4 large axial extract fans caused noise complaints over a wide area in Canada, despite multiple attempts at noise control based on conventional techniques. One email led to the noise being reduced by 99% with no site visits required - the whole project was completed over the internet.
Mitchell, the site engineer sent us an email with smartphone video clips and photos. Soundtrack analysis showed the problem to be high-level tones at the 197Hz blade pass and harmonics. We used the photos to design retro-fit aerodynamic noise-reducing components which the client made and installed to give 20dB attenuation at 100m.
"We are exceptionally happy with the overall results that were obtained, from a noise reduction, cost, and time standpoint. INVC was very professional and prompt on all deliverables. Out of all solutions attempted this was by far the best and cost-effective. The whole process was very smooth from first contact to installation … glad we went with INVC, thanks…"
In addition to the attenuation of the primary fan hum sound, the harmonics and associated tones were also dramatically reduced as shown in this frequency analysis plot. Moreover, as the performance of the fans was also improved, the project was self-financing and will pay for itself in reduced running costs.
This technology is very applicable to all types of extract fans where tonal noise is an issue. As it is immune to the effects of the passage of materials or to corrosive atmospheres (it cannot clog), it is particularly suitable to attenuate the noise from fume, scrubber, dust, or other waste extract fans.