@remotebot
Assuming you have a 4640/4800/4802/4850:
1) Configure passthrough: Settings/Audio/Digital output format = Passthrough (Auto transcodes all non-DTS audio to the highest detected Dolby level of the connected device, and may/does cause static/stuttering/drops/dropouts/bad channel remapping/latency/volume shifts)
2) Disable Sound Modes: During playback - Options (*)/Sound Settings/Customize sound modes/Volume Leveling & Dialog Enhancement = Off (Sound Modes can/do cause static/stuttering/dropouts/latency/volume shifts/loss of multichannel).
3) Disable power savings: Settings/System/Power/Auto power savings = Off (unchecked)
However, if this "loud noise" (not sure whether you are referring to the Roku "Dancing Logo" bootup audio, or HDMI audio output when switching the TV/AVR input port to the Roku) persists even after making those changes, you might consider checking your AVR/TV's HDMI port/passthrough audio settings, and otherwise seek a refund/exchange (if possible).