Please follow this tutorial link
Short version is below in case link goes dead.
apt install xrdp-pulseaudio-installer
xrdp-build-pulse-modules
sudo apt-get install xrdp-pulseaudio-installer -y
sudo xrdp-build-pulse-modules
cd /tmp
sudo apt source pulseaudio
cd /tmp/pulseaudio*
sudo ./configure
cd /usr/src/xrdp-pulseaudio-installer
make PULSE_DIR="/tmp/pulseaudio-11.1"
install -t "/var/lib/xrdp-pulseaudio-installer" -D -m 644 *.so