timangus

Well resistive heaters will often emit light as the elements glow, and I wouldn't be surprised if the AC current that powers them causes some very small kinetic perturbations due to magnetic field interactions which in turn may be expressed as sound. Obviously 99.9999whatever% is going to infrared radiation, but clearly not perfectly 100%.

Pedandically, they aren't 100% efficient, although very close to being so.

Tartan paint? Perhaps peculiar to north of the border.