Disturbance of the flow of air into the fan produces a high noise level. Wherever there are constrictions, so-called vortex string formations develop. These collide directly with the rotating blades and generate unwanted noise. With this in mind, ebm-papst developed the special FlowGrid air-inlet grille (patent pending) which has a straightening effect on the inflowing air. The vortex strings are split upon hitting the grille and considerably weakened as they flow through it. In other words, the air-inlet grille drastically reduces noise-generating disturbance – resulting in a decrease in sound pressure over the entire frequency range, however particularly at the disturbing low blade passing frequency. The air-inlet grille is suitable for use with both axial and centrifugal fans. Use of the air-inlet grille for a condenser with axial fan for example makes it possible to reduce the noise level by 3.9 dB(A) and the blade passing frequency by 16 dB. There is thus considerably less need for insulation and noise protection and the corresponding standards can be more easily satisfied. And best of all: There is virtually no effect on power input and air performance.