I’ve just noticed that if I put my flashlight to my ear, I can hear a bit of a buzzing/screeching sound. This only seems to happen with the low and medium modes but it happens with all of my lights. The noise isn’t noticeable except when I hold the light to my ear. I was just wondering what was causing the noise and if this was normal for flashlights. Thanks.
Quite normal - some are more pronounced than others, but most lights will exhibit some kind of whine/buzz/etc. What you’re hearing is PWM switching noise. The rapid on/off cycle that generates low and medium brightness happens (in most lights) at a frequency that is very audible to the human ear (100-1000 Hz). Nothing to worry about.
PPtk
only when it starts to sound like Raiden of mortalcombat should u be worried.
or, if it happens when its off
I wear my tinfoil hat……….works every time.
Don’t stick flashlights in your ears and you should be fine 
I like that sound! Makes me feel like I can hear the “light engine” running. Also, it repels Sasquatch. At least I assume it does, since I’ve never seen one. 
One of the many reasons I prefer voltage regulation over pwm. I had a computer fan that had it’s speed controlled by pwm and caused the fan to ‘rattle’. I eventually had to get a better systemboard that used voltage regulation for controlling the speed of the fan to get rid of the noise.
Except for LEDs you would want current regulation, not voltage regulation.
Agreed.
My KD C8 buzzed LOUDLY, until I tightened down the pill and the tail switch. That stopped it.