To investigate the mechanisms of wing trailing edge noise the aeroacoustic sound generation by a NACA 0018 has been computed with direct numerical simulations using the Lattice Boltzmann Method. Noise from the straight trailing edge wing is compared with the sound generated by a sawtooth serrated wing, which reduces the noise emission according to literature. It was found that for low frequencies the trailing edge serrations reduce the noise significantly, but show a limited (negative) effect at high frequencies.