Stahl Blog

Why noise reduction is key to the future of automotive interiors

Written by Martin Van den Berg | Mar 6, 2024 7:00:00 AM

Perhaps the most famous automotive advertising campaigns of all time focused on a surprising element of a well-known luxury car brand. The headline of the much-circulated 1950s ad – which has since become a case study in advertising circles – didn’t focus on the car’s powerful eight-cylinder engine or its sleek exterior. Instead, what advertising guru David Ogilvy chose to emphasize was a lack of something. This is the headline: “At 60 miles an hour, the loudest noise in this new car comes from the electric clock.” The key selling point of this most luxurious of cars was silence. 

The ad became an instant classic, boosting sales and cementing the brand’s reputation as a champion of understated luxury. But what makes the ad so effective is the way it taps into a fundamental truth about driving: without the right measures in place, it can often be an unpleasant experience. Noise levels in the cabin of a moving car can easily reach 70 dB, a threshold that can cause hearing damage over extended periods. However, the rapid growth of the electric vehicle (EV) market means that noisy engines will soon be a thing of the past.  

Indeed, EVs are swiftly democratising the luxury of a quiet driving experience. With no internal combustion noise to contend with, any car can now theoretically be as quiet as a classic 1950s luxury model. However, this new standard of quietness brings with it a fresh set of problems. Since engine noise has been drastically reduced, it is much easier to hear noises coming from inside the cabin, especially squeaky seats. So, what can EV designers do to reduce this persistent problem? First, we need to understand exactly what is causing these noises. 

 

The stick-slip effect 

To work out where squeaks come from, we must go down to the microscopic level. Most squeaks and rattles occur at the intersection of two interior components, such as the point where the backrest meets the horizontal seat cushion. Why does this happen? If you zoom in on the surface of the material, you will see many tiny ridges, like a mountain range. When the two interfacing materials rub against each other, this surface roughness causes them to interlock. And when the materials separate again, acoustic energy is emitted – as a squeak. 

Therefore, to combat this effect, all you need to do is smooth out the surface roughness so that the ‘peaks’ are less ‘jagged’. This means that there will be less opportunity for interlocking, resulting in lower friction levels. This can be achieved with the right coating, but getting lasting results is far from easy – especially in the context of the growing trend for ultra-matte interior surfaces. This finish style improves both safety and perceived quality, but the problem is that the structure of most matting agents tends to weaken coatings. 

To meet this challenge, Stahl developed PolyMatte®, our proprietary polyurethane dispersion technology that is compatible with water-based polyurethane coatings. It forms a smooth, matte surface structure during the film-forming and drying stages, and requires no fillers. It also gives the finished surface a luxurious look and feel, as well as excellent flexibility, and scratch and abrasion resistance. This forms the basis of our automotive anti-squeak solution. 

 

 

The next generation of noise reduction 

Stahl Stay Silent® is our flagship noise suppression coating. It offers market-leading noise-reduction performance that lasts for up to 100,000 km – much longer than standard solutions. The Stahl Stay Silent® range includes two distinct products – Permutex® EVO WD-3720 and Permutex® EVO WF-3721 – to meet customers’ specific finishing requirements. Both offer excellent weathering and noise-reduction performance. They are also very easy to apply, requiring only the addition of a crosslinker, and are compatible with both PVC and PU synthetics. 

Ensuring that automotive interiors are both quiet and attractive will become increasingly important as the in-cabin experience plays a greater and greater role in consumer purchasing decisions. In fact, according to McKinsey research, the quality of a vehicle’s interior is taking the spotlight away from more traditional considerations such as engine performance and exterior styling. This means that interiors will become a much more competitive arena for automakers as they seek to produce more luxurious, distinctive and comfortable offerings. 

And with the advent of autonomous driving, it is even predicted that vehicles will increasingly become ‘second homes’ for many, allowing passengers to work, relax and even sleep. That makes it essential that every ride is as quiet as possible. But even as automotive technology has evolved, one thing has remained constant: silence is the hallmark of a pleasant driving experience. And now, thanks to the use of advanced noise suppression coatings like Stahl Stay Silent®, you don’t have to be a luxury car owner to enjoy the luxury of a quiet ride. 

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