the exact same dimensions can vary substantially. This is due to tire manufacturers launching tire models with differing rubber contents – some tires are harder than others. Softer tires are generally quieter than harder.
Then the tire patterns also come into play – some patterns are noisier than others.
The European Union has launched a rating system in which tire manufacturers can submit decibel ratings of their tires (the number of decibels generated outside the car). I don’t know about elsewhere in the world, but I am sure similar systems exist or will be emerging.
I think this is great, but I have recently discovered that dB ratings from the manufacturers may not accurately mirror how they actually perform on the road. So it will be important for you to exchange experiences with other drivers, tire workshops etc to find out which tires that roll quietly in your particular surroundings (the road conditions and asphalt roughness/smoothness differs widely across the world).
Besides changing tires as a very effective measure to reduce cabin noise, you can also go about sound proofing your car by applying sound dampening/deadening materials throughout the vehicle. There are numerous companies that offer great solutions for this – two examples are HushMat and Dynamat. HushMat talks about creating a luxury ride in every car.
You basically install these materials by cutting out patches and sticking them to places like the firewall (the wall between the engine and the cabin), floor, doors, roof etc. If you feel uncomfortable about removing the inner door panels etc, then look for a local expert. However, many of the easier-to-get areas such as the floor and the boot, you can easily do yourself.
You can also treat the chassis and wheel acres with Tectyl (from Valvoline) or a similar product to prevent corrosion. As a by-product of that is claimed to be reduced road noise. However, Swedish automotive magazine Vi Bilägare conducted a detailed test of Tectyl treatment and the maximum difference measured between a treated and untreated vehicle was 0.7 decibels. So it does not seem to live up to its claims, but if you want to shave as much noise as possible, this could still be something to throw into the mix.
Please, comment below and share your experience of cars and noise. Is there an important parameter lacking from this checklist? Have you sound proofed your vehicle – how did it go?
And if you already own a quiet car that you are happy with, please recommend us your ‘optimal configuration’ based on the parameters above.