ABSTRACT
This chapter introduces the simple source, source of spherical waves and fundamental building block for acoustical analysis and discusses the quadrupole source, its various forms, directional properties and some modes of generation. It examines the piston in an infinite wall, far-field and near-field properties, radiation load, and uses for modelling and describes directional properties of sources and the concept of directivity. The chapter presents reflection and transmission at a plane two media interface and looks at sound propagation outdoors, ground reflection, atmospheric effects, methods of prediction. The presence of a reflecting surface near to a source will affect the sound radiated and the apparent directional properties of the source. The problems arising from sound propagation outdoors may range from relatively simple to very complex, depending upon the nature of the source and distribution of the affected surrounding areas. Most sound sources are directional, radiating more sound in some directions than in others.
