Comment by LargoLasskhyfv

Then it's a bad CRT, or degraded.

I remember this from decades ago, there were big differences even in new ones.

Where the silent ones not necessarily were satisfactory for cats, since their hearing is more sensitive, and perceives higher frequencies.

OTOH some cats really like to sleep atop of them, maybe because of the warmth? Or what the electrostatics do to their fur?