Why does projector have some noise?

DX819ST, GP10, GP20, JOYBEE GP2, LW61ST, LX60ST, MS504, MS521, MS616ST, MW767, MW820ST, MW821ST, MW851UST, MW870UST, MX805ST, MX819ST, MX822ST, MX850UST, SH940, SH960, SX914, W1500, W7000+, MW523, MW663, MW721, MW817ST, MX600, MX522, MX661, MX618ST, MX720, MX703, MX766, MX722, MX816ST, MX815ST, S30, SH910, SP840, SP920P, W1070, W1080ST, 3D GLASSES - DP2, 3D GLASSES - DC4, 3D GLASSES, 3D GLASSES - DP3, GP10 DVD PLAYER, CEILINGMOUNTCM00G2, MS502, MH680, MW519, MX503, MX505, MX518, MX520, MX522P, MX620ST, MX662, POINTDRAW 3, PW01, QPRESENTER-ANDROID, QPRESENTER-IPHONE, W750, W770ST, W1300, W1400, WDAM2120, WDRT8192, MS517, MS521P, MS619ST, 0.3 WALL MOUNT-WM03G2, 0.3 WALL MOUNT-WM03G3, 0.4 WALL MOUNT-WM04G2, 0.4 WALL MOUNT-WM04G3, 0.6 WALL MOUNT-WM06G2, 0.6 WALL MOUNT-WM06G3, GP3, MW621ST, W7500, SX912, SP870, CEILING MOUNT-CM00G1, EP5920, MP525P, MP575, MP615P, MP776, MP780 ST, MP780ST+, MS510, MS513, MS612ST, MS614, MW516, MW712, MW811ST, MW814ST, MW860USTI, MX501, MX511, MX514, MX613ST, MX615, MX660, MX660P, MX701, MX710, MX711, MX717, MX763, MX764, MX810ST, MX812ST, MX813ST, WIRELESS DONGLE, SP890, SP891, W1060, W1100, W1200, W6000, W7000, W710ST, MX716