General ventilation filters: what acoustic characteristics?

In the field of general ventilation, air filters are widely used, and introduced in ventilation ductworks, or air-handling units. These filters are passed through by air flow and noise. However, their characteristics of sound attenuation and sound generation are very poorly known, used and tested. This presentation reports a study done in collaboration with French air filtering manufacturers members of CETIAT. More than thirteen 592x592 mm filters representing four different types of air filters commercially available have been tested in laboratory, to characterise the insertion loss and the noise generation. Those types of filters are mini pleated (50 & 100 mm thickness), V-bank, bags and pleated, with different materials such as glass fiber and synthetic fiber. In addition, the effect of the dust loading has been investigated the sound characteristics as well as the influence of a series installation of a prefilter and a filter. These experimental data will be helpful for acoustic studies of ventilation networks. Some results about sound absorption can be related to the characteristics of the filters, thickness or shape but also to the loading and the use in series, whereas no obvious relation can be found for sound generation.