When Loud Speaker Ringer Buzzer Antenna Flex Cable Assembly for xiaomi mi4 is available in dragon-tt.com I will let you know. Maybe you need both of earpiece speaker and Loud speaker.
Try first Suppress noise during calls from Settings/Sound on/off. If it does not help then install latest firmware (again) and do full wipes from recovery.
Try first Suppress noise during calls from Settings/Sound on/off. If it does not help then install latest firmware (again) and do full wipes from recovery.