can't open /dev/mem

./demo: error while loading shared libraries: libsndfile.so.1: cannot open shared object file: No such file or directory

gcc `pkg-config --cflags sndfile` -c demo.c
gcc 'pkg-config --libs sndfile' demo.o -o demo
sudo ./demo stereo_small.wav

sudo bash
export LD_LIBRARY_PATH=/usr/local/lib
./demo stereo_small.wav

su --command="export LD_LIBRARY_PATH=/usr/local/lib && ./demo stereo_small.wav"