15.04.2024 | reading time approx. 5 min.

How do you make a fan quiet?

We have something against loud fans

Imagine you are a civil engineer who has just proudly installed a brand new ventilation system. The system works flawlessly and offers impressive efficiency that significantly improves air quality. But despite all these positive aspects, there is one problem: the ventilation system is simply too loud. But what exactly makes the fan loud and what can you do about it?

In ventilation, air conditioning or refrigeration applications, it can happen that a built-in fan becomes unexpectedly loud. This phenomenon occurs particularly with small ventilation units that are often installed in the immediate vicinity of occupied rooms, such as in residential buildings, hotels or conference rooms. The fan noise is caused by turbulence and unstable flow conditions, which can lead to disturbing noises such as droning, pumping or piping noises and can affect people’s well-being. To solve this problem, specific measures are required to reduce turbulence and stabilize the flow, depending on the installation situation.

An optimal design of the impeller geometry and special blade and vane shapes can significantly improve the flow situation and considerably reduce noise generation. Additional system components can further enhance these effects.

ZIEHL-ABEGG has developed the “ZAflow” air inlet grille for its centrifugal fan series.

The honeycomb shape, based on the biological model of honeycombs, offers the greatest possible air guiding function with minimal distortion of the air flow. In this way, the trihexagonal prismatic grille achieves efficient flow rectification with minimum material requirements and maximum stability.

Flow behavior of the air at the impeller without and with ZAflow

Noise reduction of 3 to 6 dB achieved

In tests with various ventilation systems, a noise reduction of 3 to 6 dB was achieved by using ZAflow. Whether and by how much the noise level can be reduced always depends on the respective installation situation.

If there is an inhomogeneous inflow on the suction side, the noise level will improve through the use of ZAflow.

Sustainable, biomimetic fan
technology for pleasantly quiet operation


Basically, the effect of noise reduction always depends on the respective installation situation. ZAflow can be an effective noise reduction measure, particularly on the critical suction side, if a uniform air supply is not already guaranteed. In addition, ZAflow enables a more compact and efficient overall system, which brings economic benefits and can be easily tried out.