Fan Noise Reduction
Fan Noise Reduction
(OP)
Have a 1500 RPM, 1500 HP motor with shaft mounted external centrifugal fan cooling the motor (with embedded tubes around the stator periphery). The fan is mounted before the coupling with suction from the coupling end and delivery through the embedded tubes.
The operator near the motor is objecting to the noise level - created by the above fan - which was recorded at 93 dB.
I am proposing to use a 5 mm sheet metal hood with an inch thick soft rubber lining inside, around and over the fan suction area.
Will this work ?
Any other ideas ?
The operator near the motor is objecting to the noise level - created by the above fan - which was recorded at 93 dB.
I am proposing to use a 5 mm sheet metal hood with an inch thick soft rubber lining inside, around and over the fan suction area.
Will this work ?
Any other ideas ?
*Even inside a hard-boiled egg, there is a golden heart!!!*





RE: Fan Noise Reduction
93dB is about what you would expect for such a size of motor.
Or, ear defenders for the operator?
RE: Fan Noise Reduction
The problem started because the previous motor (which failed) running in the same location had ducted cooling wiht no fans at all which resulted in quieter running.
No axial fans be fixed since the motor is tube ventilated with the tubes embedded around the stator periphery.
So, I am trying my stunt.
*Even inside a hard-boiled egg, there is a golden heart!!!*
RE: Fan Noise Reduction
A search for "industrial soundproofing" or "industrial noise reduction" will turn up some engineered options. You'll need some frequency spectrum data for the noise to optimize the solution. Just be thankful it isn't 3000 rpm.
ht
RE: Fan Noise Reduction
If the noise is particularly strong at one frequency, that would suggest an aero interaction between the fan blade tips and the tube edges. In that case the spectrum could be spread out a bit by staggering the fan blade tips or the tube edges or both, just a little, so that interaction noises don't constructively reinforce each other. Sort of like tire tread patterns are unevenly spaced.
Mike Halloran
Pembroke Pines, FL, USA
RE: Fan Noise Reduction
Our trial is planned for this week-end. Will come back here hopefully with good news.
*Even inside a hard-boiled egg, there is a golden heart!!!*
RE: Fan Noise Reduction
RE: Fan Noise Reduction
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I don't have an attitude problem. You have a perception problem...
RE: Fan Noise Reduction
Since this motor has cooler tubes around the stator outer periphery, fixing externally driven fans is not an option.
I am going to try my above method this sunday and am keeping the fingers crossed.
*Even inside a hard-boiled egg, there is a golden heart!!!*
RE: Fan Noise Reduction
If you cannot use water, have someone do a sound level spectrum analysis to determine what frequency or frequencies are causing most of the noise. That information may better help you determine what type(s) of sound absorbing materials will provide the most benefit. Just like anything else, not all sound absorbing materials are created equal. There are companies that specialize in noise reduction strategies, and that may be the most economic road to hoe.
Good luck,
Raisinbran
RE: Fan Noise Reduction
The noise level at about 1 ft of the motor came down from 102 dB to 95 dB with the enclosure.
But it came down from 87 dB to only 85 dB at the operator end, which is about 12 ft away.
The background noise (without the motor running) was 80 dB.
Advised to use ear mufflers.
*Even inside a hard-boiled egg, there is a golden heart!!!*
RE: Fan Noise Reduction
In my company we have technical person designing sound silencers for outgoing air on our projects. I remember when I was talking about them he explained about the every noise level is created by some part moving and that silencer is created to suppress some frequencies but to suppress them all he would need very big silencer and that it is expensive so he suppresses only main noise. Now you can try many things but the noise is expectable on such fans, and the problem is usually sound level regulations that consider sound outside the facility. I don't know how does the fan chamber look like (and if you have one) but you can try applying some house noise suppressing materials rather than metal sheath, either on fan chamber or on operator room. metal pases vibration, so there are better solutions because your prime concern is to lover the noise inside, metal is used in silencers to withstand air pressure when you are trying to protect outside world from your noise....