Exported audio file has buzzes and white noise when normalized

Am I reading that right? You are normalizing silence? 

Absolute silence, meaning a string of zero-value samples, would indeed still be silent after normalization. However, that lead-in probably wasn't absolutely silent to begin with, as absolute silence doesn't exist in reality. If nothing else, you've got dither and quantization noise assuring that a silent part isn't a string of zeroes. You don't usually hear it, but normalization is going to take whatever's in there and turn it up. 

Getting rid of those artefacts is part of mastering ( if you know what your doing) 

That is normal.
"Normalising" FORCES all ground noise to 0dB. Even if the ground noise is -120dB = absolut silent.
Just tested. Even muted parts will be normalised to 0dB hum.
Absolute silence means -120 dB and "normalising" adds 120 dB to it = 0dB white noise and hum.

Any audio that's been dithered will contain noise. Dithering adds noise, it's how it works. That noise is usually at such a low level it's inaudible or almost inaudible at any 'normal' plygack volume, including club systems. But if you normalise it to zero dB then yes, it's going to be loud. Because you've just boosted it by anything up to a hundred dB or more depending on bit rate.

Any audio processing, even digital, will add noise even if the plugins used aren't emulations of noisy, vintage hardware. Even good linear phase processors add some byproducts in the way of noise or phase shifting which comes out as noise. Again, normalise the noise and it will be very loud.

Software synth's filters etc. almost certainly produce some output even when the synth isn't receiving MIDI.
And you probably don't want to near how much oscillator leakage some very reputable hardware synths produce if you take their 'silence' and normalise it.

What you are hearing is perfectly normal, even if the audio was created entirely 'in the box". If it involved any hardware at all then the noise would be worse.

The motto? Don't normalise anything and expect silence.

If you sufficiently magnify the wave form for what looks like a flat line in any DAW you're very likely to find it isn't really a flat line at all if it's the result of recording or has been processed in any way at all.