Sound:
There are complaints that the UHD50/40 and the UHD300X make a lot of noise due to the pixel shifter. I can hear the pixel shifter just fine, while i'm sitting ~25 centimers from the projector with my head, writing this review. But the fan to keep the projector cool, is just a little louder on eco then the pixel shifter, and is already on such low volume, that i almost hear my pc more. A pc, ~50cm away from me that is build for silence. The pixel shifter is kind of a rattling noise, like something is loose. Or like a little bit of electricity sparkling sound. But its very vague. I am 100% certain no one of my friends or family will notice or complain about it. If you put the projector on max brightness, the fan noise becomes normal, but still more silent then the epson 2150 i had. Its definatly not intrusive, but you can definatly hear it. Basicly compare the fan noises like this. Eco is almost non-existant, and full brightness is non-intrusive but its there. XPR noise is there as well, but the fan noise on ECO is surpressing the XPR noise, and its definatly not annoying. I recommend to replace it under warrenty, if you get a until thats louder then the fan in eco mode.
As for sound from the build-in speakers, i take a bluetooth speaker (with 3,5mm line connection) with me to holidays, so i have no intention of using the build in speakers. I tried them for this review and well...they work. But they sound bad on max volume, although better then speakers from lets say phones and tablets etc. Just get a speaker with you that works on line-in.