Quote:
Originally Posted by stumped
a buzzing sound from a monitor sounds different to a coil whine from a PSU under load ( having experienced both).
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Though both are usually magnetostriction. A ferrite core affected by the pulses.
405 TV 10.125 kHz
625 TV 15.625
525 USA TV 15.725 kHz
Basic VGA 31.450 kHz
50 fps progressive HD 56.250 kHz, but I've only seen 2 models of CRT able for that.
But the scan coils or the LOPT can sometimes resonate at half the frequency.
A SVGA or higher scan rate monitor whine is likely a SMPSU / DC-DC converter. Especially in a flat screen. A CCFL flat screen back light PSU can have a whine.
A DC-DC converter or other SMPSU in a gadget or a mains supply can be anything from 11 kHz to 2 MHz. The core or transformer is much smaller than the CRT LOPT core or scan coil cores. It can often be reduced by a dab of Silicon Rubber. Must be electrical quality as the DIY sealant type produces acid (possibly acetic acid) as it sets which corrodes coatings, pins, wires and joints.
So they do sound differently and older people can only hear the lower pitch whines, less than 14 kHz usually.