The soundtrack of technology

Lively. Dynamic. Powerful. High-performing. That’s how a STIHL chainsaw is supposed to sound. “Our devices sound high quality. Nothing should rattle, clatter, or disturb. If anything is off, we have to get to work,” says Marc Rifaut, Head of the Systems, Acoustics and Vibrations Group at STIHL since 2023. Tracing noise disturbances often reminds him of detective work: Hunting down the tiniest crackle requires an ear for detail.

Meticulousness and perfectionism

The eight engineers and five mechanics working on sound development approach their task with a high level of meticulousness and perfectionism. Their analysis and optimization is supported by a range of tools including state-of-the-art measurement technology which can be used to localize disturbing noises, as well as noise profiles determined in user surveys. “There are clear guidelines for how STIHL power tools should sound, and as development engineers we follow those guidelines in what we do,” explains Marc Rifaut.

Right from the start

Where is the unwanted noise coming from? Is it a component vibrating in resonance and radiating sound through the structure? Or is it a bearing that is not running smoothly? Guided by these questions Dominik Wengner, who has been working as a development engineer in the Systems, Acoustics and Vibrations department since 2017, specifically addresses individual device components. If the cause cannot be rectified directly, passive measures can be applied, for example the addition of absorbent, i.e. damping, materials. “We always find in-house STIHL solutions here. The company’s sound and vibration experts sit right here in our department,” adds Dominik Wengner proudly. Because acoustic measures can affect the overall concept of a STIHL power tool, the team around Rifaut and Wengner is involved in development processes from the very beginning.

A swimming pool for sound

No STIHL power tools can bypass the sound measurement room. Multiple times in the course of creation they will come through here, the “heart of sound development,” for thorough testing with state-of-the-art measurement and analysis technology – and sometimes also after they are ready for series production. Battery-powered tools must also undergo testing in the sound measurement room. Not because they are noisy, but because disagreeable background noise can diminish the perception of quality, Dominik Wengner explains: “In a petrol chainsaw the noise of the combustion engine covers all other sound like a blanket.” Not so with battery power; here, other noises can suddenly come to the fore, such as a whistling fan or mechanical sounds.

The acoustic-foam-lined room stands on a 36-ton concrete foundation supported on elastomer plates, which ensure it is isolated from the rest of the structure. As Dominik Wengner describes it, “the room is literally floating within the building.” Anyone entering this test room immediately finds themselves in an extraordinary acoustic situation. Because of its foam cladding, the room is very anechoic: Rather than reflecting sound, the walls simply swallow it up. With the construction of the development center in 2004, the room was integrated and has since ensured consistent measurement conditions.
“Even though we are surrounded by numerous test benches, there are no unwanted noises in here,” Dominik Wengner explains cheerfully.

Unmistakable sound profile

This was not the situation before 2004, recalls Johannes Menzel, who joined STIHL in 1990 and led the Sound and Vibration development department from 1994 to 2023. Back then people would drive a workshop bus out to the open air and carry out noise measurements in it. However, because the measurement technology components of the time were much more complicated, this was a somewhat elaborate and therefore rather rare undertaking. The first sound measurement room was built in the early 1980s (or possibly before then) in Plant 1, inside what had previously been Mia Stihl’s hen house. It was during this era that the distinctive sound profile of STIHL chainsaws emerged. In fact it was developed in close dialog with users from the pro segment. “Back then they just had the best instinct for the products they worked with,” says Johannes Menzel, who in the early 1990s had played a key role in the development of the 023 L, the world’s first – and still to this day only – quiet chainsaw.

Quiet or light?

Sensitivity to noise has increased significantly in recent decades, at least in Europe and especially in urban areas, explains Dominik Wengner. “There is now scientific evidence about the harmful effects of noise on health. This also influences our development work.” Today there is a clear focus on battery power tools, which are quieter by default and are particularly popular among domestic users. In the professional segment on the other hand, volume is not a dominant factor motivating customers to purchase: With chainsaws, product performance and weight take precedence.

Like an electric typewriter

Less sound power, more weight? In 1995, this issue did not seem to be decisive for the sluggish sales of the 023 L. Initial user feedback on the hobby tool indicated a high level of satisfaction: “I felt relaxed, not stressed by noise.” Or as it says in the acceptance tests that Johannes Menzel uncovers in his “old sound folder” for the saw, “the whisper-quiet sound more than compensates for the loss of power.” To understand how quiet the 023 L was, look at the comparisons made at the time: For example, at a distance of ten meters from the sawing site, the 023 L sounds as loud as an electric typewriter.