Case Studies

Altra-Air HVLS Big Ceiling Fans

Commercial Fan Noise Acoustic Test & Measurement

Location: Seaforth, Ontario, Canada
Client: Envira-North Systems

HGC Engineering was retained by Envira-North Systemsa commercial fan manufacturer to investigate options for noise control of the company’s popular Altra-Air high volume, low speed big ceiling fans for large areas. These fans were initially developed for agricultural and warehouse use where the noise levels were not critical, but the company wanted to enlarge the market applications for the fans to include theatres and outdoor entertainment areas where lower levels of noise were needed from the fans.

It was suspected that the source of greatest concern was the noise generated by the fan’s gear motors. We undertook a series of sound measurements of several fans in various configurations using sound intensity methods. We determined that the majority of gear-meshing sound radiated to the surrounding air by the fan blades and not the motor and gear housing. In actuality, the sound is transmitted to the blades through the shaft and hub. Our noise reduction solution involved inserting a flexible coupling between the shaft and the hub. With the coupling addition, there was a noise reduction of 8 dBa at full speed and 3 dBa at low speed.

Acoustical Engineering Services Included:

  • Using sound intensity methods, we measured the sound emitted by various sub-components of the fan assembly, to assist in developing quieter designs
  • Acoustical analysis to correlate the sound emissions of subcomponents to the overall noise level of the fan
  • Vibro-acoustic computations to identify the sound transmission path and develop a mitigation solution

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