/usr/lib/x86_64-linux-gnu/librtaudio.so is in librtaudio-dev 4.1.1~ds0-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/librtaudio.so.4v5.1.1b
/usr/lib/x86_64-linux-gnu/librtaudio.so.4v5.1.1b