When the engine roars and hums...
Electric motors are considered reliable, tireless powerhouses—especially in continuous industrial use. They rotate, drive, convey, and ventilate. And sometimes, they make noise. Not necessarily loud, but often unpleasant. Or disruptive. Or strange.
What many consider to be “normal operating noise” is in fact often acoustic malfunction – one that can be measured, simulated, and, above all, avoided.
An engine doesn't speak – but it makes a sound
Whether in ventilation systems, compressors, or as drives for industrial plants, stationary electric motors are an indispensable part of modern production. And when they suddenly start to sound different during continuous operation, the first suspicion is often that there is a problem with the bearings, shaft, or mounting. However, it is not uncommon for the noise problem to be structural in nature.
This is because:
- Circulating magnetic forces cause the motor housing to vibrate periodically.
- These vibrations are transmitted to the air, creating noise.
- Certain components act as acoustic amplifiers, while others dampen the effect.
What makes this particularly tricky is that the audible frequencies often lie within the sensitive range of human hearing—and even if they are technically harmless, they come across as unprofessional, distracting, or “cheap.”
Simulation makes audible what disturbs the ear
At Merkle CAE Solutions, we analyze precisely these effects – before the motor is installed in the control cabinet or machine room. Because what is expensive and difficult to measure in testing can be predicted precisely in numerical simulation:
We show you:
- Which components contribute to sound radiation
- At which frequencies resonances occur
- How the sound radiation power is distributed
- And which optimizations have the greatest effect
Practical example: When the fan cover becomes a loudspeaker
In a recent project, we examined a stationary industrial motor with an axial fan. What was striking was an unpleasant humming noise at medium speed—despite high-quality bearings and clean assembly.
Our simulations showed:
The first natural frequency of the fan cover was 281 Hz – exactly within the operating frequency range. The result: resonant amplification of the sound pressure level – especially in the area around 1 m away. Through targeted structural reinforcements and minimal geometric adjustments, we were able to reduce sound radiation by almost 10 dB – audibly and measurably.
Why is this important?
Because noise is not just a comfort issue, but often also a quality feature. Customers do not complain about decibel levels – but they are bothered by “unclean sound.” And: In sensitive applications (e.g., in clean rooms, in medical technology, or in acoustically sensitive areas), a seemingly trivial hum can become a real problem.
What we offer: We listen – before your customers do
Whether it's a new development, troubleshooting, or redesign, we support you with our expertise in structural mechanics, acoustics, and flow simulation:
- Determination of dominant vibration modes
- FEM and CFD-supported optimization
- Rapid evaluation of acoustic hotspots
- Recommendations for measures to reduce sound radiation
You supply the engine – we supply the silence.
Conclusion: It doesn't have to be loud to be wrong.
Noise in the machine room, humming in the control room, vibrations in the switch cabinet—all of this can be avoided if you listen carefully early on. With digital acoustic diagnostics through simulation. No earplugs required.
Talk to us. We will make your products quieter – and your customers happier.
Yours Stefan Merkle
P.S.: I used to tinker with my moped myself when it rattled. Today, I look at natural frequencies, sound pressure distribution, and modal analysis. You can hear progress.