Describe the the feature you'd like
As of the 9.10.9 version of Mekanism for Minecraft 1.15.2, the Smelting Factories create this insane racket including a ringing noise akin to tinnitus. I would like to request a new audio file for them in a future update, if they haven't already been replaced, because it's kind of headache inducing.

Mekanism V9 will be no longer updated.
if the sound annoys you, use muffler upgrades or disable game sounds

I don't think there are currently any plans to change the sound for the energized smelter/smelting factories. You can do as Robball suggested or also use a resource pack that changes the sound to your liking.