Farewell Lecture, with film on the topic 'Aerodynamical Sound Generation', 15 July 1969 Lecture notice and manuscript and duplicated typescript. The lecture notice explains that the film was prepared by Lighthill and J.E. Ffowcs Williams under the auspices of the US National Committee for Fluid Mechanics Films. Lighthill gave a short lecture in the form of a general introduction before the film was shown. 1969