/usr/src/linux-headers-4.15.0-24-generic/sound is in linux-headers-4.15.0-24-generic 4.15.0-24.26~16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/src/linux-headers-4.15.0-24-generic/../linux-headers-4.15.0-24/sound