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Are certain types of inductors more likely to create an audible sound than others when under use? Is there any sort of best-practice or guideline to minimize such humming or buzzing sounds? I.E. oversize (max current) the inductor or mount it on a rubber pad or similar? or perhaps an alternate format, i.e. a toroid type?

vacuum impregnated inductor were suggested by jeroen74

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    \$\begingroup\$ The one coated in a liberal amount of hot glue. \$\endgroup\$ Aug 26, 2014 at 20:24
  • \$\begingroup\$ @IgnacioVazquez-Abrams If it's a power inductor, then it'd better be a thermally conductive hot glue. \$\endgroup\$ Aug 26, 2014 at 21:06
  • \$\begingroup\$ At least you can source hot glue that has a UL 94V0 flammability rating. \$\endgroup\$ Aug 26, 2014 at 21:09
  • \$\begingroup\$ Pure theory: oil-bath inductors should be quieter than free-air inductors because of the sound-damping property of oil. \$\endgroup\$ Aug 26, 2014 at 22:06
  • \$\begingroup\$ You can use acoustic dampening (heat-resistant wool) on most all inductors to, well, dampen the sound. If your design allows, the best practice is to use switching frequencies outside of (human) audible range...when possible. What are you using this inductor for? \$\endgroup\$ Aug 27, 2014 at 3:54

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Toroidal types seem less prone to making noise than "rod" type ferrite inductors.

Molded inductors are probably best, followed by vacuum impregnated types. Tape wound cores also seem to be good. Loose laminations on steel core inductors can make a terrible racket.

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  • \$\begingroup\$ +1, I've got no 'practical' knowledge. Toroidal's make sense if it's a size change thing, they're more constrained, while open ended inductors go everywhere... they do the same electrically. Toroids* seem the natural shape for inductors, or maybe pot cores. *why do no spell checkers know toroid or inductor? (It's a conspiracy :^) \$\endgroup\$ Aug 27, 2014 at 0:42
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I think most of the transformer "hum" we hear is due to magneto-stricition. (The material changes size in a magnetic field.) It only depends on the magnitude of the field so we hear the hum at 120 Hz. (here in the US.) So to reduce noise, one would have to reduce the maximum B field. I think that just means using an over-sized inductor for the job.

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