I have a 5000K SC31 Pro, it is totally silent in ANY mode, and with either tail cap.
I don’t have a SC31 but as other flashlights some noise from PWM is expected, but it should be worse at medium level, not high, and shouldn’t be so loud as to be annoying. Louder noise with the magnetic tailcap is quite interesting.
People lose the ability to hear high frequencies like 15.7KHz as they age.
Yeah it’s probably kinda like a CRT, where some people can’t hear it at all. I’m pretty sure what’s happening in the flashlight, though, is that the magnetic tailcap and the tailspring are acting like a speaker, so whenever the current quickly changes it makes sound. (either a whining sound from the PWM, or clicking and buzzing in stepped ramp and strobe modes, respectively)
I can hear high pitched noise from cfl’s or tv’s on with no sound or picture.
Nothing out of the sc31pro. Maybe something slightly off with yours.
/shrug
With the magtail? mine is pretty much silent with the regular tail. it’s just with the magnetic one that it really makes noise.
Yeah, that’s with mag. I’ll dig up the non-magnetic one and give it a go; forgot to do that (oops).
So, I tested with some other flashlights with the magtail
Sofirn SP40: ~24KHz noise in “high” (ultrasonic), silent in turbo. Makes no sound when turning on, but clicks when turning off
Sofirn SP32A V2.0: No sound in any mode, no sound when changing modes. clicks when turning off, fast clicking in strobe.
Sofirn SC31 pro (already tested): clicks when turning on, clicks when going through stepped ramp, buzzes/clicks in strobe depending on speed, and makes 15.7 KHz noise in all higher settings except turbo.
I think the SP32A V2 uses a constant current driver, so there is no detectable noise when it’s on. It also does some strange smooth transitions between brightness levels so it doesn’t make a clicking sound except when turned off.
It’s actually kinda cool, except that it means I can hear the PWM on the SC31 pro 
Maybe newer versions of it will use a constant-current driver.
Ah yes I think I have something similar! I can hear a “clunk” when I run the light above a certain current. Double press from off (-> ceiling) produces a clunk sound, but not when I turn the light from off to a lower value…
FWIW, my 6500k version is silent with mag cap.
No, people want Anduril and lumens, adapting it to a buck driver is more work and less lumens. Both the SP33 and the C8G switched from a constant current driver to a FET. Efficiency and regulation be damned.
I can feel mine vibrate in my hand while in the strobe modes when I’m using the magnetic tailcap and 18350 tube. No audible whine though.
Anyone else experience this?
True, but it’s possible to have both, like the Lume1 driver has, where it uses direct drive for turbo, but CC for lower brightness. (It also uses Andúril) Lume1-FW3X: Constant Current Buck-Boost & FET Driver with Anduril1/2 + RGB Aux
Yes, but the Lume1 driver costs only $0.94 less than a complete SC31 Pro, quality has its price.
Of course it’s expensive, but the Lume1-fw3x is a small batch custom pcb from OSHpark.
A TI TPS61088-Q1 synchronous boost converter for instance, costs about 3 dollars in quantity and is capable of 10A. I’m sure PWM and linear regulated flashlights are somewhat cheaper, but proper switching power supplies don’t cost that much.
That Lume1 driver is so clean and elegant (and totally open source) it’d be a shame not to base other flashlights on it 
That seems pretty loud, did you alter audio at all?
Nothing like that out of mine in the strobe modes.
most noticeable is the slight crackle on turbo
Totally missed this. That was a straight upload from my phone to imgur, no editing of anything.