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Switchmode supply transformers generally run anywhere from 15Khz to 42Khz and this can cause a squeal between their windings, laminations or indeed if the frequency of oscillation is out (usually a dried out electrolytic capacitor) this can cause a squeal.
As suggested many of the good older AC (non-switchmode) transformers do not squeal, but they can buzz (at 60Hz) between their core laminations (if they are cheapies).
It's also possible that the "glow wire" is a capacitive load causing the switchmode to operate outside it's tolerances. Was the supply designed for these lights?
In any case I'd go and get one of those jaycar torrodial transformers with the desired output you need. Make sure you overrate and get a transformer with more current capacity than you need.
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